-*- buffer-read-only: t -*-
!!!!!!!   DO NOT EDIT THIS FILE   !!!!!!!
This file is built by ..\autodoc.pl extracting documentation from the C
source files.
Any changes made here will be lost!

=encoding UTF-8

=head1 NAME

perlapi - autogenerated documentation for the perl public API

=head1 DESCRIPTION
X<Perl API> X<API> X<api>

This file contains most of the documentation of the perl public API, as
generated by F<embed.pl>.  Specifically, it is a listing of functions,
macros, flags, and variables that may be used by extension writers.  Some
specialized items are instead documented in F<config.h>, L<perlapio>, L<perlcall>, L<perlclib>, L<perlfilter>, L<perlguts>, L<perlmroapi>, L<perlxs>, L<perlxstut>, and L<warnings>.

L<At the end|/Undocumented functions> is a list of functions which have yet
to be documented.  Patches welcome!  The interfaces of these are subject to
change without notice.

Anything not listed here is not part of the public API, and should not be
used by extension writers at all.  For these reasons, blindly using functions
listed in proto.h is to be avoided when writing extensions.

In Perl, unlike C, a string of characters may generally contain embedded
C<NUL> characters.  Sometimes in the documentation a Perl string is referred
to as a "buffer" to distinguish it from a C string, but sometimes they are
both just referred to as strings.

Note that all Perl API global variables must be referenced with the C<PL_>
prefix.  Again, those not listed here are not to be used by extension writers,
and can be changed or removed without notice; same with macros.
Some macros are provided for compatibility with the older,
unadorned names, but this support may be disabled in a future release.

Perl was originally written to handle US-ASCII only (that is characters
whose ordinal numbers are in the range 0 - 127).
And documentation and comments may still use the term ASCII, when
sometimes in fact the entire range from 0 - 255 is meant.

The non-ASCII characters below 256 can have various meanings, depending on
various things.  (See, most notably, L<perllocale>.)  But usually the whole
range can be referred to as ISO-8859-1.  Often, the term "Latin-1" (or
"Latin1") is used as an equivalent for ISO-8859-1.  But some people treat
"Latin1" as referring just to the characters in the range 128 through 255, or
somethimes from 160 through 255.
This documentation uses "Latin1" and "Latin-1" to refer to all 256 characters.

Note that Perl can be compiled and run under either ASCII or EBCDIC (See
L<perlebcdic>).  Most of the documentation (and even comments in the code)
ignore the EBCDIC possibility.
For almost all purposes the differences are transparent.
As an example, under EBCDIC,
instead of UTF-8, UTF-EBCDIC is used to encode Unicode strings, and so
whenever this documentation refers to C<utf8>
(and variants of that name, including in function names),
it also (essentially transparently) means C<UTF-EBCDIC>.
But the ordinals of characters differ between ASCII, EBCDIC, and
the UTF- encodings, and a string encoded in UTF-EBCDIC may occupy a different
number of bytes than in UTF-8.

The listing below is alphabetical, case insensitive.


=head1 Array Manipulation Functions

=over 8

=item av_clear
X<av_clear>

Frees the all the elements of an array, leaving it empty.
The XS equivalent of C<@array = ()>.  See also L</av_undef>.

Note that it is possible that the actions of a destructor called directly
or indirectly by freeing an element of the array could cause the reference
count of the array itself to be reduced (e.g. by deleting an entry in the
symbol table). So it is a possibility that the AV could have been freed
(or even reallocated) on return from the call unless you hold a reference
to it.

	void	av_clear(AV *av)

=for hackers
Found in file av.c

=item av_create_and_push
X<av_create_and_push>


NOTE: this function is experimental and may change or be
removed without notice.


Push an SV onto the end of the array, creating the array if necessary.
A small internal helper function to remove a commonly duplicated idiom.

NOTE: this function must be explicitly called as Perl_av_create_and_push with an aTHX_ parameter.

	void	Perl_av_create_and_push(pTHX_ AV **const avp,
		                        SV *const val)

=for hackers
Found in file av.c

=item av_create_and_unshift_one
X<av_create_and_unshift_one>


NOTE: this function is experimental and may change or be
removed without notice.


Unshifts an SV onto the beginning of the array, creating the array if
necessary.
A small internal helper function to remove a commonly duplicated idiom.

NOTE: this function must be explicitly called as Perl_av_create_and_unshift_one with an aTHX_ parameter.

	SV**	Perl_av_create_and_unshift_one(pTHX_ 
		                               AV **const avp,
		                               SV *const val)

=for hackers
Found in file av.c

=item av_delete
X<av_delete>

Deletes the element indexed by C<key> from the array, makes the element
mortal, and returns it.  If C<flags> equals C<G_DISCARD>, the element is
freed and NULL is returned. NULL is also returned if C<key> is out of
range.

Perl equivalent: S<C<splice(@myarray, $key, 1, undef)>> (with the
C<splice> in void context if C<G_DISCARD> is present).

	SV*	av_delete(AV *av, SSize_t key, I32 flags)

=for hackers
Found in file av.c

=item av_exists
X<av_exists>

Returns true if the element indexed by C<key> has been initialized.

This relies on the fact that uninitialized array elements are set to
C<NULL>.

Perl equivalent: C<exists($myarray[$key])>.

	bool	av_exists(AV *av, SSize_t key)

=for hackers
Found in file av.c

=item av_extend
X<av_extend>

Pre-extend an array so that it is capable of storing values at indexes
C<0..key>. Thus C<av_extend(av,99)> guarantees that the array can store 100
elements, i.e. that C<av_store(av, 0, sv)> through C<av_store(av, 99, sv)>
on a plain array will work without any further memory allocation.

If the av argument is a tied array then will call the C<EXTEND> tied
array method with an argument of C<(key+1)>.

	void	av_extend(AV *av, SSize_t key)

=for hackers
Found in file av.c

=item av_fetch
X<av_fetch>

Returns the SV at the specified index in the array.  The C<key> is the
index.  If lval is true, you are guaranteed to get a real SV back (in case
it wasn't real before), which you can then modify.  Check that the return
value is non-null before dereferencing it to a C<SV*>.

See L<perlguts/"Understanding the Magic of Tied Hashes and Arrays"> for
more information on how to use this function on tied arrays. 

The rough perl equivalent is C<$myarray[$key]>.

	SV**	av_fetch(AV *av, SSize_t key, I32 lval)

=for hackers
Found in file av.c

=item AvFILL
X<AvFILL>

Same as C<av_top_index()> or C<av_tindex()>.

	int	AvFILL(AV* av)

=for hackers
Found in file av.h

=item av_fill
X<av_fill>

Set the highest index in the array to the given number, equivalent to
Perl's S<C<$#array = $fill;>>.

The number of elements in the array will be S<C<fill + 1>> after
C<av_fill()> returns.  If the array was previously shorter, then the
additional elements appended are set to NULL.  If the array
was longer, then the excess elements are freed.  S<C<av_fill(av, -1)>> is
the same as C<av_clear(av)>.

	void	av_fill(AV *av, SSize_t fill)

=for hackers
Found in file av.c

=item av_len
X<av_len>

Same as L</av_top_index>.  Note that, unlike what the name implies, it returns
the highest index in the array, so to get the size of the array you need to use
S<C<av_len(av) + 1>>.  This is unlike L</sv_len>, which returns what you would
expect.

	SSize_t	av_len(AV *av)

=for hackers
Found in file av.c

=item av_make
X<av_make>

Creates a new AV and populates it with a list of SVs.  The SVs are copied
into the array, so they may be freed after the call to C<av_make>.  The new AV
will have a reference count of 1.

Perl equivalent: C<my @new_array = ($scalar1, $scalar2, $scalar3...);>

	AV*	av_make(SSize_t size, SV **strp)

=for hackers
Found in file av.c

=item av_pop
X<av_pop>

Removes one SV from the end of the array, reducing its size by one and
returning the SV (transferring control of one reference count) to the
caller.  Returns C<&PL_sv_undef> if the array is empty.

Perl equivalent: C<pop(@myarray);>

	SV*	av_pop(AV *av)

=for hackers
Found in file av.c

=item av_push
X<av_push>

Pushes an SV (transferring control of one reference count) onto the end of the
array.  The array will grow automatically to accommodate the addition.

Perl equivalent: C<push @myarray, $val;>.

	void	av_push(AV *av, SV *val)

=for hackers
Found in file av.c

=item av_shift
X<av_shift>

Removes one SV from the start of the array, reducing its size by one and
returning the SV (transferring control of one reference count) to the
caller.  Returns C<&PL_sv_undef> if the array is empty.

Perl equivalent: C<shift(@myarray);>

	SV*	av_shift(AV *av)

=for hackers
Found in file av.c

=item av_store
X<av_store>

Stores an SV in an array.  The array index is specified as C<key>.  The
return value will be C<NULL> if the operation failed or if the value did not
need to be actually stored within the array (as in the case of tied
arrays).  Otherwise, it can be dereferenced
to get the C<SV*> that was stored
there (= C<val>)).

Note that the caller is responsible for suitably incrementing the reference
count of C<val> before the call, and decrementing it if the function
returned C<NULL>.

Approximate Perl equivalent: C<splice(@myarray, $key, 1, $val)>.

See L<perlguts/"Understanding the Magic of Tied Hashes and Arrays"> for
more information on how to use this function on tied arrays.

	SV**	av_store(AV *av, SSize_t key, SV *val)

=for hackers
Found in file av.c

=item av_tindex
X<av_tindex>

Same as C<av_top_index()>.

	SSize_t	av_tindex(AV *av)

=for hackers
Found in file av.h

=item av_top_index
X<av_top_index>

Returns the highest index in the array.  The number of elements in the
array is S<C<av_top_index(av) + 1>>.  Returns -1 if the array is empty.

The Perl equivalent for this is C<$#myarray>.

(A slightly shorter form is C<av_tindex>.)

	SSize_t	av_top_index(AV *av)

=for hackers
Found in file av.c

=item av_undef
X<av_undef>

Undefines the array. The XS equivalent of C<undef(@array)>.

As well as freeing all the elements of the array (like C<av_clear()>), this
also frees the memory used by the av to store its list of scalars.

See L</av_clear> for a note about the array possibly being invalid on
return.

	void	av_undef(AV *av)

=for hackers
Found in file av.c

=item av_unshift
X<av_unshift>

Unshift the given number of C<undef> values onto the beginning of the
array.  The array will grow automatically to accommodate the addition.

Perl equivalent: S<C<unshift @myarray, ((undef) x $num);>>

	void	av_unshift(AV *av, SSize_t num)

=for hackers
Found in file av.c

=item get_av
X<get_av>

Returns the AV of the specified Perl global or package array with the given
name (so it won't work on lexical variables).  C<flags> are passed 
to C<gv_fetchpv>.  If C<GV_ADD> is set and the
Perl variable does not exist then it will be created.  If C<flags> is zero
and the variable does not exist then NULL is returned.

Perl equivalent: C<@{"$name"}>.

NOTE: the perl_ form of this function is deprecated.

	AV*	get_av(const char *name, I32 flags)

=for hackers
Found in file perl.c

=item newAV
X<newAV>

Creates a new AV.  The reference count is set to 1.

Perl equivalent: C<my @array;>.

	AV*	newAV()

=for hackers
Found in file av.h

=item sortsv
X<sortsv>

In-place sort an array of SV pointers with the given comparison routine.

Currently this always uses mergesort.  See C<L</sortsv_flags>> for a more
flexible routine.

	void	sortsv(SV** array, size_t num_elts,
		       SVCOMPARE_t cmp)

=for hackers
Found in file pp_sort.c


=back

=head1 Callback Functions

=over 8

=item call_argv
X<call_argv>

Performs a callback to the specified named and package-scoped Perl subroutine 
with C<argv> (a C<NULL>-terminated array of strings) as arguments.  See
L<perlcall>.

Approximate Perl equivalent: C<&{"$sub_name"}(@$argv)>.

NOTE: the perl_ form of this function is deprecated.

	I32	call_argv(const char* sub_name, I32 flags,
		          char** argv)

=for hackers
Found in file perl.c

=item call_method
X<call_method>

Performs a callback to the specified Perl method.  The blessed object must
be on the stack.  See L<perlcall>.

NOTE: the perl_ form of this function is deprecated.

	I32	call_method(const char* methname, I32 flags)

=for hackers
Found in file perl.c

=item call_pv
X<call_pv>

Performs a callback to the specified Perl sub.  See L<perlcall>.

NOTE: the perl_ form of this function is deprecated.

	I32	call_pv(const char* sub_name, I32 flags)

=for hackers
Found in file perl.c

=item call_sv
X<call_sv>

Performs a callback to the Perl sub specified by the SV.

If neither the C<G_METHOD> nor C<G_METHOD_NAMED> flag is supplied, the
SV may be any of a CV, a GV, a reference to a CV, a reference to a GV
or C<SvPV(sv)> will be used as the name of the sub to call.

If the C<G_METHOD> flag is supplied, the SV may be a reference to a CV or
C<SvPV(sv)> will be used as the name of the method to call.

If the C<G_METHOD_NAMED> flag is supplied, C<SvPV(sv)> will be used as
the name of the method to call.

Some other values are treated specially for internal use and should
not be depended on.

See L<perlcall>.

NOTE: the perl_ form of this function is deprecated.

	I32	call_sv(SV* sv, volatile I32 flags)

=for hackers
Found in file perl.c

=item ENTER
X<ENTER>

Opening bracket on a callback.  See C<L</LEAVE>> and L<perlcall>.

		ENTER;

=for hackers
Found in file scope.h

=item ENTER_with_name
X<ENTER_with_name>

Same as C<L</ENTER>>, but when debugging is enabled it also associates the
given literal string with the new scope.

		ENTER_with_name("name");

=for hackers
Found in file scope.h

=item eval_pv
X<eval_pv>

Tells Perl to C<eval> the given string in scalar context and return an SV* result.

NOTE: the perl_ form of this function is deprecated.

	SV*	eval_pv(const char* p, I32 croak_on_error)

=for hackers
Found in file perl.c

=item eval_sv
X<eval_sv>

Tells Perl to C<eval> the string in the SV.  It supports the same flags
as C<call_sv>, with the obvious exception of C<G_EVAL>.  See L<perlcall>.

The C<G_RETHROW> flag can be used if you only need eval_sv() to
execute code specified by a string, but not catch any errors.

NOTE: the perl_ form of this function is deprecated.

	I32	eval_sv(SV* sv, I32 flags)

=for hackers
Found in file perl.c

=item FREETMPS
X<FREETMPS>

Closing bracket for temporaries on a callback.  See C<L</SAVETMPS>> and
L<perlcall>.

		FREETMPS;

=for hackers
Found in file scope.h

=item LEAVE
X<LEAVE>

Closing bracket on a callback.  See C<L</ENTER>> and L<perlcall>.

		LEAVE;

=for hackers
Found in file scope.h

=item LEAVE_with_name
X<LEAVE_with_name>

Same as C<L</LEAVE>>, but when debugging is enabled it first checks that the
scope has the given name. C<name> must be a literal string.

		LEAVE_with_name("name");

=for hackers
Found in file scope.h

=item SAVETMPS
X<SAVETMPS>

Opening bracket for temporaries on a callback.  See C<L</FREETMPS>> and
L<perlcall>.

		SAVETMPS;

=for hackers
Found in file scope.h


=back

=head1 Character case changing

Perl uses "full" Unicode case mappings.  This means that converting a single
character to another case may result in a sequence of more than one character.
For example, the uppercase of C<E<223>> (LATIN SMALL LETTER SHARP S) is the two
character sequence C<SS>.  This presents some complications   The lowercase of
all characters in the range 0..255 is a single character, and thus
C<L</toLOWER_L1>> is furnished.  But, C<toUPPER_L1> can't exist, as it couldn't
return a valid result for all legal inputs.  Instead C<L</toUPPER_uvchr>> has
an API that does allow every possible legal result to be returned.)  Likewise
no other function that is crippled by not being able to give the correct
results for the full range of possible inputs has been implemented here.


=over 8

=item toFOLD
X<toFOLD>

Converts the specified character to foldcase.  If the input is anything but an
ASCII uppercase character, that input character itself is returned.  Variant
C<toFOLD_A> is equivalent.  (There is no equivalent C<to_FOLD_L1> for the full
Latin1 range, as the full generality of L</toFOLD_uvchr> is needed there.)

	U8	toFOLD(U8 ch)

=for hackers
Found in file handy.h

=item toFOLD_utf8
X<toFOLD_utf8>

Converts the first UTF-8 encoded character in the sequence starting at C<p> and
extending no further than S<C<e - 1>> to its foldcase version, and
stores that in UTF-8 in C<s>, and its length in bytes in C<lenp>.  Note
that the buffer pointed to by C<s> needs to be at least C<UTF8_MAXBYTES_CASE+1>
bytes since the foldcase version may be longer than the original character.

The first code point of the foldcased version is returned
(but note, as explained at L<the top of this section|/Character case
changing>, that there may be more).

It will not attempt
to read beyond S<C<e - 1>>, provided that the constraint S<C<s E<lt> e>> is
true (this is asserted for in C<-DDEBUGGING> builds).  If the UTF-8 for the
input character is malformed in some way, the program may croak, or the
function may return the REPLACEMENT CHARACTER, at the discretion of the
implementation, and subject to change in future releases.

	UV	toFOLD_utf8(U8* p, U8* e, U8* s, STRLEN* lenp)

=for hackers
Found in file handy.h

=item toFOLD_utf8_safe
X<toFOLD_utf8_safe>

Same as L</toFOLD_utf8>.

	UV	toFOLD_utf8_safe(U8* p, U8* e, U8* s,
		                 STRLEN* lenp)

=for hackers
Found in file handy.h

=item toFOLD_uvchr
X<toFOLD_uvchr>

Converts the code point C<cp> to its foldcase version, and
stores that in UTF-8 in C<s>, and its length in bytes in C<lenp>.  The code
point is interpreted as native if less than 256; otherwise as Unicode.  Note
that the buffer pointed to by C<s> needs to be at least C<UTF8_MAXBYTES_CASE+1>
bytes since the foldcase version may be longer than the original character.

The first code point of the foldcased version is returned
(but note, as explained at L<the top of this section|/Character case
changing>, that there may be more).

	UV	toFOLD_uvchr(UV cp, U8* s, STRLEN* lenp)

=for hackers
Found in file handy.h

=item toLOWER
X<toLOWER>

Converts the specified character to lowercase.  If the input is anything but an
ASCII uppercase character, that input character itself is returned.  Variant
C<toLOWER_A> is equivalent.

	U8	toLOWER(U8 ch)

=for hackers
Found in file handy.h

=item toLOWER_L1
X<toLOWER_L1>

Converts the specified Latin1 character to lowercase.  The results are
undefined if the input doesn't fit in a byte.

	U8	toLOWER_L1(U8 ch)

=for hackers
Found in file handy.h

=item toLOWER_LC
X<toLOWER_LC>

Converts the specified character to lowercase using the current locale's rules,
if possible; otherwise returns the input character itself.

	U8	toLOWER_LC(U8 ch)

=for hackers
Found in file handy.h

=item toLOWER_utf8
X<toLOWER_utf8>

Converts the first UTF-8 encoded character in the sequence starting at C<p> and
extending no further than S<C<e - 1>> to its lowercase version, and
stores that in UTF-8 in C<s>, and its length in bytes in C<lenp>.  Note
that the buffer pointed to by C<s> needs to be at least C<UTF8_MAXBYTES_CASE+1>
bytes since the lowercase version may be longer than the original character.

The first code point of the lowercased version is returned
(but note, as explained at L<the top of this section|/Character case
changing>, that there may be more).
It will not attempt to read beyond S<C<e - 1>>, provided that the constraint
S<C<s E<lt> e>> is true (this is asserted for in C<-DDEBUGGING> builds).  If
the UTF-8 for the input character is malformed in some way, the program may
croak, or the function may return the REPLACEMENT CHARACTER, at the discretion
of the implementation, and subject to change in future releases.

	UV	toLOWER_utf8(U8* p, U8* e, U8* s, STRLEN* lenp)

=for hackers
Found in file handy.h

=item toLOWER_utf8_safe
X<toLOWER_utf8_safe>

Same as L</toLOWER_utf8>.

	UV	toLOWER_utf8_safe(U8* p, U8* e, U8* s,
		                  STRLEN* lenp)

=for hackers
Found in file handy.h

=item toLOWER_uvchr
X<toLOWER_uvchr>

Converts the code point C<cp> to its lowercase version, and
stores that in UTF-8 in C<s>, and its length in bytes in C<lenp>.  The code
point is interpreted as native if less than 256; otherwise as Unicode.  Note
that the buffer pointed to by C<s> needs to be at least C<UTF8_MAXBYTES_CASE+1>
bytes since the lowercase version may be longer than the original character.

The first code point of the lowercased version is returned
(but note, as explained at L<the top of this section|/Character case
changing>, that there may be more).

	UV	toLOWER_uvchr(UV cp, U8* s, STRLEN* lenp)

=for hackers
Found in file handy.h

=item toTITLE
X<toTITLE>

Converts the specified character to titlecase.  If the input is anything but an
ASCII lowercase character, that input character itself is returned.  Variant
C<toTITLE_A> is equivalent.  (There is no C<toTITLE_L1> for the full Latin1
range, as the full generality of L</toTITLE_uvchr> is needed there.  Titlecase is
not a concept used in locale handling, so there is no functionality for that.)

	U8	toTITLE(U8 ch)

=for hackers
Found in file handy.h

=item toTITLE_utf8
X<toTITLE_utf8>

Converts the first UTF-8 encoded character in the sequence starting at C<p> and
extending no further than S<C<e - 1>> to its titlecase version, and
stores that in UTF-8 in C<s>, and its length in bytes in C<lenp>.  Note
that the buffer pointed to by C<s> needs to be at least C<UTF8_MAXBYTES_CASE+1>
bytes since the titlecase version may be longer than the original character.

The first code point of the titlecased version is returned
(but note, as explained at L<the top of this section|/Character case
changing>, that there may be more).

It will not attempt
to read beyond S<C<e - 1>>, provided that the constraint S<C<s E<lt> e>> is
true (this is asserted for in C<-DDEBUGGING> builds).  If the UTF-8 for the
input character is malformed in some way, the program may croak, or the
function may return the REPLACEMENT CHARACTER, at the discretion of the
implementation, and subject to change in future releases.

	UV	toTITLE_utf8(U8* p, U8* e, U8* s, STRLEN* lenp)

=for hackers
Found in file handy.h

=item toTITLE_utf8_safe
X<toTITLE_utf8_safe>

Same as L</toTITLE_utf8>.

	UV	toTITLE_utf8_safe(U8* p, U8* e, U8* s,
		                  STRLEN* lenp)

=for hackers
Found in file handy.h

=item toTITLE_uvchr
X<toTITLE_uvchr>

Converts the code point C<cp> to its titlecase version, and
stores that in UTF-8 in C<s>, and its length in bytes in C<lenp>.  The code
point is interpreted as native if less than 256; otherwise as Unicode.  Note
that the buffer pointed to by C<s> needs to be at least C<UTF8_MAXBYTES_CASE+1>
bytes since the titlecase version may be longer than the original character.

The first code point of the titlecased version is returned
(but note, as explained at L<the top of this section|/Character case
changing>, that there may be more).

	UV	toTITLE_uvchr(UV cp, U8* s, STRLEN* lenp)

=for hackers
Found in file handy.h

=item toUPPER
X<toUPPER>

Converts the specified character to uppercase.  If the input is anything but an
ASCII lowercase character, that input character itself is returned.  Variant
C<toUPPER_A> is equivalent.

	U8	toUPPER(int ch)

=for hackers
Found in file handy.h

=item toUPPER_utf8
X<toUPPER_utf8>

Converts the first UTF-8 encoded character in the sequence starting at C<p> and
extending no further than S<C<e - 1>> to its uppercase version, and
stores that in UTF-8 in C<s>, and its length in bytes in C<lenp>.  Note
that the buffer pointed to by C<s> needs to be at least C<UTF8_MAXBYTES_CASE+1>
bytes since the uppercase version may be longer than the original character.

The first code point of the uppercased version is returned
(but note, as explained at L<the top of this section|/Character case
changing>, that there may be more).

It will not attempt to read beyond S<C<e - 1>>, provided that the constraint
S<C<s E<lt> e>> is true (this is asserted for in C<-DDEBUGGING> builds).  If
the UTF-8 for the input character is malformed in some way, the program may
croak, or the function may return the REPLACEMENT CHARACTER, at the discretion
of the implementation, and subject to change in future releases.

	UV	toUPPER_utf8(U8* p, U8* e, U8* s, STRLEN* lenp)

=for hackers
Found in file handy.h

=item toUPPER_utf8_safe
X<toUPPER_utf8_safe>

Same as L</toUPPER_utf8>.

	UV	toUPPER_utf8_safe(U8* p, U8* e, U8* s,
		                  STRLEN* lenp)

=for hackers
Found in file handy.h

=item toUPPER_uvchr
X<toUPPER_uvchr>

Converts the code point C<cp> to its uppercase version, and
stores that in UTF-8 in C<s>, and its length in bytes in C<lenp>.  The code
point is interpreted as native if less than 256; otherwise as Unicode.  Note
that the buffer pointed to by C<s> needs to be at least C<UTF8_MAXBYTES_CASE+1>
bytes since the uppercase version may be longer than the original character.

The first code point of the uppercased version is returned
(but note, as explained at L<the top of this section|/Character case
changing>, that there may be more.)

	UV	toUPPER_uvchr(UV cp, U8* s, STRLEN* lenp)

=for hackers
Found in file handy.h

=item WIDEST_UTYPE
X<WIDEST_UTYPE>

Yields the widest unsigned integer type on the platform, currently either
C<U32> or C<64>.  This can be used in declarations such as

 WIDEST_UTYPE my_uv;

or casts

 my_uv = (WIDEST_UTYPE) val;

=for hackers
Found in file handy.h


=back

=head1 Character classification

This section is about functions (really macros) that classify characters
into types, such as punctuation versus alphabetic, etc.  Most of these are
analogous to regular expression character classes.  (See
L<perlrecharclass/POSIX Character Classes>.)  There are several variants for
each class.  (Not all macros have all variants; each item below lists the
ones valid for it.)  None are affected by C<use bytes>, and only the ones
with C<LC> in the name are affected by the current locale.

The base function, e.g., C<isALPHA()>, takes any signed or unsigned value,
treating it as a code point, and returns a boolean as to whether or not the
character represented by it is (or on non-ASCII platforms, corresponds to) an
ASCII character in the named class based on platform, Unicode, and Perl rules.
If the input is a number that doesn't fit in an octet, FALSE is returned.

Variant C<isI<FOO>_A> (e.g., C<isALPHA_A()>) is identical to the base function
with no suffix C<"_A">.  This variant is used to emphasize by its name that
only ASCII-range characters can return TRUE.

Variant C<isI<FOO>_L1> imposes the Latin-1 (or EBCDIC equivalent) character set
onto the platform.  That is, the code points that are ASCII are unaffected,
since ASCII is a subset of Latin-1.  But the non-ASCII code points are treated
as if they are Latin-1 characters.  For example, C<isWORDCHAR_L1()> will return
true when called with the code point 0xDF, which is a word character in both
ASCII and EBCDIC (though it represents different characters in each).
If the input is a number that doesn't fit in an octet, FALSE is returned.
(Perl's documentation uses a colloquial definition of Latin-1, to include all
code points below 256.)

Variant C<isI<FOO>_uvchr> is exactly like the C<isI<FOO>_L1> variant, for
inputs below 256, but if the code point is larger than 255, Unicode rules are
used to determine if it is in the character class.  For example,
C<isWORDCHAR_uvchr(0x100)> returns TRUE, since 0x100 is LATIN CAPITAL LETTER A
WITH MACRON in Unicode, and is a word character.

Variants C<isI<FOO>_utf8> and C<isI<FOO>_utf8_safe> are like C<isI<FOO>_uvchr>,
but are used for UTF-8 encoded strings.  The two forms are different names for
the same thing.  Each call to one of these classifies the first character of
the string starting at C<p>.  The second parameter, C<e>, points to anywhere in
the string beyond the first character, up to one byte past the end of the
entire string.  Although both variants are identical, the suffix C<_safe> in
one name emphasizes that it will not attempt to read beyond S<C<e - 1>>,
provided that the constraint S<C<s E<lt> e>> is true (this is asserted for in
C<-DDEBUGGING> builds).  If the UTF-8 for the input character is malformed in
some way, the program may croak, or the function may return FALSE, at the
discretion of the implementation, and subject to change in future releases.

Variant C<isI<FOO>_LC> is like the C<isI<FOO>_A> and C<isI<FOO>_L1> variants,
but the result is based on the current locale, which is what C<LC> in the name
stands for.  If Perl can determine that the current locale is a UTF-8 locale,
it uses the published Unicode rules; otherwise, it uses the C library function
that gives the named classification.  For example, C<isDIGIT_LC()> when not in
a UTF-8 locale returns the result of calling C<isdigit()>.  FALSE is always
returned if the input won't fit into an octet.  On some platforms where the C
library function is known to be defective, Perl changes its result to follow
the POSIX standard's rules.

Variant C<isI<FOO>_LC_uvchr> acts exactly like C<isI<FOO>_LC> for inputs less
than 256, but for larger ones it returns the Unicode classification of the code
point.

Variants C<isI<FOO>_LC_utf8> and C<isI<FOO>_LC_utf8_safe> are like
C<isI<FOO>_LC_uvchr>, but are used for UTF-8 encoded strings.  The two forms
are different names for the same thing.  Each call to one of these classifies
the first character of the string starting at C<p>.  The second parameter,
C<e>, points to anywhere in the string beyond the first character, up to one
byte past the end of the entire string.  Although both variants are identical,
the suffix C<_safe> in one name emphasizes that it will not attempt to read
beyond S<C<e - 1>>, provided that the constraint S<C<s E<lt> e>> is true (this
is asserted for in C<-DDEBUGGING> builds).  If the UTF-8 for the input
character is malformed in some way, the program may croak, or the function may
return FALSE, at the discretion of the implementation, and subject to change in
future releases.


=over 8

=item isALPHA
X<isALPHA>

Returns a boolean indicating whether the specified input is one of C<[A-Za-z]>,
analogous to C<m/[[:alpha:]]/>.
See the L<top of this section|/Character classification> for an explanation of
variants
C<isALPHA_A>, C<isALPHA_L1>, C<isALPHA_uvchr>, C<isALPHA_utf8>,
C<isALPHA_utf8_safe>, C<isALPHA_LC>, C<isALPHA_LC_uvchr>, C<isALPHA_LC_utf8>,
and C<isALPHA_LC_utf8_safe>.

	bool	isALPHA(int ch)

=for hackers
Found in file handy.h

=item isALPHANUMERIC
X<isALPHANUMERIC>

Returns a boolean indicating whether the specified character is one of
C<[A-Za-z0-9]>, analogous to C<m/[[:alnum:]]/>.
See the L<top of this section|/Character classification> for an explanation of
variants
C<isALPHANUMERIC_A>, C<isALPHANUMERIC_L1>, C<isALPHANUMERIC_uvchr>,
C<isALPHANUMERIC_utf8>, C<isALPHANUMERIC_utf8_safe>, C<isALPHANUMERIC_LC>,
C<isALPHANUMERIC_LC_uvchr>, C<isALPHANUMERIC_LC_utf8>, and
C<isALPHANUMERIC_LC_utf8_safe>.

A (discouraged from use) synonym is C<isALNUMC> (where the C<C> suffix means
this corresponds to the C language alphanumeric definition).  Also
there are the variants
C<isALNUMC_A>, C<isALNUMC_L1>
C<isALNUMC_LC>, and C<isALNUMC_LC_uvchr>.

	bool	isALPHANUMERIC(int ch)

=for hackers
Found in file handy.h

=item isASCII
X<isASCII>

Returns a boolean indicating whether the specified character is one of the 128
characters in the ASCII character set, analogous to C<m/[[:ascii:]]/>.
On non-ASCII platforms, it returns TRUE iff this
character corresponds to an ASCII character.  Variants C<isASCII_A()> and
C<isASCII_L1()> are identical to C<isASCII()>.
See the L<top of this section|/Character classification> for an explanation of
variants
C<isASCII_uvchr>, C<isASCII_utf8>, C<isASCII_utf8_safe>, C<isASCII_LC>,
C<isASCII_LC_uvchr>, C<isASCII_LC_utf8>, and C<isASCII_LC_utf8_safe>.
Note, however, that some platforms do not have the C library routine
C<isascii()>.  In these cases, the variants whose names contain C<LC> are the
same as the corresponding ones without.

	bool	isASCII(int ch)

=for hackers
Found in file handy.h

=item isBLANK
X<isBLANK>

Returns a boolean indicating whether the specified character is a
character considered to be a blank, analogous to C<m/[[:blank:]]/>.
See the L<top of this section|/Character classification> for an explanation of
variants
C<isBLANK_A>, C<isBLANK_L1>, C<isBLANK_uvchr>, C<isBLANK_utf8>,
C<isBLANK_utf8_safe>, C<isBLANK_LC>, C<isBLANK_LC_uvchr>, C<isBLANK_LC_utf8>,
and C<isBLANK_LC_utf8_safe>.  Note,
however, that some platforms do not have the C library routine
C<isblank()>.  In these cases, the variants whose names contain C<LC> are
the same as the corresponding ones without.

	bool	isBLANK(char ch)

=for hackers
Found in file handy.h

=item isCNTRL
X<isCNTRL>

Returns a boolean indicating whether the specified character is a
control character, analogous to C<m/[[:cntrl:]]/>.
See the L<top of this section|/Character classification> for an explanation of
variants
C<isCNTRL_A>, C<isCNTRL_L1>, C<isCNTRL_uvchr>, C<isCNTRL_utf8>,
C<isCNTRL_utf8_safe>, C<isCNTRL_LC>, C<isCNTRL_LC_uvchr>, C<isCNTRL_LC_utf8>
and C<isCNTRL_LC_utf8_safe>.  On EBCDIC
platforms, you almost always want to use the C<isCNTRL_L1> variant.

	bool	isCNTRL(char ch)

=for hackers
Found in file handy.h

=item isDIGIT
X<isDIGIT>

Returns a boolean indicating whether the specified character is a
digit, analogous to C<m/[[:digit:]]/>.
Variants C<isDIGIT_A> and C<isDIGIT_L1> are identical to C<isDIGIT>.
See the L<top of this section|/Character classification> for an explanation of
variants
C<isDIGIT_uvchr>, C<isDIGIT_utf8>, C<isDIGIT_utf8_safe>, C<isDIGIT_LC>,
C<isDIGIT_LC_uvchr>, C<isDIGIT_LC_utf8>, and C<isDIGIT_LC_utf8_safe>.

	bool	isDIGIT(char ch)

=for hackers
Found in file handy.h

=item isGRAPH
X<isGRAPH>

Returns a boolean indicating whether the specified character is a
graphic character, analogous to C<m/[[:graph:]]/>.
See the L<top of this section|/Character classification> for an explanation of
variants C<isGRAPH_A>, C<isGRAPH_L1>, C<isGRAPH_uvchr>, C<isGRAPH_utf8>,
C<isGRAPH_utf8_safe>, C<isGRAPH_LC>, C<isGRAPH_LC_uvchr>,
C<isGRAPH_LC_utf8_safe>, and C<isGRAPH_LC_utf8_safe>.

	bool	isGRAPH(char ch)

=for hackers
Found in file handy.h

=item isIDCONT
X<isIDCONT>

Returns a boolean indicating whether the specified character can be the
second or succeeding character of an identifier.  This is very close to, but
not quite the same as the official Unicode property C<XID_Continue>.  The
difference is that this returns true only if the input character also matches
L</isWORDCHAR>.  See the L<top of this section|/Character classification> for
an explanation of variants C<isIDCONT_A>, C<isIDCONT_L1>, C<isIDCONT_uvchr>,
C<isIDCONT_utf8>, C<isIDCONT_utf8_safe>, C<isIDCONT_LC>, C<isIDCONT_LC_uvchr>,
C<isIDCONT_LC_utf8>, and C<isIDCONT_LC_utf8_safe>.

	bool	isIDCONT(char ch)

=for hackers
Found in file handy.h

=item isIDFIRST
X<isIDFIRST>

Returns a boolean indicating whether the specified character can be the first
character of an identifier.  This is very close to, but not quite the same as
the official Unicode property C<XID_Start>.  The difference is that this
returns true only if the input character also matches L</isWORDCHAR>.
See the L<top of this section|/Character classification> for an explanation of
variants
C<isIDFIRST_A>, C<isIDFIRST_L1>, C<isIDFIRST_uvchr>, C<isIDFIRST_utf8>,
C<isIDFIRST_utf8_safe>, C<isIDFIRST_LC>, C<isIDFIRST_LC_uvchr>,
C<isIDFIRST_LC_utf8>, and C<isIDFIRST_LC_utf8_safe>.

	bool	isIDFIRST(char ch)

=for hackers
Found in file handy.h

=item isLOWER
X<isLOWER>

Returns a boolean indicating whether the specified character is a
lowercase character, analogous to C<m/[[:lower:]]/>.
See the L<top of this section|/Character classification> for an explanation of
variants
C<isLOWER_A>, C<isLOWER_L1>, C<isLOWER_uvchr>, C<isLOWER_utf8>,
C<isLOWER_utf8_safe>, C<isLOWER_LC>, C<isLOWER_LC_uvchr>, C<isLOWER_LC_utf8>,
and C<isLOWER_LC_utf8_safe>.

	bool	isLOWER(char ch)

=for hackers
Found in file handy.h

=item isOCTAL
X<isOCTAL>

Returns a boolean indicating whether the specified character is an
octal digit, [0-7].
The only two variants are C<isOCTAL_A> and C<isOCTAL_L1>; each is identical to
C<isOCTAL>.

	bool	isOCTAL(char ch)

=for hackers
Found in file handy.h

=item isPRINT
X<isPRINT>

Returns a boolean indicating whether the specified character is a
printable character, analogous to C<m/[[:print:]]/>.
See the L<top of this section|/Character classification> for an explanation of
variants
C<isPRINT_A>, C<isPRINT_L1>, C<isPRINT_uvchr>, C<isPRINT_utf8>,
C<isPRINT_utf8_safe>, C<isPRINT_LC>, C<isPRINT_LC_uvchr>, C<isPRINT_LC_utf8>,
and C<isPRINT_LC_utf8_safe>.

	bool	isPRINT(char ch)

=for hackers
Found in file handy.h

=item isPSXSPC
X<isPSXSPC>

(short for Posix Space)
Starting in 5.18, this is identical in all its forms to the
corresponding C<isSPACE()> macros.
The locale forms of this macro are identical to their corresponding
C<isSPACE()> forms in all Perl releases.  In releases prior to 5.18, the
non-locale forms differ from their C<isSPACE()> forms only in that the
C<isSPACE()> forms don't match a Vertical Tab, and the C<isPSXSPC()> forms do.
Otherwise they are identical.  Thus this macro is analogous to what
C<m/[[:space:]]/> matches in a regular expression.
See the L<top of this section|/Character classification> for an explanation of
variants C<isPSXSPC_A>, C<isPSXSPC_L1>, C<isPSXSPC_uvchr>, C<isPSXSPC_utf8>,
C<isPSXSPC_utf8_safe>, C<isPSXSPC_LC>, C<isPSXSPC_LC_uvchr>,
C<isPSXSPC_LC_utf8>, and C<isPSXSPC_LC_utf8_safe>.

	bool	isPSXSPC(char ch)

=for hackers
Found in file handy.h

=item isPUNCT
X<isPUNCT>

Returns a boolean indicating whether the specified character is a
punctuation character, analogous to C<m/[[:punct:]]/>.
Note that the definition of what is punctuation isn't as
straightforward as one might desire.  See L<perlrecharclass/POSIX Character
Classes> for details.
See the L<top of this section|/Character classification> for an explanation of
variants C<isPUNCT_A>, C<isPUNCT_L1>, C<isPUNCT_uvchr>, C<isPUNCT_utf8>,
C<isPUNCT_utf8_safe>, C<isPUNCT_LC>, C<isPUNCT_LC_uvchr>, C<isPUNCT_LC_utf8>,
and C<isPUNCT_LC_utf8_safe>.

	bool	isPUNCT(char ch)

=for hackers
Found in file handy.h

=item isSPACE
X<isSPACE>

Returns a boolean indicating whether the specified character is a
whitespace character.  This is analogous
to what C<m/\s/> matches in a regular expression.  Starting in Perl 5.18
this also matches what C<m/[[:space:]]/> does.  Prior to 5.18, only the
locale forms of this macro (the ones with C<LC> in their names) matched
precisely what C<m/[[:space:]]/> does.  In those releases, the only difference,
in the non-locale variants, was that C<isSPACE()> did not match a vertical tab.
(See L</isPSXSPC> for a macro that matches a vertical tab in all releases.)
See the L<top of this section|/Character classification> for an explanation of
variants
C<isSPACE_A>, C<isSPACE_L1>, C<isSPACE_uvchr>, C<isSPACE_utf8>,
C<isSPACE_utf8_safe>, C<isSPACE_LC>, C<isSPACE_LC_uvchr>, C<isSPACE_LC_utf8>,
and C<isSPACE_LC_utf8_safe>.

	bool	isSPACE(char ch)

=for hackers
Found in file handy.h

=item isUPPER
X<isUPPER>

Returns a boolean indicating whether the specified character is an
uppercase character, analogous to C<m/[[:upper:]]/>.
See the L<top of this section|/Character classification> for an explanation of
variants C<isUPPER_A>, C<isUPPER_L1>, C<isUPPER_uvchr>, C<isUPPER_utf8>,
C<isUPPER_utf8_safe>, C<isUPPER_LC>, C<isUPPER_LC_uvchr>, C<isUPPER_LC_utf8>,
and C<isUPPER_LC_utf8_safe>.

	bool	isUPPER(char ch)

=for hackers
Found in file handy.h

=item isWORDCHAR
X<isWORDCHAR>

Returns a boolean indicating whether the specified character is a character
that is a word character, analogous to what C<m/\w/> and C<m/[[:word:]]/> match
in a regular expression.  A word character is an alphabetic character, a
decimal digit, a connecting punctuation character (such as an underscore), or
a "mark" character that attaches to one of those (like some sort of accent).
C<isALNUM()> is a synonym provided for backward compatibility, even though a
word character includes more than the standard C language meaning of
alphanumeric.
See the L<top of this section|/Character classification> for an explanation of
variants C<isWORDCHAR_A>, C<isWORDCHAR_L1>, C<isWORDCHAR_uvchr>,
C<isWORDCHAR_utf8>, and C<isWORDCHAR_utf8_safe>.  C<isWORDCHAR_LC>,
C<isWORDCHAR_LC_uvchr>, C<isWORDCHAR_LC_utf8>, and C<isWORDCHAR_LC_utf8_safe>
are also as described there, but additionally include the platform's native
underscore.

	bool	isWORDCHAR(char ch)

=for hackers
Found in file handy.h

=item isXDIGIT
X<isXDIGIT>

Returns a boolean indicating whether the specified character is a hexadecimal
digit.  In the ASCII range these are C<[0-9A-Fa-f]>.  Variants C<isXDIGIT_A()>
and C<isXDIGIT_L1()> are identical to C<isXDIGIT()>.
See the L<top of this section|/Character classification> for an explanation of
variants
C<isXDIGIT_uvchr>, C<isXDIGIT_utf8>, C<isXDIGIT_utf8_safe>, C<isXDIGIT_LC>,
C<isXDIGIT_LC_uvchr>, C<isXDIGIT_LC_utf8>, and C<isXDIGIT_LC_utf8_safe>.

	bool	isXDIGIT(char ch)

=for hackers
Found in file handy.h


=back

=head1 Cloning an interpreter

=over 8

=item perl_clone
X<perl_clone>

Create and return a new interpreter by cloning the current one.

C<perl_clone> takes these flags as parameters:

C<CLONEf_COPY_STACKS> - is used to, well, copy the stacks also,
without it we only clone the data and zero the stacks,
with it we copy the stacks and the new perl interpreter is
ready to run at the exact same point as the previous one.
The pseudo-fork code uses C<COPY_STACKS> while the
threads->create doesn't.

C<CLONEf_KEEP_PTR_TABLE> -
C<perl_clone> keeps a ptr_table with the pointer of the old
variable as a key and the new variable as a value,
this allows it to check if something has been cloned and not
clone it again, but rather just use the value and increase the
refcount.
If C<KEEP_PTR_TABLE> is not set then C<perl_clone> will kill the ptr_table
using the function S<C<ptr_table_free(PL_ptr_table); PL_ptr_table = NULL;>>.
A reason to keep it around is if you want to dup some of your own
variables which are outside the graph that perl scans.

C<CLONEf_CLONE_HOST> -
This is a win32 thing, it is ignored on unix, it tells perl's
win32host code (which is c++) to clone itself, this is needed on
win32 if you want to run two threads at the same time,
if you just want to do some stuff in a separate perl interpreter
and then throw it away and return to the original one,
you don't need to do anything.

	PerlInterpreter* perl_clone(
	                     PerlInterpreter *proto_perl,
	                     UV flags
	                 )

=for hackers
Found in file sv.c


=back

=head1 Compile-time scope hooks

=over 8

=item BhkDISABLE
X<BhkDISABLE>


NOTE: this function is experimental and may change or be
removed without notice.


Temporarily disable an entry in this BHK structure, by clearing the
appropriate flag.  C<which> is a preprocessor token indicating which
entry to disable.

	void	BhkDISABLE(BHK *hk, which)

=for hackers
Found in file op.h

=item BhkENABLE
X<BhkENABLE>


NOTE: this function is experimental and may change or be
removed without notice.


Re-enable an entry in this BHK structure, by setting the appropriate
flag.  C<which> is a preprocessor token indicating which entry to enable.
This will assert (under -DDEBUGGING) if the entry doesn't contain a valid
pointer.

	void	BhkENABLE(BHK *hk, which)

=for hackers
Found in file op.h

=item BhkENTRY_set
X<BhkENTRY_set>


NOTE: this function is experimental and may change or be
removed without notice.


Set an entry in the BHK structure, and set the flags to indicate it is
valid.  C<which> is a preprocessing token indicating which entry to set.
The type of C<ptr> depends on the entry.

	void	BhkENTRY_set(BHK *hk, which, void *ptr)

=for hackers
Found in file op.h

=item blockhook_register
X<blockhook_register>


NOTE: this function is experimental and may change or be
removed without notice.


Register a set of hooks to be called when the Perl lexical scope changes
at compile time.  See L<perlguts/"Compile-time scope hooks">.

NOTE: this function must be explicitly called as Perl_blockhook_register with an aTHX_ parameter.

	void	Perl_blockhook_register(pTHX_ BHK *hk)

=for hackers
Found in file op.c


=back

=head1 COP Hint Hashes

=over 8

=item cophh_2hv
X<cophh_2hv>


NOTE: this function is experimental and may change or be
removed without notice.


Generates and returns a standard Perl hash representing the full set of
key/value pairs in the cop hints hash C<cophh>.  C<flags> is currently
unused and must be zero.

	HV *	cophh_2hv(const COPHH *cophh, U32 flags)

=for hackers
Found in file cop.h

=item cophh_copy
X<cophh_copy>


NOTE: this function is experimental and may change or be
removed without notice.


Make and return a complete copy of the cop hints hash C<cophh>.

	COPHH *	cophh_copy(COPHH *cophh)

=for hackers
Found in file cop.h

=item cophh_delete_pv
X<cophh_delete_pv>


NOTE: this function is experimental and may change or be
removed without notice.


Like L</cophh_delete_pvn>, but takes a nul-terminated string instead of
a string/length pair.

	COPHH *	cophh_delete_pv(const COPHH *cophh,
		                const char *key, U32 hash,
		                U32 flags)

=for hackers
Found in file cop.h

=item cophh_delete_pvn
X<cophh_delete_pvn>


NOTE: this function is experimental and may change or be
removed without notice.


Delete a key and its associated value from the cop hints hash C<cophh>,
and returns the modified hash.  The returned hash pointer is in general
not the same as the hash pointer that was passed in.  The input hash is
consumed by the function, and the pointer to it must not be subsequently
used.  Use L</cophh_copy> if you need both hashes.

The key is specified by C<keypv> and C<keylen>.  If C<flags> has the
C<COPHH_KEY_UTF8> bit set, the key octets are interpreted as UTF-8,
otherwise they are interpreted as Latin-1.  C<hash> is a precomputed
hash of the key string, or zero if it has not been precomputed.

	COPHH *	cophh_delete_pvn(COPHH *cophh,
		                 const char *keypv,
		                 STRLEN keylen, U32 hash,
		                 U32 flags)

=for hackers
Found in file cop.h

=item cophh_delete_pvs
X<cophh_delete_pvs>


NOTE: this function is experimental and may change or be
removed without notice.


Like L</cophh_delete_pvn>, but takes a literal string instead
of a string/length pair, and no precomputed hash.

	COPHH *	cophh_delete_pvs(const COPHH *cophh, "key",
		                 U32 flags)

=for hackers
Found in file cop.h

=item cophh_delete_sv
X<cophh_delete_sv>


NOTE: this function is experimental and may change or be
removed without notice.


Like L</cophh_delete_pvn>, but takes a Perl scalar instead of a
string/length pair.

	COPHH *	cophh_delete_sv(const COPHH *cophh, SV *key,
		                U32 hash, U32 flags)

=for hackers
Found in file cop.h

=item cophh_fetch_pv
X<cophh_fetch_pv>


NOTE: this function is experimental and may change or be
removed without notice.


Like L</cophh_fetch_pvn>, but takes a nul-terminated string instead of
a string/length pair.

	SV *	cophh_fetch_pv(const COPHH *cophh,
		               const char *key, U32 hash,
		               U32 flags)

=for hackers
Found in file cop.h

=item cophh_fetch_pvn
X<cophh_fetch_pvn>


NOTE: this function is experimental and may change or be
removed without notice.


Look up the entry in the cop hints hash C<cophh> with the key specified by
C<keypv> and C<keylen>.  If C<flags> has the C<COPHH_KEY_UTF8> bit set,
the key octets are interpreted as UTF-8, otherwise they are interpreted
as Latin-1.  C<hash> is a precomputed hash of the key string, or zero if
it has not been precomputed.  Returns a mortal scalar copy of the value
associated with the key, or C<&PL_sv_placeholder> if there is no value
associated with the key.

	SV *	cophh_fetch_pvn(const COPHH *cophh,
		                const char *keypv,
		                STRLEN keylen, U32 hash,
		                U32 flags)

=for hackers
Found in file cop.h

=item cophh_fetch_pvs
X<cophh_fetch_pvs>


NOTE: this function is experimental and may change or be
removed without notice.


Like L</cophh_fetch_pvn>, but takes a literal string instead
of a string/length pair, and no precomputed hash.

	SV *	cophh_fetch_pvs(const COPHH *cophh, "key",
		                U32 flags)

=for hackers
Found in file cop.h

=item cophh_fetch_sv
X<cophh_fetch_sv>


NOTE: this function is experimental and may change or be
removed without notice.


Like L</cophh_fetch_pvn>, but takes a Perl scalar instead of a
string/length pair.

	SV *	cophh_fetch_sv(const COPHH *cophh, SV *key,
		               U32 hash, U32 flags)

=for hackers
Found in file cop.h

=item cophh_free
X<cophh_free>


NOTE: this function is experimental and may change or be
removed without notice.


Discard the cop hints hash C<cophh>, freeing all resources associated
with it.

	void	cophh_free(COPHH *cophh)

=for hackers
Found in file cop.h

=item cophh_new_empty
X<cophh_new_empty>


NOTE: this function is experimental and may change or be
removed without notice.


Generate and return a fresh cop hints hash containing no entries.

	COPHH *	cophh_new_empty()

=for hackers
Found in file cop.h

=item cophh_store_pv
X<cophh_store_pv>


NOTE: this function is experimental and may change or be
removed without notice.


Like L</cophh_store_pvn>, but takes a nul-terminated string instead of
a string/length pair.

	COPHH *	cophh_store_pv(const COPHH *cophh,
		               const char *key, U32 hash,
		               SV *value, U32 flags)

=for hackers
Found in file cop.h

=item cophh_store_pvn
X<cophh_store_pvn>


NOTE: this function is experimental and may change or be
removed without notice.


Stores a value, associated with a key, in the cop hints hash C<cophh>,
and returns the modified hash.  The returned hash pointer is in general
not the same as the hash pointer that was passed in.  The input hash is
consumed by the function, and the pointer to it must not be subsequently
used.  Use L</cophh_copy> if you need both hashes.

The key is specified by C<keypv> and C<keylen>.  If C<flags> has the
C<COPHH_KEY_UTF8> bit set, the key octets are interpreted as UTF-8,
otherwise they are interpreted as Latin-1.  C<hash> is a precomputed
hash of the key string, or zero if it has not been precomputed.

C<value> is the scalar value to store for this key.  C<value> is copied
by this function, which thus does not take ownership of any reference
to it, and later changes to the scalar will not be reflected in the
value visible in the cop hints hash.  Complex types of scalar will not
be stored with referential integrity, but will be coerced to strings.

	COPHH *	cophh_store_pvn(COPHH *cophh, const char *keypv,
		                STRLEN keylen, U32 hash,
		                SV *value, U32 flags)

=for hackers
Found in file cop.h

=item cophh_store_pvs
X<cophh_store_pvs>


NOTE: this function is experimental and may change or be
removed without notice.


Like L</cophh_store_pvn>, but takes a literal string instead
of a string/length pair, and no precomputed hash.

	COPHH *	cophh_store_pvs(const COPHH *cophh, "key",
		                SV *value, U32 flags)

=for hackers
Found in file cop.h

=item cophh_store_sv
X<cophh_store_sv>


NOTE: this function is experimental and may change or be
removed without notice.


Like L</cophh_store_pvn>, but takes a Perl scalar instead of a
string/length pair.

	COPHH *	cophh_store_sv(const COPHH *cophh, SV *key,
		               U32 hash, SV *value, U32 flags)

=for hackers
Found in file cop.h


=back

=head1 COP Hint Reading

=over 8

=item cop_hints_2hv
X<cop_hints_2hv>

Generates and returns a standard Perl hash representing the full set of
hint entries in the cop C<cop>.  C<flags> is currently unused and must
be zero.

	HV *	cop_hints_2hv(const COP *cop, U32 flags)

=for hackers
Found in file cop.h

=item cop_hints_fetch_pv
X<cop_hints_fetch_pv>

Like L</cop_hints_fetch_pvn>, but takes a nul-terminated string instead
of a string/length pair.

	SV *	cop_hints_fetch_pv(const COP *cop,
		                   const char *key, U32 hash,
		                   U32 flags)

=for hackers
Found in file cop.h

=item cop_hints_fetch_pvn
X<cop_hints_fetch_pvn>

Look up the hint entry in the cop C<cop> with the key specified by
C<keypv> and C<keylen>.  If C<flags> has the C<COPHH_KEY_UTF8> bit set,
the key octets are interpreted as UTF-8, otherwise they are interpreted
as Latin-1.  C<hash> is a precomputed hash of the key string, or zero if
it has not been precomputed.  Returns a mortal scalar copy of the value
associated with the key, or C<&PL_sv_placeholder> if there is no value
associated with the key.

	SV *	cop_hints_fetch_pvn(const COP *cop,
		                    const char *keypv,
		                    STRLEN keylen, U32 hash,
		                    U32 flags)

=for hackers
Found in file cop.h

=item cop_hints_fetch_pvs
X<cop_hints_fetch_pvs>

Like L</cop_hints_fetch_pvn>, but takes a literal string
instead of a string/length pair, and no precomputed hash.

	SV *	cop_hints_fetch_pvs(const COP *cop, "key",
		                    U32 flags)

=for hackers
Found in file cop.h

=item cop_hints_fetch_sv
X<cop_hints_fetch_sv>

Like L</cop_hints_fetch_pvn>, but takes a Perl scalar instead of a
string/length pair.

	SV *	cop_hints_fetch_sv(const COP *cop, SV *key,
		                   U32 hash, U32 flags)

=for hackers
Found in file cop.h

=item CopLABEL
X<CopLABEL>

Returns the label attached to a cop.

	const char * CopLABEL(COP *const cop)

=for hackers
Found in file cop.h

=item CopLABEL_len
X<CopLABEL_len>

Returns the label attached to a cop, and stores its length in bytes into
C<*len>.

	const char * CopLABEL_len(COP *const cop, STRLEN *len)

=for hackers
Found in file cop.h

=item CopLABEL_len_flags
X<CopLABEL_len_flags>

Returns the label attached to a cop, and stores its length in bytes into
C<*len>.  Upon return, C<*flags> will be set to either C<SVf_UTF8> or 0.

	const char * CopLABEL_len_flags(COP *const cop,
	                                STRLEN *len, U32 *flags)

=for hackers
Found in file cop.h


=back

=head1 Custom Operators

=over 8

=item custom_op_register
X<custom_op_register>

Register a custom op.  See L<perlguts/"Custom Operators">.

NOTE: this function must be explicitly called as Perl_custom_op_register with an aTHX_ parameter.

	void	Perl_custom_op_register(pTHX_ 
		                        Perl_ppaddr_t ppaddr,
		                        const XOP *xop)

=for hackers
Found in file op.c

=item Perl_custom_op_xop
X<Perl_custom_op_xop>

Return the XOP structure for a given custom op.  This macro should be
considered internal to C<OP_NAME> and the other access macros: use them instead.
This macro does call a function.  Prior
to 5.19.6, this was implemented as a
function.

	const XOP * Perl_custom_op_xop(pTHX_ const OP *o)

=for hackers
Found in file op.c

=item XopDISABLE
X<XopDISABLE>

Temporarily disable a member of the XOP, by clearing the appropriate flag.

	void	XopDISABLE(XOP *xop, which)

=for hackers
Found in file op.h

=item XopENABLE
X<XopENABLE>

Reenable a member of the XOP which has been disabled.

	void	XopENABLE(XOP *xop, which)

=for hackers
Found in file op.h

=item XopENTRY
X<XopENTRY>

Return a member of the XOP structure.  C<which> is a cpp token
indicating which entry to return.  If the member is not set
this will return a default value.  The return type depends
on C<which>.  This macro evaluates its arguments more than
once.  If you are using C<Perl_custom_op_xop> to retreive a
C<XOP *> from a C<OP *>, use the more efficient L</XopENTRYCUSTOM> instead.

		XopENTRY(XOP *xop, which)

=for hackers
Found in file op.h

=item XopENTRYCUSTOM
X<XopENTRYCUSTOM>

Exactly like C<XopENTRY(XopENTRY(Perl_custom_op_xop(aTHX_ o), which)> but more
efficient.  The C<which> parameter is identical to L</XopENTRY>.

		XopENTRYCUSTOM(const OP *o, which)

=for hackers
Found in file op.h

=item XopENTRY_set
X<XopENTRY_set>

Set a member of the XOP structure.  C<which> is a cpp token
indicating which entry to set.  See L<perlguts/"Custom Operators">
for details about the available members and how
they are used.  This macro evaluates its argument
more than once.

	void	XopENTRY_set(XOP *xop, which, value)

=for hackers
Found in file op.h

=item XopFLAGS
X<XopFLAGS>

Return the XOP's flags.

	U32	XopFLAGS(XOP *xop)

=for hackers
Found in file op.h


=back

=head1 CV Manipulation Functions

This section documents functions to manipulate CVs which are code-values,
or subroutines.  For more information, see L<perlguts>.


=over 8

=item caller_cx
X<caller_cx>

The XSUB-writer's equivalent of L<caller()|perlfunc/caller>.  The
returned C<PERL_CONTEXT> structure can be interrogated to find all the
information returned to Perl by C<caller>.  Note that XSUBs don't get a
stack frame, so C<caller_cx(0, NULL)> will return information for the
immediately-surrounding Perl code.

This function skips over the automatic calls to C<&DB::sub> made on the
behalf of the debugger.  If the stack frame requested was a sub called by
C<DB::sub>, the return value will be the frame for the call to
C<DB::sub>, since that has the correct line number/etc. for the call
site.  If I<dbcxp> is non-C<NULL>, it will be set to a pointer to the
frame for the sub call itself.

	const PERL_CONTEXT * caller_cx(
	                         I32 level,
	                         const PERL_CONTEXT **dbcxp
	                     )

=for hackers
Found in file pp_ctl.c

=item CvSTASH
X<CvSTASH>

Returns the stash of the CV.  A stash is the symbol table hash, containing
the package-scoped variables in the package where the subroutine was defined.
For more information, see L<perlguts>.

This also has a special use with XS AUTOLOAD subs.
See L<perlguts/Autoloading with XSUBs>.

	HV*	CvSTASH(CV* cv)

=for hackers
Found in file cv.h

=item find_runcv
X<find_runcv>

Locate the CV corresponding to the currently executing sub or eval.
If C<db_seqp> is non_null, skip CVs that are in the DB package and populate
C<*db_seqp> with the cop sequence number at the point that the DB:: code was
entered.  (This allows debuggers to eval in the scope of the breakpoint
rather than in the scope of the debugger itself.)

	CV*	find_runcv(U32 *db_seqp)

=for hackers
Found in file pp_ctl.c

=item get_cv
X<get_cv>

Uses C<strlen> to get the length of C<name>, then calls C<get_cvn_flags>.

NOTE: the perl_ form of this function is deprecated.

	CV*	get_cv(const char* name, I32 flags)

=for hackers
Found in file perl.c

=item get_cvn_flags
X<get_cvn_flags>

Returns the CV of the specified Perl subroutine.  C<flags> are passed to
C<gv_fetchpvn_flags>.  If C<GV_ADD> is set and the Perl subroutine does not
exist then it will be declared (which has the same effect as saying
C<sub name;>).  If C<GV_ADD> is not set and the subroutine does not exist
then NULL is returned.

	CV*	get_cvn_flags(const char* name, STRLEN len,
		              I32 flags)

=for hackers
Found in file perl.c


=back

=head1 C<xsubpp> variables and internal functions

=over 8

=item ax
X<ax>

Variable which is setup by C<xsubpp> to indicate the stack base offset,
used by the C<ST>, C<XSprePUSH> and C<XSRETURN> macros.  The C<dMARK> macro
must be called prior to setup the C<MARK> variable.

	I32	ax

=for hackers
Found in file XSUB.h

=item CLASS
X<CLASS>

Variable which is setup by C<xsubpp> to indicate the 
class name for a C++ XS constructor.  This is always a C<char*>.  See
C<L</THIS>>.

	char*	CLASS

=for hackers
Found in file XSUB.h

=item dAX
X<dAX>

Sets up the C<ax> variable.
This is usually handled automatically by C<xsubpp> by calling C<dXSARGS>.

		dAX;

=for hackers
Found in file XSUB.h

=item dAXMARK
X<dAXMARK>

Sets up the C<ax> variable and stack marker variable C<mark>.
This is usually handled automatically by C<xsubpp> by calling C<dXSARGS>.

		dAXMARK;

=for hackers
Found in file XSUB.h

=item dITEMS
X<dITEMS>

Sets up the C<items> variable.
This is usually handled automatically by C<xsubpp> by calling C<dXSARGS>.

		dITEMS;

=for hackers
Found in file XSUB.h

=item dUNDERBAR
X<dUNDERBAR>

Sets up any variable needed by the C<UNDERBAR> macro.  It used to define
C<padoff_du>, but it is currently a noop.  However, it is strongly advised
to still use it for ensuring past and future compatibility.

		dUNDERBAR;

=for hackers
Found in file XSUB.h

=item dXSARGS
X<dXSARGS>

Sets up stack and mark pointers for an XSUB, calling C<dSP> and C<dMARK>.
Sets up the C<ax> and C<items> variables by calling C<dAX> and C<dITEMS>.
This is usually handled automatically by C<xsubpp>.

		dXSARGS;

=for hackers
Found in file XSUB.h

=item dXSI32
X<dXSI32>

Sets up the C<ix> variable for an XSUB which has aliases.  This is usually
handled automatically by C<xsubpp>.

		dXSI32;

=for hackers
Found in file XSUB.h

=item items
X<items>

Variable which is setup by C<xsubpp> to indicate the number of 
items on the stack.  See L<perlxs/"Variable-length Parameter Lists">.

	I32	items

=for hackers
Found in file XSUB.h

=item ix
X<ix>

Variable which is setup by C<xsubpp> to indicate which of an 
XSUB's aliases was used to invoke it.  See L<perlxs/"The ALIAS: Keyword">.

	I32	ix

=for hackers
Found in file XSUB.h

=item RETVAL
X<RETVAL>

Variable which is setup by C<xsubpp> to hold the return value for an 
XSUB.  This is always the proper type for the XSUB.  See 
L<perlxs/"The RETVAL Variable">.

	(whatever)	RETVAL

=for hackers
Found in file XSUB.h

=item ST
X<ST>

Used to access elements on the XSUB's stack.

	SV*	ST(int ix)

=for hackers
Found in file XSUB.h

=item THIS
X<THIS>

Variable which is setup by C<xsubpp> to designate the object in a C++ 
XSUB.  This is always the proper type for the C++ object.  See C<L</CLASS>> and
L<perlxs/"Using XS With C++">.

	(whatever)	THIS

=for hackers
Found in file XSUB.h

=item UNDERBAR
X<UNDERBAR>

The SV* corresponding to the C<$_> variable.  Works even if there
is a lexical C<$_> in scope.

=for hackers
Found in file XSUB.h

=item XS
X<XS>

Macro to declare an XSUB and its C parameter list.  This is handled by
C<xsubpp>.  It is the same as using the more explicit C<XS_EXTERNAL> macro.

=for hackers
Found in file XSUB.h

=item XS_EXTERNAL
X<XS_EXTERNAL>

Macro to declare an XSUB and its C parameter list explicitly exporting the symbols.

=for hackers
Found in file XSUB.h

=item XS_INTERNAL
X<XS_INTERNAL>

Macro to declare an XSUB and its C parameter list without exporting the symbols.
This is handled by C<xsubpp> and generally preferable over exporting the XSUB
symbols unnecessarily.

=for hackers
Found in file XSUB.h


=back

=head1 Debugging Utilities

=over 8

=item dump_all
X<dump_all>

Dumps the entire optree of the current program starting at C<PL_main_root> to 
C<STDERR>.  Also dumps the optrees for all visible subroutines in
C<PL_defstash>.

	void	dump_all()

=for hackers
Found in file dump.c

=item dump_packsubs
X<dump_packsubs>

Dumps the optrees for all visible subroutines in C<stash>.

	void	dump_packsubs(const HV* stash)

=for hackers
Found in file dump.c

=item op_class
X<op_class>

Given an op, determine what type of struct it has been allocated as.
Returns one of the OPclass enums, such as OPclass_LISTOP.

	OPclass	op_class(const OP *o)

=for hackers
Found in file dump.c

=item op_dump
X<op_dump>

Dumps the optree starting at OP C<o> to C<STDERR>.

	void	op_dump(const OP *o)

=for hackers
Found in file dump.c

=item sv_dump
X<sv_dump>

Dumps the contents of an SV to the C<STDERR> filehandle.

For an example of its output, see L<Devel::Peek>.

	void	sv_dump(SV* sv)

=for hackers
Found in file dump.c


=back

=head1 Display and Dump functions

=over 8

=item pv_display
X<pv_display>

Similar to

  pv_escape(dsv,pv,cur,pvlim,PERL_PV_ESCAPE_QUOTE);

except that an additional "\0" will be appended to the string when
len > cur and pv[cur] is "\0".

Note that the final string may be up to 7 chars longer than pvlim.

	char*	pv_display(SV *dsv, const char *pv, STRLEN cur,
		           STRLEN len, STRLEN pvlim)

=for hackers
Found in file dump.c

=item pv_escape
X<pv_escape>

Escapes at most the first C<count> chars of C<pv> and puts the results into
C<dsv> such that the size of the escaped string will not exceed C<max> chars
and will not contain any incomplete escape sequences.  The number of bytes
escaped will be returned in the C<STRLEN *escaped> parameter if it is not null.
When the C<dsv> parameter is null no escaping actually occurs, but the number
of bytes that would be escaped were it not null will be calculated.

If flags contains C<PERL_PV_ESCAPE_QUOTE> then any double quotes in the string
will also be escaped.

Normally the SV will be cleared before the escaped string is prepared,
but when C<PERL_PV_ESCAPE_NOCLEAR> is set this will not occur.

If C<PERL_PV_ESCAPE_UNI> is set then the input string is treated as UTF-8
if C<PERL_PV_ESCAPE_UNI_DETECT> is set then the input string is scanned
using C<is_utf8_string()> to determine if it is UTF-8.

If C<PERL_PV_ESCAPE_ALL> is set then all input chars will be output
using C<\x01F1> style escapes, otherwise if C<PERL_PV_ESCAPE_NONASCII> is set, only
non-ASCII chars will be escaped using this style; otherwise, only chars above
255 will be so escaped; other non printable chars will use octal or
common escaped patterns like C<\n>.
Otherwise, if C<PERL_PV_ESCAPE_NOBACKSLASH>
then all chars below 255 will be treated as printable and
will be output as literals.

If C<PERL_PV_ESCAPE_FIRSTCHAR> is set then only the first char of the
string will be escaped, regardless of max.  If the output is to be in hex,
then it will be returned as a plain hex
sequence.  Thus the output will either be a single char,
an octal escape sequence, a special escape like C<\n> or a hex value.

If C<PERL_PV_ESCAPE_RE> is set then the escape char used will be a C<"%"> and
not a C<"\\">.  This is because regexes very often contain backslashed
sequences, whereas C<"%"> is not a particularly common character in patterns.

Returns a pointer to the escaped text as held by C<dsv>.

	char*	pv_escape(SV *dsv, char const * const str,
		          const STRLEN count, const STRLEN max,
		          STRLEN * const escaped,
		          const U32 flags)

=for hackers
Found in file dump.c

=item pv_pretty
X<pv_pretty>

Converts a string into something presentable, handling escaping via
C<pv_escape()> and supporting quoting and ellipses.

If the C<PERL_PV_PRETTY_QUOTE> flag is set then the result will be
double quoted with any double quotes in the string escaped.  Otherwise
if the C<PERL_PV_PRETTY_LTGT> flag is set then the result be wrapped in
angle brackets. 

If the C<PERL_PV_PRETTY_ELLIPSES> flag is set and not all characters in
string were output then an ellipsis C<...> will be appended to the
string.  Note that this happens AFTER it has been quoted.

If C<start_color> is non-null then it will be inserted after the opening
quote (if there is one) but before the escaped text.  If C<end_color>
is non-null then it will be inserted after the escaped text but before
any quotes or ellipses.

Returns a pointer to the prettified text as held by C<dsv>.

	char*	pv_pretty(SV *dsv, char const * const str,
		          const STRLEN count, const STRLEN max,
		          char const * const start_color,
		          char const * const end_color,
		          const U32 flags)

=for hackers
Found in file dump.c


=back

=head1 Embedding Functions

=over 8

=item cv_clone
X<cv_clone>

Clone a CV, making a lexical closure.  C<proto> supplies the prototype
of the function: its code, pad structure, and other attributes.
The prototype is combined with a capture of outer lexicals to which the
code refers, which are taken from the currently-executing instance of
the immediately surrounding code.

	CV*	cv_clone(CV* proto)

=for hackers
Found in file pad.c

=item cv_name
X<cv_name>

Returns an SV containing the name of the CV, mainly for use in error
reporting.  The CV may actually be a GV instead, in which case the returned
SV holds the GV's name.  Anything other than a GV or CV is treated as a
string already holding the sub name, but this could change in the future.

An SV may be passed as a second argument.  If so, the name will be assigned
to it and it will be returned.  Otherwise the returned SV will be a new
mortal.

If C<flags> has the C<CV_NAME_NOTQUAL> bit set, then the package name will not be
included.  If the first argument is neither a CV nor a GV, this flag is
ignored (subject to change).

	SV *	cv_name(CV *cv, SV *sv, U32 flags)

=for hackers
Found in file pad.c

=item cv_undef
X<cv_undef>

Clear out all the active components of a CV.  This can happen either
by an explicit C<undef &foo>, or by the reference count going to zero.
In the former case, we keep the C<CvOUTSIDE> pointer, so that any anonymous
children can still follow the full lexical scope chain.

	void	cv_undef(CV* cv)

=for hackers
Found in file pad.c

=item find_rundefsv
X<find_rundefsv>

Returns the global variable C<$_>.

	SV*	find_rundefsv()

=for hackers
Found in file pad.c

=item find_rundefsvoffset
X<find_rundefsvoffset>


DEPRECATED!  It is planned to remove this function from a
future release of Perl.  Do not use it for new code; remove it from
existing code.


Until the lexical C<$_> feature was removed, this function would
find the position of the lexical C<$_> in the pad of the
currently-executing function and return the offset in the current pad,
or C<NOT_IN_PAD>.

Now it always returns C<NOT_IN_PAD>.

	PADOFFSET find_rundefsvoffset()

=for hackers
Found in file pad.c

=item intro_my
X<intro_my>

"Introduce" C<my> variables to visible status.  This is called during parsing
at the end of each statement to make lexical variables visible to subsequent
statements.

	U32	intro_my()

=for hackers
Found in file pad.c

=item load_module
X<load_module>

Loads the module whose name is pointed to by the string part of C<name>.
Note that the actual module name, not its filename, should be given.
Eg, "Foo::Bar" instead of "Foo/Bar.pm". ver, if specified and not NULL,
provides version semantics similar to C<use Foo::Bar VERSION>. The optional
trailing arguments can be used to specify arguments to the module's C<import()>
method, similar to C<use Foo::Bar VERSION LIST>; their precise handling depends
on the flags. The flags argument is a bitwise-ORed collection of any of
C<PERL_LOADMOD_DENY>, C<PERL_LOADMOD_NOIMPORT>, or C<PERL_LOADMOD_IMPORT_OPS>
(or 0 for no flags).

If C<PERL_LOADMOD_NOIMPORT> is set, the module is loaded as if with an empty
import list, as in C<use Foo::Bar ()>; this is the only circumstance in which
the trailing optional arguments may be omitted entirely. Otherwise, if
C<PERL_LOADMOD_IMPORT_OPS> is set, the trailing arguments must consist of
exactly one C<OP*>, containing the op tree that produces the relevant import
arguments. Otherwise, the trailing arguments must all be C<SV*> values that
will be used as import arguments; and the list must be terminated with C<(SV*)
NULL>. If neither C<PERL_LOADMOD_NOIMPORT> nor C<PERL_LOADMOD_IMPORT_OPS> is
set, the trailing C<NULL> pointer is needed even if no import arguments are
desired. The reference count for each specified C<SV*> argument is
decremented. In addition, the C<name> argument is modified.

If C<PERL_LOADMOD_DENY> is set, the module is loaded as if with C<no> rather
than C<use>.

	void	load_module(U32 flags, SV* name, SV* ver, ...)

=for hackers
Found in file op.c

=item my_exit
X<my_exit>

A wrapper for the C library L<exit(3)>, honoring what L<perlapi/PL_exit_flags>
say to do.

	void	my_exit(U32 status)

=for hackers
Found in file perl.c

=item newPADNAMELIST
X<newPADNAMELIST>


NOTE: this function is experimental and may change or be
removed without notice.


Creates a new pad name list.  C<max> is the highest index for which space
is allocated.

	PADNAMELIST * newPADNAMELIST(size_t max)

=for hackers
Found in file pad.c

=item newPADNAMEouter
X<newPADNAMEouter>


NOTE: this function is experimental and may change or be
removed without notice.


Constructs and returns a new pad name.  Only use this function for names
that refer to outer lexicals.  (See also L</newPADNAMEpvn>.)  C<outer> is
the outer pad name that this one mirrors.  The returned pad name has the
C<PADNAMEt_OUTER> flag already set.

	PADNAME * newPADNAMEouter(PADNAME *outer)

=for hackers
Found in file pad.c

=item newPADNAMEpvn
X<newPADNAMEpvn>


NOTE: this function is experimental and may change or be
removed without notice.


Constructs and returns a new pad name.  C<s> must be a UTF-8 string.  Do not
use this for pad names that point to outer lexicals.  See
C<L</newPADNAMEouter>>.

	PADNAME * newPADNAMEpvn(const char *s, STRLEN len)

=for hackers
Found in file pad.c

=item nothreadhook
X<nothreadhook>

Stub that provides thread hook for perl_destruct when there are
no threads.

	int	nothreadhook()

=for hackers
Found in file perl.c

=item pad_add_anon
X<pad_add_anon>

Allocates a place in the currently-compiling pad (via L</pad_alloc>)
for an anonymous function that is lexically scoped inside the
currently-compiling function.
The function C<func> is linked into the pad, and its C<CvOUTSIDE> link
to the outer scope is weakened to avoid a reference loop.

One reference count is stolen, so you may need to do C<SvREFCNT_inc(func)>.

C<optype> should be an opcode indicating the type of operation that the
pad entry is to support.  This doesn't affect operational semantics,
but is used for debugging.

	PADOFFSET pad_add_anon(CV* func, I32 optype)

=for hackers
Found in file pad.c

=item pad_add_name_pv
X<pad_add_name_pv>

Exactly like L</pad_add_name_pvn>, but takes a nul-terminated string
instead of a string/length pair.

	PADOFFSET pad_add_name_pv(const char *name,
	                          const U32 flags,
	                          HV *typestash, HV *ourstash)

=for hackers
Found in file pad.c

=item pad_add_name_pvn
X<pad_add_name_pvn>

Allocates a place in the currently-compiling pad for a named lexical
variable.  Stores the name and other metadata in the name part of the
pad, and makes preparations to manage the variable's lexical scoping.
Returns the offset of the allocated pad slot.

C<namepv>/C<namelen> specify the variable's name, including leading sigil.
If C<typestash> is non-null, the name is for a typed lexical, and this
identifies the type.  If C<ourstash> is non-null, it's a lexical reference
to a package variable, and this identifies the package.  The following
flags can be OR'ed together:

 padadd_OUR          redundantly specifies if it's a package var
 padadd_STATE        variable will retain value persistently
 padadd_NO_DUP_CHECK skip check for lexical shadowing

	PADOFFSET pad_add_name_pvn(const char *namepv,
	                           STRLEN namelen, U32 flags,
	                           HV *typestash, HV *ourstash)

=for hackers
Found in file pad.c

=item pad_add_name_sv
X<pad_add_name_sv>

Exactly like L</pad_add_name_pvn>, but takes the name string in the form
of an SV instead of a string/length pair.

	PADOFFSET pad_add_name_sv(SV *name, U32 flags,
	                          HV *typestash, HV *ourstash)

=for hackers
Found in file pad.c

=item pad_alloc
X<pad_alloc>


NOTE: this function is experimental and may change or be
removed without notice.


Allocates a place in the currently-compiling pad,
returning the offset of the allocated pad slot.
No name is initially attached to the pad slot.
C<tmptype> is a set of flags indicating the kind of pad entry required,
which will be set in the value SV for the allocated pad entry:

    SVs_PADMY    named lexical variable ("my", "our", "state")
    SVs_PADTMP   unnamed temporary store
    SVf_READONLY constant shared between recursion levels

C<SVf_READONLY> has been supported here only since perl 5.20.  To work with
earlier versions as well, use C<SVf_READONLY|SVs_PADTMP>.  C<SVf_READONLY>
does not cause the SV in the pad slot to be marked read-only, but simply
tells C<pad_alloc> that it I<will> be made read-only (by the caller), or at
least should be treated as such.

C<optype> should be an opcode indicating the type of operation that the
pad entry is to support.  This doesn't affect operational semantics,
but is used for debugging.

	PADOFFSET pad_alloc(I32 optype, U32 tmptype)

=for hackers
Found in file pad.c

=item pad_findmy_pv
X<pad_findmy_pv>

Exactly like L</pad_findmy_pvn>, but takes a nul-terminated string
instead of a string/length pair.

	PADOFFSET pad_findmy_pv(const char* name, U32 flags)

=for hackers
Found in file pad.c

=item pad_findmy_pvn
X<pad_findmy_pvn>

Given the name of a lexical variable, find its position in the
currently-compiling pad.
C<namepv>/C<namelen> specify the variable's name, including leading sigil.
C<flags> is reserved and must be zero.
If it is not in the current pad but appears in the pad of any lexically
enclosing scope, then a pseudo-entry for it is added in the current pad.
Returns the offset in the current pad,
or C<NOT_IN_PAD> if no such lexical is in scope.

	PADOFFSET pad_findmy_pvn(const char* namepv,
	                         STRLEN namelen, U32 flags)

=for hackers
Found in file pad.c

=item pad_findmy_sv
X<pad_findmy_sv>

Exactly like L</pad_findmy_pvn>, but takes the name string in the form
of an SV instead of a string/length pair.

	PADOFFSET pad_findmy_sv(SV* name, U32 flags)

=for hackers
Found in file pad.c

=item padnamelist_fetch
X<padnamelist_fetch>


NOTE: this function is experimental and may change or be
removed without notice.


Fetches the pad name from the given index.

	PADNAME * padnamelist_fetch(PADNAMELIST *pnl,
	                            SSize_t key)

=for hackers
Found in file pad.c

=item padnamelist_store
X<padnamelist_store>


NOTE: this function is experimental and may change or be
removed without notice.


Stores the pad name (which may be null) at the given index, freeing any
existing pad name in that slot.

	PADNAME ** padnamelist_store(PADNAMELIST *pnl,
	                             SSize_t key, PADNAME *val)

=for hackers
Found in file pad.c

=item pad_setsv
X<pad_setsv>

Set the value at offset C<po> in the current (compiling or executing) pad.
Use the macro C<PAD_SETSV()> rather than calling this function directly.

	void	pad_setsv(PADOFFSET po, SV* sv)

=for hackers
Found in file pad.c

=item pad_sv
X<pad_sv>

Get the value at offset C<po> in the current (compiling or executing) pad.
Use macro C<PAD_SV> instead of calling this function directly.

	SV*	pad_sv(PADOFFSET po)

=for hackers
Found in file pad.c

=item pad_tidy
X<pad_tidy>


NOTE: this function is experimental and may change or be
removed without notice.


Tidy up a pad at the end of compilation of the code to which it belongs.
Jobs performed here are: remove most stuff from the pads of anonsub
prototypes; give it a C<@_>; mark temporaries as such.  C<type> indicates
the kind of subroutine:

    padtidy_SUB        ordinary subroutine
    padtidy_SUBCLONE   prototype for lexical closure
    padtidy_FORMAT     format

	void	pad_tidy(padtidy_type type)

=for hackers
Found in file pad.c

=item perl_alloc
X<perl_alloc>

Allocates a new Perl interpreter.  See L<perlembed>.

	PerlInterpreter* perl_alloc()

=for hackers
Found in file perl.c

=item perl_construct
X<perl_construct>

Initializes a new Perl interpreter.  See L<perlembed>.

	void	perl_construct(PerlInterpreter *my_perl)

=for hackers
Found in file perl.c

=item perl_destruct
X<perl_destruct>

Shuts down a Perl interpreter.  See L<perlembed> for a tutorial.

C<my_perl> points to the Perl interpreter.  It must have been previously
created through the use of L</perl_alloc> and L</perl_construct>.  It may
have been initialised through L</perl_parse>, and may have been used
through L</perl_run> and other means.  This function should be called for
any Perl interpreter that has been constructed with L</perl_construct>,
even if subsequent operations on it failed, for example if L</perl_parse>
returned a non-zero value.

If the interpreter's C<PL_exit_flags> word has the
C<PERL_EXIT_DESTRUCT_END> flag set, then this function will execute code
in C<END> blocks before performing the rest of destruction.  If it is
desired to make any use of the interpreter between L</perl_parse> and
L</perl_destruct> other than just calling L</perl_run>, then this flag
should be set early on.  This matters if L</perl_run> will not be called,
or if anything else will be done in addition to calling L</perl_run>.

Returns a value be a suitable value to pass to the C library function
C<exit> (or to return from C<main>), to serve as an exit code indicating
the nature of the way the interpreter terminated.  This takes into account
any failure of L</perl_parse> and any early exit from L</perl_run>.
The exit code is of the type required by the host operating system,
so because of differing exit code conventions it is not portable to
interpret specific numeric values as having specific meanings.

	int	perl_destruct(PerlInterpreter *my_perl)

=for hackers
Found in file perl.c

=item perl_free
X<perl_free>

Releases a Perl interpreter.  See L<perlembed>.

	void	perl_free(PerlInterpreter *my_perl)

=for hackers
Found in file perl.c

=item perl_parse
X<perl_parse>

Tells a Perl interpreter to parse a Perl script.  This performs most
of the initialisation of a Perl interpreter.  See L<perlembed> for
a tutorial.

C<my_perl> points to the Perl interpreter that is to parse the script.
It must have been previously created through the use of L</perl_alloc>
and L</perl_construct>.  C<xsinit> points to a callback function that
will be called to set up the ability for this Perl interpreter to load
XS extensions, or may be null to perform no such setup.

C<argc> and C<argv> supply a set of command-line arguments to the Perl
interpreter, as would normally be passed to the C<main> function of
a C program.  C<argv[argc]> must be null.  These arguments are where
the script to parse is specified, either by naming a script file or by
providing a script in a C<-e> option.
If L<C<$0>|perlvar/$0> will be written to in the Perl interpreter, then
the argument strings must be in writable memory, and so mustn't just be
string constants.

C<env> specifies a set of environment variables that will be used by
this Perl interpreter.  If non-null, it must point to a null-terminated
array of environment strings.  If null, the Perl interpreter will use
the environment supplied by the C<environ> global variable.

This function initialises the interpreter, and parses and compiles the
script specified by the command-line arguments.  This includes executing
code in C<BEGIN>, C<UNITCHECK>, and C<CHECK> blocks.  It does not execute
C<INIT> blocks or the main program.

Returns an integer of slightly tricky interpretation.  The correct
use of the return value is as a truth value indicating whether there
was a failure in initialisation.  If zero is returned, this indicates
that initialisation was successful, and it is safe to proceed to call
L</perl_run> and make other use of it.  If a non-zero value is returned,
this indicates some problem that means the interpreter wants to terminate.
The interpreter should not be just abandoned upon such failure; the caller
should proceed to shut the interpreter down cleanly with L</perl_destruct>
and free it with L</perl_free>.

For historical reasons, the non-zero return value also attempts to
be a suitable value to pass to the C library function C<exit> (or to
return from C<main>), to serve as an exit code indicating the nature
of the way initialisation terminated.  However, this isn't portable,
due to differing exit code conventions.  A historical bug is preserved
for the time being: if the Perl built-in C<exit> is called during this
function's execution, with a type of exit entailing a zero exit code
under the host operating system's conventions, then this function
returns zero rather than a non-zero value.  This bug, [perl #2754],
leads to C<perl_run> being called (and therefore C<INIT> blocks and the
main program running) despite a call to C<exit>.  It has been preserved
because a popular module-installing module has come to rely on it and
needs time to be fixed.  This issue is [perl #132577], and the original
bug is due to be fixed in Perl 5.30.

	int	perl_parse(PerlInterpreter *my_perl,
		           XSINIT_t xsinit, int argc,
		           char** argv, char** env)

=for hackers
Found in file perl.c

=item perl_run
X<perl_run>

Tells a Perl interpreter to run its main program.  See L<perlembed>
for a tutorial.

C<my_perl> points to the Perl interpreter.  It must have been previously
created through the use of L</perl_alloc> and L</perl_construct>, and
initialised through L</perl_parse>.  This function should not be called
if L</perl_parse> returned a non-zero value, indicating a failure in
initialisation or compilation.

This function executes code in C<INIT> blocks, and then executes the
main program.  The code to be executed is that established by the prior
call to L</perl_parse>.  If the interpreter's C<PL_exit_flags> word
does not have the C<PERL_EXIT_DESTRUCT_END> flag set, then this function
will also execute code in C<END> blocks.  If it is desired to make any
further use of the interpreter after calling this function, then C<END>
blocks should be postponed to L</perl_destruct> time by setting that flag.

Returns an integer of slightly tricky interpretation.  The correct use
of the return value is as a truth value indicating whether the program
terminated non-locally.  If zero is returned, this indicates that
the program ran to completion, and it is safe to make other use of the
interpreter (provided that the C<PERL_EXIT_DESTRUCT_END> flag was set as
described above).  If a non-zero value is returned, this indicates that
the interpreter wants to terminate early.  The interpreter should not be
just abandoned because of this desire to terminate; the caller should
proceed to shut the interpreter down cleanly with L</perl_destruct>
and free it with L</perl_free>.

For historical reasons, the non-zero return value also attempts to
be a suitable value to pass to the C library function C<exit> (or to
return from C<main>), to serve as an exit code indicating the nature of
the way the program terminated.  However, this isn't portable, due to
differing exit code conventions.  An attempt is made to return an exit
code of the type required by the host operating system, but because
it is constrained to be non-zero, it is not necessarily possible to
indicate every type of exit.  It is only reliable on Unix, where a zero
exit code can be augmented with a set bit that will be ignored.  In any
case, this function is not the correct place to acquire an exit code:
one should get that from L</perl_destruct>.

	int	perl_run(PerlInterpreter *my_perl)

=for hackers
Found in file perl.c

=item require_pv
X<require_pv>

Tells Perl to C<require> the file named by the string argument.  It is
analogous to the Perl code C<eval "require '$file'">.  It's even
implemented that way; consider using load_module instead.

NOTE: the perl_ form of this function is deprecated.

	void	require_pv(const char* pv)

=for hackers
Found in file perl.c


=back

=head1 Exception Handling (simple) Macros

=over 8

=item dXCPT
X<dXCPT>

Set up necessary local variables for exception handling.
See L<perlguts/"Exception Handling">.

		dXCPT;

=for hackers
Found in file XSUB.h

=item XCPT_CATCH
X<XCPT_CATCH>

Introduces a catch block.  See L<perlguts/"Exception Handling">.

=for hackers
Found in file XSUB.h

=item XCPT_RETHROW
X<XCPT_RETHROW>

Rethrows a previously caught exception.  See L<perlguts/"Exception Handling">.

		XCPT_RETHROW;

=for hackers
Found in file XSUB.h

=item XCPT_TRY_END
X<XCPT_TRY_END>

Ends a try block.  See L<perlguts/"Exception Handling">.

=for hackers
Found in file XSUB.h

=item XCPT_TRY_START
X<XCPT_TRY_START>

Starts a try block.  See L<perlguts/"Exception Handling">.

=for hackers
Found in file XSUB.h


=back

=head1 Functions in file vutil.c


=over 8

=item new_version
X<new_version>

Returns a new version object based on the passed in SV:

    SV *sv = new_version(SV *ver);

Does not alter the passed in ver SV.  See "upg_version" if you
want to upgrade the SV.

	SV*	new_version(SV *ver)

=for hackers
Found in file vutil.c

=item prescan_version
X<prescan_version>

Validate that a given string can be parsed as a version object, but doesn't
actually perform the parsing.  Can use either strict or lax validation rules.
Can optionally set a number of hint variables to save the parsing code
some time when tokenizing.

	const char* prescan_version(const char *s, bool strict,
	                            const char** errstr,
	                            bool *sqv,
	                            int *ssaw_decimal,
	                            int *swidth, bool *salpha)

=for hackers
Found in file vutil.c

=item scan_version
X<scan_version>

Returns a pointer to the next character after the parsed
version string, as well as upgrading the passed in SV to
an RV.

Function must be called with an already existing SV like

    sv = newSV(0);
    s = scan_version(s, SV *sv, bool qv);

Performs some preprocessing to the string to ensure that
it has the correct characteristics of a version.  Flags the
object if it contains an underscore (which denotes this
is an alpha version).  The boolean qv denotes that the version
should be interpreted as if it had multiple decimals, even if
it doesn't.

	const char* scan_version(const char *s, SV *rv, bool qv)

=for hackers
Found in file vutil.c

=item upg_version
X<upg_version>

In-place upgrade of the supplied SV to a version object.

    SV *sv = upg_version(SV *sv, bool qv);

Returns a pointer to the upgraded SV.  Set the boolean qv if you want
to force this SV to be interpreted as an "extended" version.

	SV*	upg_version(SV *ver, bool qv)

=for hackers
Found in file vutil.c

=item vcmp
X<vcmp>

Version object aware cmp.  Both operands must already have been 
converted into version objects.

	int	vcmp(SV *lhv, SV *rhv)

=for hackers
Found in file vutil.c

=item vnormal
X<vnormal>

Accepts a version object and returns the normalized string
representation.  Call like:

    sv = vnormal(rv);

NOTE: you can pass either the object directly or the SV
contained within the RV.

The SV returned has a refcount of 1.

	SV*	vnormal(SV *vs)

=for hackers
Found in file vutil.c

=item vnumify
X<vnumify>

Accepts a version object and returns the normalized floating
point representation.  Call like:

    sv = vnumify(rv);

NOTE: you can pass either the object directly or the SV
contained within the RV.

The SV returned has a refcount of 1.

	SV*	vnumify(SV *vs)

=for hackers
Found in file vutil.c

=item vstringify
X<vstringify>

In order to maintain maximum compatibility with earlier versions
of Perl, this function will return either the floating point
notation or the multiple dotted notation, depending on whether
the original version contained 1 or more dots, respectively.

The SV returned has a refcount of 1.

	SV*	vstringify(SV *vs)

=for hackers
Found in file vutil.c

=item vverify
X<vverify>

Validates that the SV contains valid internal structure for a version object.
It may be passed either the version object (RV) or the hash itself (HV).  If
the structure is valid, it returns the HV.  If the structure is invalid,
it returns NULL.

    SV *hv = vverify(sv);

Note that it only confirms the bare minimum structure (so as not to get
confused by derived classes which may contain additional hash entries):

=over 4

=item * The SV is an HV or a reference to an HV

=item * The hash contains a "version" key

=item * The "version" key has a reference to an AV as its value

=back

	SV*	vverify(SV *vs)

=for hackers
Found in file vutil.c


=back

=head1 "Gimme" Values

=over 8

=item G_ARRAY
X<G_ARRAY>

Used to indicate list context.  See C<L</GIMME_V>>, C<L</GIMME>> and
L<perlcall>.

=for hackers
Found in file cop.h

=item G_DISCARD
X<G_DISCARD>

Indicates that arguments returned from a callback should be discarded.  See
L<perlcall>.

=for hackers
Found in file cop.h

=item G_EVAL
X<G_EVAL>

Used to force a Perl C<eval> wrapper around a callback.  See
L<perlcall>.

=for hackers
Found in file cop.h

=item GIMME
X<GIMME>

A backward-compatible version of C<GIMME_V> which can only return
C<G_SCALAR> or C<G_ARRAY>; in a void context, it returns C<G_SCALAR>.
Deprecated.  Use C<GIMME_V> instead.

	U32	GIMME

=for hackers
Found in file op.h

=item GIMME_V
X<GIMME_V>

The XSUB-writer's equivalent to Perl's C<wantarray>.  Returns C<G_VOID>,
C<G_SCALAR> or C<G_ARRAY> for void, scalar or list context,
respectively.  See L<perlcall> for a usage example.

	U32	GIMME_V

=for hackers
Found in file op.h

=item G_NOARGS
X<G_NOARGS>

Indicates that no arguments are being sent to a callback.  See
L<perlcall>.

=for hackers
Found in file cop.h

=item G_SCALAR
X<G_SCALAR>

Used to indicate scalar context.  See C<L</GIMME_V>>, C<L</GIMME>>, and
L<perlcall>.

=for hackers
Found in file cop.h

=item G_VOID
X<G_VOID>

Used to indicate void context.  See C<L</GIMME_V>> and L<perlcall>.

=for hackers
Found in file cop.h


=back

=head1 Global Variables

These variables are global to an entire process.  They are shared between
all interpreters and all threads in a process.  Any variables not documented
here may be changed or removed without notice, so don't use them!
If you feel you really do need to use an unlisted variable, first send email to
L<perl5-porters@perl.org|mailto:perl5-porters@perl.org>.  It may be that
someone there will point out a way to accomplish what you need without using an
internal variable.  But if not, you should get a go-ahead to document and then
use the variable.


=over 8

=item PL_check
X<PL_check>

Array, indexed by opcode, of functions that will be called for the "check"
phase of optree building during compilation of Perl code.  For most (but
not all) types of op, once the op has been initially built and populated
with child ops it will be filtered through the check function referenced
by the appropriate element of this array.  The new op is passed in as the
sole argument to the check function, and the check function returns the
completed op.  The check function may (as the name suggests) check the op
for validity and signal errors.  It may also initialise or modify parts of
the ops, or perform more radical surgery such as adding or removing child
ops, or even throw the op away and return a different op in its place.

This array of function pointers is a convenient place to hook into the
compilation process.  An XS module can put its own custom check function
in place of any of the standard ones, to influence the compilation of a
particular type of op.  However, a custom check function must never fully
replace a standard check function (or even a custom check function from
another module).  A module modifying checking must instead B<wrap> the
preexisting check function.  A custom check function must be selective
about when to apply its custom behaviour.  In the usual case where
it decides not to do anything special with an op, it must chain the
preexisting op function.  Check functions are thus linked in a chain,
with the core's base checker at the end.

For thread safety, modules should not write directly to this array.
Instead, use the function L</wrap_op_checker>.

=for hackers
Found in file perlvars.h

=item PL_keyword_plugin
X<PL_keyword_plugin>


NOTE: this function is experimental and may change or be
removed without notice.


Function pointer, pointing at a function used to handle extended keywords.
The function should be declared as

	int keyword_plugin_function(pTHX_
		char *keyword_ptr, STRLEN keyword_len,
		OP **op_ptr)

The function is called from the tokeniser, whenever a possible keyword
is seen.  C<keyword_ptr> points at the word in the parser's input
buffer, and C<keyword_len> gives its length; it is not null-terminated.
The function is expected to examine the word, and possibly other state
such as L<%^H|perlvar/%^H>, to decide whether it wants to handle it
as an extended keyword.  If it does not, the function should return
C<KEYWORD_PLUGIN_DECLINE>, and the normal parser process will continue.

If the function wants to handle the keyword, it first must
parse anything following the keyword that is part of the syntax
introduced by the keyword.  See L</Lexer interface> for details.

When a keyword is being handled, the plugin function must build
a tree of C<OP> structures, representing the code that was parsed.
The root of the tree must be stored in C<*op_ptr>.  The function then
returns a constant indicating the syntactic role of the construct that
it has parsed: C<KEYWORD_PLUGIN_STMT> if it is a complete statement, or
C<KEYWORD_PLUGIN_EXPR> if it is an expression.  Note that a statement
construct cannot be used inside an expression (except via C<do BLOCK>
and similar), and an expression is not a complete statement (it requires
at least a terminating semicolon).

When a keyword is handled, the plugin function may also have
(compile-time) side effects.  It may modify C<%^H>, define functions, and
so on.  Typically, if side effects are the main purpose of a handler,
it does not wish to generate any ops to be included in the normal
compilation.  In this case it is still required to supply an op tree,
but it suffices to generate a single null op.

That's how the C<*PL_keyword_plugin> function needs to behave overall.
Conventionally, however, one does not completely replace the existing
handler function.  Instead, take a copy of C<PL_keyword_plugin> before
assigning your own function pointer to it.  Your handler function should
look for keywords that it is interested in and handle those.  Where it
is not interested, it should call the saved plugin function, passing on
the arguments it received.  Thus C<PL_keyword_plugin> actually points
at a chain of handler functions, all of which have an opportunity to
handle keywords, and only the last function in the chain (built into
the Perl core) will normally return C<KEYWORD_PLUGIN_DECLINE>.

For thread safety, modules should not set this variable directly.
Instead, use the function L</wrap_keyword_plugin>.

=for hackers
Found in file perlvars.h

=item PL_phase
X<PL_phase>

A value that indicates the current Perl interpreter's phase. Possible values
include C<PERL_PHASE_CONSTRUCT>, C<PERL_PHASE_START>, C<PERL_PHASE_CHECK>,
C<PERL_PHASE_INIT>, C<PERL_PHASE_RUN>, C<PERL_PHASE_END>, and
C<PERL_PHASE_DESTRUCT>.

For example, the following determines whether the interpreter is in
global destruction:

    if (PL_phase == PERL_PHASE_DESTRUCT) {
        // we are in global destruction
    }

C<PL_phase> was introduced in Perl 5.14; in prior perls you can use
C<PL_dirty> (boolean) to determine whether the interpreter is in global
destruction. (Use of C<PL_dirty> is discouraged since 5.14.)

	enum perl_phase	PL_phase

=for hackers
Found in file perlvars.h


=back

=head1 GV Functions

A GV is a structure which corresponds to to a Perl typeglob, ie *foo.
It is a structure that holds a pointer to a scalar, an array, a hash etc,
corresponding to $foo, @foo, %foo.

GVs are usually found as values in stashes (symbol table hashes) where
Perl stores its global variables.


=over 8

=item GvAV
X<GvAV>

Return the AV from the GV.

	AV*	GvAV(GV* gv)

=for hackers
Found in file gv.h

=item gv_const_sv
X<gv_const_sv>

If C<gv> is a typeglob whose subroutine entry is a constant sub eligible for
inlining, or C<gv> is a placeholder reference that would be promoted to such
a typeglob, then returns the value returned by the sub.  Otherwise, returns
C<NULL>.

	SV*	gv_const_sv(GV* gv)

=for hackers
Found in file gv.c

=item GvCV
X<GvCV>

Return the CV from the GV.

	CV*	GvCV(GV* gv)

=for hackers
Found in file gv.h

=item gv_fetchmeth
X<gv_fetchmeth>

Like L</gv_fetchmeth_pvn>, but lacks a flags parameter.

	GV*	gv_fetchmeth(HV* stash, const char* name,
		             STRLEN len, I32 level)

=for hackers
Found in file gv.c

=item gv_fetchmethod_autoload
X<gv_fetchmethod_autoload>

Returns the glob which contains the subroutine to call to invoke the method
on the C<stash>.  In fact in the presence of autoloading this may be the
glob for "AUTOLOAD".  In this case the corresponding variable C<$AUTOLOAD> is
already setup.

The third parameter of C<gv_fetchmethod_autoload> determines whether
AUTOLOAD lookup is performed if the given method is not present: non-zero
means yes, look for AUTOLOAD; zero means no, don't look for AUTOLOAD.
Calling C<gv_fetchmethod> is equivalent to calling C<gv_fetchmethod_autoload>
with a non-zero C<autoload> parameter.

These functions grant C<"SUPER"> token
as a prefix of the method name.  Note
that if you want to keep the returned glob for a long time, you need to
check for it being "AUTOLOAD", since at the later time the call may load a
different subroutine due to C<$AUTOLOAD> changing its value.  Use the glob
created as a side effect to do this.

These functions have the same side-effects as C<gv_fetchmeth> with
C<level==0>.  The warning against passing the GV returned by
C<gv_fetchmeth> to C<call_sv> applies equally to these functions.

	GV*	gv_fetchmethod_autoload(HV* stash,
		                        const char* name,
		                        I32 autoload)

=for hackers
Found in file gv.c

=item gv_fetchmeth_autoload
X<gv_fetchmeth_autoload>

This is the old form of L</gv_fetchmeth_pvn_autoload>, which has no flags
parameter.

	GV*	gv_fetchmeth_autoload(HV* stash,
		                      const char* name,
		                      STRLEN len, I32 level)

=for hackers
Found in file gv.c

=item gv_fetchmeth_pv
X<gv_fetchmeth_pv>

Exactly like L</gv_fetchmeth_pvn>, but takes a nul-terminated string 
instead of a string/length pair.

	GV*	gv_fetchmeth_pv(HV* stash, const char* name,
		                I32 level, U32 flags)

=for hackers
Found in file gv.c

=item gv_fetchmeth_pvn
X<gv_fetchmeth_pvn>

Returns the glob with the given C<name> and a defined subroutine or
C<NULL>.  The glob lives in the given C<stash>, or in the stashes
accessible via C<@ISA> and C<UNIVERSAL::>.

The argument C<level> should be either 0 or -1.  If C<level==0>, as a
side-effect creates a glob with the given C<name> in the given C<stash>
which in the case of success contains an alias for the subroutine, and sets
up caching info for this glob.

The only significant values for C<flags> are C<GV_SUPER> and C<SVf_UTF8>.

C<GV_SUPER> indicates that we want to look up the method in the superclasses
of the C<stash>.

The
GV returned from C<gv_fetchmeth> may be a method cache entry, which is not
visible to Perl code.  So when calling C<call_sv>, you should not use
the GV directly; instead, you should use the method's CV, which can be
obtained from the GV with the C<GvCV> macro.

	GV*	gv_fetchmeth_pvn(HV* stash, const char* name,
		                 STRLEN len, I32 level,
		                 U32 flags)

=for hackers
Found in file gv.c

=item gv_fetchmeth_pvn_autoload
X<gv_fetchmeth_pvn_autoload>

Same as C<gv_fetchmeth_pvn()>, but looks for autoloaded subroutines too.
Returns a glob for the subroutine.

For an autoloaded subroutine without a GV, will create a GV even
if C<level < 0>.  For an autoloaded subroutine without a stub, C<GvCV()>
of the result may be zero.

Currently, the only significant value for C<flags> is C<SVf_UTF8>.

	GV*	gv_fetchmeth_pvn_autoload(HV* stash,
		                          const char* name,
		                          STRLEN len, I32 level,
		                          U32 flags)

=for hackers
Found in file gv.c

=item gv_fetchmeth_pv_autoload
X<gv_fetchmeth_pv_autoload>

Exactly like L</gv_fetchmeth_pvn_autoload>, but takes a nul-terminated string
instead of a string/length pair.

	GV*	gv_fetchmeth_pv_autoload(HV* stash,
		                         const char* name,
		                         I32 level, U32 flags)

=for hackers
Found in file gv.c

=item gv_fetchmeth_sv
X<gv_fetchmeth_sv>

Exactly like L</gv_fetchmeth_pvn>, but takes the name string in the form
of an SV instead of a string/length pair.

	GV*	gv_fetchmeth_sv(HV* stash, SV* namesv,
		                I32 level, U32 flags)

=for hackers
Found in file gv.c

=item gv_fetchmeth_sv_autoload
X<gv_fetchmeth_sv_autoload>

Exactly like L</gv_fetchmeth_pvn_autoload>, but takes the name string in the form
of an SV instead of a string/length pair.

	GV*	gv_fetchmeth_sv_autoload(HV* stash, SV* namesv,
		                         I32 level, U32 flags)

=for hackers
Found in file gv.c

=item GvHV
X<GvHV>

Return the HV from the GV.

	HV*	GvHV(GV* gv)

=for hackers
Found in file gv.h

=item gv_init
X<gv_init>

The old form of C<gv_init_pvn()>.  It does not work with UTF-8 strings, as it
has no flags parameter.  If the C<multi> parameter is set, the
C<GV_ADDMULTI> flag will be passed to C<gv_init_pvn()>.

	void	gv_init(GV* gv, HV* stash, const char* name,
		        STRLEN len, int multi)

=for hackers
Found in file gv.c

=item gv_init_pv
X<gv_init_pv>

Same as C<gv_init_pvn()>, but takes a nul-terminated string for the name
instead of separate char * and length parameters.

	void	gv_init_pv(GV* gv, HV* stash, const char* name,
		           U32 flags)

=for hackers
Found in file gv.c

=item gv_init_pvn
X<gv_init_pvn>

Converts a scalar into a typeglob.  This is an incoercible typeglob;
assigning a reference to it will assign to one of its slots, instead of
overwriting it as happens with typeglobs created by C<SvSetSV>.  Converting
any scalar that is C<SvOK()> may produce unpredictable results and is reserved
for perl's internal use.

C<gv> is the scalar to be converted.

C<stash> is the parent stash/package, if any.

C<name> and C<len> give the name.  The name must be unqualified;
that is, it must not include the package name.  If C<gv> is a
stash element, it is the caller's responsibility to ensure that the name
passed to this function matches the name of the element.  If it does not
match, perl's internal bookkeeping will get out of sync.

C<flags> can be set to C<SVf_UTF8> if C<name> is a UTF-8 string, or
the return value of SvUTF8(sv).  It can also take the
C<GV_ADDMULTI> flag, which means to pretend that the GV has been
seen before (i.e., suppress "Used once" warnings).

	void	gv_init_pvn(GV* gv, HV* stash, const char* name,
		            STRLEN len, U32 flags)

=for hackers
Found in file gv.c

=item gv_init_sv
X<gv_init_sv>

Same as C<gv_init_pvn()>, but takes an SV * for the name instead of separate
char * and length parameters.  C<flags> is currently unused.

	void	gv_init_sv(GV* gv, HV* stash, SV* namesv,
		           U32 flags)

=for hackers
Found in file gv.c

=item gv_stashpv
X<gv_stashpv>

Returns a pointer to the stash for a specified package.  Uses C<strlen> to
determine the length of C<name>, then calls C<gv_stashpvn()>.

	HV*	gv_stashpv(const char* name, I32 flags)

=for hackers
Found in file gv.c

=item gv_stashpvn
X<gv_stashpvn>

Returns a pointer to the stash for a specified package.  The C<namelen>
parameter indicates the length of the C<name>, in bytes.  C<flags> is passed
to C<gv_fetchpvn_flags()>, so if set to C<GV_ADD> then the package will be
created if it does not already exist.  If the package does not exist and
C<flags> is 0 (or any other setting that does not create packages) then C<NULL>
is returned.

Flags may be one of:

    GV_ADD
    SVf_UTF8
    GV_NOADD_NOINIT
    GV_NOINIT
    GV_NOEXPAND
    GV_ADDMG

The most important of which are probably C<GV_ADD> and C<SVf_UTF8>.

Note, use of C<gv_stashsv> instead of C<gv_stashpvn> where possible is strongly
recommended for performance reasons.

	HV*	gv_stashpvn(const char* name, U32 namelen,
		            I32 flags)

=for hackers
Found in file gv.c

=item gv_stashpvs
X<gv_stashpvs>

Like C<gv_stashpvn>, but takes a literal string instead of a
string/length pair.

	HV*	gv_stashpvs("name", I32 create)

=for hackers
Found in file handy.h

=item gv_stashsv
X<gv_stashsv>

Returns a pointer to the stash for a specified package.  See
C<L</gv_stashpvn>>.

Note this interface is strongly preferred over C<gv_stashpvn> for performance
reasons.

	HV*	gv_stashsv(SV* sv, I32 flags)

=for hackers
Found in file gv.c

=item GvSV
X<GvSV>

Return the SV from the GV.

	SV*	GvSV(GV* gv)

=for hackers
Found in file gv.h

=item save_gp
X<save_gp>

Saves the current GP of gv on the save stack to be restored on scope exit.

If empty is true, replace the GP with a new GP.

If empty is false, mark gv with GVf_INTRO so the next reference
assigned is localized, which is how C< local *foo = $someref; > works.

	void	save_gp(GV* gv, I32 empty)

=for hackers
Found in file scope.c

=item setdefout
X<setdefout>

Sets C<PL_defoutgv>, the default file handle for output, to the passed in
typeglob.  As C<PL_defoutgv> "owns" a reference on its typeglob, the reference
count of the passed in typeglob is increased by one, and the reference count
of the typeglob that C<PL_defoutgv> points to is decreased by one.

	void	setdefout(GV* gv)

=for hackers
Found in file pp_sys.c


=back

=head1 Handy Values

=over 8

=item C_ARRAY_END
X<C_ARRAY_END>

Returns a pointer to one element past the final element of the input C array.

	void *	C_ARRAY_END(void *a)

=for hackers
Found in file handy.h

=item C_ARRAY_LENGTH
X<C_ARRAY_LENGTH>

Returns the number of elements in the input C array (so you want your
zero-based indices to be less than but not equal to).

	STRLEN	C_ARRAY_LENGTH(void *a)

=for hackers
Found in file handy.h

=item cBOOL
X<cBOOL>

Cast-to-bool.  A simple S<C<(bool) I<expr>>> cast may not do the right thing:
if C<bool> is defined as C<char>, for example, then the cast from C<int> is
implementation-defined.

C<(bool)!!(cbool)> in a ternary triggers a bug in xlc on AIX

	bool	cBOOL(bool expr)

=for hackers
Found in file handy.h

=item Nullav
X<Nullav>


DEPRECATED!  It is planned to remove this function from a
future release of Perl.  Do not use it for new code; remove it from
existing code.


Null AV pointer.

(deprecated - use C<(AV *)NULL> instead)

=for hackers
Found in file av.h

=item Nullch
X<Nullch>

Null character pointer.  (No longer available when C<PERL_CORE> is
defined.)

=for hackers
Found in file handy.h

=item Nullcv
X<Nullcv>


DEPRECATED!  It is planned to remove this function from a
future release of Perl.  Do not use it for new code; remove it from
existing code.


Null CV pointer.

(deprecated - use C<(CV *)NULL> instead)

=for hackers
Found in file cv.h

=item Nullhv
X<Nullhv>


DEPRECATED!  It is planned to remove this function from a
future release of Perl.  Do not use it for new code; remove it from
existing code.


Null HV pointer.

(deprecated - use C<(HV *)NULL> instead)

=for hackers
Found in file hv.h

=item Nullsv
X<Nullsv>

Null SV pointer.  (No longer available when C<PERL_CORE> is defined.)

=for hackers
Found in file handy.h

=item STR_WITH_LEN
X<STR_WITH_LEN>

Returns two comma separated tokens of the input literal string, and its length.
This is convenience macro which helps out in some API calls.
Note that it can't be used as an argument to macros or functions that under
some configurations might be macros, which means that it requires the full
Perl_xxx(aTHX_ ...) form for any API calls where it's used.

	pair	STR_WITH_LEN("literal string")

=for hackers
Found in file handy.h

=item __ASSERT_
X<__ASSERT_>

This is a helper macro to avoid preprocessor issues, replaced by nothing
unless under DEBUGGING, where it expands to an assert of its argument,
followed by a comma (hence the comma operator).  If we just used a straight
assert(), we would get a comma with nothing before it when not DEBUGGING.

	void	__ASSERT_(bool expr)

=for hackers
Found in file handy.h


=back

=head1 Hash Manipulation Functions

A HV structure represents a Perl hash.  It consists mainly of an array
of pointers, each of which points to a linked list of HE structures.  The
array is indexed by the hash function of the key, so each linked list
represents all the hash entries with the same hash value.  Each HE contains
a pointer to the actual value, plus a pointer to a HEK structure which
holds the key and hash value.


=over 8

=item cop_fetch_label
X<cop_fetch_label>


NOTE: this function is experimental and may change or be
removed without notice.


Returns the label attached to a cop, and stores its length in bytes into
C<*len>.
Upon return, C<*flags> will be set to either C<SVf_UTF8> or 0.

Alternatively, use the macro L</C<CopLABEL_len_flags>>;
or if you don't need to know if the label is UTF-8 or not, the macro
L</C<CopLABEL_len>>;
or if you additionally dont need to know the length, L</C<CopLABEL>>.

	const char * cop_fetch_label(COP *const cop,
	                             STRLEN *len, U32 *flags)

=for hackers
Found in file hv.c

=item cop_store_label
X<cop_store_label>


NOTE: this function is experimental and may change or be
removed without notice.


Save a label into a C<cop_hints_hash>.
You need to set flags to C<SVf_UTF8>
for a UTF-8 label.  Any other flag is ignored.

	void	cop_store_label(COP *const cop,
		                const char *label, STRLEN len,
		                U32 flags)

=for hackers
Found in file hv.c

=item get_hv
X<get_hv>

Returns the HV of the specified Perl hash.  C<flags> are passed to
C<gv_fetchpv>.  If C<GV_ADD> is set and the
Perl variable does not exist then it will be created.  If C<flags> is zero
and the variable does not exist then C<NULL> is returned.

NOTE: the perl_ form of this function is deprecated.

	HV*	get_hv(const char *name, I32 flags)

=for hackers
Found in file perl.c

=item HEf_SVKEY
X<HEf_SVKEY>

This flag, used in the length slot of hash entries and magic structures,
specifies the structure contains an C<SV*> pointer where a C<char*> pointer
is to be expected.  (For information only--not to be used).

=for hackers
Found in file hv.h

=item HeHASH
X<HeHASH>

Returns the computed hash stored in the hash entry.

	U32	HeHASH(HE* he)

=for hackers
Found in file hv.h

=item HeKEY
X<HeKEY>

Returns the actual pointer stored in the key slot of the hash entry.  The
pointer may be either C<char*> or C<SV*>, depending on the value of
C<HeKLEN()>.  Can be assigned to.  The C<HePV()> or C<HeSVKEY()> macros are
usually preferable for finding the value of a key.

	void*	HeKEY(HE* he)

=for hackers
Found in file hv.h

=item HeKLEN
X<HeKLEN>

If this is negative, and amounts to C<HEf_SVKEY>, it indicates the entry
holds an C<SV*> key.  Otherwise, holds the actual length of the key.  Can
be assigned to.  The C<HePV()> macro is usually preferable for finding key
lengths.

	STRLEN	HeKLEN(HE* he)

=for hackers
Found in file hv.h

=item HePV
X<HePV>

Returns the key slot of the hash entry as a C<char*> value, doing any
necessary dereferencing of possibly C<SV*> keys.  The length of the string
is placed in C<len> (this is a macro, so do I<not> use C<&len>).  If you do
not care about what the length of the key is, you may use the global
variable C<PL_na>, though this is rather less efficient than using a local
variable.  Remember though, that hash keys in perl are free to contain
embedded nulls, so using C<strlen()> or similar is not a good way to find
the length of hash keys.  This is very similar to the C<SvPV()> macro
described elsewhere in this document.  See also C<L</HeUTF8>>.

If you are using C<HePV> to get values to pass to C<newSVpvn()> to create a
new SV, you should consider using C<newSVhek(HeKEY_hek(he))> as it is more
efficient.

	char*	HePV(HE* he, STRLEN len)

=for hackers
Found in file hv.h

=item HeSVKEY
X<HeSVKEY>

Returns the key as an C<SV*>, or C<NULL> if the hash entry does not
contain an C<SV*> key.

	SV*	HeSVKEY(HE* he)

=for hackers
Found in file hv.h

=item HeSVKEY_force
X<HeSVKEY_force>

Returns the key as an C<SV*>.  Will create and return a temporary mortal
C<SV*> if the hash entry contains only a C<char*> key.

	SV*	HeSVKEY_force(HE* he)

=for hackers
Found in file hv.h

=item HeSVKEY_set
X<HeSVKEY_set>

Sets the key to a given C<SV*>, taking care to set the appropriate flags to
indicate the presence of an C<SV*> key, and returns the same
C<SV*>.

	SV*	HeSVKEY_set(HE* he, SV* sv)

=for hackers
Found in file hv.h

=item HeUTF8
X<HeUTF8>

Returns whether the C<char *> value returned by C<HePV> is encoded in UTF-8,
doing any necessary dereferencing of possibly C<SV*> keys.  The value returned
will be 0 or non-0, not necessarily 1 (or even a value with any low bits set),
so B<do not> blindly assign this to a C<bool> variable, as C<bool> may be a
typedef for C<char>.

	U32	HeUTF8(HE* he)

=for hackers
Found in file hv.h

=item HeVAL
X<HeVAL>

Returns the value slot (type C<SV*>)
stored in the hash entry.  Can be assigned
to.

  SV *foo= HeVAL(hv);
  HeVAL(hv)= sv;


	SV*	HeVAL(HE* he)

=for hackers
Found in file hv.h

=item hv_assert
X<hv_assert>

Check that a hash is in an internally consistent state.

NOTE: this function must be explicitly called as Perl_hv_assert with an aTHX_ parameter.

	void	Perl_hv_assert(pTHX_ HV *hv)

=for hackers
Found in file hv.c

=item hv_bucket_ratio
X<hv_bucket_ratio>


NOTE: this function is experimental and may change or be
removed without notice.


If the hash is tied dispatches through to the SCALAR tied method,
otherwise if the hash contains no keys returns 0, otherwise returns
a mortal sv containing a string specifying the number of used buckets,
followed by a slash, followed by the number of available buckets.

This function is expensive, it must scan all of the buckets
to determine which are used, and the count is NOT cached.
In a large hash this could be a lot of buckets.

	SV*	hv_bucket_ratio(HV *hv)

=for hackers
Found in file hv.c

=item hv_clear
X<hv_clear>

Frees the all the elements of a hash, leaving it empty.
The XS equivalent of C<%hash = ()>.  See also L</hv_undef>.

See L</av_clear> for a note about the hash possibly being invalid on
return.

	void	hv_clear(HV *hv)

=for hackers
Found in file hv.c

=item hv_clear_placeholders
X<hv_clear_placeholders>

Clears any placeholders from a hash.  If a restricted hash has any of its keys
marked as readonly and the key is subsequently deleted, the key is not actually
deleted but is marked by assigning it a value of C<&PL_sv_placeholder>.  This tags
it so it will be ignored by future operations such as iterating over the hash,
but will still allow the hash to have a value reassigned to the key at some
future point.  This function clears any such placeholder keys from the hash.
See C<L<Hash::Util::lock_keys()|Hash::Util/lock_keys>> for an example of its
use.

	void	hv_clear_placeholders(HV *hv)

=for hackers
Found in file hv.c

=item hv_copy_hints_hv
X<hv_copy_hints_hv>

A specialised version of L</newHVhv> for copying C<%^H>.  C<ohv> must be
a pointer to a hash (which may have C<%^H> magic, but should be generally
non-magical), or C<NULL> (interpreted as an empty hash).  The content
of C<ohv> is copied to a new hash, which has the C<%^H>-specific magic
added to it.  A pointer to the new hash is returned.

	HV *	hv_copy_hints_hv(HV *const ohv)

=for hackers
Found in file hv.c

=item hv_delete
X<hv_delete>

Deletes a key/value pair in the hash.  The value's SV is removed from
the hash, made mortal, and returned to the caller.  The absolute
value of C<klen> is the length of the key.  If C<klen> is negative the
key is assumed to be in UTF-8-encoded Unicode.  The C<flags> value
will normally be zero; if set to C<G_DISCARD> then C<NULL> will be returned.
C<NULL> will also be returned if the key is not found.

	SV*	hv_delete(HV *hv, const char *key, I32 klen,
		          I32 flags)

=for hackers
Found in file hv.c

=item hv_delete_ent
X<hv_delete_ent>

Deletes a key/value pair in the hash.  The value SV is removed from the hash,
made mortal, and returned to the caller.  The C<flags> value will normally be
zero; if set to C<G_DISCARD> then C<NULL> will be returned.  C<NULL> will also
be returned if the key is not found.  C<hash> can be a valid precomputed hash
value, or 0 to ask for it to be computed.

	SV*	hv_delete_ent(HV *hv, SV *keysv, I32 flags,
		              U32 hash)

=for hackers
Found in file hv.c

=item HvENAME
X<HvENAME>

Returns the effective name of a stash, or NULL if there is none.  The
effective name represents a location in the symbol table where this stash
resides.  It is updated automatically when packages are aliased or deleted.
A stash that is no longer in the symbol table has no effective name.  This
name is preferable to C<HvNAME> for use in MRO linearisations and isa
caches.

	char*	HvENAME(HV* stash)

=for hackers
Found in file hv.h

=item HvENAMELEN
X<HvENAMELEN>

Returns the length of the stash's effective name.

	STRLEN	HvENAMELEN(HV *stash)

=for hackers
Found in file hv.h

=item HvENAMEUTF8
X<HvENAMEUTF8>

Returns true if the effective name is in UTF-8 encoding.

	unsigned char HvENAMEUTF8(HV *stash)

=for hackers
Found in file hv.h

=item hv_exists
X<hv_exists>

Returns a boolean indicating whether the specified hash key exists.  The
absolute value of C<klen> is the length of the key.  If C<klen> is
negative the key is assumed to be in UTF-8-encoded Unicode.

	bool	hv_exists(HV *hv, const char *key, I32 klen)

=for hackers
Found in file hv.c

=item hv_exists_ent
X<hv_exists_ent>

Returns a boolean indicating whether
the specified hash key exists.  C<hash>
can be a valid precomputed hash value, or 0 to ask for it to be
computed.

	bool	hv_exists_ent(HV *hv, SV *keysv, U32 hash)

=for hackers
Found in file hv.c

=item hv_fetch
X<hv_fetch>

Returns the SV which corresponds to the specified key in the hash.
The absolute value of C<klen> is the length of the key.  If C<klen> is
negative the key is assumed to be in UTF-8-encoded Unicode.  If
C<lval> is set then the fetch will be part of a store.  This means that if
there is no value in the hash associated with the given key, then one is
created and a pointer to it is returned.  The C<SV*> it points to can be
assigned to.  But always check that the
return value is non-null before dereferencing it to an C<SV*>.

See L<perlguts/"Understanding the Magic of Tied Hashes and Arrays"> for more
information on how to use this function on tied hashes.

	SV**	hv_fetch(HV *hv, const char *key, I32 klen,
		         I32 lval)

=for hackers
Found in file hv.c

=item hv_fetchs
X<hv_fetchs>

Like C<hv_fetch>, but takes a literal string instead of a
string/length pair.

	SV**	hv_fetchs(HV* tb, "key", I32 lval)

=for hackers
Found in file handy.h

=item hv_fetch_ent
X<hv_fetch_ent>

Returns the hash entry which corresponds to the specified key in the hash.
C<hash> must be a valid precomputed hash number for the given C<key>, or 0
if you want the function to compute it.  IF C<lval> is set then the fetch
will be part of a store.  Make sure the return value is non-null before
accessing it.  The return value when C<hv> is a tied hash is a pointer to a
static location, so be sure to make a copy of the structure if you need to
store it somewhere.

See L<perlguts/"Understanding the Magic of Tied Hashes and Arrays"> for more
information on how to use this function on tied hashes.

	HE*	hv_fetch_ent(HV *hv, SV *keysv, I32 lval,
		             U32 hash)

=for hackers
Found in file hv.c

=item HvFILL
X<HvFILL>

See L</hv_fill>.

	STRLEN	HvFILL(HV *const hv)

=for hackers
Found in file hv.h

=item hv_fill
X<hv_fill>

Returns the number of hash buckets that happen to be in use.

This function is wrapped by the macro C<HvFILL>.

As of perl 5.25 this function is used only for debugging
purposes, and the number of used hash buckets is not
in any way cached, thus this function can be costly
to execute as it must iterate over all the buckets in the
hash.

NOTE: this function must be explicitly called as Perl_hv_fill with an aTHX_ parameter.

	STRLEN	Perl_hv_fill(pTHX_ HV *const hv)

=for hackers
Found in file hv.c

=item hv_iterinit
X<hv_iterinit>

Prepares a starting point to traverse a hash table.  Returns the number of
keys in the hash, including placeholders (i.e. the same as C<HvTOTALKEYS(hv)>).
The return value is currently only meaningful for hashes without tie magic.

NOTE: Before version 5.004_65, C<hv_iterinit> used to return the number of
hash buckets that happen to be in use.  If you still need that esoteric
value, you can get it through the macro C<HvFILL(hv)>.


	I32	hv_iterinit(HV *hv)

=for hackers
Found in file hv.c

=item hv_iterkey
X<hv_iterkey>

Returns the key from the current position of the hash iterator.  See
C<L</hv_iterinit>>.

	char*	hv_iterkey(HE* entry, I32* retlen)

=for hackers
Found in file hv.c

=item hv_iterkeysv
X<hv_iterkeysv>

Returns the key as an C<SV*> from the current position of the hash
iterator.  The return value will always be a mortal copy of the key.  Also
see C<L</hv_iterinit>>.

	SV*	hv_iterkeysv(HE* entry)

=for hackers
Found in file hv.c

=item hv_iternext
X<hv_iternext>

Returns entries from a hash iterator.  See C<L</hv_iterinit>>.

You may call C<hv_delete> or C<hv_delete_ent> on the hash entry that the
iterator currently points to, without losing your place or invalidating your
iterator.  Note that in this case the current entry is deleted from the hash
with your iterator holding the last reference to it.  Your iterator is flagged
to free the entry on the next call to C<hv_iternext>, so you must not discard
your iterator immediately else the entry will leak - call C<hv_iternext> to
trigger the resource deallocation.

	HE*	hv_iternext(HV *hv)

=for hackers
Found in file hv.c

=item hv_iternextsv
X<hv_iternextsv>

Performs an C<hv_iternext>, C<hv_iterkey>, and C<hv_iterval> in one
operation.

	SV*	hv_iternextsv(HV *hv, char **key, I32 *retlen)

=for hackers
Found in file hv.c

=item hv_iternext_flags
X<hv_iternext_flags>


NOTE: this function is experimental and may change or be
removed without notice.


Returns entries from a hash iterator.  See C<L</hv_iterinit>> and
C<L</hv_iternext>>.
The C<flags> value will normally be zero; if C<HV_ITERNEXT_WANTPLACEHOLDERS> is
set the placeholders keys (for restricted hashes) will be returned in addition
to normal keys.  By default placeholders are automatically skipped over.
Currently a placeholder is implemented with a value that is
C<&PL_sv_placeholder>.  Note that the implementation of placeholders and
restricted hashes may change, and the implementation currently is
insufficiently abstracted for any change to be tidy.

	HE*	hv_iternext_flags(HV *hv, I32 flags)

=for hackers
Found in file hv.c

=item hv_iterval
X<hv_iterval>

Returns the value from the current position of the hash iterator.  See
C<L</hv_iterkey>>.

	SV*	hv_iterval(HV *hv, HE *entry)

=for hackers
Found in file hv.c

=item hv_magic
X<hv_magic>

Adds magic to a hash.  See C<L</sv_magic>>.

	void	hv_magic(HV *hv, GV *gv, int how)

=for hackers
Found in file hv.c

=item HvNAME
X<HvNAME>

Returns the package name of a stash, or C<NULL> if C<stash> isn't a stash.
See C<L</SvSTASH>>, C<L</CvSTASH>>.

	char*	HvNAME(HV* stash)

=for hackers
Found in file hv.h

=item HvNAMELEN
X<HvNAMELEN>

Returns the length of the stash's name.

	STRLEN	HvNAMELEN(HV *stash)

=for hackers
Found in file hv.h

=item HvNAMEUTF8
X<HvNAMEUTF8>

Returns true if the name is in UTF-8 encoding.

	unsigned char HvNAMEUTF8(HV *stash)

=for hackers
Found in file hv.h

=item hv_scalar
X<hv_scalar>

Evaluates the hash in scalar context and returns the result.

When the hash is tied dispatches through to the SCALAR method,
otherwise returns a mortal SV containing the number of keys
in the hash.

Note, prior to 5.25 this function returned what is now
returned by the hv_bucket_ratio() function.

	SV*	hv_scalar(HV *hv)

=for hackers
Found in file hv.c

=item hv_store
X<hv_store>

Stores an SV in a hash.  The hash key is specified as C<key> and the
absolute value of C<klen> is the length of the key.  If C<klen> is
negative the key is assumed to be in UTF-8-encoded Unicode.  The
C<hash> parameter is the precomputed hash value; if it is zero then
Perl will compute it.

The return value will be
C<NULL> if the operation failed or if the value did not need to be actually
stored within the hash (as in the case of tied hashes).  Otherwise it can
be dereferenced to get the original C<SV*>.  Note that the caller is
responsible for suitably incrementing the reference count of C<val> before
the call, and decrementing it if the function returned C<NULL>.  Effectively
a successful C<hv_store> takes ownership of one reference to C<val>.  This is
usually what you want; a newly created SV has a reference count of one, so
if all your code does is create SVs then store them in a hash, C<hv_store>
will own the only reference to the new SV, and your code doesn't need to do
anything further to tidy up.  C<hv_store> is not implemented as a call to
C<hv_store_ent>, and does not create a temporary SV for the key, so if your
key data is not already in SV form then use C<hv_store> in preference to
C<hv_store_ent>.

See L<perlguts/"Understanding the Magic of Tied Hashes and Arrays"> for more
information on how to use this function on tied hashes.

	SV**	hv_store(HV *hv, const char *key, I32 klen,
		         SV *val, U32 hash)

=for hackers
Found in file hv.c

=item hv_stores
X<hv_stores>

Like C<hv_store>, but takes a literal string instead of a
string/length pair
and omits the hash parameter.

	SV**	hv_stores(HV* tb, "key", SV* val)

=for hackers
Found in file handy.h

=item hv_store_ent
X<hv_store_ent>

Stores C<val> in a hash.  The hash key is specified as C<key>.  The C<hash>
parameter is the precomputed hash value; if it is zero then Perl will
compute it.  The return value is the new hash entry so created.  It will be
C<NULL> if the operation failed or if the value did not need to be actually
stored within the hash (as in the case of tied hashes).  Otherwise the
contents of the return value can be accessed using the C<He?> macros
described here.  Note that the caller is responsible for suitably
incrementing the reference count of C<val> before the call, and
decrementing it if the function returned NULL.  Effectively a successful
C<hv_store_ent> takes ownership of one reference to C<val>.  This is
usually what you want; a newly created SV has a reference count of one, so
if all your code does is create SVs then store them in a hash, C<hv_store>
will own the only reference to the new SV, and your code doesn't need to do
anything further to tidy up.  Note that C<hv_store_ent> only reads the C<key>;
unlike C<val> it does not take ownership of it, so maintaining the correct
reference count on C<key> is entirely the caller's responsibility.  The reason
it does not take ownership, is that C<key> is not used after this function
returns, and so can be freed immediately.  C<hv_store>
is not implemented as a call to C<hv_store_ent>, and does not create a temporary
SV for the key, so if your key data is not already in SV form then use
C<hv_store> in preference to C<hv_store_ent>.

See L<perlguts/"Understanding the Magic of Tied Hashes and Arrays"> for more
information on how to use this function on tied hashes.

	HE*	hv_store_ent(HV *hv, SV *key, SV *val, U32 hash)

=for hackers
Found in file hv.c

=item hv_undef
X<hv_undef>

Undefines the hash.  The XS equivalent of C<undef(%hash)>.

As well as freeing all the elements of the hash (like C<hv_clear()>), this
also frees any auxiliary data and storage associated with the hash.

See L</av_clear> for a note about the hash possibly being invalid on
return.

	void	hv_undef(HV *hv)

=for hackers
Found in file hv.c

=item newHV
X<newHV>

Creates a new HV.  The reference count is set to 1.

	HV*	newHV()

=for hackers
Found in file hv.h


=back

=head1 Hook manipulation

These functions provide convenient and thread-safe means of manipulating
hook variables.


=over 8

=item wrap_op_checker
X<wrap_op_checker>

Puts a C function into the chain of check functions for a specified op
type.  This is the preferred way to manipulate the L</PL_check> array.
C<opcode> specifies which type of op is to be affected.  C<new_checker>
is a pointer to the C function that is to be added to that opcode's
check chain, and C<old_checker_p> points to the storage location where a
pointer to the next function in the chain will be stored.  The value of
C<new_checker> is written into the L</PL_check> array, while the value
previously stored there is written to C<*old_checker_p>.

L</PL_check> is global to an entire process, and a module wishing to
hook op checking may find itself invoked more than once per process,
typically in different threads.  To handle that situation, this function
is idempotent.  The location C<*old_checker_p> must initially (once
per process) contain a null pointer.  A C variable of static duration
(declared at file scope, typically also marked C<static> to give
it internal linkage) will be implicitly initialised appropriately,
if it does not have an explicit initialiser.  This function will only
actually modify the check chain if it finds C<*old_checker_p> to be null.
This function is also thread safe on the small scale.  It uses appropriate
locking to avoid race conditions in accessing L</PL_check>.

When this function is called, the function referenced by C<new_checker>
must be ready to be called, except for C<*old_checker_p> being unfilled.
In a threading situation, C<new_checker> may be called immediately,
even before this function has returned.  C<*old_checker_p> will always
be appropriately set before C<new_checker> is called.  If C<new_checker>
decides not to do anything special with an op that it is given (which
is the usual case for most uses of op check hooking), it must chain the
check function referenced by C<*old_checker_p>.

Taken all together, XS code to hook an op checker should typically look
something like this:

    static Perl_check_t nxck_frob;
    static OP *myck_frob(pTHX_ OP *op) {
	...
	op = nxck_frob(aTHX_ op);
	...
	return op;
    }
    BOOT:
	wrap_op_checker(OP_FROB, myck_frob, &nxck_frob);

If you want to influence compilation of calls to a specific subroutine,
then use L</cv_set_call_checker_flags> rather than hooking checking of
all C<entersub> ops.

	void	wrap_op_checker(Optype opcode,
		                Perl_check_t new_checker,
		                Perl_check_t *old_checker_p)

=for hackers
Found in file op.c


=back

=head1 Lexer interface

This is the lower layer of the Perl parser, managing characters and tokens.


=over 8

=item lex_bufutf8
X<lex_bufutf8>


NOTE: this function is experimental and may change or be
removed without notice.


Indicates whether the octets in the lexer buffer
(L</PL_parser-E<gt>linestr>) should be interpreted as the UTF-8 encoding
of Unicode characters.  If not, they should be interpreted as Latin-1
characters.  This is analogous to the C<SvUTF8> flag for scalars.

In UTF-8 mode, it is not guaranteed that the lexer buffer actually
contains valid UTF-8.  Lexing code must be robust in the face of invalid
encoding.

The actual C<SvUTF8> flag of the L</PL_parser-E<gt>linestr> scalar
is significant, but not the whole story regarding the input character
encoding.  Normally, when a file is being read, the scalar contains octets
and its C<SvUTF8> flag is off, but the octets should be interpreted as
UTF-8 if the C<use utf8> pragma is in effect.  During a string eval,
however, the scalar may have the C<SvUTF8> flag on, and in this case its
octets should be interpreted as UTF-8 unless the C<use bytes> pragma
is in effect.  This logic may change in the future; use this function
instead of implementing the logic yourself.

	bool	lex_bufutf8()

=for hackers
Found in file toke.c

=item lex_discard_to
X<lex_discard_to>


NOTE: this function is experimental and may change or be
removed without notice.


Discards the first part of the L</PL_parser-E<gt>linestr> buffer,
up to C<ptr>.  The remaining content of the buffer will be moved, and
all pointers into the buffer updated appropriately.  C<ptr> must not
be later in the buffer than the position of L</PL_parser-E<gt>bufptr>:
it is not permitted to discard text that has yet to be lexed.

Normally it is not necessarily to do this directly, because it suffices to
use the implicit discarding behaviour of L</lex_next_chunk> and things
based on it.  However, if a token stretches across multiple lines,
and the lexing code has kept multiple lines of text in the buffer for
that purpose, then after completion of the token it would be wise to
explicitly discard the now-unneeded earlier lines, to avoid future
multi-line tokens growing the buffer without bound.

	void	lex_discard_to(char* ptr)

=for hackers
Found in file toke.c

=item lex_grow_linestr
X<lex_grow_linestr>


NOTE: this function is experimental and may change or be
removed without notice.


Reallocates the lexer buffer (L</PL_parser-E<gt>linestr>) to accommodate
at least C<len> octets (including terminating C<NUL>).  Returns a
pointer to the reallocated buffer.  This is necessary before making
any direct modification of the buffer that would increase its length.
L</lex_stuff_pvn> provides a more convenient way to insert text into
the buffer.

Do not use C<SvGROW> or C<sv_grow> directly on C<PL_parser-E<gt>linestr>;
this function updates all of the lexer's variables that point directly
into the buffer.

	char*	lex_grow_linestr(STRLEN len)

=for hackers
Found in file toke.c

=item lex_next_chunk
X<lex_next_chunk>


NOTE: this function is experimental and may change or be
removed without notice.


Reads in the next chunk of text to be lexed, appending it to
L</PL_parser-E<gt>linestr>.  This should be called when lexing code has
looked to the end of the current chunk and wants to know more.  It is
usual, but not necessary, for lexing to have consumed the entirety of
the current chunk at this time.

If L</PL_parser-E<gt>bufptr> is pointing to the very end of the current
chunk (i.e., the current chunk has been entirely consumed), normally the
current chunk will be discarded at the same time that the new chunk is
read in.  If C<flags> has the C<LEX_KEEP_PREVIOUS> bit set, the current chunk
will not be discarded.  If the current chunk has not been entirely
consumed, then it will not be discarded regardless of the flag.

Returns true if some new text was added to the buffer, or false if the
buffer has reached the end of the input text.

	bool	lex_next_chunk(U32 flags)

=for hackers
Found in file toke.c

=item lex_peek_unichar
X<lex_peek_unichar>


NOTE: this function is experimental and may change or be
removed without notice.


Looks ahead one (Unicode) character in the text currently being lexed.
Returns the codepoint (unsigned integer value) of the next character,
or -1 if lexing has reached the end of the input text.  To consume the
peeked character, use L</lex_read_unichar>.

If the next character is in (or extends into) the next chunk of input
text, the next chunk will be read in.  Normally the current chunk will be
discarded at the same time, but if C<flags> has the C<LEX_KEEP_PREVIOUS>
bit set, then the current chunk will not be discarded.

If the input is being interpreted as UTF-8 and a UTF-8 encoding error
is encountered, an exception is generated.

	I32	lex_peek_unichar(U32 flags)

=for hackers
Found in file toke.c

=item lex_read_space
X<lex_read_space>


NOTE: this function is experimental and may change or be
removed without notice.


Reads optional spaces, in Perl style, in the text currently being
lexed.  The spaces may include ordinary whitespace characters and
Perl-style comments.  C<#line> directives are processed if encountered.
L</PL_parser-E<gt>bufptr> is moved past the spaces, so that it points
at a non-space character (or the end of the input text).

If spaces extend into the next chunk of input text, the next chunk will
be read in.  Normally the current chunk will be discarded at the same
time, but if C<flags> has the C<LEX_KEEP_PREVIOUS> bit set, then the current
chunk will not be discarded.

	void	lex_read_space(U32 flags)

=for hackers
Found in file toke.c

=item lex_read_to
X<lex_read_to>


NOTE: this function is experimental and may change or be
removed without notice.


Consume text in the lexer buffer, from L</PL_parser-E<gt>bufptr> up
to C<ptr>.  This advances L</PL_parser-E<gt>bufptr> to match C<ptr>,
performing the correct bookkeeping whenever a newline character is passed.
This is the normal way to consume lexed text.

Interpretation of the buffer's octets can be abstracted out by
using the slightly higher-level functions L</lex_peek_unichar> and
L</lex_read_unichar>.

	void	lex_read_to(char* ptr)

=for hackers
Found in file toke.c

=item lex_read_unichar
X<lex_read_unichar>


NOTE: this function is experimental and may change or be
removed without notice.


Reads the next (Unicode) character in the text currently being lexed.
Returns the codepoint (unsigned integer value) of the character read,
and moves L</PL_parser-E<gt>bufptr> past the character, or returns -1
if lexing has reached the end of the input text.  To non-destructively
examine the next character, use L</lex_peek_unichar> instead.

If the next character is in (or extends into) the next chunk of input
text, the next chunk will be read in.  Normally the current chunk will be
discarded at the same time, but if C<flags> has the C<LEX_KEEP_PREVIOUS>
bit set, then the current chunk will not be discarded.

If the input is being interpreted as UTF-8 and a UTF-8 encoding error
is encountered, an exception is generated.

	I32	lex_read_unichar(U32 flags)

=for hackers
Found in file toke.c

=item lex_start
X<lex_start>


NOTE: this function is experimental and may change or be
removed without notice.


Creates and initialises a new lexer/parser state object, supplying
a context in which to lex and parse from a new source of Perl code.
A pointer to the new state object is placed in L</PL_parser>.  An entry
is made on the save stack so that upon unwinding, the new state object
will be destroyed and the former value of L</PL_parser> will be restored.
Nothing else need be done to clean up the parsing context.

The code to be parsed comes from C<line> and C<rsfp>.  C<line>, if
non-null, provides a string (in SV form) containing code to be parsed.
A copy of the string is made, so subsequent modification of C<line>
does not affect parsing.  C<rsfp>, if non-null, provides an input stream
from which code will be read to be parsed.  If both are non-null, the
code in C<line> comes first and must consist of complete lines of input,
and C<rsfp> supplies the remainder of the source.

The C<flags> parameter is reserved for future use.  Currently it is only
used by perl internally, so extensions should always pass zero.

	void	lex_start(SV* line, PerlIO *rsfp, U32 flags)

=for hackers
Found in file toke.c

=item lex_stuff_pv
X<lex_stuff_pv>


NOTE: this function is experimental and may change or be
removed without notice.


Insert characters into the lexer buffer (L</PL_parser-E<gt>linestr>),
immediately after the current lexing point (L</PL_parser-E<gt>bufptr>),
reallocating the buffer if necessary.  This means that lexing code that
runs later will see the characters as if they had appeared in the input.
It is not recommended to do this as part of normal parsing, and most
uses of this facility run the risk of the inserted characters being
interpreted in an unintended manner.

The string to be inserted is represented by octets starting at C<pv>
and continuing to the first nul.  These octets are interpreted as either
UTF-8 or Latin-1, according to whether the C<LEX_STUFF_UTF8> flag is set
in C<flags>.  The characters are recoded for the lexer buffer, according
to how the buffer is currently being interpreted (L</lex_bufutf8>).
If it is not convenient to nul-terminate a string to be inserted, the
L</lex_stuff_pvn> function is more appropriate.

	void	lex_stuff_pv(const char* pv, U32 flags)

=for hackers
Found in file toke.c

=item lex_stuff_pvn
X<lex_stuff_pvn>


NOTE: this function is experimental and may change or be
removed without notice.


Insert characters into the lexer buffer (L</PL_parser-E<gt>linestr>),
immediately after the current lexing point (L</PL_parser-E<gt>bufptr>),
reallocating the buffer if necessary.  This means that lexing code that
runs later will see the characters as if they had appeared in the input.
It is not recommended to do this as part of normal parsing, and most
uses of this facility run the risk of the inserted characters being
interpreted in an unintended manner.

The string to be inserted is represented by C<len> octets starting
at C<pv>.  These octets are interpreted as either UTF-8 or Latin-1,
according to whether the C<LEX_STUFF_UTF8> flag is set in C<flags>.
The characters are recoded for the lexer buffer, according to how the
buffer is currently being interpreted (L</lex_bufutf8>).  If a string
to be inserted is available as a Perl scalar, the L</lex_stuff_sv>
function is more convenient.

	void	lex_stuff_pvn(const char* pv, STRLEN len,
		              U32 flags)

=for hackers
Found in file toke.c

=item lex_stuff_pvs
X<lex_stuff_pvs>


NOTE: this function is experimental and may change or be
removed without notice.


Like L</lex_stuff_pvn>, but takes a literal string instead of
a string/length pair.

	void	lex_stuff_pvs("pv", U32 flags)

=for hackers
Found in file handy.h

=item lex_stuff_sv
X<lex_stuff_sv>


NOTE: this function is experimental and may change or be
removed without notice.


Insert characters into the lexer buffer (L</PL_parser-E<gt>linestr>),
immediately after the current lexing point (L</PL_parser-E<gt>bufptr>),
reallocating the buffer if necessary.  This means that lexing code that
runs later will see the characters as if they had appeared in the input.
It is not recommended to do this as part of normal parsing, and most
uses of this facility run the risk of the inserted characters being
interpreted in an unintended manner.

The string to be inserted is the string value of C<sv>.  The characters
are recoded for the lexer buffer, according to how the buffer is currently
being interpreted (L</lex_bufutf8>).  If a string to be inserted is
not already a Perl scalar, the L</lex_stuff_pvn> function avoids the
need to construct a scalar.

	void	lex_stuff_sv(SV* sv, U32 flags)

=for hackers
Found in file toke.c

=item lex_unstuff
X<lex_unstuff>


NOTE: this function is experimental and may change or be
removed without notice.


Discards text about to be lexed, from L</PL_parser-E<gt>bufptr> up to
C<ptr>.  Text following C<ptr> will be moved, and the buffer shortened.
This hides the discarded text from any lexing code that runs later,
as if the text had never appeared.

This is not the normal way to consume lexed text.  For that, use
L</lex_read_to>.

	void	lex_unstuff(char* ptr)

=for hackers
Found in file toke.c

=item parse_arithexpr
X<parse_arithexpr>


NOTE: this function is experimental and may change or be
removed without notice.


Parse a Perl arithmetic expression.  This may contain operators of precedence
down to the bit shift operators.  The expression must be followed (and thus
terminated) either by a comparison or lower-precedence operator or by
something that would normally terminate an expression such as semicolon.
If C<flags> has the C<PARSE_OPTIONAL> bit set, then the expression is optional,
otherwise it is mandatory.  It is up to the caller to ensure that the
dynamic parser state (L</PL_parser> et al) is correctly set to reflect
the source of the code to be parsed and the lexical context for the
expression.

The op tree representing the expression is returned.  If an optional
expression is absent, a null pointer is returned, otherwise the pointer
will be non-null.

If an error occurs in parsing or compilation, in most cases a valid op
tree is returned anyway.  The error is reflected in the parser state,
normally resulting in a single exception at the top level of parsing
which covers all the compilation errors that occurred.  Some compilation
errors, however, will throw an exception immediately.

	OP*	parse_arithexpr(U32 flags)

=for hackers
Found in file toke.c

=item parse_barestmt
X<parse_barestmt>


NOTE: this function is experimental and may change or be
removed without notice.


Parse a single unadorned Perl statement.  This may be a normal imperative
statement or a declaration that has compile-time effect.  It does not
include any label or other affixture.  It is up to the caller to ensure
that the dynamic parser state (L</PL_parser> et al) is correctly set to
reflect the source of the code to be parsed and the lexical context for
the statement.

The op tree representing the statement is returned.  This may be a
null pointer if the statement is null, for example if it was actually
a subroutine definition (which has compile-time side effects).  If not
null, it will be ops directly implementing the statement, suitable to
pass to L</newSTATEOP>.  It will not normally include a C<nextstate> or
equivalent op (except for those embedded in a scope contained entirely
within the statement).

If an error occurs in parsing or compilation, in most cases a valid op
tree (most likely null) is returned anyway.  The error is reflected in
the parser state, normally resulting in a single exception at the top
level of parsing which covers all the compilation errors that occurred.
Some compilation errors, however, will throw an exception immediately.

The C<flags> parameter is reserved for future use, and must always
be zero.

	OP*	parse_barestmt(U32 flags)

=for hackers
Found in file toke.c

=item parse_block
X<parse_block>


NOTE: this function is experimental and may change or be
removed without notice.


Parse a single complete Perl code block.  This consists of an opening
brace, a sequence of statements, and a closing brace.  The block
constitutes a lexical scope, so C<my> variables and various compile-time
effects can be contained within it.  It is up to the caller to ensure
that the dynamic parser state (L</PL_parser> et al) is correctly set to
reflect the source of the code to be parsed and the lexical context for
the statement.

The op tree representing the code block is returned.  This is always a
real op, never a null pointer.  It will normally be a C<lineseq> list,
including C<nextstate> or equivalent ops.  No ops to construct any kind
of runtime scope are included by virtue of it being a block.

If an error occurs in parsing or compilation, in most cases a valid op
tree (most likely null) is returned anyway.  The error is reflected in
the parser state, normally resulting in a single exception at the top
level of parsing which covers all the compilation errors that occurred.
Some compilation errors, however, will throw an exception immediately.

The C<flags> parameter is reserved for future use, and must always
be zero.

	OP*	parse_block(U32 flags)

=for hackers
Found in file toke.c

=item parse_fullexpr
X<parse_fullexpr>


NOTE: this function is experimental and may change or be
removed without notice.


Parse a single complete Perl expression.  This allows the full
expression grammar, including the lowest-precedence operators such
as C<or>.  The expression must be followed (and thus terminated) by a
token that an expression would normally be terminated by: end-of-file,
closing bracketing punctuation, semicolon, or one of the keywords that
signals a postfix expression-statement modifier.  If C<flags> has the
C<PARSE_OPTIONAL> bit set, then the expression is optional, otherwise it is
mandatory.  It is up to the caller to ensure that the dynamic parser
state (L</PL_parser> et al) is correctly set to reflect the source of
the code to be parsed and the lexical context for the expression.

The op tree representing the expression is returned.  If an optional
expression is absent, a null pointer is returned, otherwise the pointer
will be non-null.

If an error occurs in parsing or compilation, in most cases a valid op
tree is returned anyway.  The error is reflected in the parser state,
normally resulting in a single exception at the top level of parsing
which covers all the compilation errors that occurred.  Some compilation
errors, however, will throw an exception immediately.

	OP*	parse_fullexpr(U32 flags)

=for hackers
Found in file toke.c

=item parse_fullstmt
X<parse_fullstmt>


NOTE: this function is experimental and may change or be
removed without notice.


Parse a single complete Perl statement.  This may be a normal imperative
statement or a declaration that has compile-time effect, and may include
optional labels.  It is up to the caller to ensure that the dynamic
parser state (L</PL_parser> et al) is correctly set to reflect the source
of the code to be parsed and the lexical context for the statement.

The op tree representing the statement is returned.  This may be a
null pointer if the statement is null, for example if it was actually
a subroutine definition (which has compile-time side effects).  If not
null, it will be the result of a L</newSTATEOP> call, normally including
a C<nextstate> or equivalent op.

If an error occurs in parsing or compilation, in most cases a valid op
tree (most likely null) is returned anyway.  The error is reflected in
the parser state, normally resulting in a single exception at the top
level of parsing which covers all the compilation errors that occurred.
Some compilation errors, however, will throw an exception immediately.

The C<flags> parameter is reserved for future use, and must always
be zero.

	OP*	parse_fullstmt(U32 flags)

=for hackers
Found in file toke.c

=item parse_label
X<parse_label>


NOTE: this function is experimental and may change or be
removed without notice.


Parse a single label, possibly optional, of the type that may prefix a
Perl statement.  It is up to the caller to ensure that the dynamic parser
state (L</PL_parser> et al) is correctly set to reflect the source of
the code to be parsed.  If C<flags> has the C<PARSE_OPTIONAL> bit set, then the
label is optional, otherwise it is mandatory.

The name of the label is returned in the form of a fresh scalar.  If an
optional label is absent, a null pointer is returned.

If an error occurs in parsing, which can only occur if the label is
mandatory, a valid label is returned anyway.  The error is reflected in
the parser state, normally resulting in a single exception at the top
level of parsing which covers all the compilation errors that occurred.

	SV*	parse_label(U32 flags)

=for hackers
Found in file toke.c

=item parse_listexpr
X<parse_listexpr>


NOTE: this function is experimental and may change or be
removed without notice.


Parse a Perl list expression.  This may contain operators of precedence
down to the comma operator.  The expression must be followed (and thus
terminated) either by a low-precedence logic operator such as C<or> or by
something that would normally terminate an expression such as semicolon.
If C<flags> has the C<PARSE_OPTIONAL> bit set, then the expression is optional,
otherwise it is mandatory.  It is up to the caller to ensure that the
dynamic parser state (L</PL_parser> et al) is correctly set to reflect
the source of the code to be parsed and the lexical context for the
expression.

The op tree representing the expression is returned.  If an optional
expression is absent, a null pointer is returned, otherwise the pointer
will be non-null.

If an error occurs in parsing or compilation, in most cases a valid op
tree is returned anyway.  The error is reflected in the parser state,
normally resulting in a single exception at the top level of parsing
which covers all the compilation errors that occurred.  Some compilation
errors, however, will throw an exception immediately.

	OP*	parse_listexpr(U32 flags)

=for hackers
Found in file toke.c

=item parse_stmtseq
X<parse_stmtseq>


NOTE: this function is experimental and may change or be
removed without notice.


Parse a sequence of zero or more Perl statements.  These may be normal
imperative statements, including optional labels, or declarations
that have compile-time effect, or any mixture thereof.  The statement
sequence ends when a closing brace or end-of-file is encountered in a
place where a new statement could have validly started.  It is up to
the caller to ensure that the dynamic parser state (L</PL_parser> et al)
is correctly set to reflect the source of the code to be parsed and the
lexical context for the statements.

The op tree representing the statement sequence is returned.  This may
be a null pointer if the statements were all null, for example if there
were no statements or if there were only subroutine definitions (which
have compile-time side effects).  If not null, it will be a C<lineseq>
list, normally including C<nextstate> or equivalent ops.

If an error occurs in parsing or compilation, in most cases a valid op
tree is returned anyway.  The error is reflected in the parser state,
normally resulting in a single exception at the top level of parsing
which covers all the compilation errors that occurred.  Some compilation
errors, however, will throw an exception immediately.

The C<flags> parameter is reserved for future use, and must always
be zero.

	OP*	parse_stmtseq(U32 flags)

=for hackers
Found in file toke.c

=item parse_subsignature
X<parse_subsignature>


NOTE: this function is experimental and may change or be
removed without notice.


Parse a subroutine signature declaration. This is the contents of the
parentheses following a named or anonymous subroutine declaration when the
C<signatures> feature is enabled. Note that this function neither expects
nor consumes the opening and closing parentheses around the signature; it
is the caller's job to handle these.

This function must only be called during parsing of a subroutine; after
L</start_subparse> has been called. It might allocate lexical variables on
the pad for the current subroutine.

The op tree to unpack the arguments from the stack at runtime is returned.
This op tree should appear at the beginning of the compiled function. The
caller may wish to use L</op_append_list> to build their function body
after it, or splice it together with the body before calling L</newATTRSUB>.

The C<flags> parameter is reserved for future use, and must always
be zero.

	OP*	parse_subsignature(U32 flags)

=for hackers
Found in file toke.c

=item parse_termexpr
X<parse_termexpr>


NOTE: this function is experimental and may change or be
removed without notice.


Parse a Perl term expression.  This may contain operators of precedence
down to the assignment operators.  The expression must be followed (and thus
terminated) either by a comma or lower-precedence operator or by
something that would normally terminate an expression such as semicolon.
If C<flags> has the C<PARSE_OPTIONAL> bit set, then the expression is optional,
otherwise it is mandatory.  It is up to the caller to ensure that the
dynamic parser state (L</PL_parser> et al) is correctly set to reflect
the source of the code to be parsed and the lexical context for the
expression.

The op tree representing the expression is returned.  If an optional
expression is absent, a null pointer is returned, otherwise the pointer
will be non-null.

If an error occurs in parsing or compilation, in most cases a valid op
tree is returned anyway.  The error is reflected in the parser state,
normally resulting in a single exception at the top level of parsing
which covers all the compilation errors that occurred.  Some compilation
errors, however, will throw an exception immediately.

	OP*	parse_termexpr(U32 flags)

=for hackers
Found in file toke.c

=item PL_parser
X<PL_parser>

Pointer to a structure encapsulating the state of the parsing operation
currently in progress.  The pointer can be locally changed to perform
a nested parse without interfering with the state of an outer parse.
Individual members of C<PL_parser> have their own documentation.

=for hackers
Found in file toke.c

=item PL_parser-E<gt>bufend
X<PL_parser-E<gt>bufend>


NOTE: this function is experimental and may change or be
removed without notice.


Direct pointer to the end of the chunk of text currently being lexed, the
end of the lexer buffer.  This is equal to C<SvPVX(PL_parser-E<gt>linestr)
+ SvCUR(PL_parser-E<gt>linestr)>.  A C<NUL> character (zero octet) is
always located at the end of the buffer, and does not count as part of
the buffer's contents.

=for hackers
Found in file toke.c

=item PL_parser-E<gt>bufptr
X<PL_parser-E<gt>bufptr>


NOTE: this function is experimental and may change or be
removed without notice.


Points to the current position of lexing inside the lexer buffer.
Characters around this point may be freely examined, within
the range delimited by C<SvPVX(L</PL_parser-E<gt>linestr>)> and
L</PL_parser-E<gt>bufend>.  The octets of the buffer may be intended to be
interpreted as either UTF-8 or Latin-1, as indicated by L</lex_bufutf8>.

Lexing code (whether in the Perl core or not) moves this pointer past
the characters that it consumes.  It is also expected to perform some
bookkeeping whenever a newline character is consumed.  This movement
can be more conveniently performed by the function L</lex_read_to>,
which handles newlines appropriately.

Interpretation of the buffer's octets can be abstracted out by
using the slightly higher-level functions L</lex_peek_unichar> and
L</lex_read_unichar>.

=for hackers
Found in file toke.c

=item PL_parser-E<gt>linestart
X<PL_parser-E<gt>linestart>


NOTE: this function is experimental and may change or be
removed without notice.


Points to the start of the current line inside the lexer buffer.
This is useful for indicating at which column an error occurred, and
not much else.  This must be updated by any lexing code that consumes
a newline; the function L</lex_read_to> handles this detail.

=for hackers
Found in file toke.c

=item PL_parser-E<gt>linestr
X<PL_parser-E<gt>linestr>


NOTE: this function is experimental and may change or be
removed without notice.


Buffer scalar containing the chunk currently under consideration of the
text currently being lexed.  This is always a plain string scalar (for
which C<SvPOK> is true).  It is not intended to be used as a scalar by
normal scalar means; instead refer to the buffer directly by the pointer
variables described below.

The lexer maintains various C<char*> pointers to things in the
C<PL_parser-E<gt>linestr> buffer.  If C<PL_parser-E<gt>linestr> is ever
reallocated, all of these pointers must be updated.  Don't attempt to
do this manually, but rather use L</lex_grow_linestr> if you need to
reallocate the buffer.

The content of the text chunk in the buffer is commonly exactly one
complete line of input, up to and including a newline terminator,
but there are situations where it is otherwise.  The octets of the
buffer may be intended to be interpreted as either UTF-8 or Latin-1.
The function L</lex_bufutf8> tells you which.  Do not use the C<SvUTF8>
flag on this scalar, which may disagree with it.

For direct examination of the buffer, the variable
L</PL_parser-E<gt>bufend> points to the end of the buffer.  The current
lexing position is pointed to by L</PL_parser-E<gt>bufptr>.  Direct use
of these pointers is usually preferable to examination of the scalar
through normal scalar means.

=for hackers
Found in file toke.c

=item wrap_keyword_plugin
X<wrap_keyword_plugin>


NOTE: this function is experimental and may change or be
removed without notice.


Puts a C function into the chain of keyword plugins.  This is the
preferred way to manipulate the L</PL_keyword_plugin> variable.
C<new_plugin> is a pointer to the C function that is to be added to the
keyword plugin chain, and C<old_plugin_p> points to the storage location
where a pointer to the next function in the chain will be stored.  The
value of C<new_plugin> is written into the L</PL_keyword_plugin> variable,
while the value previously stored there is written to C<*old_plugin_p>.

L</PL_keyword_plugin> is global to an entire process, and a module wishing
to hook keyword parsing may find itself invoked more than once per
process, typically in different threads.  To handle that situation, this
function is idempotent.  The location C<*old_plugin_p> must initially
(once per process) contain a null pointer.  A C variable of static
duration (declared at file scope, typically also marked C<static> to give
it internal linkage) will be implicitly initialised appropriately, if it
does not have an explicit initialiser.  This function will only actually
modify the plugin chain if it finds C<*old_plugin_p> to be null.  This
function is also thread safe on the small scale.  It uses appropriate
locking to avoid race conditions in accessing L</PL_keyword_plugin>.

When this function is called, the function referenced by C<new_plugin>
must be ready to be called, except for C<*old_plugin_p> being unfilled.
In a threading situation, C<new_plugin> may be called immediately, even
before this function has returned.  C<*old_plugin_p> will always be
appropriately set before C<new_plugin> is called.  If C<new_plugin>
decides not to do anything special with the identifier that it is given
(which is the usual case for most calls to a keyword plugin), it must
chain the plugin function referenced by C<*old_plugin_p>.

Taken all together, XS code to install a keyword plugin should typically
look something like this:

    static Perl_keyword_plugin_t next_keyword_plugin;
    static OP *my_keyword_plugin(pTHX_
        char *keyword_ptr, STRLEN keyword_len, OP **op_ptr)
    {
        if (memEQs(keyword_ptr, keyword_len,
                   "my_new_keyword")) {
            ...
        } else {
            return next_keyword_plugin(aTHX_
                keyword_ptr, keyword_len, op_ptr);
        }
    }
    BOOT:
        wrap_keyword_plugin(my_keyword_plugin,
                            &next_keyword_plugin);

Direct access to L</PL_keyword_plugin> should be avoided.

	void	wrap_keyword_plugin(
		    Perl_keyword_plugin_t new_plugin,
		    Perl_keyword_plugin_t *old_plugin_p
		)

=for hackers
Found in file toke.c


=back

=head1 Locale-related functions and macros

=over 8

=item DECLARATION_FOR_LC_NUMERIC_MANIPULATION
X<DECLARATION_FOR_LC_NUMERIC_MANIPULATION>

This macro should be used as a statement.  It declares a private variable
(whose name begins with an underscore) that is needed by the other macros in
this section.  Failing to include this correctly should lead to a syntax error.
For compatibility with C89 C compilers it should be placed in a block before
any executable statements.

	void	DECLARATION_FOR_LC_NUMERIC_MANIPULATION

=for hackers
Found in file perl.h

=item IN_LOCALE
X<IN_LOCALE>

Evaluates to TRUE if the plain locale pragma without a parameter (S<C<use
locale>>) is in effect.

	bool	IN_LOCALE

=for hackers
Found in file perl.h

=item IN_LOCALE_COMPILETIME
X<IN_LOCALE_COMPILETIME>

Evaluates to TRUE if, when compiling a perl program (including an C<eval>) if
the plain locale pragma without a parameter (S<C<use locale>>) is in effect.

	bool	IN_LOCALE_COMPILETIME

=for hackers
Found in file perl.h

=item IN_LOCALE_RUNTIME
X<IN_LOCALE_RUNTIME>

Evaluates to TRUE if, when executing a perl program (including an C<eval>) if
the plain locale pragma without a parameter (S<C<use locale>>) is in effect.

	bool	IN_LOCALE_RUNTIME

=for hackers
Found in file perl.h

=item Perl_langinfo
X<Perl_langinfo>

This is an (almost) drop-in replacement for the system C<L<nl_langinfo(3)>>,
taking the same C<item> parameter values, and returning the same information.
But it is more thread-safe than regular C<nl_langinfo()>, and hides the quirks
of Perl's locale handling from your code, and can be used on systems that lack
a native C<nl_langinfo>.

Expanding on these:

=over

=item *

The reason it isn't quite a drop-in replacement is actually an advantage.  The
only difference is that it returns S<C<const char *>>, whereas plain
C<nl_langinfo()> returns S<C<char *>>, but you are (only by documentation)
forbidden to write into the buffer.  By declaring this C<const>, the compiler
enforces this restriction, so if it is violated, you know at compilation time,
rather than getting segfaults at runtime.

=item *

It delivers the correct results for the C<RADIXCHAR> and C<THOUSEP> items,
without you having to write extra code.  The reason for the extra code would be
because these are from the C<LC_NUMERIC> locale category, which is normally
kept set by Perl so that the radix is a dot, and the separator is the empty
string, no matter what the underlying locale is supposed to be, and so to get
the expected results, you have to temporarily toggle into the underlying
locale, and later toggle back.  (You could use plain C<nl_langinfo> and
C<L</STORE_LC_NUMERIC_FORCE_TO_UNDERLYING>> for this but then you wouldn't get
the other advantages of C<Perl_langinfo()>; not keeping C<LC_NUMERIC> in the C
(or equivalent) locale would break a lot of CPAN, which is expecting the radix
(decimal point) character to be a dot.)

=item *

The system function it replaces can have its static return buffer trashed,
not only by a subesequent call to that function, but by a C<freelocale>,
C<setlocale>, or other locale change.  The returned buffer of this function is
not changed until the next call to it, so the buffer is never in a trashed
state.

=item *

Its return buffer is per-thread, so it also is never overwritten by a call to
this function from another thread;  unlike the function it replaces.

=item *

But most importantly, it works on systems that don't have C<nl_langinfo>, such
as Windows, hence makes your code more portable.  Of the fifty-some possible
items specified by the POSIX 2008 standard,
L<http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/langinfo.h.html>,
only one is completely unimplemented, though on non-Windows platforms, another
significant one is also not implemented).  It uses various techniques to
recover the other items, including calling C<L<localeconv(3)>>, and
C<L<strftime(3)>>, both of which are specified in C89, so should be always be
available.  Later C<strftime()> versions have additional capabilities; C<""> is
returned for those not available on your system.

It is important to note that when called with an item that is recovered by
using C<localeconv>, the buffer from any previous explicit call to
C<localeconv> will be overwritten.  This means you must save that buffer's
contents if you need to access them after a call to this function.  (But note
that you might not want to be using C<localeconv()> directly anyway, because of
issues like the ones listed in the second item of this list (above) for
C<RADIXCHAR> and C<THOUSEP>.  You can use the methods given in L<perlcall> to
call L<POSIX/localeconv> and avoid all the issues, but then you have a hash to
unpack).

The details for those items which may deviate from what this emulation returns
and what a native C<nl_langinfo()> would return are specified in
L<I18N::Langinfo>.

=back

When using C<Perl_langinfo> on systems that don't have a native
C<nl_langinfo()>, you must

 #include "perl_langinfo.h"

before the C<perl.h> C<#include>.  You can replace your C<langinfo.h>
C<#include> with this one.  (Doing it this way keeps out the symbols that plain
C<langinfo.h> would try to import into the namespace for code that doesn't need
it.)

The original impetus for C<Perl_langinfo()> was so that code that needs to
find out the current currency symbol, floating point radix character, or digit
grouping separator can use, on all systems, the simpler and more
thread-friendly C<nl_langinfo> API instead of C<L<localeconv(3)>> which is a
pain to make thread-friendly.  For other fields returned by C<localeconv>, it
is better to use the methods given in L<perlcall> to call
L<C<POSIX::localeconv()>|POSIX/localeconv>, which is thread-friendly.

	const char* Perl_langinfo(const nl_item item)

=for hackers
Found in file locale.c

=item Perl_setlocale
X<Perl_setlocale>

This is an (almost) drop-in replacement for the system L<C<setlocale(3)>>,
taking the same parameters, and returning the same information, except that it
returns the correct underlying C<LC_NUMERIC> locale.  Regular C<setlocale> will
instead return C<C> if the underlying locale has a non-dot decimal point
character, or a non-empty thousands separator for displaying floating point
numbers.  This is because perl keeps that locale category such that it has a
dot and empty separator, changing the locale briefly during the operations
where the underlying one is required. C<Perl_setlocale> knows about this, and
compensates; regular C<setlocale> doesn't.

Another reason it isn't completely a drop-in replacement is that it is
declared to return S<C<const char *>>, whereas the system setlocale omits the
C<const> (presumably because its API was specified long ago, and can't be
updated; it is illegal to change the information C<setlocale> returns; doing
so leads to segfaults.)

Finally, C<Perl_setlocale> works under all circumstances, whereas plain
C<setlocale> can be completely ineffective on some platforms under some
configurations.

C<Perl_setlocale> should not be used to change the locale except on systems
where the predefined variable C<${^SAFE_LOCALES}> is 1.  On some such systems,
the system C<setlocale()> is ineffective, returning the wrong information, and
failing to actually change the locale.  C<Perl_setlocale>, however works
properly in all circumstances.

The return points to a per-thread static buffer, which is overwritten the next
time C<Perl_setlocale> is called from the same thread.

	const char* Perl_setlocale(const int category,
	                           const char* locale)

=for hackers
Found in file locale.c

=item RESTORE_LC_NUMERIC
X<RESTORE_LC_NUMERIC>

This is used in conjunction with one of the macros
L</STORE_LC_NUMERIC_SET_TO_NEEDED>
and L</STORE_LC_NUMERIC_FORCE_TO_UNDERLYING> to properly restore the
C<LC_NUMERIC> state.

A call to L</DECLARATION_FOR_LC_NUMERIC_MANIPULATION> must have been made to
declare at compile time a private variable used by this macro and the two
C<STORE> ones.  This macro should be called as a single statement, not an
expression, but with an empty argument list, like this:

 {
    DECLARATION_FOR_LC_NUMERIC_MANIPULATION;
     ...
    RESTORE_LC_NUMERIC();
     ...
 }

	void	RESTORE_LC_NUMERIC()

=for hackers
Found in file perl.h

=item STORE_LC_NUMERIC_FORCE_TO_UNDERLYING
X<STORE_LC_NUMERIC_FORCE_TO_UNDERLYING>

This is used by XS code that is C<LC_NUMERIC> locale-aware to force the
locale for category C<LC_NUMERIC> to be what perl thinks is the current
underlying locale.  (The perl interpreter could be wrong about what the
underlying locale actually is if some C or XS code has called the C library
function L<setlocale(3)> behind its back; calling L</sync_locale> before calling
this macro will update perl's records.)

A call to L</DECLARATION_FOR_LC_NUMERIC_MANIPULATION> must have been made to
declare at compile time a private variable used by this macro.  This macro
should be called as a single statement, not an expression, but with an empty
argument list, like this:

 {
    DECLARATION_FOR_LC_NUMERIC_MANIPULATION;
     ...
    STORE_LC_NUMERIC_FORCE_TO_UNDERLYING();
     ...
    RESTORE_LC_NUMERIC();
     ...
 }

The private variable is used to save the current locale state, so
that the requisite matching call to L</RESTORE_LC_NUMERIC> can restore it.

On threaded perls not operating with thread-safe functionality, this macro uses
a mutex to force a critical section.  Therefore the matching RESTORE should be
close by, and guaranteed to be called.

	void	STORE_LC_NUMERIC_FORCE_TO_UNDERLYING()

=for hackers
Found in file perl.h

=item STORE_LC_NUMERIC_SET_TO_NEEDED
X<STORE_LC_NUMERIC_SET_TO_NEEDED>

This is used to help wrap XS or C code that is C<LC_NUMERIC> locale-aware.
This locale category is generally kept set to a locale where the decimal radix
character is a dot, and the separator between groups of digits is empty.  This
is because most XS code that reads floating point numbers is expecting them to
have this syntax.

This macro makes sure the current C<LC_NUMERIC> state is set properly, to be
aware of locale if the call to the XS or C code from the Perl program is
from within the scope of a S<C<use locale>>; or to ignore locale if the call is
instead from outside such scope.

This macro is the start of wrapping the C or XS code; the wrap ending is done
by calling the L</RESTORE_LC_NUMERIC> macro after the operation.  Otherwise
the state can be changed that will adversely affect other XS code.

A call to L</DECLARATION_FOR_LC_NUMERIC_MANIPULATION> must have been made to
declare at compile time a private variable used by this macro.  This macro
should be called as a single statement, not an expression, but with an empty
argument list, like this:

 {
    DECLARATION_FOR_LC_NUMERIC_MANIPULATION;
     ...
    STORE_LC_NUMERIC_SET_TO_NEEDED();
     ...
    RESTORE_LC_NUMERIC();
     ...
 }

On threaded perls not operating with thread-safe functionality, this macro uses
a mutex to force a critical section.  Therefore the matching RESTORE should be
close by, and guaranteed to be called; see L</WITH_LC_NUMERIC_SET_TO_NEEDED>
for a more contained way to ensure that.

	void	STORE_LC_NUMERIC_SET_TO_NEEDED()

=for hackers
Found in file perl.h

=item STORE_LC_NUMERIC_SET_TO_NEEDED_IN
X<STORE_LC_NUMERIC_SET_TO_NEEDED_IN>

Same as L</STORE_LC_NUMERIC_SET_TO_NEEDED> with in_lc_numeric provided
as the precalculated value of C<IN_LC(LC_NUMERIC)>. It is the caller's
responsibility to ensure that the status of C<PL_compiling> and C<PL_hints>
cannot have changed since the precalculation.

	void	STORE_LC_NUMERIC_SET_TO_NEEDED_IN(
		    bool in_lc_numeric
		)

=for hackers
Found in file perl.h

=item switch_to_global_locale
X<switch_to_global_locale>

On systems without locale support, or on typical single-threaded builds, or on
platforms that do not support per-thread locale operations, this function does
nothing.  On such systems that do have locale support, only a locale global to
the whole program is available.

On multi-threaded builds on systems that do have per-thread locale operations,
this function converts the thread it is running in to use the global locale.
This is for code that has not yet or cannot be updated to handle multi-threaded
locale operation.  As long as only a single thread is so-converted, everything
works fine, as all the other threads continue to ignore the global one, so only
this thread looks at it.

However, on Windows systems this isn't quite true prior to Visual Studio 15,
at which point Microsoft fixed a bug.  A race can occur if you use the
following operations on earlier Windows platforms:

=over

=item L<POSIX::localeconv|POSIX/localeconv>

=item L<I18N::Langinfo>, items C<CRNCYSTR> and C<THOUSEP>

=item L<perlapi/Perl_langinfo>, items C<CRNCYSTR> and C<THOUSEP>

=back

The first item is not fixable (except by upgrading to a later Visual Studio
release), but it would be possible to work around the latter two items by using
the Windows API functions C<GetNumberFormat> and C<GetCurrencyFormat>; patches
welcome.

Without this function call, threads that use the L<C<setlocale(3)>> system
function will not work properly, as all the locale-sensitive functions will
look at the per-thread locale, and C<setlocale> will have no effect on this
thread.

Perl code should convert to either call
L<C<Perl_setlocale>|perlapi/Perl_setlocale> (which is a drop-in for the system
C<setlocale>) or use the methods given in L<perlcall> to call
L<C<POSIX::setlocale>|POSIX/setlocale>.  Either one will transparently properly
handle all cases of single- vs multi-thread, POSIX 2008-supported or not.

Non-Perl libraries, such as C<gtk>, that call the system C<setlocale> can
continue to work if this function is called before transferring control to the
library.

Upon return from the code that needs to use the global locale,
L<C<sync_locale()>|perlapi/sync_locale> should be called to restore the safe
multi-thread operation.

	void	switch_to_global_locale()

=for hackers
Found in file locale.c

=item sync_locale
X<sync_locale>

L<C<Perl_setlocale>|perlapi/Perl_setlocale> can be used at any time to query or
change the locale (though changing the locale is antisocial and dangerous on
multi-threaded systems that don't have multi-thread safe locale operations.
(See L<perllocale/Multi-threaded operation>).  Using the system
L<C<setlocale(3)>> should be avoided.  Nevertheless, certain non-Perl libraries
called from XS, such as C<Gtk> do so, and this can't be changed.  When the
locale is changed by XS code that didn't use
L<C<Perl_setlocale>|perlapi/Perl_setlocale>, Perl needs to be told that the
locale has changed.  Use this function to do so, before returning to Perl.

The return value is a boolean: TRUE if the global locale at the time of call
was in effect; and FALSE if a per-thread locale was in effect.  This can be
used by the caller that needs to restore things as-they-were to decide whether
or not to call
L<C<Perl_switch_to_global_locale>|perlapi/switch_to_global_locale>.

	bool	sync_locale()

=for hackers
Found in file locale.c

=item WITH_LC_NUMERIC_SET_TO_NEEDED
X<WITH_LC_NUMERIC_SET_TO_NEEDED>

This macro invokes the supplied statement or block within the context
of a L</STORE_LC_NUMERIC_SET_TO_NEEDED> .. L</RESTORE_LC_NUMERIC> pair
if required, so eg:

  WITH_LC_NUMERIC_SET_TO_NEEDED(
    SNPRINTF_G(fv, ebuf, sizeof(ebuf), precis)
  );

is equivalent to:

  {
#ifdef USE_LOCALE_NUMERIC
    DECLARATION_FOR_LC_NUMERIC_MANIPULATION;
    STORE_LC_NUMERIC_SET_TO_NEEDED();
#endif
    SNPRINTF_G(fv, ebuf, sizeof(ebuf), precis);
#ifdef USE_LOCALE_NUMERIC
    RESTORE_LC_NUMERIC();
#endif
  }

	void	WITH_LC_NUMERIC_SET_TO_NEEDED(block)

=for hackers
Found in file perl.h

=item WITH_LC_NUMERIC_SET_TO_NEEDED_IN
X<WITH_LC_NUMERIC_SET_TO_NEEDED_IN>

Same as L</WITH_LC_NUMERIC_SET_TO_NEEDED> with in_lc_numeric provided
as the precalculated value of C<IN_LC(LC_NUMERIC)>. It is the caller's
responsibility to ensure that the status of C<PL_compiling> and C<PL_hints>
cannot have changed since the precalculation.

	void	WITH_LC_NUMERIC_SET_TO_NEEDED_IN(
		    bool in_lc_numeric, block
		)

=for hackers
Found in file perl.h


=back

=head1 Magical Functions

=over 8

=item mg_clear
X<mg_clear>

Clear something magical that the SV represents.  See C<L</sv_magic>>.

	int	mg_clear(SV* sv)

=for hackers
Found in file mg.c

=item mg_copy
X<mg_copy>

Copies the magic from one SV to another.  See C<L</sv_magic>>.

	int	mg_copy(SV *sv, SV *nsv, const char *key,
		        I32 klen)

=for hackers
Found in file mg.c

=item mg_find
X<mg_find>

Finds the magic pointer for C<type> matching the SV.  See C<L</sv_magic>>.

	MAGIC*	mg_find(const SV* sv, int type)

=for hackers
Found in file mg.c

=item mg_findext
X<mg_findext>

Finds the magic pointer of C<type> with the given C<vtbl> for the C<SV>.  See
C<L</sv_magicext>>.

	MAGIC*	mg_findext(const SV* sv, int type,
		           const MGVTBL *vtbl)

=for hackers
Found in file mg.c

=item mg_free
X<mg_free>

Free any magic storage used by the SV.  See C<L</sv_magic>>.

	int	mg_free(SV* sv)

=for hackers
Found in file mg.c

=item mg_freeext
X<mg_freeext>

Remove any magic of type C<how> using virtual table C<vtbl> from the
SV C<sv>.  See L</sv_magic>.

C<mg_freeext(sv, how, NULL)> is equivalent to C<mg_free_type(sv, how)>.

	void	mg_freeext(SV* sv, int how, const MGVTBL *vtbl)

=for hackers
Found in file mg.c

=item mg_free_type
X<mg_free_type>

Remove any magic of type C<how> from the SV C<sv>.  See L</sv_magic>.

	void	mg_free_type(SV* sv, int how)

=for hackers
Found in file mg.c

=item mg_get
X<mg_get>

Do magic before a value is retrieved from the SV.  The type of SV must
be >= C<SVt_PVMG>.  See C<L</sv_magic>>.

	int	mg_get(SV* sv)

=for hackers
Found in file mg.c

=item mg_length
X<mg_length>


DEPRECATED!  It is planned to remove this function from a
future release of Perl.  Do not use it for new code; remove it from
existing code.


Reports on the SV's length in bytes, calling length magic if available,
but does not set the UTF8 flag on C<sv>.  It will fall back to 'get'
magic if there is no 'length' magic, but with no indication as to
whether it called 'get' magic.  It assumes C<sv> is a C<PVMG> or
higher.  Use C<sv_len()> instead.

	U32	mg_length(SV* sv)

=for hackers
Found in file mg.c

=item mg_magical
X<mg_magical>

Turns on the magical status of an SV.  See C<L</sv_magic>>.

	void	mg_magical(SV* sv)

=for hackers
Found in file mg.c

=item mg_set
X<mg_set>

Do magic after a value is assigned to the SV.  See C<L</sv_magic>>.

	int	mg_set(SV* sv)

=for hackers
Found in file mg.c

=item SvGETMAGIC
X<SvGETMAGIC>

Invokes C<mg_get> on an SV if it has 'get' magic.  For example, this
will call C<FETCH> on a tied variable.  This macro evaluates its
argument more than once.

	void	SvGETMAGIC(SV* sv)

=for hackers
Found in file sv.h

=item SvLOCK
X<SvLOCK>

Arranges for a mutual exclusion lock to be obtained on C<sv> if a suitable module
has been loaded.

	void	SvLOCK(SV* sv)

=for hackers
Found in file sv.h

=item SvSETMAGIC
X<SvSETMAGIC>

Invokes C<mg_set> on an SV if it has 'set' magic.  This is necessary
after modifying a scalar, in case it is a magical variable like C<$|>
or a tied variable (it calls C<STORE>).  This macro evaluates its
argument more than once.

	void	SvSETMAGIC(SV* sv)

=for hackers
Found in file sv.h

=item SvSetMagicSV
X<SvSetMagicSV>

Like C<SvSetSV>, but does any set magic required afterwards.

	void	SvSetMagicSV(SV* dsv, SV* ssv)

=for hackers
Found in file sv.h

=item SvSetMagicSV_nosteal
X<SvSetMagicSV_nosteal>

Like C<SvSetSV_nosteal>, but does any set magic required afterwards.

	void	SvSetMagicSV_nosteal(SV* dsv, SV* ssv)

=for hackers
Found in file sv.h

=item SvSetSV
X<SvSetSV>

Calls C<sv_setsv> if C<dsv> is not the same as C<ssv>.  May evaluate arguments
more than once.  Does not handle 'set' magic on the destination SV.

	void	SvSetSV(SV* dsv, SV* ssv)

=for hackers
Found in file sv.h

=item SvSetSV_nosteal
X<SvSetSV_nosteal>

Calls a non-destructive version of C<sv_setsv> if C<dsv> is not the same as
C<ssv>.  May evaluate arguments more than once.

	void	SvSetSV_nosteal(SV* dsv, SV* ssv)

=for hackers
Found in file sv.h

=item SvSHARE
X<SvSHARE>

Arranges for C<sv> to be shared between threads if a suitable module
has been loaded.

	void	SvSHARE(SV* sv)

=for hackers
Found in file sv.h

=item sv_string_from_errnum
X<sv_string_from_errnum>

Generates the message string describing an OS error and returns it as
an SV.  C<errnum> must be a value that C<errno> could take, identifying
the type of error.

If C<tgtsv> is non-null then the string will be written into that SV
(overwriting existing content) and it will be returned.  If C<tgtsv>
is a null pointer then the string will be written into a new mortal SV
which will be returned.

The message will be taken from whatever locale would be used by C<$!>,
and will be encoded in the SV in whatever manner would be used by C<$!>.
The details of this process are subject to future change.  Currently,
the message is taken from the C locale by default (usually producing an
English message), and from the currently selected locale when in the scope
of the C<use locale> pragma.  A heuristic attempt is made to decode the
message from the locale's character encoding, but it will only be decoded
as either UTF-8 or ISO-8859-1.  It is always correctly decoded in a UTF-8
locale, usually in an ISO-8859-1 locale, and never in any other locale.

The SV is always returned containing an actual string, and with no other
OK bits set.  Unlike C<$!>, a message is even yielded for C<errnum> zero
(meaning success), and if no useful message is available then a useless
string (currently empty) is returned.

	SV*	sv_string_from_errnum(int errnum, SV* tgtsv)

=for hackers
Found in file mg.c

=item SvUNLOCK
X<SvUNLOCK>

Releases a mutual exclusion lock on C<sv> if a suitable module
has been loaded.

	void	SvUNLOCK(SV* sv)

=for hackers
Found in file sv.h


=back

=head1 Memory Management

=over 8

=item Copy
X<Copy>

The XSUB-writer's interface to the C C<memcpy> function.  The C<src> is the
source, C<dest> is the destination, C<nitems> is the number of items, and
C<type> is the type.  May fail on overlapping copies.  See also C<L</Move>>.

	void	Copy(void* src, void* dest, int nitems, type)

=for hackers
Found in file handy.h

=item CopyD
X<CopyD>

Like C<Copy> but returns C<dest>.  Useful
for encouraging compilers to tail-call
optimise.

	void *	CopyD(void* src, void* dest, int nitems, type)

=for hackers
Found in file handy.h

=item Move
X<Move>

The XSUB-writer's interface to the C C<memmove> function.  The C<src> is the
source, C<dest> is the destination, C<nitems> is the number of items, and
C<type> is the type.  Can do overlapping moves.  See also C<L</Copy>>.

	void	Move(void* src, void* dest, int nitems, type)

=for hackers
Found in file handy.h

=item MoveD
X<MoveD>

Like C<Move> but returns C<dest>.  Useful
for encouraging compilers to tail-call
optimise.

	void *	MoveD(void* src, void* dest, int nitems, type)

=for hackers
Found in file handy.h

=item Newx
X<Newx>

The XSUB-writer's interface to the C C<malloc> function.

Memory obtained by this should B<ONLY> be freed with L</"Safefree">.

In 5.9.3, Newx() and friends replace the older New() API, and drops
the first parameter, I<x>, a debug aid which allowed callers to identify
themselves.  This aid has been superseded by a new build option,
PERL_MEM_LOG (see L<perlhacktips/PERL_MEM_LOG>).  The older API is still
there for use in XS modules supporting older perls.

	void	Newx(void* ptr, int nitems, type)

=for hackers
Found in file handy.h

=item Newxc
X<Newxc>

The XSUB-writer's interface to the C C<malloc> function, with
cast.  See also C<L</Newx>>.

Memory obtained by this should B<ONLY> be freed with L</"Safefree">.

	void	Newxc(void* ptr, int nitems, type, cast)

=for hackers
Found in file handy.h

=item Newxz
X<Newxz>

The XSUB-writer's interface to the C C<malloc> function.  The allocated
memory is zeroed with C<memzero>.  See also C<L</Newx>>.

Memory obtained by this should B<ONLY> be freed with L</"Safefree">.

	void	Newxz(void* ptr, int nitems, type)

=for hackers
Found in file handy.h

=item Poison
X<Poison>

PoisonWith(0xEF) for catching access to freed memory.

	void	Poison(void* dest, int nitems, type)

=for hackers
Found in file handy.h

=item PoisonFree
X<PoisonFree>

PoisonWith(0xEF) for catching access to freed memory.

	void	PoisonFree(void* dest, int nitems, type)

=for hackers
Found in file handy.h

=item PoisonNew
X<PoisonNew>

PoisonWith(0xAB) for catching access to allocated but uninitialized memory.

	void	PoisonNew(void* dest, int nitems, type)

=for hackers
Found in file handy.h

=item PoisonWith
X<PoisonWith>

Fill up memory with a byte pattern (a byte repeated over and over
again) that hopefully catches attempts to access uninitialized memory.

	void	PoisonWith(void* dest, int nitems, type,
		           U8 byte)

=for hackers
Found in file handy.h

=item Renew
X<Renew>

The XSUB-writer's interface to the C C<realloc> function.

Memory obtained by this should B<ONLY> be freed with L</"Safefree">.

	void	Renew(void* ptr, int nitems, type)

=for hackers
Found in file handy.h

=item Renewc
X<Renewc>

The XSUB-writer's interface to the C C<realloc> function, with
cast.

Memory obtained by this should B<ONLY> be freed with L</"Safefree">.

	void	Renewc(void* ptr, int nitems, type, cast)

=for hackers
Found in file handy.h

=item Safefree
X<Safefree>

The XSUB-writer's interface to the C C<free> function.

This should B<ONLY> be used on memory obtained using L</"Newx"> and friends.

	void	Safefree(void* ptr)

=for hackers
Found in file handy.h

=item savepv
X<savepv>

Perl's version of C<strdup()>.  Returns a pointer to a newly allocated
string which is a duplicate of C<pv>.  The size of the string is
determined by C<strlen()>, which means it may not contain embedded C<NUL>
characters and must have a trailing C<NUL>.  To prevent memory leaks, the
memory allocated for the new string needs to be freed when no longer needed.
This can be done with the L</C<Safefree>> function, or
L<C<SAVEFREEPV>|perlguts/SAVEFREEPV(p)>.

On some platforms, Windows for example, all allocated memory owned by a thread
is deallocated when that thread ends.  So if you need that not to happen, you
need to use the shared memory functions, such as C<L</savesharedpv>>.

	char*	savepv(const char* pv)

=for hackers
Found in file util.c

=item savepvn
X<savepvn>

Perl's version of what C<strndup()> would be if it existed.  Returns a
pointer to a newly allocated string which is a duplicate of the first
C<len> bytes from C<pv>, plus a trailing
C<NUL> byte.  The memory allocated for
the new string can be freed with the C<Safefree()> function.

On some platforms, Windows for example, all allocated memory owned by a thread
is deallocated when that thread ends.  So if you need that not to happen, you
need to use the shared memory functions, such as C<L</savesharedpvn>>.

	char*	savepvn(const char* pv, Size_t len)

=for hackers
Found in file util.c

=item savepvs
X<savepvs>

Like C<savepvn>, but takes a literal string instead of a
string/length pair.

	char*	savepvs("literal string")

=for hackers
Found in file handy.h

=item savesharedpv
X<savesharedpv>

A version of C<savepv()> which allocates the duplicate string in memory
which is shared between threads.

	char*	savesharedpv(const char* pv)

=for hackers
Found in file util.c

=item savesharedpvn
X<savesharedpvn>

A version of C<savepvn()> which allocates the duplicate string in memory
which is shared between threads.  (With the specific difference that a C<NULL>
pointer is not acceptable)

	char*	savesharedpvn(const char *const pv,
		              const STRLEN len)

=for hackers
Found in file util.c

=item savesharedpvs
X<savesharedpvs>

A version of C<savepvs()> which allocates the duplicate string in memory
which is shared between threads.

	char*	savesharedpvs("literal string")

=for hackers
Found in file handy.h

=item savesharedsvpv
X<savesharedsvpv>

A version of C<savesharedpv()> which allocates the duplicate string in
memory which is shared between threads.

	char*	savesharedsvpv(SV *sv)

=for hackers
Found in file util.c

=item savesvpv
X<savesvpv>

A version of C<savepv()>/C<savepvn()> which gets the string to duplicate from
the passed in SV using C<SvPV()>

On some platforms, Windows for example, all allocated memory owned by a thread
is deallocated when that thread ends.  So if you need that not to happen, you
need to use the shared memory functions, such as C<L</savesharedsvpv>>.

	char*	savesvpv(SV* sv)

=for hackers
Found in file util.c

=item StructCopy
X<StructCopy>

This is an architecture-independent macro to copy one structure to another.

	void	StructCopy(type *src, type *dest, type)

=for hackers
Found in file handy.h

=item Zero
X<Zero>

The XSUB-writer's interface to the C C<memzero> function.  The C<dest> is the
destination, C<nitems> is the number of items, and C<type> is the type.

	void	Zero(void* dest, int nitems, type)

=for hackers
Found in file handy.h

=item ZeroD
X<ZeroD>

Like C<Zero> but returns dest.  Useful
for encouraging compilers to tail-call
optimise.

	void *	ZeroD(void* dest, int nitems, type)

=for hackers
Found in file handy.h


=back

=head1 Miscellaneous Functions

=over 8

=item dump_c_backtrace
X<dump_c_backtrace>

Dumps the C backtrace to the given C<fp>.

Returns true if a backtrace could be retrieved, false if not.

	bool	dump_c_backtrace(PerlIO* fp, int max_depth,
		                 int skip)

=for hackers
Found in file util.c

=item fbm_compile
X<fbm_compile>

Analyzes the string in order to make fast searches on it using C<fbm_instr()>
-- the Boyer-Moore algorithm.

	void	fbm_compile(SV* sv, U32 flags)

=for hackers
Found in file util.c

=item fbm_instr
X<fbm_instr>

Returns the location of the SV in the string delimited by C<big> and
C<bigend> (C<bigend>) is the char following the last char).
It returns C<NULL> if the string can't be found.  The C<sv>
does not have to be C<fbm_compiled>, but the search will not be as fast
then.

	char*	fbm_instr(unsigned char* big,
		          unsigned char* bigend, SV* littlestr,
		          U32 flags)

=for hackers
Found in file util.c

=item foldEQ
X<foldEQ>

Returns true if the leading C<len> bytes of the strings C<s1> and C<s2> are the
same
case-insensitively; false otherwise.  Uppercase and lowercase ASCII range bytes
match themselves and their opposite case counterparts.  Non-cased and non-ASCII
range bytes match only themselves.

	I32	foldEQ(const char* a, const char* b, I32 len)

=for hackers
Found in file inline.h

=item foldEQ_locale
X<foldEQ_locale>

Returns true if the leading C<len> bytes of the strings C<s1> and C<s2> are the
same case-insensitively in the current locale; false otherwise.

	I32	foldEQ_locale(const char* a, const char* b,
		              I32 len)

=for hackers
Found in file inline.h

=item form
X<form>

Takes a sprintf-style format pattern and conventional
(non-SV) arguments and returns the formatted string.

    (char *) Perl_form(pTHX_ const char* pat, ...)

can be used any place a string (char *) is required:

    char * s = Perl_form("%d.%d",major,minor);

Uses a single private buffer so if you want to format several strings you
must explicitly copy the earlier strings away (and free the copies when you
are done).

	char*	form(const char* pat, ...)

=for hackers
Found in file util.c

=item getcwd_sv
X<getcwd_sv>

Fill C<sv> with current working directory

	int	getcwd_sv(SV* sv)

=for hackers
Found in file util.c

=item get_c_backtrace_dump
X<get_c_backtrace_dump>

Returns a SV containing a dump of C<depth> frames of the call stack, skipping
the C<skip> innermost ones.  C<depth> of 20 is usually enough.

The appended output looks like:

...
1   10e004812:0082   Perl_croak   util.c:1716    /usr/bin/perl
2   10df8d6d2:1d72   perl_parse   perl.c:3975    /usr/bin/perl
...

The fields are tab-separated.  The first column is the depth (zero
being the innermost non-skipped frame).  In the hex:offset, the hex is
where the program counter was in C<S_parse_body>, and the :offset (might
be missing) tells how much inside the C<S_parse_body> the program counter was.

The C<util.c:1716> is the source code file and line number.

The F</usr/bin/perl> is obvious (hopefully).

Unknowns are C<"-">.  Unknowns can happen unfortunately quite easily:
if the platform doesn't support retrieving the information;
if the binary is missing the debug information;
if the optimizer has transformed the code by for example inlining.

	SV*	get_c_backtrace_dump(int max_depth, int skip)

=for hackers
Found in file util.c

=item ibcmp
X<ibcmp>

This is a synonym for S<C<(! foldEQ())>>

	I32	ibcmp(const char* a, const char* b, I32 len)

=for hackers
Found in file util.h

=item ibcmp_locale
X<ibcmp_locale>

This is a synonym for S<C<(! foldEQ_locale())>>

	I32	ibcmp_locale(const char* a, const char* b,
		             I32 len)

=for hackers
Found in file util.h

=item instr
X<instr>

Same as L<strstr(3)>, which finds and returns a pointer to the first occurrence
of the NUL-terminated substring C<little> in the NUL-terminated string C<big>,
returning NULL if not found.  The terminating NUL bytes are not compared.

	char*	instr(const char* big, const char* little)

=for hackers
Found in file util.h

=item IS_SAFE_SYSCALL
X<IS_SAFE_SYSCALL>

Same as L</is_safe_syscall>.

	bool	IS_SAFE_SYSCALL(NN const char *pv, STRLEN len,
		                NN const char *what,
		                NN const char *op_name)

=for hackers
Found in file perl.h

=item is_safe_syscall
X<is_safe_syscall>

Test that the given C<pv> (with length C<len>) doesn't contain any internal
C<NUL> characters.
If it does, set C<errno> to C<ENOENT>, optionally warn using the C<syscalls>
category, and return FALSE.

Return TRUE if the name is safe.

C<what> and C<op_name> are used in any warning.

Used by the C<IS_SAFE_SYSCALL()> macro.

	bool	is_safe_syscall(const char *pv, STRLEN len,
		                const char *what,
		                const char *op_name)

=for hackers
Found in file inline.h

=item LIKELY
X<LIKELY>

Returns the input unchanged, but at the same time it gives a branch prediction
hint to the compiler that this condition is likely to be true.

=for hackers
Found in file perl.h

=item memCHRs
X<memCHRs>

Returns the position of the first occurence of the byte C<c> in the literal
string C<"list">, or NULL if C<c> doesn't appear in C<"list">.  All bytes are
treated as unsigned char.  Thus this macro can be used to determine if C<c> is
in a set of particular characters.  Unlike L<strchr(3)>, it works even if C<c>
is C<NUL> (and the set doesn't include C<NUL>).

	bool	memCHRs("list", char c)

=for hackers
Found in file handy.h

=item memEQ
X<memEQ>

Test two buffers (which may contain embedded C<NUL> characters, to see if they
are equal.  The C<len> parameter indicates the number of bytes to compare.
Returns zero if equal, or non-zero if non-equal.

	bool	memEQ(char* s1, char* s2, STRLEN len)

=for hackers
Found in file handy.h

=item memEQs
X<memEQs>

Like L</memEQ>, but the second string is a literal enclosed in double quotes,
C<l1> gives the number of bytes in C<s1>.
Returns zero if equal, or non-zero if non-equal.

	bool	memEQs(char* s1, STRLEN l1, "s2")

=for hackers
Found in file handy.h

=item memNE
X<memNE>

Test two buffers (which may contain embedded C<NUL> characters, to see if they
are not equal.  The C<len> parameter indicates the number of bytes to compare.
Returns zero if non-equal, or non-zero if equal.

	bool	memNE(char* s1, char* s2, STRLEN len)

=for hackers
Found in file handy.h

=item memNEs
X<memNEs>

Like L</memNE>, but the second string is a literal enclosed in double quotes,
C<l1> gives the number of bytes in C<s1>.
Returns zero if non-equal, or zero if non-equal.

	bool	memNEs(char* s1, STRLEN l1, "s2")

=for hackers
Found in file handy.h

=item mess
X<mess>

Take a sprintf-style format pattern and argument list.  These are used to
generate a string message.  If the message does not end with a newline,
then it will be extended with some indication of the current location
in the code, as described for L</mess_sv>.

Normally, the resulting message is returned in a new mortal SV.
During global destruction a single SV may be shared between uses of
this function.

	SV*	mess(const char* pat, ...)

=for hackers
Found in file util.c

=item mess_sv
X<mess_sv>

Expands a message, intended for the user, to include an indication of
the current location in the code, if the message does not already appear
to be complete.

C<basemsg> is the initial message or object.  If it is a reference, it
will be used as-is and will be the result of this function.  Otherwise it
is used as a string, and if it already ends with a newline, it is taken
to be complete, and the result of this function will be the same string.
If the message does not end with a newline, then a segment such as C<at
foo.pl line 37> will be appended, and possibly other clauses indicating
the current state of execution.  The resulting message will end with a
dot and a newline.

Normally, the resulting message is returned in a new mortal SV.
During global destruction a single SV may be shared between uses of this
function.  If C<consume> is true, then the function is permitted (but not
required) to modify and return C<basemsg> instead of allocating a new SV.

	SV*	mess_sv(SV* basemsg, bool consume)

=for hackers
Found in file util.c

=item my_snprintf
X<my_snprintf>

The C library C<snprintf> functionality, if available and
standards-compliant (uses C<vsnprintf>, actually).  However, if the
C<vsnprintf> is not available, will unfortunately use the unsafe
C<vsprintf> which can overrun the buffer (there is an overrun check,
but that may be too late).  Consider using C<sv_vcatpvf> instead, or
getting C<vsnprintf>.

	int	my_snprintf(char *buffer, const Size_t len,
		            const char *format, ...)

=for hackers
Found in file util.c

=item my_sprintf
X<my_sprintf>


DEPRECATED!  It is planned to remove this function from a
future release of Perl.  Do not use it for new code; remove it from
existing code.


Do NOT use this due to the possibility of overflowing C<buffer>.  Instead use
my_snprintf()

	int	my_sprintf(NN char *buffer, NN const char *pat,
		           ...)

=for hackers
Found in file perl.h

=item my_strlcat
X<my_strlcat>

The C library C<strlcat> if available, or a Perl implementation of it.
This operates on C C<NUL>-terminated strings.

C<my_strlcat()> appends string C<src> to the end of C<dst>.  It will append at
most S<C<size - strlen(dst) - 1>> characters.  It will then C<NUL>-terminate,
unless C<size> is 0 or the original C<dst> string was longer than C<size> (in
practice this should not happen as it means that either C<size> is incorrect or
that C<dst> is not a proper C<NUL>-terminated string).

Note that C<size> is the full size of the destination buffer and
the result is guaranteed to be C<NUL>-terminated if there is room.  Note that
room for the C<NUL> should be included in C<size>.

The return value is the total length that C<dst> would have if C<size> is
sufficiently large.  Thus it is the initial length of C<dst> plus the length of
C<src>.  If C<size> is smaller than the return, the excess was not appended.

	Size_t	my_strlcat(char *dst, const char *src,
		           Size_t size)

=for hackers
Found in file util.c

=item my_strlcpy
X<my_strlcpy>

The C library C<strlcpy> if available, or a Perl implementation of it.
This operates on C C<NUL>-terminated strings.

C<my_strlcpy()> copies up to S<C<size - 1>> characters from the string C<src>
to C<dst>, C<NUL>-terminating the result if C<size> is not 0.

The return value is the total length C<src> would be if the copy completely
succeeded.  If it is larger than C<size>, the excess was not copied.

	Size_t	my_strlcpy(char *dst, const char *src,
		           Size_t size)

=for hackers
Found in file util.c

=item my_strnlen
X<my_strnlen>

The C library C<strnlen> if available, or a Perl implementation of it.

C<my_strnlen()> computes the length of the string, up to C<maxlen>
characters.  It will never attempt to address more than C<maxlen>
characters, making it suitable for use with strings that are not
guaranteed to be NUL-terminated.

	Size_t	my_strnlen(const char *str, Size_t maxlen)

=for hackers
Found in file inline.h

=item my_vsnprintf
X<my_vsnprintf>

The C library C<vsnprintf> if available and standards-compliant.
However, if the C<vsnprintf> is not available, will unfortunately
use the unsafe C<vsprintf> which can overrun the buffer (there is an
overrun check, but that may be too late).  Consider using
C<sv_vcatpvf> instead, or getting C<vsnprintf>.

	int	my_vsnprintf(char *buffer, const Size_t len,
		             const char *format, va_list ap)

=for hackers
Found in file util.c

=item ninstr
X<ninstr>

Find the first (leftmost) occurrence of a sequence of bytes within another
sequence.  This is the Perl version of C<strstr()>, extended to handle
arbitrary sequences, potentially containing embedded C<NUL> characters (C<NUL>
is what the initial C<n> in the function name stands for; some systems have an
equivalent, C<memmem()>, but with a somewhat different API).

Another way of thinking about this function is finding a needle in a haystack.
C<big> points to the first byte in the haystack.  C<big_end> points to one byte
beyond the final byte in the haystack.  C<little> points to the first byte in
the needle.  C<little_end> points to one byte beyond the final byte in the
needle.  All the parameters must be non-C<NULL>.

The function returns C<NULL> if there is no occurrence of C<little> within
C<big>.  If C<little> is the empty string, C<big> is returned.

Because this function operates at the byte level, and because of the inherent
characteristics of UTF-8 (or UTF-EBCDIC), it will work properly if both the
needle and the haystack are strings with the same UTF-8ness, but not if the
UTF-8ness differs.

	char*	ninstr(const char* big, const char* bigend,
		       const char* little, const char* lend)

=for hackers
Found in file util.c

=item PERL_SYS_INIT
X<PERL_SYS_INIT>

Provides system-specific tune up of the C runtime environment necessary to
run Perl interpreters.  This should be called only once, before creating
any Perl interpreters.

	void	PERL_SYS_INIT(int *argc, char*** argv)

=for hackers
Found in file perl.h

=item PERL_SYS_INIT3
X<PERL_SYS_INIT3>

Provides system-specific tune up of the C runtime environment necessary to
run Perl interpreters.  This should be called only once, before creating
any Perl interpreters.

	void	PERL_SYS_INIT3(int *argc, char*** argv,
		               char*** env)

=for hackers
Found in file perl.h

=item PERL_SYS_TERM
X<PERL_SYS_TERM>

Provides system-specific clean up of the C runtime environment after
running Perl interpreters.  This should be called only once, after
freeing any remaining Perl interpreters.

	void	PERL_SYS_TERM()

=for hackers
Found in file perl.h

=item READ_XDIGIT
X<READ_XDIGIT>

Returns the value of an ASCII-range hex digit and advances the string pointer.
Behaviour is only well defined when isXDIGIT(*str) is true.

	U8	READ_XDIGIT(char str*)

=for hackers
Found in file handy.h

=item rninstr
X<rninstr>

Like C<L</ninstr>>, but instead finds the final (rightmost) occurrence of a
sequence of bytes within another sequence, returning C<NULL> if there is no
such occurrence.

	char*	rninstr(const char* big, const char* bigend,
		        const char* little, const char* lend)

=for hackers
Found in file util.c

=item STMT_START
X<STMT_START>

 STMT_START { statements; } STMT_END;

can be used as a single statement, as in

 if (x) STMT_START { ... } STMT_END; else ...

These are often used in macro definitions.  Note that you can't return a value
out of them.

=for hackers
Found in file perl.h

=item strEQ
X<strEQ>

Test two C<NUL>-terminated strings to see if they are equal.  Returns true or
false.

	bool	strEQ(char* s1, char* s2)

=for hackers
Found in file handy.h

=item strGE
X<strGE>

Test two C<NUL>-terminated strings to see if the first, C<s1>, is greater than
or equal to the second, C<s2>.  Returns true or false.

	bool	strGE(char* s1, char* s2)

=for hackers
Found in file handy.h

=item strGT
X<strGT>

Test two C<NUL>-terminated strings to see if the first, C<s1>, is greater than
the second, C<s2>.  Returns true or false.

	bool	strGT(char* s1, char* s2)

=for hackers
Found in file handy.h

=item strLE
X<strLE>

Test two C<NUL>-terminated strings to see if the first, C<s1>, is less than or
equal to the second, C<s2>.  Returns true or false.

	bool	strLE(char* s1, char* s2)

=for hackers
Found in file handy.h

=item strLT
X<strLT>

Test two C<NUL>-terminated strings to see if the first, C<s1>, is less than the
second, C<s2>.  Returns true or false.

	bool	strLT(char* s1, char* s2)

=for hackers
Found in file handy.h

=item strNE
X<strNE>

Test two C<NUL>-terminated strings to see if they are different.  Returns true
or false.

	bool	strNE(char* s1, char* s2)

=for hackers
Found in file handy.h

=item strnEQ
X<strnEQ>

Test two C<NUL>-terminated strings to see if they are equal.  The C<len>
parameter indicates the number of bytes to compare.  Returns true or false.  (A
wrapper for C<strncmp>).

	bool	strnEQ(char* s1, char* s2, STRLEN len)

=for hackers
Found in file handy.h

=item strnNE
X<strnNE>

Test two C<NUL>-terminated strings to see if they are different.  The C<len>
parameter indicates the number of bytes to compare.  Returns true or false.  (A
wrapper for C<strncmp>).

	bool	strnNE(char* s1, char* s2, STRLEN len)

=for hackers
Found in file handy.h

=item sv_destroyable
X<sv_destroyable>

Dummy routine which reports that object can be destroyed when there is no
sharing module present.  It ignores its single SV argument, and returns
'true'.  Exists to avoid test for a C<NULL> function pointer and because it
could potentially warn under some level of strict-ness.

	bool	sv_destroyable(SV *sv)

=for hackers
Found in file util.c

=item sv_nosharing
X<sv_nosharing>

Dummy routine which "shares" an SV when there is no sharing module present.
Or "locks" it.  Or "unlocks" it.  In other
words, ignores its single SV argument.
Exists to avoid test for a C<NULL> function pointer and because it could
potentially warn under some level of strict-ness.

	void	sv_nosharing(SV *sv)

=for hackers
Found in file util.c

=item UNLIKELY
X<UNLIKELY>

Returns the input unchanged, but at the same time it gives a branch prediction
hint to the compiler that this condition is likely to be false.

=for hackers
Found in file perl.h

=item vmess
X<vmess>

C<pat> and C<args> are a sprintf-style format pattern and encapsulated
argument list, respectively.  These are used to generate a string message.  If
the
message does not end with a newline, then it will be extended with
some indication of the current location in the code, as described for
L</mess_sv>.

Normally, the resulting message is returned in a new mortal SV.
During global destruction a single SV may be shared between uses of
this function.

	SV*	vmess(const char* pat, va_list* args)

=for hackers
Found in file util.c


=back

=head1 MRO Functions

These functions are related to the method resolution order of perl classes
Also see L<perlmroapi>.


=over 8

=item mro_get_linear_isa
X<mro_get_linear_isa>

Returns the mro linearisation for the given stash.  By default, this
will be whatever C<mro_get_linear_isa_dfs> returns unless some
other MRO is in effect for the stash.  The return value is a
read-only AV*.

You are responsible for C<SvREFCNT_inc()> on the
return value if you plan to store it anywhere
semi-permanently (otherwise it might be deleted
out from under you the next time the cache is
invalidated).

	AV*	mro_get_linear_isa(HV* stash)

=for hackers
Found in file mro_core.c

=item mro_method_changed_in
X<mro_method_changed_in>

Invalidates method caching on any child classes
of the given stash, so that they might notice
the changes in this one.

Ideally, all instances of C<PL_sub_generation++> in
perl source outside of F<mro.c> should be
replaced by calls to this.

Perl automatically handles most of the common
ways a method might be redefined.  However, there
are a few ways you could change a method in a stash
without the cache code noticing, in which case you
need to call this method afterwards:

1) Directly manipulating the stash HV entries from
XS code.

2) Assigning a reference to a readonly scalar
constant into a stash entry in order to create
a constant subroutine (like F<constant.pm>
does).

This same method is available from pure perl
via, C<mro::method_changed_in(classname)>.

	void	mro_method_changed_in(HV* stash)

=for hackers
Found in file mro_core.c

=item mro_register
X<mro_register>

Registers a custom mro plugin.  See L<perlmroapi> for details on this and other
mro functions.

NOTE: this function must be explicitly called as Perl_mro_register with an aTHX_ parameter.

	void	Perl_mro_register(pTHX_ 
		                  const struct mro_alg *mro)

=for hackers
Found in file mro_core.c


=back

=head1 Multicall Functions

=over 8

=item dMULTICALL
X<dMULTICALL>

Declare local variables for a multicall.  See L<perlcall/LIGHTWEIGHT CALLBACKS>.

		dMULTICALL;

=for hackers
Found in file cop.h

=item MULTICALL
X<MULTICALL>

Make a lightweight callback.  See L<perlcall/LIGHTWEIGHT CALLBACKS>.

		MULTICALL;

=for hackers
Found in file cop.h

=item POP_MULTICALL
X<POP_MULTICALL>

Closing bracket for a lightweight callback.
See L<perlcall/LIGHTWEIGHT CALLBACKS>.

		POP_MULTICALL;

=for hackers
Found in file cop.h

=item PUSH_MULTICALL
X<PUSH_MULTICALL>

Opening bracket for a lightweight callback.
See L<perlcall/LIGHTWEIGHT CALLBACKS>.

		PUSH_MULTICALL(CV* the_cv);

=for hackers
Found in file cop.h


=back

=head1 Numeric functions

=over 8

=item grok_bin
X<grok_bin>

converts a string representing a binary number to numeric form.

On entry C<start> and C<*len_p> give the string to scan, C<*flags> gives
conversion flags, and C<result> should be C<NULL> or a pointer to an NV.  The
scan stops at the end of the string, or at just before the first invalid
character.  Unless C<PERL_SCAN_SILENT_ILLDIGIT> is set in C<*flags>,
encountering an invalid character (except NUL) will also trigger a warning.  On
return C<*len_p> is set to the length of the scanned string, and C<*flags>
gives output flags.

If the value is <= C<UV_MAX> it is returned as a UV, the output flags are clear,
and nothing is written to C<*result>.  If the value is > C<UV_MAX>, C<grok_bin>
returns C<UV_MAX>, sets C<PERL_SCAN_GREATER_THAN_UV_MAX> in the output flags,
and writes an approximation of the correct value into C<*result> (which is an
NV; or the approximation is discarded if C<result> is NULL).

The binary number may optionally be prefixed with C<"0b"> or C<"b"> unless
C<PERL_SCAN_DISALLOW_PREFIX> is set in C<*flags> on entry.

If C<PERL_SCAN_ALLOW_UNDERSCORES> is set in C<*flags> then any or all pairs of
digits may be separated from each other by a single underscore; also a single
leading underscore is accepted.

	UV	grok_bin(const char* start, STRLEN* len_p,
		         I32* flags, NV *result)

=for hackers
Found in file numeric.c

=item grok_hex
X<grok_hex>

converts a string representing a hex number to numeric form.

On entry C<start> and C<*len_p> give the string to scan, C<*flags> gives
conversion flags, and C<result> should be C<NULL> or a pointer to an NV.  The
scan stops at the end of the string, or at just before the first invalid
character.  Unless C<PERL_SCAN_SILENT_ILLDIGIT> is set in C<*flags>,
encountering an invalid character (except NUL) will also trigger a warning.  On
return C<*len_p> is set to the length of the scanned string, and C<*flags>
gives output flags.

If the value is <= C<UV_MAX> it is returned as a UV, the output flags are clear,
and nothing is written to C<*result>.  If the value is > C<UV_MAX>, C<grok_hex>
returns C<UV_MAX>, sets C<PERL_SCAN_GREATER_THAN_UV_MAX> in the output flags,
and writes an approximation of the correct value into C<*result> (which is an
NV; or the approximation is discarded if C<result> is NULL).

The hex number may optionally be prefixed with C<"0x"> or C<"x"> unless
C<PERL_SCAN_DISALLOW_PREFIX> is set in C<*flags> on entry.

If C<PERL_SCAN_ALLOW_UNDERSCORES> is set in C<*flags> then any or all pairs of
digits may be separated from each other by a single underscore; also a single
leading underscore is accepted.

	UV	grok_hex(const char* start, STRLEN* len_p,
		         I32* flags, NV *result)

=for hackers
Found in file numeric.c

=item grok_infnan
X<grok_infnan>

Helper for C<grok_number()>, accepts various ways of spelling "infinity"
or "not a number", and returns one of the following flag combinations:

  IS_NUMBER_INFINITY
  IS_NUMBER_NAN
  IS_NUMBER_INFINITY | IS_NUMBER_NEG
  IS_NUMBER_NAN | IS_NUMBER_NEG
  0

possibly |-ed with C<IS_NUMBER_TRAILING>.

If an infinity or a not-a-number is recognized, C<*sp> will point to
one byte past the end of the recognized string.  If the recognition fails,
zero is returned, and C<*sp> will not move.

	int	grok_infnan(const char** sp, const char *send)

=for hackers
Found in file numeric.c

=item grok_number
X<grok_number>

Identical to C<grok_number_flags()> with C<flags> set to zero.

	int	grok_number(const char *pv, STRLEN len,
		            UV *valuep)

=for hackers
Found in file numeric.c

=item grok_number_flags
X<grok_number_flags>

Recognise (or not) a number.  The type of the number is returned
(0 if unrecognised), otherwise it is a bit-ORed combination of
C<IS_NUMBER_IN_UV>, C<IS_NUMBER_GREATER_THAN_UV_MAX>, C<IS_NUMBER_NOT_INT>,
C<IS_NUMBER_NEG>, C<IS_NUMBER_INFINITY>, C<IS_NUMBER_NAN> (defined in perl.h).

If the value of the number can fit in a UV, it is returned in C<*valuep>.
C<IS_NUMBER_IN_UV> will be set to indicate that C<*valuep> is valid, C<IS_NUMBER_IN_UV>
will never be set unless C<*valuep> is valid, but C<*valuep> may have been assigned
to during processing even though C<IS_NUMBER_IN_UV> is not set on return.
If C<valuep> is C<NULL>, C<IS_NUMBER_IN_UV> will be set for the same cases as when
C<valuep> is non-C<NULL>, but no actual assignment (or SEGV) will occur.

C<IS_NUMBER_NOT_INT> will be set with C<IS_NUMBER_IN_UV> if trailing decimals were
seen (in which case C<*valuep> gives the true value truncated to an integer), and
C<IS_NUMBER_NEG> if the number is negative (in which case C<*valuep> holds the
absolute value).  C<IS_NUMBER_IN_UV> is not set if e notation was used or the
number is larger than a UV.

C<flags> allows only C<PERL_SCAN_TRAILING>, which allows for trailing
non-numeric text on an otherwise successful I<grok>, setting
C<IS_NUMBER_TRAILING> on the result.

	int	grok_number_flags(const char *pv, STRLEN len,
		                  UV *valuep, U32 flags)

=for hackers
Found in file numeric.c

=item GROK_NUMERIC_RADIX
X<GROK_NUMERIC_RADIX>

A synonym for L</grok_numeric_radix>

	bool	GROK_NUMERIC_RADIX(NN const char **sp,
		                   NN const char *send)

=for hackers
Found in file perl.h

=item grok_numeric_radix
X<grok_numeric_radix>

Scan and skip for a numeric decimal separator (radix).

	bool	grok_numeric_radix(const char **sp,
		                   const char *send)

=for hackers
Found in file numeric.c

=item grok_oct
X<grok_oct>

converts a string representing an octal number to numeric form.

On entry C<start> and C<*len_p> give the string to scan, C<*flags> gives
conversion flags, and C<result> should be C<NULL> or a pointer to an NV.  The
scan stops at the end of the string, or at just before the first invalid
character.  Unless C<PERL_SCAN_SILENT_ILLDIGIT> is set in C<*flags>,
encountering an invalid character (except NUL) will also trigger a warning.  On
return C<*len_p> is set to the length of the scanned string, and C<*flags>
gives output flags.

If the value is <= C<UV_MAX> it is returned as a UV, the output flags are clear,
and nothing is written to C<*result>.  If the value is > C<UV_MAX>, C<grok_oct>
returns C<UV_MAX>, sets C<PERL_SCAN_GREATER_THAN_UV_MAX> in the output flags,
and writes an approximation of the correct value into C<*result> (which is an
NV; or the approximation is discarded if C<result> is NULL).

If C<PERL_SCAN_ALLOW_UNDERSCORES> is set in C<*flags> then any or all pairs of
digits may be separated from each other by a single underscore; also a single
leading underscore is accepted.

The C<PERL_SCAN_DISALLOW_PREFIX> flag is always treated as being set for
this function.

	UV	grok_oct(const char* start, STRLEN* len_p,
		         I32* flags, NV *result)

=for hackers
Found in file numeric.c

=item isinfnan
X<isinfnan>

C<Perl_isinfnan()> is a utility function that returns true if the NV
argument is either an infinity or a C<NaN>, false otherwise.  To test
in more detail, use C<Perl_isinf()> and C<Perl_isnan()>.

This is also the logical inverse of Perl_isfinite().

	bool	isinfnan(NV nv)

=for hackers
Found in file numeric.c

=item IS_NUMBER_GREATER_THAN_UV_MAX
X<IS_NUMBER_GREATER_THAN_UV_MAX>
	bool	IS_NUMBER_GREATER_THAN_UV_MAX

=for hackers
Found in file numeric.c

=item IS_NUMBER_INFINITY
X<IS_NUMBER_INFINITY>
	bool	IS_NUMBER_INFINITY

=for hackers
Found in file numeric.c

=item IS_NUMBER_IN_UV
X<IS_NUMBER_IN_UV>
	bool	IS_NUMBER_IN_UV

=for hackers
Found in file numeric.c

=item IS_NUMBER_NAN
X<IS_NUMBER_NAN>
	bool	IS_NUMBER_NAN

=for hackers
Found in file numeric.c

=item IS_NUMBER_NEG
X<IS_NUMBER_NEG>
	bool	IS_NUMBER_NEG

=for hackers
Found in file numeric.c

=item IS_NUMBER_NOT_INT
X<IS_NUMBER_NOT_INT>

	bool	IS_NUMBER_NOT_INT

=for hackers
Found in file numeric.c

=item my_strtod
X<my_strtod>

This function is equivalent to the libc strtod() function, and is available
even on platforms that lack plain strtod().  Its return value is the best
available precision depending on platform capabilities and F<Configure>
options.

It properly handles the locale radix character, meaning it expects a dot except
when called from within the scope of S<C<use locale>>, in which case the radix
character should be that specified by the current locale.

The synonym Strtod() may be used instead.

	NV	my_strtod(const char * const s, char ** e)

=for hackers
Found in file numeric.c

=item PERL_ABS
X<PERL_ABS>

Typeless C<abs> or C<fabs>, I<etc>.  (The usage below indicates it is for
integers, but it works for any type.)  Use instead of these, since the C
library ones force their argument to be what it is expecting, potentially
leading to disaster.  But also beware that this evaluates its argument twice,
so no C<x++>.

	int	PERL_ABS(int)

=for hackers
Found in file perl.h

=item PERL_INT_MAX
X<PERL_INT_MAX>

This and
C<PERL_INT_MIN>,
C<PERL_LONG_MAX>,
C<PERL_LONG_MIN>,
C<PERL_QUAD_MAX>,
C<PERL_SHORT_MAX>,
C<PERL_SHORT_MIN>,
C<PERL_UCHAR_MAX>,
C<PERL_UCHAR_MIN>,
C<PERL_UINT_MAX>,
C<PERL_ULONG_MAX>,
C<PERL_ULONG_MIN>,
C<PERL_UQUAD_MAX>,
C<PERL_UQUAD_MIN>,
C<PERL_USHORT_MAX>,
C<PERL_USHORT_MIN>,
C<PERL_QUAD_MIN>
give the largest and smallest number representable in the current
platform in variables of the corresponding types.

For signed types, the smallest representable number is the most negative
number, the one furthest away from zero.

For C99 and later compilers, these correspond to things like C<INT_MAX>, which
are available to the C code.  But these constants, furnished by Perl,
allow code compiled on earlier compilers to portably have access to the same
constants.

=for hackers
Found in file perl.h

=item Perl_signbit
X<Perl_signbit>


NOTE: this function is experimental and may change or be
removed without notice.


Return a non-zero integer if the sign bit on an NV is set, and 0 if
it is not.

If F<Configure> detects this system has a C<signbit()> that will work with
our NVs, then we just use it via the C<#define> in F<perl.h>.  Otherwise,
fall back on this implementation.  The main use of this function
is catching C<-0.0>.

C<Configure> notes:  This function is called C<'Perl_signbit'> instead of a
plain C<'signbit'> because it is easy to imagine a system having a C<signbit()>
function or macro that doesn't happen to work with our particular choice
of NVs.  We shouldn't just re-C<#define> C<signbit> as C<Perl_signbit> and expect
the standard system headers to be happy.  Also, this is a no-context
function (no C<pTHX_>) because C<Perl_signbit()> is usually re-C<#defined> in
F<perl.h> as a simple macro call to the system's C<signbit()>.
Users should just always call C<Perl_signbit()>.

	int	Perl_signbit(NV f)

=for hackers
Found in file numeric.c

=item scan_bin
X<scan_bin>

For backwards compatibility.  Use C<grok_bin> instead.

	NV	scan_bin(const char* start, STRLEN len,
		         STRLEN* retlen)

=for hackers
Found in file numeric.c

=item scan_hex
X<scan_hex>

For backwards compatibility.  Use C<grok_hex> instead.

	NV	scan_hex(const char* start, STRLEN len,
		         STRLEN* retlen)

=for hackers
Found in file numeric.c

=item scan_oct
X<scan_oct>

For backwards compatibility.  Use C<grok_oct> instead.

	NV	scan_oct(const char* start, STRLEN len,
		         STRLEN* retlen)

=for hackers
Found in file numeric.c

=item Strtod
X<Strtod>

This is a synonym for L</my_strtod>.

	NV	Strtod(NN const char * const s,
		       NULLOK char ** e)

=for hackers
Found in file perl.h

=item Strtol
X<Strtol>

Platform and configuration independent C<strtol>.  This expands to the
appropriate C<strotol>-like function based on the platform and F<Configure>
options>.  For example it could expand to C<strtoll> or C<strtoq> instead of
C<strtol>.

	NV	Strtol(NN const char * const s,
		       NULLOK char ** e, int base)

=for hackers
Found in file perl.h

=item Strtoul
X<Strtoul>

Platform and configuration independent C<strtoul>.  This expands to the
appropriate C<strotoul>-like function based on the platform and F<Configure>
options>.  For example it could expand to C<strtoull> or C<strtouq> instead of
C<strtoul>.

	NV	Strtoul(NN const char * const s,
		        NULLOK char ** e, int base)

=for hackers
Found in file perl.h


=back

=head1 Obsolete backwards compatibility functions

Some of these are also deprecated.  You can exclude these from
your compiled Perl by adding this option to Configure:
C<-Accflags='-DNO_MATHOMS'>


=over 8

=item custom_op_desc
X<custom_op_desc>


DEPRECATED!  It is planned to remove this function from a
future release of Perl.  Do not use it for new code; remove it from
existing code.


Return the description of a given custom op.  This was once used by the
C<OP_DESC> macro, but is no longer: it has only been kept for
compatibility, and should not be used.

	const char * custom_op_desc(const OP *o)

=for hackers
Found in file mathoms.c

=item custom_op_name
X<custom_op_name>


DEPRECATED!  It is planned to remove this function from a
future release of Perl.  Do not use it for new code; remove it from
existing code.


Return the name for a given custom op.  This was once used by the C<OP_NAME>
macro, but is no longer: it has only been kept for compatibility, and
should not be used.

	const char * custom_op_name(const OP *o)

=for hackers
Found in file mathoms.c

=item gv_fetchmethod
X<gv_fetchmethod>

See L</gv_fetchmethod_autoload>.

	GV*	gv_fetchmethod(HV* stash, const char* name)

=for hackers
Found in file mathoms.c

=item is_utf8_char
X<is_utf8_char>


DEPRECATED!  It is planned to remove this function from a
future release of Perl.  Do not use it for new code; remove it from
existing code.


Tests if some arbitrary number of bytes begins in a valid UTF-8
character.  Note that an INVARIANT (i.e. ASCII on non-EBCDIC machines)
character is a valid UTF-8 character.  The actual number of bytes in the UTF-8
character will be returned if it is valid, otherwise 0.

This function is deprecated due to the possibility that malformed input could
cause reading beyond the end of the input buffer.  Use L</isUTF8_CHAR>
instead.

	STRLEN	is_utf8_char(const U8 *s)

=for hackers
Found in file mathoms.c

=item is_utf8_char_buf
X<is_utf8_char_buf>

This is identical to the macro L<perlapi/isUTF8_CHAR>.

	STRLEN	is_utf8_char_buf(const U8 *buf,
		                 const U8 *buf_end)

=for hackers
Found in file mathoms.c

=item pack_cat
X<pack_cat>

The engine implementing C<pack()> Perl function.  Note: parameters
C<next_in_list> and C<flags> are not used.  This call should not be used; use
C<packlist> instead.

	void	pack_cat(SV *cat, const char *pat,
		         const char *patend, SV **beglist,
		         SV **endlist, SV ***next_in_list,
		         U32 flags)

=for hackers
Found in file mathoms.c

=item pad_compname_type
X<pad_compname_type>

Looks up the type of the lexical variable at position C<po> in the
currently-compiling pad.  If the variable is typed, the stash of the
class to which it is typed is returned.  If not, C<NULL> is returned.

	HV*	pad_compname_type(const PADOFFSET po)

=for hackers
Found in file mathoms.c

=item sv_2pvbyte_nolen
X<sv_2pvbyte_nolen>

Return a pointer to the byte-encoded representation of the SV.
May cause the SV to be downgraded from UTF-8 as a side-effect.

Usually accessed via the C<SvPVbyte_nolen> macro.

	char*	sv_2pvbyte_nolen(SV* sv)

=for hackers
Found in file mathoms.c

=item sv_2pvutf8_nolen
X<sv_2pvutf8_nolen>

Return a pointer to the UTF-8-encoded representation of the SV.
May cause the SV to be upgraded to UTF-8 as a side-effect.

Usually accessed via the C<SvPVutf8_nolen> macro.

	char*	sv_2pvutf8_nolen(SV* sv)

=for hackers
Found in file mathoms.c

=item sv_2pv_nolen
X<sv_2pv_nolen>

Like C<sv_2pv()>, but doesn't return the length too.  You should usually
use the macro wrapper C<SvPV_nolen(sv)> instead.

	char*	sv_2pv_nolen(SV* sv)

=for hackers
Found in file mathoms.c

=item sv_catpvn_mg
X<sv_catpvn_mg>

Like C<sv_catpvn>, but also handles 'set' magic.

	void	sv_catpvn_mg(SV *sv, const char *ptr,
		             STRLEN len)

=for hackers
Found in file mathoms.c

=item sv_catsv_mg
X<sv_catsv_mg>

Like C<sv_catsv>, but also handles 'set' magic.

	void	sv_catsv_mg(SV *dsv, SV *ssv)

=for hackers
Found in file mathoms.c

=item sv_force_normal
X<sv_force_normal>

Undo various types of fakery on an SV: if the PV is a shared string, make
a private copy; if we're a ref, stop refing; if we're a glob, downgrade to
an C<xpvmg>.  See also C<L</sv_force_normal_flags>>.

	void	sv_force_normal(SV *sv)

=for hackers
Found in file mathoms.c

=item sv_iv
X<sv_iv>


DEPRECATED!  It is planned to remove this function from a
future release of Perl.  Do not use it for new code; remove it from
existing code.


A private implementation of the C<SvIVx> macro for compilers which can't
cope with complex macro expressions.  Always use the macro instead.

	IV	sv_iv(SV* sv)

=for hackers
Found in file mathoms.c

=item sv_nolocking
X<sv_nolocking>


DEPRECATED!  It is planned to remove this function from a
future release of Perl.  Do not use it for new code; remove it from
existing code.


Dummy routine which "locks" an SV when there is no locking module present.
Exists to avoid test for a C<NULL> function pointer and because it could
potentially warn under some level of strict-ness.

"Superseded" by C<sv_nosharing()>.

	void	sv_nolocking(SV *sv)

=for hackers
Found in file mathoms.c

=item sv_nounlocking
X<sv_nounlocking>


DEPRECATED!  It is planned to remove this function from a
future release of Perl.  Do not use it for new code; remove it from
existing code.


Dummy routine which "unlocks" an SV when there is no locking module present.
Exists to avoid test for a C<NULL> function pointer and because it could
potentially warn under some level of strict-ness.

"Superseded" by C<sv_nosharing()>.

	void	sv_nounlocking(SV *sv)

=for hackers
Found in file mathoms.c

=item sv_nv
X<sv_nv>


DEPRECATED!  It is planned to remove this function from a
future release of Perl.  Do not use it for new code; remove it from
existing code.


A private implementation of the C<SvNVx> macro for compilers which can't
cope with complex macro expressions.  Always use the macro instead.

	NV	sv_nv(SV* sv)

=for hackers
Found in file mathoms.c

=item sv_pv
X<sv_pv>

Use the C<SvPV_nolen> macro instead

	char*	sv_pv(SV *sv)

=for hackers
Found in file mathoms.c

=item sv_pvbyte
X<sv_pvbyte>

Use C<SvPVbyte_nolen> instead.

	char*	sv_pvbyte(SV *sv)

=for hackers
Found in file mathoms.c

=item sv_pvbyten
X<sv_pvbyten>


DEPRECATED!  It is planned to remove this function from a
future release of Perl.  Do not use it for new code; remove it from
existing code.


A private implementation of the C<SvPVbyte> macro for compilers
which can't cope with complex macro expressions.  Always use the macro
instead.

	char*	sv_pvbyten(SV *sv, STRLEN *lp)

=for hackers
Found in file mathoms.c

=item sv_pvn
X<sv_pvn>


DEPRECATED!  It is planned to remove this function from a
future release of Perl.  Do not use it for new code; remove it from
existing code.


A private implementation of the C<SvPV> macro for compilers which can't
cope with complex macro expressions.  Always use the macro instead.

	char*	sv_pvn(SV *sv, STRLEN *lp)

=for hackers
Found in file mathoms.c

=item sv_pvutf8
X<sv_pvutf8>

Use the C<SvPVutf8_nolen> macro instead

	char*	sv_pvutf8(SV *sv)

=for hackers
Found in file mathoms.c

=item sv_pvutf8n
X<sv_pvutf8n>


DEPRECATED!  It is planned to remove this function from a
future release of Perl.  Do not use it for new code; remove it from
existing code.


A private implementation of the C<SvPVutf8> macro for compilers
which can't cope with complex macro expressions.  Always use the macro
instead.

	char*	sv_pvutf8n(SV *sv, STRLEN *lp)

=for hackers
Found in file mathoms.c

=item sv_taint
X<sv_taint>

Taint an SV.  Use C<SvTAINTED_on> instead.

	void	sv_taint(SV* sv)

=for hackers
Found in file mathoms.c

=item sv_unref
X<sv_unref>

Unsets the RV status of the SV, and decrements the reference count of
whatever was being referenced by the RV.  This can almost be thought of
as a reversal of C<newSVrv>.  This is C<sv_unref_flags> with the C<flag>
being zero.  See C<L</SvROK_off>>.

	void	sv_unref(SV* sv)

=for hackers
Found in file mathoms.c

=item sv_usepvn
X<sv_usepvn>

Tells an SV to use C<ptr> to find its string value.  Implemented by
calling C<sv_usepvn_flags> with C<flags> of 0, hence does not handle 'set'
magic.  See C<L</sv_usepvn_flags>>.

	void	sv_usepvn(SV* sv, char* ptr, STRLEN len)

=for hackers
Found in file mathoms.c

=item sv_usepvn_mg
X<sv_usepvn_mg>

Like C<sv_usepvn>, but also handles 'set' magic.

	void	sv_usepvn_mg(SV *sv, char *ptr, STRLEN len)

=for hackers
Found in file mathoms.c

=item sv_uv
X<sv_uv>


DEPRECATED!  It is planned to remove this function from a
future release of Perl.  Do not use it for new code; remove it from
existing code.


A private implementation of the C<SvUVx> macro for compilers which can't
cope with complex macro expressions.  Always use the macro instead.

	UV	sv_uv(SV* sv)

=for hackers
Found in file mathoms.c

=item unpack_str
X<unpack_str>


DEPRECATED!  It is planned to remove this function from a
future release of Perl.  Do not use it for new code; remove it from
existing code.


The engine implementing C<unpack()> Perl function.  Note: parameters C<strbeg>,
C<new_s> and C<ocnt> are not used.  This call should not be used, use
C<unpackstring> instead.

	SSize_t	unpack_str(const char *pat, const char *patend,
		           const char *s, const char *strbeg,
		           const char *strend, char **new_s,
		           I32 ocnt, U32 flags)

=for hackers
Found in file mathoms.c

=item utf8_to_uvchr
X<utf8_to_uvchr>


DEPRECATED!  It is planned to remove this function from a
future release of Perl.  Do not use it for new code; remove it from
existing code.


Returns the native code point of the first character in the string C<s>
which is assumed to be in UTF-8 encoding; C<retlen> will be set to the
length, in bytes, of that character.

Some, but not all, UTF-8 malformations are detected, and in fact, some
malformed input could cause reading beyond the end of the input buffer, which
is why this function is deprecated.  Use L</utf8_to_uvchr_buf> instead.

If C<s> points to one of the detected malformations, and UTF8 warnings are
enabled, zero is returned and C<*retlen> is set (if C<retlen> isn't
C<NULL>) to -1.  If those warnings are off, the computed value if well-defined (or
the Unicode REPLACEMENT CHARACTER, if not) is silently returned, and C<*retlen>
is set (if C<retlen> isn't NULL) so that (S<C<s> + C<*retlen>>) is the
next possible position in C<s> that could begin a non-malformed character.
See L</utf8n_to_uvchr> for details on when the REPLACEMENT CHARACTER is returned.

	UV	utf8_to_uvchr(const U8 *s, STRLEN *retlen)

=for hackers
Found in file mathoms.c


=back

=head1 Optree construction

=over 8

=item newASSIGNOP
X<newASSIGNOP>

Constructs, checks, and returns an assignment op.  C<left> and C<right>
supply the parameters of the assignment; they are consumed by this
function and become part of the constructed op tree.

If C<optype> is C<OP_ANDASSIGN>, C<OP_ORASSIGN>, or C<OP_DORASSIGN>, then
a suitable conditional optree is constructed.  If C<optype> is the opcode
of a binary operator, such as C<OP_BIT_OR>, then an op is constructed that
performs the binary operation and assigns the result to the left argument.
Either way, if C<optype> is non-zero then C<flags> has no effect.

If C<optype> is zero, then a plain scalar or list assignment is
constructed.  Which type of assignment it is is automatically determined.
C<flags> gives the eight bits of C<op_flags>, except that C<OPf_KIDS>
will be set automatically, and, shifted up eight bits, the eight bits
of C<op_private>, except that the bit with value 1 or 2 is automatically
set as required.

	OP*	newASSIGNOP(I32 flags, OP* left, I32 optype,
		            OP* right)

=for hackers
Found in file op.c

=item newBINOP
X<newBINOP>

Constructs, checks, and returns an op of any binary type.  C<type>
is the opcode.  C<flags> gives the eight bits of C<op_flags>, except
that C<OPf_KIDS> will be set automatically, and, shifted up eight bits,
the eight bits of C<op_private>, except that the bit with value 1 or
2 is automatically set as required.  C<first> and C<last> supply up to
two ops to be the direct children of the binary op; they are consumed
by this function and become part of the constructed op tree.

	OP*	newBINOP(I32 type, I32 flags, OP* first,
		         OP* last)

=for hackers
Found in file op.c

=item newCONDOP
X<newCONDOP>

Constructs, checks, and returns a conditional-expression (C<cond_expr>)
op.  C<flags> gives the eight bits of C<op_flags>, except that C<OPf_KIDS>
will be set automatically, and, shifted up eight bits, the eight bits of
C<op_private>, except that the bit with value 1 is automatically set.
C<first> supplies the expression selecting between the two branches,
and C<trueop> and C<falseop> supply the branches; they are consumed by
this function and become part of the constructed op tree.

	OP*	newCONDOP(I32 flags, OP* first, OP* trueop,
		          OP* falseop)

=for hackers
Found in file op.c

=item newDEFSVOP
X<newDEFSVOP>

Constructs and returns an op to access C<$_>.

	OP*	newDEFSVOP()

=for hackers
Found in file op.c

=item newFOROP
X<newFOROP>

Constructs, checks, and returns an op tree expressing a C<foreach>
loop (iteration through a list of values).  This is a heavyweight loop,
with structure that allows exiting the loop by C<last> and suchlike.

C<sv> optionally supplies the variable that will be aliased to each
item in turn; if null, it defaults to C<$_>.
C<expr> supplies the list of values to iterate over.  C<block> supplies
the main body of the loop, and C<cont> optionally supplies a C<continue>
block that operates as a second half of the body.  All of these optree
inputs are consumed by this function and become part of the constructed
op tree.

C<flags> gives the eight bits of C<op_flags> for the C<leaveloop>
op and, shifted up eight bits, the eight bits of C<op_private> for
the C<leaveloop> op, except that (in both cases) some bits will be set
automatically.

	OP*	newFOROP(I32 flags, OP* sv, OP* expr, OP* block,
		         OP* cont)

=for hackers
Found in file op.c

=item newGIVENOP
X<newGIVENOP>

Constructs, checks, and returns an op tree expressing a C<given> block.
C<cond> supplies the expression to whose value C<$_> will be locally
aliased, and C<block> supplies the body of the C<given> construct; they
are consumed by this function and become part of the constructed op tree.
C<defsv_off> must be zero (it used to identity the pad slot of lexical $_).

	OP*	newGIVENOP(OP* cond, OP* block,
		           PADOFFSET defsv_off)

=for hackers
Found in file op.c

=item newGVOP
X<newGVOP>

Constructs, checks, and returns an op of any type that involves an
embedded reference to a GV.  C<type> is the opcode.  C<flags> gives the
eight bits of C<op_flags>.  C<gv> identifies the GV that the op should
reference; calling this function does not transfer ownership of any
reference to it.

	OP*	newGVOP(I32 type, I32 flags, GV* gv)

=for hackers
Found in file op.c

=item newLISTOP
X<newLISTOP>

Constructs, checks, and returns an op of any list type.  C<type> is
the opcode.  C<flags> gives the eight bits of C<op_flags>, except that
C<OPf_KIDS> will be set automatically if required.  C<first> and C<last>
supply up to two ops to be direct children of the list op; they are
consumed by this function and become part of the constructed op tree.

For most list operators, the check function expects all the kid ops to be
present already, so calling C<newLISTOP(OP_JOIN, ...)> (e.g.) is not
appropriate.  What you want to do in that case is create an op of type
C<OP_LIST>, append more children to it, and then call L</op_convert_list>.
See L</op_convert_list> for more information.


	OP*	newLISTOP(I32 type, I32 flags, OP* first,
		          OP* last)

=for hackers
Found in file op.c

=item newLOGOP
X<newLOGOP>

Constructs, checks, and returns a logical (flow control) op.  C<type>
is the opcode.  C<flags> gives the eight bits of C<op_flags>, except
that C<OPf_KIDS> will be set automatically, and, shifted up eight bits,
the eight bits of C<op_private>, except that the bit with value 1 is
automatically set.  C<first> supplies the expression controlling the
flow, and C<other> supplies the side (alternate) chain of ops; they are
consumed by this function and become part of the constructed op tree.

	OP*	newLOGOP(I32 optype, I32 flags, OP *first,
		         OP *other)

=for hackers
Found in file op.c

=item newLOOPEX
X<newLOOPEX>

Constructs, checks, and returns a loop-exiting op (such as C<goto>
or C<last>).  C<type> is the opcode.  C<label> supplies the parameter
determining the target of the op; it is consumed by this function and
becomes part of the constructed op tree.

	OP*	newLOOPEX(I32 type, OP* label)

=for hackers
Found in file op.c

=item newLOOPOP
X<newLOOPOP>

Constructs, checks, and returns an op tree expressing a loop.  This is
only a loop in the control flow through the op tree; it does not have
the heavyweight loop structure that allows exiting the loop by C<last>
and suchlike.  C<flags> gives the eight bits of C<op_flags> for the
top-level op, except that some bits will be set automatically as required.
C<expr> supplies the expression controlling loop iteration, and C<block>
supplies the body of the loop; they are consumed by this function and
become part of the constructed op tree.  C<debuggable> is currently
unused and should always be 1.

	OP*	newLOOPOP(I32 flags, I32 debuggable, OP* expr,
		          OP* block)

=for hackers
Found in file op.c

=item newMETHOP
X<newMETHOP>

Constructs, checks, and returns an op of method type with a method name
evaluated at runtime.  C<type> is the opcode.  C<flags> gives the eight
bits of C<op_flags>, except that C<OPf_KIDS> will be set automatically,
and, shifted up eight bits, the eight bits of C<op_private>, except that
the bit with value 1 is automatically set.  C<dynamic_meth> supplies an
op which evaluates method name; it is consumed by this function and
become part of the constructed op tree.
Supported optypes: C<OP_METHOD>.

	OP*	newMETHOP(I32 type, I32 flags, OP* dynamic_meth)

=for hackers
Found in file op.c

=item newMETHOP_named
X<newMETHOP_named>

Constructs, checks, and returns an op of method type with a constant
method name.  C<type> is the opcode.  C<flags> gives the eight bits of
C<op_flags>, and, shifted up eight bits, the eight bits of
C<op_private>.  C<const_meth> supplies a constant method name;
it must be a shared COW string.
Supported optypes: C<OP_METHOD_NAMED>.

	OP*	newMETHOP_named(I32 type, I32 flags,
		                SV* const_meth)

=for hackers
Found in file op.c

=item newNULLLIST
X<newNULLLIST>

Constructs, checks, and returns a new C<stub> op, which represents an
empty list expression.

	OP*	newNULLLIST()

=for hackers
Found in file op.c

=item newOP
X<newOP>

Constructs, checks, and returns an op of any base type (any type that
has no extra fields).  C<type> is the opcode.  C<flags> gives the
eight bits of C<op_flags>, and, shifted up eight bits, the eight bits
of C<op_private>.

	OP*	newOP(I32 optype, I32 flags)

=for hackers
Found in file op.c

=item newPADOP
X<newPADOP>

Constructs, checks, and returns an op of any type that involves a
reference to a pad element.  C<type> is the opcode.  C<flags> gives the
eight bits of C<op_flags>.  A pad slot is automatically allocated, and
is populated with C<sv>; this function takes ownership of one reference
to it.

This function only exists if Perl has been compiled to use ithreads.

	OP*	newPADOP(I32 type, I32 flags, SV* sv)

=for hackers
Found in file op.c

=item newPMOP
X<newPMOP>

Constructs, checks, and returns an op of any pattern matching type.
C<type> is the opcode.  C<flags> gives the eight bits of C<op_flags>
and, shifted up eight bits, the eight bits of C<op_private>.

	OP*	newPMOP(I32 type, I32 flags)

=for hackers
Found in file op.c

=item newPVOP
X<newPVOP>

Constructs, checks, and returns an op of any type that involves an
embedded C-level pointer (PV).  C<type> is the opcode.  C<flags> gives
the eight bits of C<op_flags>.  C<pv> supplies the C-level pointer.
Depending on the op type, the memory referenced by C<pv> may be freed
when the op is destroyed.  If the op is of a freeing type, C<pv> must
have been allocated using C<PerlMemShared_malloc>.

	OP*	newPVOP(I32 type, I32 flags, char* pv)

=for hackers
Found in file op.c

=item newRANGE
X<newRANGE>

Constructs and returns a C<range> op, with subordinate C<flip> and
C<flop> ops.  C<flags> gives the eight bits of C<op_flags> for the
C<flip> op and, shifted up eight bits, the eight bits of C<op_private>
for both the C<flip> and C<range> ops, except that the bit with value
1 is automatically set.  C<left> and C<right> supply the expressions
controlling the endpoints of the range; they are consumed by this function
and become part of the constructed op tree.

	OP*	newRANGE(I32 flags, OP* left, OP* right)

=for hackers
Found in file op.c

=item newSLICEOP
X<newSLICEOP>

Constructs, checks, and returns an C<lslice> (list slice) op.  C<flags>
gives the eight bits of C<op_flags>, except that C<OPf_KIDS> will
be set automatically, and, shifted up eight bits, the eight bits of
C<op_private>, except that the bit with value 1 or 2 is automatically
set as required.  C<listval> and C<subscript> supply the parameters of
the slice; they are consumed by this function and become part of the
constructed op tree.

	OP*	newSLICEOP(I32 flags, OP* subscript, OP* listop)

=for hackers
Found in file op.c

=item newSTATEOP
X<newSTATEOP>

Constructs a state op (COP).  The state op is normally a C<nextstate> op,
but will be a C<dbstate> op if debugging is enabled for currently-compiled
code.  The state op is populated from C<PL_curcop> (or C<PL_compiling>).
If C<label> is non-null, it supplies the name of a label to attach to
the state op; this function takes ownership of the memory pointed at by
C<label>, and will free it.  C<flags> gives the eight bits of C<op_flags>
for the state op.

If C<o> is null, the state op is returned.  Otherwise the state op is
combined with C<o> into a C<lineseq> list op, which is returned.  C<o>
is consumed by this function and becomes part of the returned op tree.

	OP*	newSTATEOP(I32 flags, char* label, OP* o)

=for hackers
Found in file op.c

=item newSVOP
X<newSVOP>

Constructs, checks, and returns an op of any type that involves an
embedded SV.  C<type> is the opcode.  C<flags> gives the eight bits
of C<op_flags>.  C<sv> gives the SV to embed in the op; this function
takes ownership of one reference to it.

	OP*	newSVOP(I32 type, I32 flags, SV* sv)

=for hackers
Found in file op.c

=item newUNOP
X<newUNOP>

Constructs, checks, and returns an op of any unary type.  C<type> is
the opcode.  C<flags> gives the eight bits of C<op_flags>, except that
C<OPf_KIDS> will be set automatically if required, and, shifted up eight
bits, the eight bits of C<op_private>, except that the bit with value 1
is automatically set.  C<first> supplies an optional op to be the direct
child of the unary op; it is consumed by this function and become part
of the constructed op tree.

	OP*	newUNOP(I32 type, I32 flags, OP* first)

=for hackers
Found in file op.c

=item newUNOP_AUX
X<newUNOP_AUX>

Similar to C<newUNOP>, but creates an C<UNOP_AUX> struct instead, with C<op_aux>
initialised to C<aux>

	OP*	newUNOP_AUX(I32 type, I32 flags, OP* first,
		            UNOP_AUX_item *aux)

=for hackers
Found in file op.c

=item newWHENOP
X<newWHENOP>

Constructs, checks, and returns an op tree expressing a C<when> block.
C<cond> supplies the test expression, and C<block> supplies the block
that will be executed if the test evaluates to true; they are consumed
by this function and become part of the constructed op tree.  C<cond>
will be interpreted DWIMically, often as a comparison against C<$_>,
and may be null to generate a C<default> block.

	OP*	newWHENOP(OP* cond, OP* block)

=for hackers
Found in file op.c

=item newWHILEOP
X<newWHILEOP>

Constructs, checks, and returns an op tree expressing a C<while> loop.
This is a heavyweight loop, with structure that allows exiting the loop
by C<last> and suchlike.

C<loop> is an optional preconstructed C<enterloop> op to use in the
loop; if it is null then a suitable op will be constructed automatically.
C<expr> supplies the loop's controlling expression.  C<block> supplies the
main body of the loop, and C<cont> optionally supplies a C<continue> block
that operates as a second half of the body.  All of these optree inputs
are consumed by this function and become part of the constructed op tree.

C<flags> gives the eight bits of C<op_flags> for the C<leaveloop>
op and, shifted up eight bits, the eight bits of C<op_private> for
the C<leaveloop> op, except that (in both cases) some bits will be set
automatically.  C<debuggable> is currently unused and should always be 1.
C<has_my> can be supplied as true to force the
loop body to be enclosed in its own scope.

	OP*	newWHILEOP(I32 flags, I32 debuggable,
		           LOOP* loop, OP* expr, OP* block,
		           OP* cont, I32 has_my)

=for hackers
Found in file op.c


=back

=head1 Optree Manipulation Functions

=over 8

=item alloccopstash
X<alloccopstash>


NOTE: this function is experimental and may change or be
removed without notice.


Available only under threaded builds, this function allocates an entry in
C<PL_stashpad> for the stash passed to it.

	PADOFFSET alloccopstash(HV *hv)

=for hackers
Found in file op.c

=item block_end
X<block_end>

Handles compile-time scope exit.  C<floor>
is the savestack index returned by
C<block_start>, and C<seq> is the body of the block.  Returns the block,
possibly modified.

	OP*	block_end(I32 floor, OP* seq)

=for hackers
Found in file op.c

=item block_start
X<block_start>

Handles compile-time scope entry.
Arranges for hints to be restored on block
exit and also handles pad sequence numbers to make lexical variables scope
right.  Returns a savestack index for use with C<block_end>.

	int	block_start(int full)

=for hackers
Found in file op.c

=item ck_entersub_args_list
X<ck_entersub_args_list>

Performs the default fixup of the arguments part of an C<entersub>
op tree.  This consists of applying list context to each of the
argument ops.  This is the standard treatment used on a call marked
with C<&>, or a method call, or a call through a subroutine reference,
or any other call where the callee can't be identified at compile time,
or a call where the callee has no prototype.

	OP*	ck_entersub_args_list(OP *entersubop)

=for hackers
Found in file op.c

=item ck_entersub_args_proto
X<ck_entersub_args_proto>

Performs the fixup of the arguments part of an C<entersub> op tree
based on a subroutine prototype.  This makes various modifications to
the argument ops, from applying context up to inserting C<refgen> ops,
and checking the number and syntactic types of arguments, as directed by
the prototype.  This is the standard treatment used on a subroutine call,
not marked with C<&>, where the callee can be identified at compile time
and has a prototype.

C<protosv> supplies the subroutine prototype to be applied to the call.
It may be a normal defined scalar, of which the string value will be used.
Alternatively, for convenience, it may be a subroutine object (a C<CV*>
that has been cast to C<SV*>) which has a prototype.  The prototype
supplied, in whichever form, does not need to match the actual callee
referenced by the op tree.

If the argument ops disagree with the prototype, for example by having
an unacceptable number of arguments, a valid op tree is returned anyway.
The error is reflected in the parser state, normally resulting in a single
exception at the top level of parsing which covers all the compilation
errors that occurred.  In the error message, the callee is referred to
by the name defined by the C<namegv> parameter.

	OP*	ck_entersub_args_proto(OP *entersubop,
		                       GV *namegv, SV *protosv)

=for hackers
Found in file op.c

=item ck_entersub_args_proto_or_list
X<ck_entersub_args_proto_or_list>

Performs the fixup of the arguments part of an C<entersub> op tree either
based on a subroutine prototype or using default list-context processing.
This is the standard treatment used on a subroutine call, not marked
with C<&>, where the callee can be identified at compile time.

C<protosv> supplies the subroutine prototype to be applied to the call,
or indicates that there is no prototype.  It may be a normal scalar,
in which case if it is defined then the string value will be used
as a prototype, and if it is undefined then there is no prototype.
Alternatively, for convenience, it may be a subroutine object (a C<CV*>
that has been cast to C<SV*>), of which the prototype will be used if it
has one.  The prototype (or lack thereof) supplied, in whichever form,
does not need to match the actual callee referenced by the op tree.

If the argument ops disagree with the prototype, for example by having
an unacceptable number of arguments, a valid op tree is returned anyway.
The error is reflected in the parser state, normally resulting in a single
exception at the top level of parsing which covers all the compilation
errors that occurred.  In the error message, the callee is referred to
by the name defined by the C<namegv> parameter.

	OP*	ck_entersub_args_proto_or_list(OP *entersubop,
		                               GV *namegv,
		                               SV *protosv)

=for hackers
Found in file op.c

=item cv_const_sv
X<cv_const_sv>

If C<cv> is a constant sub eligible for inlining, returns the constant
value returned by the sub.  Otherwise, returns C<NULL>.

Constant subs can be created with C<newCONSTSUB> or as described in
L<perlsub/"Constant Functions">.

	SV*	cv_const_sv(const CV *const cv)

=for hackers
Found in file op.c

=item cv_get_call_checker
X<cv_get_call_checker>

The original form of L</cv_get_call_checker_flags>, which does not return
checker flags.  When using a checker function returned by this function,
it is only safe to call it with a genuine GV as its C<namegv> argument.

	void	cv_get_call_checker(CV *cv,
		                    Perl_call_checker *ckfun_p,
		                    SV **ckobj_p)

=for hackers
Found in file op.c

=item cv_get_call_checker_flags
X<cv_get_call_checker_flags>

Retrieves the function that will be used to fix up a call to C<cv>.
Specifically, the function is applied to an C<entersub> op tree for a
subroutine call, not marked with C<&>, where the callee can be identified
at compile time as C<cv>.

The C-level function pointer is returned in C<*ckfun_p>, an SV argument
for it is returned in C<*ckobj_p>, and control flags are returned in
C<*ckflags_p>.  The function is intended to be called in this manner:

 entersubop = (*ckfun_p)(aTHX_ entersubop, namegv, (*ckobj_p));

In this call, C<entersubop> is a pointer to the C<entersub> op,
which may be replaced by the check function, and C<namegv> supplies
the name that should be used by the check function to refer
to the callee of the C<entersub> op if it needs to emit any diagnostics.
It is permitted to apply the check function in non-standard situations,
such as to a call to a different subroutine or to a method call.

C<namegv> may not actually be a GV.  If the C<CALL_CHECKER_REQUIRE_GV>
bit is clear in C<*ckflags_p>, it is permitted to pass a CV or other SV
instead, anything that can be used as the first argument to L</cv_name>.
If the C<CALL_CHECKER_REQUIRE_GV> bit is set in C<*ckflags_p> then the
check function requires C<namegv> to be a genuine GV.

By default, the check function is
L<Perl_ck_entersub_args_proto_or_list|/ck_entersub_args_proto_or_list>,
the SV parameter is C<cv> itself, and the C<CALL_CHECKER_REQUIRE_GV>
flag is clear.  This implements standard prototype processing.  It can
be changed, for a particular subroutine, by L</cv_set_call_checker_flags>.

If the C<CALL_CHECKER_REQUIRE_GV> bit is set in C<gflags> then it
indicates that the caller only knows about the genuine GV version of
C<namegv>, and accordingly the corresponding bit will always be set in
C<*ckflags_p>, regardless of the check function's recorded requirements.
If the C<CALL_CHECKER_REQUIRE_GV> bit is clear in C<gflags> then it
indicates the caller knows about the possibility of passing something
other than a GV as C<namegv>, and accordingly the corresponding bit may
be either set or clear in C<*ckflags_p>, indicating the check function's
recorded requirements.

C<gflags> is a bitset passed into C<cv_get_call_checker_flags>, in which
only the C<CALL_CHECKER_REQUIRE_GV> bit currently has a defined meaning
(for which see above).  All other bits should be clear.

	void	cv_get_call_checker_flags(
		    CV *cv, U32 gflags,
		    Perl_call_checker *ckfun_p, SV **ckobj_p,
		    U32 *ckflags_p
		)

=for hackers
Found in file op.c

=item cv_set_call_checker
X<cv_set_call_checker>

The original form of L</cv_set_call_checker_flags>, which passes it the
C<CALL_CHECKER_REQUIRE_GV> flag for backward-compatibility.  The effect
of that flag setting is that the check function is guaranteed to get a
genuine GV as its C<namegv> argument.

	void	cv_set_call_checker(CV *cv,
		                    Perl_call_checker ckfun,
		                    SV *ckobj)

=for hackers
Found in file op.c

=item cv_set_call_checker_flags
X<cv_set_call_checker_flags>

Sets the function that will be used to fix up a call to C<cv>.
Specifically, the function is applied to an C<entersub> op tree for a
subroutine call, not marked with C<&>, where the callee can be identified
at compile time as C<cv>.

The C-level function pointer is supplied in C<ckfun>, an SV argument for
it is supplied in C<ckobj>, and control flags are supplied in C<ckflags>.
The function should be defined like this:

    STATIC OP * ckfun(pTHX_ OP *op, GV *namegv, SV *ckobj)

It is intended to be called in this manner:

    entersubop = ckfun(aTHX_ entersubop, namegv, ckobj);

In this call, C<entersubop> is a pointer to the C<entersub> op,
which may be replaced by the check function, and C<namegv> supplies
the name that should be used by the check function to refer
to the callee of the C<entersub> op if it needs to emit any diagnostics.
It is permitted to apply the check function in non-standard situations,
such as to a call to a different subroutine or to a method call.

C<namegv> may not actually be a GV.  For efficiency, perl may pass a
CV or other SV instead.  Whatever is passed can be used as the first
argument to L</cv_name>.  You can force perl to pass a GV by including
C<CALL_CHECKER_REQUIRE_GV> in the C<ckflags>.

C<ckflags> is a bitset, in which only the C<CALL_CHECKER_REQUIRE_GV>
bit currently has a defined meaning (for which see above).  All other
bits should be clear.

The current setting for a particular CV can be retrieved by
L</cv_get_call_checker_flags>.

	void	cv_set_call_checker_flags(
		    CV *cv, Perl_call_checker ckfun, SV *ckobj,
		    U32 ckflags
		)

=for hackers
Found in file op.c

=item LINKLIST
X<LINKLIST>

Given the root of an optree, link the tree in execution order using the
C<op_next> pointers and return the first op executed.  If this has
already been done, it will not be redone, and C<< o->op_next >> will be
returned.  If C<< o->op_next >> is not already set, C<o> should be at
least an C<UNOP>.

	OP*	LINKLIST(OP *o)

=for hackers
Found in file op.h

=item newCONSTSUB
X<newCONSTSUB>

Behaves like L</newCONSTSUB_flags>, except that C<name> is nul-terminated
rather than of counted length, and no flags are set.  (This means that
C<name> is always interpreted as Latin-1.)

	CV*	newCONSTSUB(HV* stash, const char* name, SV* sv)

=for hackers
Found in file op.c

=item newCONSTSUB_flags
X<newCONSTSUB_flags>

Construct a constant subroutine, also performing some surrounding
jobs.  A scalar constant-valued subroutine is eligible for inlining
at compile-time, and in Perl code can be created by S<C<sub FOO () {
123 }>>.  Other kinds of constant subroutine have other treatment.

The subroutine will have an empty prototype and will ignore any arguments
when called.  Its constant behaviour is determined by C<sv>.  If C<sv>
is null, the subroutine will yield an empty list.  If C<sv> points to a
scalar, the subroutine will always yield that scalar.  If C<sv> points
to an array, the subroutine will always yield a list of the elements of
that array in list context, or the number of elements in the array in
scalar context.  This function takes ownership of one counted reference
to the scalar or array, and will arrange for the object to live as long
as the subroutine does.  If C<sv> points to a scalar then the inlining
assumes that the value of the scalar will never change, so the caller
must ensure that the scalar is not subsequently written to.  If C<sv>
points to an array then no such assumption is made, so it is ostensibly
safe to mutate the array or its elements, but whether this is really
supported has not been determined.

The subroutine will have C<CvFILE> set according to C<PL_curcop>.
Other aspects of the subroutine will be left in their default state.
The caller is free to mutate the subroutine beyond its initial state
after this function has returned.

If C<name> is null then the subroutine will be anonymous, with its
C<CvGV> referring to an C<__ANON__> glob.  If C<name> is non-null then the
subroutine will be named accordingly, referenced by the appropriate glob.
C<name> is a string of length C<len> bytes giving a sigilless symbol
name, in UTF-8 if C<flags> has the C<SVf_UTF8> bit set and in Latin-1
otherwise.  The name may be either qualified or unqualified.  If the
name is unqualified then it defaults to being in the stash specified by
C<stash> if that is non-null, or to C<PL_curstash> if C<stash> is null.
The symbol is always added to the stash if necessary, with C<GV_ADDMULTI>
semantics.

C<flags> should not have bits set other than C<SVf_UTF8>.

If there is already a subroutine of the specified name, then the new sub
will replace the existing one in the glob.  A warning may be generated
about the redefinition.

If the subroutine has one of a few special names, such as C<BEGIN> or
C<END>, then it will be claimed by the appropriate queue for automatic
running of phase-related subroutines.  In this case the relevant glob will
be left not containing any subroutine, even if it did contain one before.
Execution of the subroutine will likely be a no-op, unless C<sv> was
a tied array or the caller modified the subroutine in some interesting
way before it was executed.  In the case of C<BEGIN>, the treatment is
buggy: the sub will be executed when only half built, and may be deleted
prematurely, possibly causing a crash.

The function returns a pointer to the constructed subroutine.  If the sub
is anonymous then ownership of one counted reference to the subroutine
is transferred to the caller.  If the sub is named then the caller does
not get ownership of a reference.  In most such cases, where the sub
has a non-phase name, the sub will be alive at the point it is returned
by virtue of being contained in the glob that names it.  A phase-named
subroutine will usually be alive by virtue of the reference owned by
the phase's automatic run queue.  A C<BEGIN> subroutine may have been
destroyed already by the time this function returns, but currently bugs
occur in that case before the caller gets control.  It is the caller's
responsibility to ensure that it knows which of these situations applies.

	CV*	newCONSTSUB_flags(HV* stash, const char* name,
		                  STRLEN len, U32 flags, SV* sv)

=for hackers
Found in file op.c

=item newXS
X<newXS>

Used by C<xsubpp> to hook up XSUBs as Perl subs.  C<filename> needs to be
static storage, as it is used directly as CvFILE(), without a copy being made.

=for hackers
Found in file op.c

=item op_append_elem
X<op_append_elem>

Append an item to the list of ops contained directly within a list-type
op, returning the lengthened list.  C<first> is the list-type op,
and C<last> is the op to append to the list.  C<optype> specifies the
intended opcode for the list.  If C<first> is not already a list of the
right type, it will be upgraded into one.  If either C<first> or C<last>
is null, the other is returned unchanged.

	OP*	op_append_elem(I32 optype, OP* first, OP* last)

=for hackers
Found in file op.c

=item op_append_list
X<op_append_list>

Concatenate the lists of ops contained directly within two list-type ops,
returning the combined list.  C<first> and C<last> are the list-type ops
to concatenate.  C<optype> specifies the intended opcode for the list.
If either C<first> or C<last> is not already a list of the right type,
it will be upgraded into one.  If either C<first> or C<last> is null,
the other is returned unchanged.

	OP*	op_append_list(I32 optype, OP* first, OP* last)

=for hackers
Found in file op.c

=item OP_CLASS
X<OP_CLASS>

Return the class of the provided OP: that is, which of the *OP
structures it uses.  For core ops this currently gets the information out
of C<PL_opargs>, which does not always accurately reflect the type used;
in v5.26 onwards, see also the function C<L</op_class>> which can do a better
job of determining the used type.

For custom ops the type is returned from the registration, and it is up
to the registree to ensure it is accurate.  The value returned will be
one of the C<OA_>* constants from F<op.h>.

	U32	OP_CLASS(OP *o)

=for hackers
Found in file op.h

=item op_contextualize
X<op_contextualize>

Applies a syntactic context to an op tree representing an expression.
C<o> is the op tree, and C<context> must be C<G_SCALAR>, C<G_ARRAY>,
or C<G_VOID> to specify the context to apply.  The modified op tree
is returned.

	OP*	op_contextualize(OP* o, I32 context)

=for hackers
Found in file op.c

=item op_convert_list
X<op_convert_list>

Converts C<o> into a list op if it is not one already, and then converts it
into the specified C<type>, calling its check function, allocating a target if
it needs one, and folding constants.

A list-type op is usually constructed one kid at a time via C<newLISTOP>,
C<op_prepend_elem> and C<op_append_elem>.  Then finally it is passed to
C<op_convert_list> to make it the right type.

	OP*	op_convert_list(I32 optype, I32 flags, OP* o)

=for hackers
Found in file op.c

=item OP_DESC
X<OP_DESC>

Return a short description of the provided OP.

	const char * OP_DESC(OP *o)

=for hackers
Found in file op.h

=item op_free
X<op_free>

Free an op and its children. Only use this when an op is no longer linked
to from any optree.

	void	op_free(OP* arg)

=for hackers
Found in file op.c

=item OpHAS_SIBLING
X<OpHAS_SIBLING>

Returns true if C<o> has a sibling

	bool	OpHAS_SIBLING(OP *o)

=for hackers
Found in file op.h

=item OpLASTSIB_set
X<OpLASTSIB_set>

Marks C<o> as having no further siblings and marks
o as having the specified parent. See also C<L</OpMORESIB_set>> and
C<OpMAYBESIB_set>. For a higher-level interface, see
C<L</op_sibling_splice>>.

	void	OpLASTSIB_set(OP *o, OP *parent)

=for hackers
Found in file op.h

=item op_linklist
X<op_linklist>

This function is the implementation of the L</LINKLIST> macro.  It should
not be called directly.

	OP*	op_linklist(OP *o)

=for hackers
Found in file op.c

=item op_lvalue
X<op_lvalue>


NOTE: this function is experimental and may change or be
removed without notice.


Propagate lvalue ("modifiable") context to an op and its children.
C<type> represents the context type, roughly based on the type of op that
would do the modifying, although C<local()> is represented by C<OP_NULL>,
because it has no op type of its own (it is signalled by a flag on
the lvalue op).

This function detects things that can't be modified, such as C<$x+1>, and
generates errors for them.  For example, C<$x+1 = 2> would cause it to be
called with an op of type C<OP_ADD> and a C<type> argument of C<OP_SASSIGN>.

It also flags things that need to behave specially in an lvalue context,
such as C<$$x = 5> which might have to vivify a reference in C<$x>.

	OP*	op_lvalue(OP* o, I32 type)

=for hackers
Found in file op.c

=item OpMAYBESIB_set
X<OpMAYBESIB_set>

Conditionally does C<OpMORESIB_set> or C<OpLASTSIB_set> depending on whether
C<sib> is non-null. For a higher-level interface, see C<L</op_sibling_splice>>.

	void	OpMAYBESIB_set(OP *o, OP *sib, OP *parent)

=for hackers
Found in file op.h

=item OpMORESIB_set
X<OpMORESIB_set>

Sets the sibling of C<o> to the non-zero value C<sib>. See also C<L</OpLASTSIB_set>>
and C<L</OpMAYBESIB_set>>. For a higher-level interface, see
C<L</op_sibling_splice>>.

	void	OpMORESIB_set(OP *o, OP *sib)

=for hackers
Found in file op.h

=item OP_NAME
X<OP_NAME>

Return the name of the provided OP.  For core ops this looks up the name
from the op_type; for custom ops from the op_ppaddr.

	const char * OP_NAME(OP *o)

=for hackers
Found in file op.h

=item op_null
X<op_null>

Neutralizes an op when it is no longer needed, but is still linked to from
other ops.

	void	op_null(OP* o)

=for hackers
Found in file op.c

=item op_parent
X<op_parent>

Returns the parent OP of C<o>, if it has a parent. Returns C<NULL> otherwise.

	OP*	op_parent(OP *o)

=for hackers
Found in file op.c

=item op_prepend_elem
X<op_prepend_elem>

Prepend an item to the list of ops contained directly within a list-type
op, returning the lengthened list.  C<first> is the op to prepend to the
list, and C<last> is the list-type op.  C<optype> specifies the intended
opcode for the list.  If C<last> is not already a list of the right type,
it will be upgraded into one.  If either C<first> or C<last> is null,
the other is returned unchanged.

	OP*	op_prepend_elem(I32 optype, OP* first, OP* last)

=for hackers
Found in file op.c

=item op_scope
X<op_scope>


NOTE: this function is experimental and may change or be
removed without notice.


Wraps up an op tree with some additional ops so that at runtime a dynamic
scope will be created.  The original ops run in the new dynamic scope,
and then, provided that they exit normally, the scope will be unwound.
The additional ops used to create and unwind the dynamic scope will
normally be an C<enter>/C<leave> pair, but a C<scope> op may be used
instead if the ops are simple enough to not need the full dynamic scope
structure.

	OP*	op_scope(OP* o)

=for hackers
Found in file op.c

=item OpSIBLING
X<OpSIBLING>

Returns the sibling of C<o>, or C<NULL> if there is no sibling

	OP*	OpSIBLING(OP *o)

=for hackers
Found in file op.h

=item op_sibling_splice
X<op_sibling_splice>

A general function for editing the structure of an existing chain of
op_sibling nodes.  By analogy with the perl-level C<splice()> function, allows
you to delete zero or more sequential nodes, replacing them with zero or
more different nodes.  Performs the necessary op_first/op_last
housekeeping on the parent node and op_sibling manipulation on the
children.  The last deleted node will be marked as the last node by
updating the op_sibling/op_sibparent or op_moresib field as appropriate.

Note that op_next is not manipulated, and nodes are not freed; that is the
responsibility of the caller.  It also won't create a new list op for an
empty list etc; use higher-level functions like op_append_elem() for that.

C<parent> is the parent node of the sibling chain. It may passed as C<NULL> if
the splicing doesn't affect the first or last op in the chain.

C<start> is the node preceding the first node to be spliced.  Node(s)
following it will be deleted, and ops will be inserted after it.  If it is
C<NULL>, the first node onwards is deleted, and nodes are inserted at the
beginning.

C<del_count> is the number of nodes to delete.  If zero, no nodes are deleted.
If -1 or greater than or equal to the number of remaining kids, all
remaining kids are deleted.

C<insert> is the first of a chain of nodes to be inserted in place of the nodes.
If C<NULL>, no nodes are inserted.

The head of the chain of deleted ops is returned, or C<NULL> if no ops were
deleted.

For example:

    action                    before      after         returns
    ------                    -----       -----         -------

                              P           P
    splice(P, A, 2, X-Y-Z)    |           |             B-C
                              A-B-C-D     A-X-Y-Z-D

                              P           P
    splice(P, NULL, 1, X-Y)   |           |             A
                              A-B-C-D     X-Y-B-C-D

                              P           P
    splice(P, NULL, 3, NULL)  |           |             A-B-C
                              A-B-C-D     D

                              P           P
    splice(P, B, 0, X-Y)      |           |             NULL
                              A-B-C-D     A-B-X-Y-C-D


For lower-level direct manipulation of C<op_sibparent> and C<op_moresib>,
see C<L</OpMORESIB_set>>, C<L</OpLASTSIB_set>>, C<L</OpMAYBESIB_set>>.

	OP*	op_sibling_splice(OP *parent, OP *start,
		                  int del_count, OP* insert)

=for hackers
Found in file op.c

=item OP_TYPE_IS
X<OP_TYPE_IS>

Returns true if the given OP is not a C<NULL> pointer
and if it is of the given type.

The negation of this macro, C<OP_TYPE_ISNT> is also available
as well as C<OP_TYPE_IS_NN> and C<OP_TYPE_ISNT_NN> which elide
the NULL pointer check.

	bool	OP_TYPE_IS(OP *o, Optype type)

=for hackers
Found in file op.h

=item OP_TYPE_IS_OR_WAS
X<OP_TYPE_IS_OR_WAS>

Returns true if the given OP is not a NULL pointer and
if it is of the given type or used to be before being
replaced by an OP of type OP_NULL.

The negation of this macro, C<OP_TYPE_ISNT_AND_WASNT>
is also available as well as C<OP_TYPE_IS_OR_WAS_NN>
and C<OP_TYPE_ISNT_AND_WASNT_NN> which elide
the C<NULL> pointer check.

	bool	OP_TYPE_IS_OR_WAS(OP *o, Optype type)

=for hackers
Found in file op.h

=item rv2cv_op_cv
X<rv2cv_op_cv>

Examines an op, which is expected to identify a subroutine at runtime,
and attempts to determine at compile time which subroutine it identifies.
This is normally used during Perl compilation to determine whether
a prototype can be applied to a function call.  C<cvop> is the op
being considered, normally an C<rv2cv> op.  A pointer to the identified
subroutine is returned, if it could be determined statically, and a null
pointer is returned if it was not possible to determine statically.

Currently, the subroutine can be identified statically if the RV that the
C<rv2cv> is to operate on is provided by a suitable C<gv> or C<const> op.
A C<gv> op is suitable if the GV's CV slot is populated.  A C<const> op is
suitable if the constant value must be an RV pointing to a CV.  Details of
this process may change in future versions of Perl.  If the C<rv2cv> op
has the C<OPpENTERSUB_AMPER> flag set then no attempt is made to identify
the subroutine statically: this flag is used to suppress compile-time
magic on a subroutine call, forcing it to use default runtime behaviour.

If C<flags> has the bit C<RV2CVOPCV_MARK_EARLY> set, then the handling
of a GV reference is modified.  If a GV was examined and its CV slot was
found to be empty, then the C<gv> op has the C<OPpEARLY_CV> flag set.
If the op is not optimised away, and the CV slot is later populated with
a subroutine having a prototype, that flag eventually triggers the warning
"called too early to check prototype".

If C<flags> has the bit C<RV2CVOPCV_RETURN_NAME_GV> set, then instead
of returning a pointer to the subroutine it returns a pointer to the
GV giving the most appropriate name for the subroutine in this context.
Normally this is just the C<CvGV> of the subroutine, but for an anonymous
(C<CvANON>) subroutine that is referenced through a GV it will be the
referencing GV.  The resulting C<GV*> is cast to C<CV*> to be returned.
A null pointer is returned as usual if there is no statically-determinable
subroutine.

	CV*	rv2cv_op_cv(OP *cvop, U32 flags)

=for hackers
Found in file op.c


=back

=head1 Pack and Unpack

=over 8

=item packlist
X<packlist>

The engine implementing C<pack()> Perl function.

	void	packlist(SV *cat, const char *pat,
		         const char *patend, SV **beglist,
		         SV **endlist)

=for hackers
Found in file pp_pack.c

=item unpackstring
X<unpackstring>

The engine implementing the C<unpack()> Perl function.

Using the template C<pat..patend>, this function unpacks the string
C<s..strend> into a number of mortal SVs, which it pushes onto the perl
argument (C<@_>) stack (so you will need to issue a C<PUTBACK> before and
C<SPAGAIN> after the call to this function).  It returns the number of
pushed elements.

The C<strend> and C<patend> pointers should point to the byte following the
last character of each string.

Although this function returns its values on the perl argument stack, it
doesn't take any parameters from that stack (and thus in particular
there's no need to do a C<PUSHMARK> before calling it, unlike L</call_pv> for
example).

	SSize_t	unpackstring(const char *pat,
		             const char *patend, const char *s,
		             const char *strend, U32 flags)

=for hackers
Found in file pp_pack.c


=back

=head1 Pad Data Structures

=over 8

=item CvPADLIST
X<CvPADLIST>


NOTE: this function is experimental and may change or be
removed without notice.


CV's can have CvPADLIST(cv) set to point to a PADLIST.  This is the CV's
scratchpad, which stores lexical variables and opcode temporary and
per-thread values.

For these purposes "formats" are a kind-of CV; eval""s are too (except they're
not callable at will and are always thrown away after the eval"" is done
executing).  Require'd files are simply evals without any outer lexical
scope.

XSUBs do not have a C<CvPADLIST>.  C<dXSTARG> fetches values from C<PL_curpad>,
but that is really the callers pad (a slot of which is allocated by
every entersub). Do not get or set C<CvPADLIST> if a CV is an XSUB (as
determined by C<CvISXSUB()>), C<CvPADLIST> slot is reused for a different
internal purpose in XSUBs.

The PADLIST has a C array where pads are stored.

The 0th entry of the PADLIST is a PADNAMELIST
which represents the "names" or rather
the "static type information" for lexicals.  The individual elements of a
PADNAMELIST are PADNAMEs.  Future
refactorings might stop the PADNAMELIST from being stored in the PADLIST's
array, so don't rely on it.  See L</PadlistNAMES>.

The CvDEPTH'th entry of a PADLIST is a PAD (an AV) which is the stack frame
at that depth of recursion into the CV.  The 0th slot of a frame AV is an
AV which is C<@_>.  Other entries are storage for variables and op targets.

Iterating over the PADNAMELIST iterates over all possible pad
items.  Pad slots for targets (C<SVs_PADTMP>)
and GVs end up having &PL_padname_undef "names", while slots for constants 
have C<&PL_padname_const> "names" (see C<L</pad_alloc>>).  That
C<&PL_padname_undef>
and C<&PL_padname_const> are used is an implementation detail subject to
change.  To test for them, use C<!PadnamePV(name)> and
S<C<PadnamePV(name) && !PadnameLEN(name)>>, respectively.

Only C<my>/C<our> variable slots get valid names.
The rest are op targets/GVs/constants which are statically allocated
or resolved at compile time.  These don't have names by which they
can be looked up from Perl code at run time through eval"" the way
C<my>/C<our> variables can be.  Since they can't be looked up by "name"
but only by their index allocated at compile time (which is usually
in C<< PL_op->op_targ >>), wasting a name SV for them doesn't make sense.

The pad names in the PADNAMELIST have their PV holding the name of
the variable.  The C<COP_SEQ_RANGE_LOW> and C<_HIGH> fields form a range
(low+1..high inclusive) of cop_seq numbers for which the name is
valid.  During compilation, these fields may hold the special value
PERL_PADSEQ_INTRO to indicate various stages:

 COP_SEQ_RANGE_LOW        _HIGH
 -----------------        -----
 PERL_PADSEQ_INTRO            0   variable not yet introduced:
                                  { my ($x
 valid-seq#   PERL_PADSEQ_INTRO   variable in scope:
                                  { my ($x);
 valid-seq#          valid-seq#   compilation of scope complete:
                                  { my ($x); .... }

When a lexical var hasn't yet been introduced, it already exists from the
perspective of duplicate declarations, but not for variable lookups, e.g.

    my ($x, $x); # '"my" variable $x masks earlier declaration'
    my $x = $x;  # equal to my $x = $::x;

For typed lexicals C<PadnameTYPE> points at the type stash.  For C<our>
lexicals, C<PadnameOURSTASH> points at the stash of the associated global (so
that duplicate C<our> declarations in the same package can be detected).
C<PadnameGEN> is sometimes used to store the generation number during
compilation.

If C<PadnameOUTER> is set on the pad name, then that slot in the frame AV
is a REFCNT'ed reference to a lexical from "outside".  Such entries
are sometimes referred to as 'fake'.  In this case, the name does not
use 'low' and 'high' to store a cop_seq range, since it is in scope
throughout.  Instead 'high' stores some flags containing info about
the real lexical (is it declared in an anon, and is it capable of being
instantiated multiple times?), and for fake ANONs, 'low' contains the index
within the parent's pad where the lexical's value is stored, to make
cloning quicker.

If the 'name' is C<&> the corresponding entry in the PAD
is a CV representing a possible closure.

Note that formats are treated as anon subs, and are cloned each time
write is called (if necessary).

The flag C<SVs_PADSTALE> is cleared on lexicals each time the C<my()> is executed,
and set on scope exit.  This allows the
C<"Variable $x is not available"> warning
to be generated in evals, such as 

    { my $x = 1; sub f { eval '$x'} } f();

For state vars, C<SVs_PADSTALE> is overloaded to mean 'not yet initialised',
but this internal state is stored in a separate pad entry.

	PADLIST * CvPADLIST(CV *cv)

=for hackers
Found in file pad.c

=item pad_add_name_pvs
X<pad_add_name_pvs>

Exactly like L</pad_add_name_pvn>, but takes a literal string
instead of a string/length pair.

	PADOFFSET pad_add_name_pvs("name", U32 flags,
	                           HV *typestash, HV *ourstash)

=for hackers
Found in file pad.h

=item PadARRAY
X<PadARRAY>


NOTE: this function is experimental and may change or be
removed without notice.


The C array of pad entries.

	SV **	PadARRAY(PAD * pad)

=for hackers
Found in file pad.h

=item pad_findmy_pvs
X<pad_findmy_pvs>

Exactly like L</pad_findmy_pvn>, but takes a literal string
instead of a string/length pair.

	PADOFFSET pad_findmy_pvs("name", U32 flags)

=for hackers
Found in file pad.h

=item PadlistARRAY
X<PadlistARRAY>


NOTE: this function is experimental and may change or be
removed without notice.


The C array of a padlist, containing the pads.  Only subscript it with
numbers >= 1, as the 0th entry is not guaranteed to remain usable.

	PAD **	PadlistARRAY(PADLIST * padlist)

=for hackers
Found in file pad.h

=item PadlistMAX
X<PadlistMAX>


NOTE: this function is experimental and may change or be
removed without notice.


The index of the last allocated space in the padlist.  Note that the last
pad may be in an earlier slot.  Any entries following it will be C<NULL> in
that case.

	SSize_t	PadlistMAX(PADLIST * padlist)

=for hackers
Found in file pad.h

=item PadlistNAMES
X<PadlistNAMES>


NOTE: this function is experimental and may change or be
removed without notice.


The names associated with pad entries.

	PADNAMELIST * PadlistNAMES(PADLIST * padlist)

=for hackers
Found in file pad.h

=item PadlistNAMESARRAY
X<PadlistNAMESARRAY>


NOTE: this function is experimental and may change or be
removed without notice.


The C array of pad names.

	PADNAME ** PadlistNAMESARRAY(PADLIST * padlist)

=for hackers
Found in file pad.h

=item PadlistNAMESMAX
X<PadlistNAMESMAX>


NOTE: this function is experimental and may change or be
removed without notice.


The index of the last pad name.

	SSize_t	PadlistNAMESMAX(PADLIST * padlist)

=for hackers
Found in file pad.h

=item PadlistREFCNT
X<PadlistREFCNT>


NOTE: this function is experimental and may change or be
removed without notice.


The reference count of the padlist.  Currently this is always 1.

	U32	PadlistREFCNT(PADLIST * padlist)

=for hackers
Found in file pad.h

=item PadMAX
X<PadMAX>


NOTE: this function is experimental and may change or be
removed without notice.


The index of the last pad entry.

	SSize_t	PadMAX(PAD * pad)

=for hackers
Found in file pad.h

=item PadnameLEN
X<PadnameLEN>


NOTE: this function is experimental and may change or be
removed without notice.


The length of the name.

	STRLEN	PadnameLEN(PADNAME * pn)

=for hackers
Found in file pad.h

=item PadnamelistARRAY
X<PadnamelistARRAY>


NOTE: this function is experimental and may change or be
removed without notice.


The C array of pad names.

	PADNAME ** PadnamelistARRAY(PADNAMELIST * pnl)

=for hackers
Found in file pad.h

=item PadnamelistMAX
X<PadnamelistMAX>


NOTE: this function is experimental and may change or be
removed without notice.


The index of the last pad name.

	SSize_t	PadnamelistMAX(PADNAMELIST * pnl)

=for hackers
Found in file pad.h

=item PadnamelistREFCNT
X<PadnamelistREFCNT>


NOTE: this function is experimental and may change or be
removed without notice.


The reference count of the pad name list.

	SSize_t	PadnamelistREFCNT(PADNAMELIST * pnl)

=for hackers
Found in file pad.h

=item PadnamelistREFCNT_dec
X<PadnamelistREFCNT_dec>


NOTE: this function is experimental and may change or be
removed without notice.


Lowers the reference count of the pad name list.

	void	PadnamelistREFCNT_dec(PADNAMELIST * pnl)

=for hackers
Found in file pad.h

=item PadnamePV
X<PadnamePV>


NOTE: this function is experimental and may change or be
removed without notice.


The name stored in the pad name struct.  This returns C<NULL> for a target
slot.

	char *	PadnamePV(PADNAME * pn)

=for hackers
Found in file pad.h

=item PadnameREFCNT
X<PadnameREFCNT>


NOTE: this function is experimental and may change or be
removed without notice.


The reference count of the pad name.

	SSize_t	PadnameREFCNT(PADNAME * pn)

=for hackers
Found in file pad.h

=item PadnameREFCNT_dec
X<PadnameREFCNT_dec>


NOTE: this function is experimental and may change or be
removed without notice.


Lowers the reference count of the pad name.


	void	PadnameREFCNT_dec(PADNAME * pn)

=for hackers
Found in file pad.h

=item PadnameSV
X<PadnameSV>


NOTE: this function is experimental and may change or be
removed without notice.


Returns the pad name as a mortal SV.

	SV *	PadnameSV(PADNAME * pn)

=for hackers
Found in file pad.h

=item PadnameUTF8
X<PadnameUTF8>


NOTE: this function is experimental and may change or be
removed without notice.


Whether PadnamePV is in UTF-8.  Currently, this is always true.

	bool	PadnameUTF8(PADNAME * pn)

=for hackers
Found in file pad.h

=item pad_new
X<pad_new>

Create a new padlist, updating the global variables for the
currently-compiling padlist to point to the new padlist.  The following
flags can be OR'ed together:

    padnew_CLONE	this pad is for a cloned CV
    padnew_SAVE		save old globals on the save stack
    padnew_SAVESUB	also save extra stuff for start of sub

	PADLIST* pad_new(int flags)

=for hackers
Found in file pad.c

=item PL_comppad
X<PL_comppad>


NOTE: this function is experimental and may change or be
removed without notice.


During compilation, this points to the array containing the values
part of the pad for the currently-compiling code.  (At runtime a CV may
have many such value arrays; at compile time just one is constructed.)
At runtime, this points to the array containing the currently-relevant
values for the pad for the currently-executing code.

=for hackers
Found in file pad.c

=item PL_comppad_name
X<PL_comppad_name>


NOTE: this function is experimental and may change or be
removed without notice.


During compilation, this points to the array containing the names part
of the pad for the currently-compiling code.

=for hackers
Found in file pad.c

=item PL_curpad
X<PL_curpad>


NOTE: this function is experimental and may change or be
removed without notice.


Points directly to the body of the L</PL_comppad> array.
(I.e., this is C<PadARRAY(PL_comppad)>.)

=for hackers
Found in file pad.c


=back

=head1 Per-Interpreter Variables

=over 8

=item PL_curcop
X<PL_curcop>

The currently active COP (control op) roughly representing the current
statement in the source.

	COP*	PL_curcop

=for hackers
Found in file intrpvar.h

=item PL_curstash
X<PL_curstash>

The stash for the package code will be compiled into.

	HV*	PL_curstash

=for hackers
Found in file intrpvar.h

=item PL_defgv
X<PL_defgv>

The GV representing C<*_>.  Useful for access to C<$_>.

	GV *	PL_defgv

=for hackers
Found in file intrpvar.h

=item PL_exit_flags
X<PL_exit_flags>

Contains flags controlling perl's behaviour on exit():

=over

=item * C<PERL_EXIT_DESTRUCT_END>

If set, END blocks are executed when the interpreter is destroyed.
This is normally set by perl itself after the interpreter is
constructed.

=item * C<PERL_EXIT_ABORT>

Call C<abort()> on exit.  This is used internally by perl itself to
abort if exit is called while processing exit.

=item * C<PERL_EXIT_WARN>

Warn on exit.

=item * C<PERL_EXIT_EXPECTED>

Set by the L<perlfunc/exit> operator.

=back

	U8	PL_exit_flags

=for hackers
Found in file intrpvar.h

=item PL_modglobal
X<PL_modglobal>

C<PL_modglobal> is a general purpose, interpreter global HV for use by
extensions that need to keep information on a per-interpreter basis.
In a pinch, it can also be used as a symbol table for extensions
to share data among each other.  It is a good idea to use keys
prefixed by the package name of the extension that owns the data.

	HV*	PL_modglobal

=for hackers
Found in file intrpvar.h

=item PL_na
X<PL_na>

A convenience variable which is typically used with C<SvPV> when one
doesn't care about the length of the string.  It is usually more efficient
to either declare a local variable and use that instead or to use the
C<SvPV_nolen> macro.

	STRLEN	PL_na

=for hackers
Found in file intrpvar.h

=item PL_opfreehook
X<PL_opfreehook>

When non-C<NULL>, the function pointed by this variable will be called each time an OP is freed with the corresponding OP as the argument.
This allows extensions to free any extra attribute they have locally attached to an OP.
It is also assured to first fire for the parent OP and then for its kids.

When you replace this variable, it is considered a good practice to store the possibly previously installed hook and that you recall it inside your own.

	Perl_ophook_t	PL_opfreehook

=for hackers
Found in file intrpvar.h

=item PL_peepp
X<PL_peepp>

Pointer to the per-subroutine peephole optimiser.  This is a function
that gets called at the end of compilation of a Perl subroutine (or
equivalently independent piece of Perl code) to perform fixups of
some ops and to perform small-scale optimisations.  The function is
called once for each subroutine that is compiled, and is passed, as sole
parameter, a pointer to the op that is the entry point to the subroutine.
It modifies the op tree in place.

The peephole optimiser should never be completely replaced.  Rather,
add code to it by wrapping the existing optimiser.  The basic way to do
this can be seen in L<perlguts/Compile pass 3: peephole optimization>.
If the new code wishes to operate on ops throughout the subroutine's
structure, rather than just at the top level, it is likely to be more
convenient to wrap the L</PL_rpeepp> hook.

	peep_t	PL_peepp

=for hackers
Found in file intrpvar.h

=item PL_perl_destruct_level
X<PL_perl_destruct_level>

This value may be set when embedding for full cleanup.

Possible values:

=over

=item * 0 - none

=item * 1 - full

=item * 2 or greater - full with checks.

=back

If C<$ENV{PERL_DESTRUCT_LEVEL}> is set to an integer greater than the
value of C<PL_perl_destruct_level> its value is used instead.

	signed char	PL_perl_destruct_level

=for hackers
Found in file intrpvar.h

=item PL_rpeepp
X<PL_rpeepp>

Pointer to the recursive peephole optimiser.  This is a function
that gets called at the end of compilation of a Perl subroutine (or
equivalently independent piece of Perl code) to perform fixups of some
ops and to perform small-scale optimisations.  The function is called
once for each chain of ops linked through their C<op_next> fields;
it is recursively called to handle each side chain.  It is passed, as
sole parameter, a pointer to the op that is at the head of the chain.
It modifies the op tree in place.

The peephole optimiser should never be completely replaced.  Rather,
add code to it by wrapping the existing optimiser.  The basic way to do
this can be seen in L<perlguts/Compile pass 3: peephole optimization>.
If the new code wishes to operate only on ops at a subroutine's top level,
rather than throughout the structure, it is likely to be more convenient
to wrap the L</PL_peepp> hook.

	peep_t	PL_rpeepp

=for hackers
Found in file intrpvar.h

=item PL_runops
X<PL_runops>

See L<perlguts/Pluggable runops>.

	runops_proc_t	PL_runops

=for hackers
Found in file intrpvar.h

=item PL_sv_no
X<PL_sv_no>

This is the C<false> SV.  See C<L</PL_sv_yes>>.  Always refer to this as
C<&PL_sv_no>.

	SV	PL_sv_no

=for hackers
Found in file intrpvar.h

=item PL_sv_undef
X<PL_sv_undef>

This is the C<undef> SV.  Always refer to this as C<&PL_sv_undef>.

	SV	PL_sv_undef

=for hackers
Found in file intrpvar.h

=item PL_sv_yes
X<PL_sv_yes>

This is the C<true> SV.  See C<L</PL_sv_no>>.  Always refer to this as
C<&PL_sv_yes>.

	SV	PL_sv_yes

=for hackers
Found in file intrpvar.h

=item PL_sv_zero
X<PL_sv_zero>

This readonly SV has a zero numeric value and a C<"0"> string value. It's
similar to C<L</PL_sv_no>> except for its string value. Can be used as a
cheap alternative to C<mXPUSHi(0)> for example.  Always refer to this as
C<&PL_sv_zero>. Introduced in 5.28.

	SV	PL_sv_zero

=for hackers
Found in file intrpvar.h


=back

=head1 REGEXP Functions

=over 8

=item SvRX
X<SvRX>

Convenience macro to get the REGEXP from a SV.  This is approximately
equivalent to the following snippet:

    if (SvMAGICAL(sv))
        mg_get(sv);
    if (SvROK(sv))
        sv = MUTABLE_SV(SvRV(sv));
    if (SvTYPE(sv) == SVt_REGEXP)
        return (REGEXP*) sv;

C<NULL> will be returned if a REGEXP* is not found.

	REGEXP * SvRX(SV *sv)

=for hackers
Found in file regexp.h

=item SvRXOK
X<SvRXOK>

Returns a boolean indicating whether the SV (or the one it references)
is a REGEXP.

If you want to do something with the REGEXP* later use SvRX instead
and check for NULL.

	bool	SvRXOK(SV* sv)

=for hackers
Found in file regexp.h


=back

=head1 Stack Manipulation Macros

=over 8

=item dMARK
X<dMARK>

Declare a stack marker variable, C<mark>, for the XSUB.  See C<L</MARK>> and
C<L</dORIGMARK>>.

		dMARK;

=for hackers
Found in file pp.h

=item dORIGMARK
X<dORIGMARK>

Saves the original stack mark for the XSUB.  See C<L</ORIGMARK>>.

		dORIGMARK;

=for hackers
Found in file pp.h

=item dSP
X<dSP>

Declares a local copy of perl's stack pointer for the XSUB, available via
the C<SP> macro.  See C<L</SP>>.

		dSP;

=for hackers
Found in file pp.h

=item EXTEND
X<EXTEND>

Used to extend the argument stack for an XSUB's return values.  Once
used, guarantees that there is room for at least C<nitems> to be pushed
onto the stack.

	void	EXTEND(SP, SSize_t nitems)

=for hackers
Found in file pp.h

=item MARK
X<MARK>

Stack marker variable for the XSUB.  See C<L</dMARK>>.

=for hackers
Found in file pp.h

=item mPUSHi
X<mPUSHi>

Push an integer onto the stack.  The stack must have room for this element.
Does not use C<TARG>.  See also C<L</PUSHi>>, C<L</mXPUSHi>> and C<L</XPUSHi>>.

	void	mPUSHi(IV iv)

=for hackers
Found in file pp.h

=item mPUSHn
X<mPUSHn>

Push a double onto the stack.  The stack must have room for this element.
Does not use C<TARG>.  See also C<L</PUSHn>>, C<L</mXPUSHn>> and C<L</XPUSHn>>.

	void	mPUSHn(NV nv)

=for hackers
Found in file pp.h

=item mPUSHp
X<mPUSHp>

Push a string onto the stack.  The stack must have room for this element.
The C<len> indicates the length of the string.  Does not use C<TARG>.
See also C<L</PUSHp>>, C<L</mXPUSHp>> and C<L</XPUSHp>>.

	void	mPUSHp(char* str, STRLEN len)

=for hackers
Found in file pp.h

=item mPUSHs
X<mPUSHs>

Push an SV onto the stack and mortalizes the SV.  The stack must have room
for this element.  Does not use C<TARG>.  See also C<L</PUSHs>> and
C<L</mXPUSHs>>.

	void	mPUSHs(SV* sv)

=for hackers
Found in file pp.h

=item mPUSHu
X<mPUSHu>

Push an unsigned integer onto the stack.  The stack must have room for this
element.  Does not use C<TARG>.  See also C<L</PUSHu>>, C<L</mXPUSHu>> and
C<L</XPUSHu>>.

	void	mPUSHu(UV uv)

=for hackers
Found in file pp.h

=item mXPUSHi
X<mXPUSHi>

Push an integer onto the stack, extending the stack if necessary.
Does not use C<TARG>.  See also C<L</XPUSHi>>, C<L</mPUSHi>> and C<L</PUSHi>>.

	void	mXPUSHi(IV iv)

=for hackers
Found in file pp.h

=item mXPUSHn
X<mXPUSHn>

Push a double onto the stack, extending the stack if necessary.
Does not use C<TARG>.  See also C<L</XPUSHn>>, C<L</mPUSHn>> and C<L</PUSHn>>.

	void	mXPUSHn(NV nv)

=for hackers
Found in file pp.h

=item mXPUSHp
X<mXPUSHp>

Push a string onto the stack, extending the stack if necessary.  The C<len>
indicates the length of the string.  Does not use C<TARG>.  See also
C<L</XPUSHp>>, C<mPUSHp> and C<PUSHp>.

	void	mXPUSHp(char* str, STRLEN len)

=for hackers
Found in file pp.h

=item mXPUSHs
X<mXPUSHs>

Push an SV onto the stack, extending the stack if necessary and mortalizes
the SV.  Does not use C<TARG>.  See also C<L</XPUSHs>> and C<L</mPUSHs>>.

	void	mXPUSHs(SV* sv)

=for hackers
Found in file pp.h

=item mXPUSHu
X<mXPUSHu>

Push an unsigned integer onto the stack, extending the stack if necessary.
Does not use C<TARG>.  See also C<L</XPUSHu>>, C<L</mPUSHu>> and C<L</PUSHu>>.

	void	mXPUSHu(UV uv)

=for hackers
Found in file pp.h

=item ORIGMARK
X<ORIGMARK>

The original stack mark for the XSUB.  See C<L</dORIGMARK>>.

=for hackers
Found in file pp.h

=item POPi
X<POPi>

Pops an integer off the stack.

	IV	POPi

=for hackers
Found in file pp.h

=item POPl
X<POPl>

Pops a long off the stack.

	long	POPl

=for hackers
Found in file pp.h

=item POPn
X<POPn>

Pops a double off the stack.

	NV	POPn

=for hackers
Found in file pp.h

=item POPp
X<POPp>

Pops a string off the stack.

	char*	POPp

=for hackers
Found in file pp.h

=item POPpbytex
X<POPpbytex>

Pops a string off the stack which must consist of bytes i.e. characters < 256.

	char*	POPpbytex

=for hackers
Found in file pp.h

=item POPpx
X<POPpx>

Pops a string off the stack.  Identical to POPp.  There are two names for
historical reasons.

	char*	POPpx

=for hackers
Found in file pp.h

=item POPs
X<POPs>

Pops an SV off the stack.

	SV*	POPs

=for hackers
Found in file pp.h

=item POPu
X<POPu>

Pops an unsigned integer off the stack.

	UV	POPu

=for hackers
Found in file pp.h

=item POPul
X<POPul>

Pops an unsigned long off the stack.

	long	POPul

=for hackers
Found in file pp.h

=item PUSHi
X<PUSHi>

Push an integer onto the stack.  The stack must have room for this element.
Handles 'set' magic.  Uses C<TARG>, so C<dTARGET> or C<dXSTARG> should be
called to declare it.  Do not call multiple C<TARG>-oriented macros to 
return lists from XSUB's - see C<L</mPUSHi>> instead.  See also C<L</XPUSHi>>
and C<L</mXPUSHi>>.

	void	PUSHi(IV iv)

=for hackers
Found in file pp.h

=item PUSHMARK
X<PUSHMARK>

Opening bracket for arguments on a callback.  See C<L</PUTBACK>> and
L<perlcall>.

	void	PUSHMARK(SP)

=for hackers
Found in file pp.h

=item PUSHmortal
X<PUSHmortal>

Push a new mortal SV onto the stack.  The stack must have room for this
element.  Does not use C<TARG>.  See also C<L</PUSHs>>, C<L</XPUSHmortal>> and
C<L</XPUSHs>>.

	void	PUSHmortal

=for hackers
Found in file pp.h

=item PUSHn
X<PUSHn>

Push a double onto the stack.  The stack must have room for this element.
Handles 'set' magic.  Uses C<TARG>, so C<dTARGET> or C<dXSTARG> should be
called to declare it.  Do not call multiple C<TARG>-oriented macros to
return lists from XSUB's - see C<L</mPUSHn>> instead.  See also C<L</XPUSHn>>
and C<L</mXPUSHn>>.

	void	PUSHn(NV nv)

=for hackers
Found in file pp.h

=item PUSHp
X<PUSHp>

Push a string onto the stack.  The stack must have room for this element.
The C<len> indicates the length of the string.  Handles 'set' magic.  Uses
C<TARG>, so C<dTARGET> or C<dXSTARG> should be called to declare it.  Do not
call multiple C<TARG>-oriented macros to return lists from XSUB's - see
C<L</mPUSHp>> instead.  See also C<L</XPUSHp>> and C<L</mXPUSHp>>.

	void	PUSHp(char* str, STRLEN len)

=for hackers
Found in file pp.h

=item PUSHs
X<PUSHs>

Push an SV onto the stack.  The stack must have room for this element.
Does not handle 'set' magic.  Does not use C<TARG>.  See also
C<L</PUSHmortal>>, C<L</XPUSHs>>, and C<L</XPUSHmortal>>.

	void	PUSHs(SV* sv)

=for hackers
Found in file pp.h

=item PUSHu
X<PUSHu>

Push an unsigned integer onto the stack.  The stack must have room for this
element.  Handles 'set' magic.  Uses C<TARG>, so C<dTARGET> or C<dXSTARG>
should be called to declare it.  Do not call multiple C<TARG>-oriented
macros to return lists from XSUB's - see C<L</mPUSHu>> instead.  See also
C<L</XPUSHu>> and C<L</mXPUSHu>>.

	void	PUSHu(UV uv)

=for hackers
Found in file pp.h

=item PUTBACK
X<PUTBACK>

Closing bracket for XSUB arguments.  This is usually handled by C<xsubpp>.
See C<L</PUSHMARK>> and L<perlcall> for other uses.

		PUTBACK;

=for hackers
Found in file pp.h

=item SP
X<SP>

Stack pointer.  This is usually handled by C<xsubpp>.  See C<L</dSP>> and
C<SPAGAIN>.

=for hackers
Found in file pp.h

=item SPAGAIN
X<SPAGAIN>

Refetch the stack pointer.  Used after a callback.  See L<perlcall>.

		SPAGAIN;

=for hackers
Found in file pp.h

=item XPUSHi
X<XPUSHi>

Push an integer onto the stack, extending the stack if necessary.  Handles
'set' magic.  Uses C<TARG>, so C<dTARGET> or C<dXSTARG> should be called to
declare it.  Do not call multiple C<TARG>-oriented macros to return lists
from XSUB's - see C<L</mXPUSHi>> instead.  See also C<L</PUSHi>> and
C<L</mPUSHi>>.

	void	XPUSHi(IV iv)

=for hackers
Found in file pp.h

=item XPUSHmortal
X<XPUSHmortal>

Push a new mortal SV onto the stack, extending the stack if necessary.
Does not use C<TARG>.  See also C<L</XPUSHs>>, C<L</PUSHmortal>> and
C<L</PUSHs>>.

	void	XPUSHmortal

=for hackers
Found in file pp.h

=item XPUSHn
X<XPUSHn>

Push a double onto the stack, extending the stack if necessary.  Handles
'set' magic.  Uses C<TARG>, so C<dTARGET> or C<dXSTARG> should be called to
declare it.  Do not call multiple C<TARG>-oriented macros to return lists
from XSUB's - see C<L</mXPUSHn>> instead.  See also C<L</PUSHn>> and
C<L</mPUSHn>>.

	void	XPUSHn(NV nv)

=for hackers
Found in file pp.h

=item XPUSHp
X<XPUSHp>

Push a string onto the stack, extending the stack if necessary.  The C<len>
indicates the length of the string.  Handles 'set' magic.  Uses C<TARG>, so
C<dTARGET> or C<dXSTARG> should be called to declare it.  Do not call
multiple C<TARG>-oriented macros to return lists from XSUB's - see
C<L</mXPUSHp>> instead.  See also C<L</PUSHp>> and C<L</mPUSHp>>.

	void	XPUSHp(char* str, STRLEN len)

=for hackers
Found in file pp.h

=item XPUSHs
X<XPUSHs>

Push an SV onto the stack, extending the stack if necessary.  Does not
handle 'set' magic.  Does not use C<TARG>.  See also C<L</XPUSHmortal>>,
C<PUSHs> and C<PUSHmortal>.

	void	XPUSHs(SV* sv)

=for hackers
Found in file pp.h

=item XPUSHu
X<XPUSHu>

Push an unsigned integer onto the stack, extending the stack if necessary.
Handles 'set' magic.  Uses C<TARG>, so C<dTARGET> or C<dXSTARG> should be
called to declare it.  Do not call multiple C<TARG>-oriented macros to
return lists from XSUB's - see C<L</mXPUSHu>> instead.  See also C<L</PUSHu>> and
C<L</mPUSHu>>.

	void	XPUSHu(UV uv)

=for hackers
Found in file pp.h

=item XSRETURN
X<XSRETURN>

Return from XSUB, indicating number of items on the stack.  This is usually
handled by C<xsubpp>.

	void	XSRETURN(int nitems)

=for hackers
Found in file XSUB.h

=item XSRETURN_EMPTY
X<XSRETURN_EMPTY>

Return an empty list from an XSUB immediately.

		XSRETURN_EMPTY;

=for hackers
Found in file XSUB.h

=item XSRETURN_IV
X<XSRETURN_IV>

Return an integer from an XSUB immediately.  Uses C<XST_mIV>.

	void	XSRETURN_IV(IV iv)

=for hackers
Found in file XSUB.h

=item XSRETURN_NO
X<XSRETURN_NO>

Return C<&PL_sv_no> from an XSUB immediately.  Uses C<XST_mNO>.

		XSRETURN_NO;

=for hackers
Found in file XSUB.h

=item XSRETURN_NV
X<XSRETURN_NV>

Return a double from an XSUB immediately.  Uses C<XST_mNV>.

	void	XSRETURN_NV(NV nv)

=for hackers
Found in file XSUB.h

=item XSRETURN_PV
X<XSRETURN_PV>

Return a copy of a string from an XSUB immediately.  Uses C<XST_mPV>.

	void	XSRETURN_PV(char* str)

=for hackers
Found in file XSUB.h

=item XSRETURN_UNDEF
X<XSRETURN_UNDEF>

Return C<&PL_sv_undef> from an XSUB immediately.  Uses C<XST_mUNDEF>.

		XSRETURN_UNDEF;

=for hackers
Found in file XSUB.h

=item XSRETURN_UV
X<XSRETURN_UV>

Return an integer from an XSUB immediately.  Uses C<XST_mUV>.

	void	XSRETURN_UV(IV uv)

=for hackers
Found in file XSUB.h

=item XSRETURN_YES
X<XSRETURN_YES>

Return C<&PL_sv_yes> from an XSUB immediately.  Uses C<XST_mYES>.

		XSRETURN_YES;

=for hackers
Found in file XSUB.h

=item XST_mIV
X<XST_mIV>

Place an integer into the specified position C<pos> on the stack.  The
value is stored in a new mortal SV.

	void	XST_mIV(int pos, IV iv)

=for hackers
Found in file XSUB.h

=item XST_mNO
X<XST_mNO>

Place C<&PL_sv_no> into the specified position C<pos> on the
stack.

	void	XST_mNO(int pos)

=for hackers
Found in file XSUB.h

=item XST_mNV
X<XST_mNV>

Place a double into the specified position C<pos> on the stack.  The value
is stored in a new mortal SV.

	void	XST_mNV(int pos, NV nv)

=for hackers
Found in file XSUB.h

=item XST_mPV
X<XST_mPV>

Place a copy of a string into the specified position C<pos> on the stack. 
The value is stored in a new mortal SV.

	void	XST_mPV(int pos, char* str)

=for hackers
Found in file XSUB.h

=item XST_mUNDEF
X<XST_mUNDEF>

Place C<&PL_sv_undef> into the specified position C<pos> on the
stack.

	void	XST_mUNDEF(int pos)

=for hackers
Found in file XSUB.h

=item XST_mUV
X<XST_mUV>

Place an unsigned integer into the specified position C<pos> on the stack.  The
value is stored in a new mortal SV.

	void	XST_mUV(int pos, UV uv)

=for hackers
Found in file XSUB.h

=item XST_mYES
X<XST_mYES>

Place C<&PL_sv_yes> into the specified position C<pos> on the
stack.

	void	XST_mYES(int pos)

=for hackers
Found in file XSUB.h


=back

=head1 SV Flags

=over 8

=item SVt_IV
X<SVt_IV>

Type flag for scalars.  See L</svtype>.

=for hackers
Found in file sv.h

=item SVt_NULL
X<SVt_NULL>

Type flag for scalars.  See L</svtype>.

=for hackers
Found in file sv.h

=item SVt_NV
X<SVt_NV>

Type flag for scalars.  See L</svtype>.

=for hackers
Found in file sv.h

=item SVt_PV
X<SVt_PV>

Type flag for scalars.  See L</svtype>.

=for hackers
Found in file sv.h

=item SVt_PVAV
X<SVt_PVAV>

Type flag for arrays.  See L</svtype>.

=for hackers
Found in file sv.h

=item SVt_PVCV
X<SVt_PVCV>

Type flag for subroutines.  See L</svtype>.

=for hackers
Found in file sv.h

=item SVt_PVFM
X<SVt_PVFM>

Type flag for formats.  See L</svtype>.

=for hackers
Found in file sv.h

=item SVt_PVGV
X<SVt_PVGV>

Type flag for typeglobs.  See L</svtype>.

=for hackers
Found in file sv.h

=item SVt_PVHV
X<SVt_PVHV>

Type flag for hashes.  See L</svtype>.

=for hackers
Found in file sv.h

=item SVt_PVIO
X<SVt_PVIO>

Type flag for I/O objects.  See L</svtype>.

=for hackers
Found in file sv.h

=item SVt_PVIV
X<SVt_PVIV>

Type flag for scalars.  See L</svtype>.

=for hackers
Found in file sv.h

=item SVt_PVLV
X<SVt_PVLV>

Type flag for scalars.  See L</svtype>.

=for hackers
Found in file sv.h

=item SVt_PVMG
X<SVt_PVMG>

Type flag for scalars.  See L</svtype>.

=for hackers
Found in file sv.h

=item SVt_PVNV
X<SVt_PVNV>

Type flag for scalars.  See L</svtype>.

=for hackers
Found in file sv.h

=item SVt_REGEXP
X<SVt_REGEXP>

Type flag for regular expressions.  See L</svtype>.

=for hackers
Found in file sv.h

=item svtype
X<svtype>

An enum of flags for Perl types.  These are found in the file F<sv.h>
in the C<svtype> enum.  Test these flags with the C<SvTYPE> macro.

The types are:

    SVt_NULL
    SVt_IV
    SVt_NV
    SVt_RV
    SVt_PV
    SVt_PVIV
    SVt_PVNV
    SVt_PVMG
    SVt_INVLIST
    SVt_REGEXP
    SVt_PVGV
    SVt_PVLV
    SVt_PVAV
    SVt_PVHV
    SVt_PVCV
    SVt_PVFM
    SVt_PVIO

These are most easily explained from the bottom up.

C<SVt_PVIO> is for I/O objects, C<SVt_PVFM> for formats, C<SVt_PVCV> for
subroutines, C<SVt_PVHV> for hashes and C<SVt_PVAV> for arrays.

All the others are scalar types, that is, things that can be bound to a
C<$> variable.  For these, the internal types are mostly orthogonal to
types in the Perl language.

Hence, checking C<< SvTYPE(sv) < SVt_PVAV >> is the best way to see whether
something is a scalar.

C<SVt_PVGV> represents a typeglob.  If C<!SvFAKE(sv)>, then it is a real,
incoercible typeglob.  If C<SvFAKE(sv)>, then it is a scalar to which a
typeglob has been assigned.  Assigning to it again will stop it from being
a typeglob.  C<SVt_PVLV> represents a scalar that delegates to another scalar
behind the scenes.  It is used, e.g., for the return value of C<substr> and
for tied hash and array elements.  It can hold any scalar value, including
a typeglob.  C<SVt_REGEXP> is for regular
expressions.  C<SVt_INVLIST> is for Perl
core internal use only.

C<SVt_PVMG> represents a "normal" scalar (not a typeglob, regular expression,
or delegate).  Since most scalars do not need all the internal fields of a
PVMG, we save memory by allocating smaller structs when possible.  All the
other types are just simpler forms of C<SVt_PVMG>, with fewer internal fields.
C<SVt_NULL> can only hold undef.  C<SVt_IV> can hold undef, an integer, or a
reference.  (C<SVt_RV> is an alias for C<SVt_IV>, which exists for backward
compatibility.)  C<SVt_NV> can hold any of those or a double.  C<SVt_PV> can only
hold C<undef> or a string.  C<SVt_PVIV> is a superset of C<SVt_PV> and C<SVt_IV>.
C<SVt_PVNV> is similar.  C<SVt_PVMG> can hold anything C<SVt_PVNV> can hold, but it
can, but does not have to, be blessed or magical.

=for hackers
Found in file sv.h


=back

=head1 SV Manipulation Functions

=over 8

=item boolSV
X<boolSV>

Returns a true SV if C<b> is a true value, or a false SV if C<b> is 0.

See also C<L</PL_sv_yes>> and C<L</PL_sv_no>>.

	SV *	boolSV(bool b)

=for hackers
Found in file sv.h

=item croak_xs_usage
X<croak_xs_usage>

A specialised variant of C<croak()> for emitting the usage message for xsubs

    croak_xs_usage(cv, "eee_yow");

works out the package name and subroutine name from C<cv>, and then calls
C<croak()>.  Hence if C<cv> is C<&ouch::awk>, it would call C<croak> as:

 Perl_croak(aTHX_ "Usage: %" SVf "::%" SVf "(%s)", "ouch" "awk",
                                                     "eee_yow");

	void	croak_xs_usage(const CV *const cv,
		               const char *const params)

=for hackers
Found in file universal.c

=item get_sv
X<get_sv>

Returns the SV of the specified Perl scalar.  C<flags> are passed to
C<gv_fetchpv>.  If C<GV_ADD> is set and the
Perl variable does not exist then it will be created.  If C<flags> is zero
and the variable does not exist then NULL is returned.

NOTE: the perl_ form of this function is deprecated.

	SV*	get_sv(const char *name, I32 flags)

=for hackers
Found in file perl.c

=item looks_like_number
X<looks_like_number>

Test if the content of an SV looks like a number (or is a number).
C<Inf> and C<Infinity> are treated as numbers (so will not issue a
non-numeric warning), even if your C<atof()> doesn't grok them.  Get-magic is
ignored.

	I32	looks_like_number(SV *const sv)

=for hackers
Found in file sv.c

=item newRV_inc
X<newRV_inc>

Creates an RV wrapper for an SV.  The reference count for the original SV is
incremented.

	SV*	newRV_inc(SV* sv)

=for hackers
Found in file sv.h

=item newRV_noinc
X<newRV_noinc>

Creates an RV wrapper for an SV.  The reference count for the original
SV is B<not> incremented.

	SV*	newRV_noinc(SV *const tmpRef)

=for hackers
Found in file sv.c

=item newSV
X<newSV>

Creates a new SV.  A non-zero C<len> parameter indicates the number of
bytes of preallocated string space the SV should have.  An extra byte for a
trailing C<NUL> is also reserved.  (C<SvPOK> is not set for the SV even if string
space is allocated.)  The reference count for the new SV is set to 1.

In 5.9.3, C<newSV()> replaces the older C<NEWSV()> API, and drops the first
parameter, I<x>, a debug aid which allowed callers to identify themselves.
This aid has been superseded by a new build option, C<PERL_MEM_LOG> (see
L<perlhacktips/PERL_MEM_LOG>).  The older API is still there for use in XS
modules supporting older perls.

	SV*	newSV(const STRLEN len)

=for hackers
Found in file sv.c

=item newSVhek
X<newSVhek>

Creates a new SV from the hash key structure.  It will generate scalars that
point to the shared string table where possible.  Returns a new (undefined)
SV if C<hek> is NULL.

	SV*	newSVhek(const HEK *const hek)

=for hackers
Found in file sv.c

=item newSViv
X<newSViv>

Creates a new SV and copies an integer into it.  The reference count for the
SV is set to 1.

	SV*	newSViv(const IV i)

=for hackers
Found in file sv.c

=item newSVnv
X<newSVnv>

Creates a new SV and copies a floating point value into it.
The reference count for the SV is set to 1.

	SV*	newSVnv(const NV n)

=for hackers
Found in file sv.c

=item newSVpadname
X<newSVpadname>


NOTE: this function is experimental and may change or be
removed without notice.


Creates a new SV containing the pad name.

	SV*	newSVpadname(PADNAME *pn)

=for hackers
Found in file sv.h

=item newSVpv
X<newSVpv>

Creates a new SV and copies a string (which may contain C<NUL> (C<\0>)
characters) into it.  The reference count for the
SV is set to 1.  If C<len> is zero, Perl will compute the length using
C<strlen()>, (which means if you use this option, that C<s> can't have embedded
C<NUL> characters and has to have a terminating C<NUL> byte).

This function can cause reliability issues if you are likely to pass in
empty strings that are not null terminated, because it will run
strlen on the string and potentially run past valid memory.

Using L</newSVpvn> is a safer alternative for non C<NUL> terminated strings.
For string literals use L</newSVpvs> instead.  This function will work fine for
C<NUL> terminated strings, but if you want to avoid the if statement on whether
to call C<strlen> use C<newSVpvn> instead (calling C<strlen> yourself).

	SV*	newSVpv(const char *const s, const STRLEN len)

=for hackers
Found in file sv.c

=item newSVpvf
X<newSVpvf>

Creates a new SV and initializes it with the string formatted like
C<sv_catpvf>.

	SV*	newSVpvf(const char *const pat, ...)

=for hackers
Found in file sv.c

=item newSVpvn
X<newSVpvn>

Creates a new SV and copies a string into it, which may contain C<NUL> characters
(C<\0>) and other binary data.  The reference count for the SV is set to 1.
Note that if C<len> is zero, Perl will create a zero length (Perl) string.  You
are responsible for ensuring that the source buffer is at least
C<len> bytes long.  If the C<buffer> argument is NULL the new SV will be
undefined.

	SV*	newSVpvn(const char *const buffer,
		         const STRLEN len)

=for hackers
Found in file sv.c

=item newSVpvn_flags
X<newSVpvn_flags>

Creates a new SV and copies a string (which may contain C<NUL> (C<\0>)
characters) into it.  The reference count for the
SV is set to 1.  Note that if C<len> is zero, Perl will create a zero length
string.  You are responsible for ensuring that the source string is at least
C<len> bytes long.  If the C<s> argument is NULL the new SV will be undefined.
Currently the only flag bits accepted are C<SVf_UTF8> and C<SVs_TEMP>.
If C<SVs_TEMP> is set, then C<sv_2mortal()> is called on the result before
returning.  If C<SVf_UTF8> is set, C<s>
is considered to be in UTF-8 and the
C<SVf_UTF8> flag will be set on the new SV.
C<newSVpvn_utf8()> is a convenience wrapper for this function, defined as

    #define newSVpvn_utf8(s, len, u)			\
	newSVpvn_flags((s), (len), (u) ? SVf_UTF8 : 0)

	SV*	newSVpvn_flags(const char *const s,
		               const STRLEN len,
		               const U32 flags)

=for hackers
Found in file sv.c

=item newSVpvn_share
X<newSVpvn_share>

Creates a new SV with its C<SvPVX_const> pointing to a shared string in the string
table.  If the string does not already exist in the table, it is
created first.  Turns on the C<SvIsCOW> flag (or C<READONLY>
and C<FAKE> in 5.16 and earlier).  If the C<hash> parameter
is non-zero, that value is used; otherwise the hash is computed.
The string's hash can later be retrieved from the SV
with the C<SvSHARED_HASH()> macro.  The idea here is
that as the string table is used for shared hash keys these strings will have
C<SvPVX_const == HeKEY> and hash lookup will avoid string compare.

	SV*	newSVpvn_share(const char* s, I32 len, U32 hash)

=for hackers
Found in file sv.c

=item newSVpvn_utf8
X<newSVpvn_utf8>

Creates a new SV and copies a string (which may contain C<NUL> (C<\0>)
characters) into it.  If C<utf8> is true, calls
C<SvUTF8_on> on the new SV.  Implemented as a wrapper around C<newSVpvn_flags>.

	SV*	newSVpvn_utf8(const char* s, STRLEN len,
		              U32 utf8)

=for hackers
Found in file sv.h

=item newSVpvs
X<newSVpvs>

Like C<newSVpvn>, but takes a literal string instead of a
string/length pair.

	SV*	newSVpvs("literal string")

=for hackers
Found in file handy.h

=item newSVpvs_flags
X<newSVpvs_flags>

Like C<newSVpvn_flags>, but takes a literal string instead of
a string/length pair.

	SV*	newSVpvs_flags("literal string", U32 flags)

=for hackers
Found in file handy.h

=item newSVpv_share
X<newSVpv_share>

Like C<newSVpvn_share>, but takes a C<NUL>-terminated string instead of a
string/length pair.

	SV*	newSVpv_share(const char* s, U32 hash)

=for hackers
Found in file sv.c

=item newSVpvs_share
X<newSVpvs_share>

Like C<newSVpvn_share>, but takes a literal string instead of
a string/length pair and omits the hash parameter.

	SV*	newSVpvs_share("literal string")

=for hackers
Found in file handy.h

=item newSVrv
X<newSVrv>

Creates a new SV for the existing RV, C<rv>, to point to.  If C<rv> is not an
RV then it will be upgraded to one.  If C<classname> is non-null then the new
SV will be blessed in the specified package.  The new SV is returned and its
reference count is 1.  The reference count 1 is owned by C<rv>. See also
newRV_inc() and newRV_noinc() for creating a new RV properly.

	SV*	newSVrv(SV *const rv,
		        const char *const classname)

=for hackers
Found in file sv.c

=item newSVsv
X<newSVsv>

Creates a new SV which is an exact duplicate of the original SV.
(Uses C<sv_setsv>.)

	SV*	newSVsv(SV *const old)

=for hackers
Found in file sv.c

=item newSVsv_nomg
X<newSVsv_nomg>

Like C<newSVsv> but does not process get magic.

	SV*	newSVsv_nomg(SV *const old)

=for hackers
Found in file sv.c

=item newSV_type
X<newSV_type>

Creates a new SV, of the type specified.  The reference count for the new SV
is set to 1.

	SV*	newSV_type(const svtype type)

=for hackers
Found in file sv.c

=item newSVuv
X<newSVuv>

Creates a new SV and copies an unsigned integer into it.
The reference count for the SV is set to 1.

	SV*	newSVuv(const UV u)

=for hackers
Found in file sv.c

=item sortsv_flags
X<sortsv_flags>

In-place sort an array of SV pointers with the given comparison routine,
with various SORTf_* flag options.

	void	sortsv_flags(SV** array, size_t num_elts,
		             SVCOMPARE_t cmp, U32 flags)

=for hackers
Found in file pp_sort.c

=item sv_2bool
X<sv_2bool>

This macro is only used by C<sv_true()> or its macro equivalent, and only if
the latter's argument is neither C<SvPOK>, C<SvIOK> nor C<SvNOK>.
It calls C<sv_2bool_flags> with the C<SV_GMAGIC> flag.

	bool	sv_2bool(SV *const sv)

=for hackers
Found in file sv.c

=item sv_2bool_flags
X<sv_2bool_flags>

This function is only used by C<sv_true()> and friends,  and only if
the latter's argument is neither C<SvPOK>, C<SvIOK> nor C<SvNOK>.  If the flags
contain C<SV_GMAGIC>, then it does an C<mg_get()> first.


	bool	sv_2bool_flags(SV *sv, I32 flags)

=for hackers
Found in file sv.c

=item sv_2cv
X<sv_2cv>

Using various gambits, try to get a CV from an SV; in addition, try if
possible to set C<*st> and C<*gvp> to the stash and GV associated with it.
The flags in C<lref> are passed to C<gv_fetchsv>.

	CV*	sv_2cv(SV* sv, HV **const st, GV **const gvp,
		       const I32 lref)

=for hackers
Found in file sv.c

=item sv_2io
X<sv_2io>

Using various gambits, try to get an IO from an SV: the IO slot if its a
GV; or the recursive result if we're an RV; or the IO slot of the symbol
named after the PV if we're a string.

'Get' magic is ignored on the C<sv> passed in, but will be called on
C<SvRV(sv)> if C<sv> is an RV.

	IO*	sv_2io(SV *const sv)

=for hackers
Found in file sv.c

=item sv_2iv_flags
X<sv_2iv_flags>

Return the integer value of an SV, doing any necessary string
conversion.  If C<flags> has the C<SV_GMAGIC> bit set, does an C<mg_get()> first.
Normally used via the C<SvIV(sv)> and C<SvIVx(sv)> macros.

	IV	sv_2iv_flags(SV *const sv, const I32 flags)

=for hackers
Found in file sv.c

=item sv_2mortal
X<sv_2mortal>

Marks an existing SV as mortal.  The SV will be destroyed "soon", either
by an explicit call to C<FREETMPS>, or by an implicit call at places such as
statement boundaries.  C<SvTEMP()> is turned on which means that the SV's
string buffer can be "stolen" if this SV is copied.  See also
C<L</sv_newmortal>> and C<L</sv_mortalcopy>>.

	SV*	sv_2mortal(SV *const sv)

=for hackers
Found in file sv.c

=item sv_2nv_flags
X<sv_2nv_flags>

Return the num value of an SV, doing any necessary string or integer
conversion.  If C<flags> has the C<SV_GMAGIC> bit set, does an C<mg_get()> first.
Normally used via the C<SvNV(sv)> and C<SvNVx(sv)> macros.

	NV	sv_2nv_flags(SV *const sv, const I32 flags)

=for hackers
Found in file sv.c

=item sv_2pvbyte
X<sv_2pvbyte>

Return a pointer to the byte-encoded representation of the SV, and set C<*lp>
to its length.  If the SV is marked as being encoded as UTF-8, it will
downgrade it to a byte string as a side-effect, if possible.  If the SV cannot
be downgraded, this croaks.

Usually accessed via the C<SvPVbyte> macro.

	char*	sv_2pvbyte(SV *sv, STRLEN *const lp)

=for hackers
Found in file sv.c

=item sv_2pvutf8
X<sv_2pvutf8>

Return a pointer to the UTF-8-encoded representation of the SV, and set C<*lp>
to its length.  May cause the SV to be upgraded to UTF-8 as a side-effect.

Usually accessed via the C<SvPVutf8> macro.

	char*	sv_2pvutf8(SV *sv, STRLEN *const lp)

=for hackers
Found in file sv.c

=item sv_2pv_flags
X<sv_2pv_flags>

Returns a pointer to the string value of an SV, and sets C<*lp> to its length.
If flags has the C<SV_GMAGIC> bit set, does an C<mg_get()> first.  Coerces C<sv> to a
string if necessary.  Normally invoked via the C<SvPV_flags> macro.
C<sv_2pv()> and C<sv_2pv_nomg> usually end up here too.

	char*	sv_2pv_flags(SV *const sv, STRLEN *const lp,
		             const I32 flags)

=for hackers
Found in file sv.c

=item sv_2uv_flags
X<sv_2uv_flags>

Return the unsigned integer value of an SV, doing any necessary string
conversion.  If C<flags> has the C<SV_GMAGIC> bit set, does an C<mg_get()> first.
Normally used via the C<SvUV(sv)> and C<SvUVx(sv)> macros.

	UV	sv_2uv_flags(SV *const sv, const I32 flags)

=for hackers
Found in file sv.c

=item sv_backoff
X<sv_backoff>

Remove any string offset.  You should normally use the C<SvOOK_off> macro
wrapper instead.

	void	sv_backoff(SV *const sv)

=for hackers
Found in file sv.c

=item sv_bless
X<sv_bless>

Blesses an SV into a specified package.  The SV must be an RV.  The package
must be designated by its stash (see C<L</gv_stashpv>>).  The reference count
of the SV is unaffected.

	SV*	sv_bless(SV *const sv, HV *const stash)

=for hackers
Found in file sv.c

=item sv_catpv
X<sv_catpv>

Concatenates the C<NUL>-terminated string onto the end of the string which is
in the SV.
If the SV has the UTF-8 status set, then the bytes appended should be
valid UTF-8.  Handles 'get' magic, but not 'set' magic.  See
C<L</sv_catpv_mg>>.

	void	sv_catpv(SV *const sv, const char* ptr)

=for hackers
Found in file sv.c

=item sv_catpvf
X<sv_catpvf>

Processes its arguments like C<sprintf>, and appends the formatted
output to an SV.  As with C<sv_vcatpvfn> called with a non-null C-style
variable argument list, argument reordering is not supported.
If the appended data contains "wide" characters
(including, but not limited to, SVs with a UTF-8 PV formatted with C<%s>,
and characters >255 formatted with C<%c>), the original SV might get
upgraded to UTF-8.  Handles 'get' magic, but not 'set' magic.  See
C<L</sv_catpvf_mg>>.  If the original SV was UTF-8, the pattern should be
valid UTF-8; if the original SV was bytes, the pattern should be too.

	void	sv_catpvf(SV *const sv, const char *const pat,
		          ...)

=for hackers
Found in file sv.c

=item sv_catpvf_mg
X<sv_catpvf_mg>

Like C<sv_catpvf>, but also handles 'set' magic.

	void	sv_catpvf_mg(SV *const sv,
		             const char *const pat, ...)

=for hackers
Found in file sv.c

=item sv_catpvn
X<sv_catpvn>

Concatenates the string onto the end of the string which is in the SV.
C<len> indicates number of bytes to copy.  If the SV has the UTF-8
status set, then the bytes appended should be valid UTF-8.
Handles 'get' magic, but not 'set' magic.  See C<L</sv_catpvn_mg>>.

	void	sv_catpvn(SV *dsv, const char *sstr, STRLEN len)

=for hackers
Found in file sv.c

=item sv_catpvn_flags
X<sv_catpvn_flags>

Concatenates the string onto the end of the string which is in the SV.  The
C<len> indicates number of bytes to copy.

By default, the string appended is assumed to be valid UTF-8 if the SV has
the UTF-8 status set, and a string of bytes otherwise.  One can force the
appended string to be interpreted as UTF-8 by supplying the C<SV_CATUTF8>
flag, and as bytes by supplying the C<SV_CATBYTES> flag; the SV or the
string appended will be upgraded to UTF-8 if necessary.

If C<flags> has the C<SV_SMAGIC> bit set, will
C<mg_set> on C<dsv> afterwards if appropriate.
C<sv_catpvn> and C<sv_catpvn_nomg> are implemented
in terms of this function.

	void	sv_catpvn_flags(SV *const dstr,
		                const char *sstr,
		                const STRLEN len,
		                const I32 flags)

=for hackers
Found in file sv.c

=item sv_catpvn_nomg
X<sv_catpvn_nomg>

Like C<sv_catpvn> but doesn't process magic.

	void	sv_catpvn_nomg(SV* sv, const char* ptr,
		               STRLEN len)

=for hackers
Found in file sv.h

=item sv_catpvs
X<sv_catpvs>

Like C<sv_catpvn>, but takes a literal string instead of a
string/length pair.

	void	sv_catpvs(SV* sv, "literal string")

=for hackers
Found in file handy.h

=item sv_catpvs_flags
X<sv_catpvs_flags>

Like C<sv_catpvn_flags>, but takes a literal string instead
of a string/length pair.

	void	sv_catpvs_flags(SV* sv, "literal string",
		                I32 flags)

=for hackers
Found in file handy.h

=item sv_catpvs_mg
X<sv_catpvs_mg>

Like C<sv_catpvn_mg>, but takes a literal string instead of a
string/length pair.

	void	sv_catpvs_mg(SV* sv, "literal string")

=for hackers
Found in file handy.h

=item sv_catpvs_nomg
X<sv_catpvs_nomg>

Like C<sv_catpvn_nomg>, but takes a literal string instead of
a string/length pair.

	void	sv_catpvs_nomg(SV* sv, "literal string")

=for hackers
Found in file handy.h

=item sv_catpv_flags
X<sv_catpv_flags>

Concatenates the C<NUL>-terminated string onto the end of the string which is
in the SV.
If the SV has the UTF-8 status set, then the bytes appended should
be valid UTF-8.  If C<flags> has the C<SV_SMAGIC> bit set, will C<mg_set>
on the modified SV if appropriate.

	void	sv_catpv_flags(SV *dstr, const char *sstr,
		               const I32 flags)

=for hackers
Found in file sv.c

=item sv_catpv_mg
X<sv_catpv_mg>

Like C<sv_catpv>, but also handles 'set' magic.

	void	sv_catpv_mg(SV *const sv, const char *const ptr)

=for hackers
Found in file sv.c

=item sv_catpv_nomg
X<sv_catpv_nomg>

Like C<sv_catpv> but doesn't process magic.

	void	sv_catpv_nomg(SV* sv, const char* ptr)

=for hackers
Found in file sv.h

=item sv_catsv
X<sv_catsv>

Concatenates the string from SV C<ssv> onto the end of the string in SV
C<dsv>.  If C<ssv> is null, does nothing; otherwise modifies only C<dsv>.
Handles 'get' magic on both SVs, but no 'set' magic.  See C<L</sv_catsv_mg>>
and C<L</sv_catsv_nomg>>.

	void	sv_catsv(SV *dstr, SV *sstr)

=for hackers
Found in file sv.c

=item sv_catsv_flags
X<sv_catsv_flags>

Concatenates the string from SV C<ssv> onto the end of the string in SV
C<dsv>.  If C<ssv> is null, does nothing; otherwise modifies only C<dsv>.
If C<flags> has the C<SV_GMAGIC> bit set, will call C<mg_get> on both SVs if
appropriate.  If C<flags> has the C<SV_SMAGIC> bit set, C<mg_set> will be called on
the modified SV afterward, if appropriate.  C<sv_catsv>, C<sv_catsv_nomg>,
and C<sv_catsv_mg> are implemented in terms of this function.

	void	sv_catsv_flags(SV *const dsv, SV *const ssv,
		               const I32 flags)

=for hackers
Found in file sv.c

=item sv_catsv_nomg
X<sv_catsv_nomg>

Like C<sv_catsv> but doesn't process magic.

	void	sv_catsv_nomg(SV* dsv, SV* ssv)

=for hackers
Found in file sv.h

=item sv_chop
X<sv_chop>

Efficient removal of characters from the beginning of the string buffer.
C<SvPOK(sv)>, or at least C<SvPOKp(sv)>, must be true and C<ptr> must be a
pointer to somewhere inside the string buffer.  C<ptr> becomes the first
character of the adjusted string.  Uses the C<OOK> hack.  On return, only
C<SvPOK(sv)> and C<SvPOKp(sv)> among the C<OK> flags will be true.

Beware: after this function returns, C<ptr> and SvPVX_const(sv) may no longer
refer to the same chunk of data.

The unfortunate similarity of this function's name to that of Perl's C<chop>
operator is strictly coincidental.  This function works from the left;
C<chop> works from the right.

	void	sv_chop(SV *const sv, const char *const ptr)

=for hackers
Found in file sv.c

=item sv_clear
X<sv_clear>

Clear an SV: call any destructors, free up any memory used by the body,
and free the body itself.  The SV's head is I<not> freed, although
its type is set to all 1's so that it won't inadvertently be assumed
to be live during global destruction etc.
This function should only be called when C<REFCNT> is zero.  Most of the time
you'll want to call C<sv_free()> (or its macro wrapper C<SvREFCNT_dec>)
instead.

	void	sv_clear(SV *const orig_sv)

=for hackers
Found in file sv.c

=item sv_cmp
X<sv_cmp>

Compares the strings in two SVs.  Returns -1, 0, or 1 indicating whether the
string in C<sv1> is less than, equal to, or greater than the string in
C<sv2>.  Is UTF-8 and S<C<'use bytes'>> aware, handles get magic, and will
coerce its args to strings if necessary.  See also C<L</sv_cmp_locale>>.

	I32	sv_cmp(SV *const sv1, SV *const sv2)

=for hackers
Found in file sv.c

=item sv_cmp_flags
X<sv_cmp_flags>

Compares the strings in two SVs.  Returns -1, 0, or 1 indicating whether the
string in C<sv1> is less than, equal to, or greater than the string in
C<sv2>.  Is UTF-8 and S<C<'use bytes'>> aware and will coerce its args to strings
if necessary.  If the flags has the C<SV_GMAGIC> bit set, it handles get magic.  See
also C<L</sv_cmp_locale_flags>>.

	I32	sv_cmp_flags(SV *const sv1, SV *const sv2,
		             const U32 flags)

=for hackers
Found in file sv.c

=item sv_cmp_locale
X<sv_cmp_locale>

Compares the strings in two SVs in a locale-aware manner.  Is UTF-8 and
S<C<'use bytes'>> aware, handles get magic, and will coerce its args to strings
if necessary.  See also C<L</sv_cmp>>.

	I32	sv_cmp_locale(SV *const sv1, SV *const sv2)

=for hackers
Found in file sv.c

=item sv_cmp_locale_flags
X<sv_cmp_locale_flags>

Compares the strings in two SVs in a locale-aware manner.  Is UTF-8 and
S<C<'use bytes'>> aware and will coerce its args to strings if necessary.  If
the flags contain C<SV_GMAGIC>, it handles get magic.  See also
C<L</sv_cmp_flags>>.

	I32	sv_cmp_locale_flags(SV *const sv1,
		                    SV *const sv2,
		                    const U32 flags)

=for hackers
Found in file sv.c

=item sv_collxfrm
X<sv_collxfrm>

This calls C<sv_collxfrm_flags> with the SV_GMAGIC flag.  See
C<L</sv_collxfrm_flags>>.

	char*	sv_collxfrm(SV *const sv, STRLEN *const nxp)

=for hackers
Found in file sv.c

=item sv_collxfrm_flags
X<sv_collxfrm_flags>

Add Collate Transform magic to an SV if it doesn't already have it.  If the
flags contain C<SV_GMAGIC>, it handles get-magic.

Any scalar variable may carry C<PERL_MAGIC_collxfrm> magic that contains the
scalar data of the variable, but transformed to such a format that a normal
memory comparison can be used to compare the data according to the locale
settings.

	char*	sv_collxfrm_flags(SV *const sv,
		                  STRLEN *const nxp,
		                  I32 const flags)

=for hackers
Found in file sv.c

=item sv_copypv
X<sv_copypv>

Copies a stringified representation of the source SV into the
destination SV.  Automatically performs any necessary C<mg_get> and
coercion of numeric values into strings.  Guaranteed to preserve
C<UTF8> flag even from overloaded objects.  Similar in nature to
C<sv_2pv[_flags]> but operates directly on an SV instead of just the
string.  Mostly uses C<sv_2pv_flags> to do its work, except when that
would lose the UTF-8'ness of the PV.

	void	sv_copypv(SV *const dsv, SV *const ssv)

=for hackers
Found in file sv.c

=item sv_copypv_flags
X<sv_copypv_flags>

Implementation of C<sv_copypv> and C<sv_copypv_nomg>.  Calls get magic iff flags
has the C<SV_GMAGIC> bit set.

	void	sv_copypv_flags(SV *const dsv, SV *const ssv,
		                const I32 flags)

=for hackers
Found in file sv.c

=item sv_copypv_nomg
X<sv_copypv_nomg>

Like C<sv_copypv>, but doesn't invoke get magic first.

	void	sv_copypv_nomg(SV *const dsv, SV *const ssv)

=for hackers
Found in file sv.c

=item SvCUR
X<SvCUR>

Returns the length of the string which is in the SV.  See C<L</SvLEN>>.

	STRLEN	SvCUR(SV* sv)

=for hackers
Found in file sv.h

=item SvCUR_set
X<SvCUR_set>

Set the current length of the string which is in the SV.  See C<L</SvCUR>>
and C<SvIV_set>>.

	void	SvCUR_set(SV* sv, STRLEN len)

=for hackers
Found in file sv.h

=item sv_dec
X<sv_dec>

Auto-decrement of the value in the SV, doing string to numeric conversion
if necessary.  Handles 'get' magic and operator overloading.

	void	sv_dec(SV *const sv)

=for hackers
Found in file sv.c

=item sv_dec_nomg
X<sv_dec_nomg>

Auto-decrement of the value in the SV, doing string to numeric conversion
if necessary.  Handles operator overloading.  Skips handling 'get' magic.

	void	sv_dec_nomg(SV *const sv)

=for hackers
Found in file sv.c

=item sv_derived_from
X<sv_derived_from>

Exactly like L</sv_derived_from_pv>, but doesn't take a C<flags> parameter.

	bool	sv_derived_from(SV* sv, const char *const name)

=for hackers
Found in file universal.c

=item sv_derived_from_pv
X<sv_derived_from_pv>

Exactly like L</sv_derived_from_pvn>, but takes a nul-terminated string 
instead of a string/length pair.

	bool	sv_derived_from_pv(SV* sv,
		                   const char *const name,
		                   U32 flags)

=for hackers
Found in file universal.c

=item sv_derived_from_pvn
X<sv_derived_from_pvn>

Returns a boolean indicating whether the SV is derived from the specified class
I<at the C level>.  To check derivation at the Perl level, call C<isa()> as a
normal Perl method.

Currently, the only significant value for C<flags> is SVf_UTF8.

	bool	sv_derived_from_pvn(SV* sv,
		                    const char *const name,
		                    const STRLEN len, U32 flags)

=for hackers
Found in file universal.c

=item sv_derived_from_sv
X<sv_derived_from_sv>

Exactly like L</sv_derived_from_pvn>, but takes the name string in the form
of an SV instead of a string/length pair. This is the advised form.

	bool	sv_derived_from_sv(SV* sv, SV *namesv,
		                   U32 flags)

=for hackers
Found in file universal.c

=item sv_does
X<sv_does>

Like L</sv_does_pv>, but doesn't take a C<flags> parameter.

	bool	sv_does(SV* sv, const char *const name)

=for hackers
Found in file universal.c

=item sv_does_pv
X<sv_does_pv>

Like L</sv_does_sv>, but takes a nul-terminated string instead of an SV.

	bool	sv_does_pv(SV* sv, const char *const name,
		           U32 flags)

=for hackers
Found in file universal.c

=item sv_does_pvn
X<sv_does_pvn>

Like L</sv_does_sv>, but takes a string/length pair instead of an SV.

	bool	sv_does_pvn(SV* sv, const char *const name,
		            const STRLEN len, U32 flags)

=for hackers
Found in file universal.c

=item sv_does_sv
X<sv_does_sv>

Returns a boolean indicating whether the SV performs a specific, named role.
The SV can be a Perl object or the name of a Perl class.

	bool	sv_does_sv(SV* sv, SV* namesv, U32 flags)

=for hackers
Found in file universal.c

=item SvEND
X<SvEND>

Returns a pointer to the spot just after the last character in
the string which is in the SV, where there is usually a trailing
C<NUL> character (even though Perl scalars do not strictly require it).
See C<L</SvCUR>>.  Access the character as C<*(SvEND(sv))>.

Warning: If C<SvCUR> is equal to C<SvLEN>, then C<SvEND> points to
unallocated memory.

	char*	SvEND(SV* sv)

=for hackers
Found in file sv.h

=item sv_eq
X<sv_eq>

Returns a boolean indicating whether the strings in the two SVs are
identical.  Is UTF-8 and S<C<'use bytes'>> aware, handles get magic, and will
coerce its args to strings if necessary.

	I32	sv_eq(SV* sv1, SV* sv2)

=for hackers
Found in file sv.c

=item sv_eq_flags
X<sv_eq_flags>

Returns a boolean indicating whether the strings in the two SVs are
identical.  Is UTF-8 and S<C<'use bytes'>> aware and coerces its args to strings
if necessary.  If the flags has the C<SV_GMAGIC> bit set, it handles get-magic, too.

	I32	sv_eq_flags(SV* sv1, SV* sv2, const U32 flags)

=for hackers
Found in file sv.c

=item sv_force_normal_flags
X<sv_force_normal_flags>

Undo various types of fakery on an SV, where fakery means
"more than" a string: if the PV is a shared string, make
a private copy; if we're a ref, stop refing; if we're a glob, downgrade to
an C<xpvmg>; if we're a copy-on-write scalar, this is the on-write time when
we do the copy, and is also used locally; if this is a
vstring, drop the vstring magic.  If C<SV_COW_DROP_PV> is set
then a copy-on-write scalar drops its PV buffer (if any) and becomes
C<SvPOK_off> rather than making a copy.  (Used where this
scalar is about to be set to some other value.)  In addition,
the C<flags> parameter gets passed to C<sv_unref_flags()>
when unreffing.  C<sv_force_normal> calls this function
with flags set to 0.

This function is expected to be used to signal to perl that this SV is
about to be written to, and any extra book-keeping needs to be taken care
of.  Hence, it croaks on read-only values.

	void	sv_force_normal_flags(SV *const sv,
		                      const U32 flags)

=for hackers
Found in file sv.c

=item sv_free
X<sv_free>

Decrement an SV's reference count, and if it drops to zero, call
C<sv_clear> to invoke destructors and free up any memory used by
the body; finally, deallocating the SV's head itself.
Normally called via a wrapper macro C<SvREFCNT_dec>.

	void	sv_free(SV *const sv)

=for hackers
Found in file sv.c

=item SvGAMAGIC
X<SvGAMAGIC>

Returns true if the SV has get magic or
overloading.  If either is true then
the scalar is active data, and has the potential to return a new value every
time it is accessed.  Hence you must be careful to
only read it once per user logical operation and work
with that returned value.  If neither is true then
the scalar's value cannot change unless written to.

	U32	SvGAMAGIC(SV* sv)

=for hackers
Found in file sv.h

=item sv_gets
X<sv_gets>

Get a line from the filehandle and store it into the SV, optionally
appending to the currently-stored string.  If C<append> is not 0, the
line is appended to the SV instead of overwriting it.  C<append> should
be set to the byte offset that the appended string should start at
in the SV (typically, C<SvCUR(sv)> is a suitable choice).

	char*	sv_gets(SV *const sv, PerlIO *const fp,
		        I32 append)

=for hackers
Found in file sv.c

=item sv_get_backrefs
X<sv_get_backrefs>


NOTE: this function is experimental and may change or be
removed without notice.


If C<sv> is the target of a weak reference then it returns the back
references structure associated with the sv; otherwise return C<NULL>.

When returning a non-null result the type of the return is relevant. If it
is an AV then the elements of the AV are the weak reference RVs which
point at this item. If it is any other type then the item itself is the
weak reference.

See also C<Perl_sv_add_backref()>, C<Perl_sv_del_backref()>,
C<Perl_sv_kill_backrefs()>

	SV*	sv_get_backrefs(SV *const sv)

=for hackers
Found in file sv.c

=item SvGROW
X<SvGROW>

Expands the character buffer in the SV so that it has room for the
indicated number of bytes (remember to reserve space for an extra trailing
C<NUL> character).  Calls C<sv_grow> to perform the expansion if necessary.
Returns a pointer to the character
buffer.  SV must be of type >= C<SVt_PV>.  One
alternative is to call C<sv_grow> if you are not sure of the type of SV.

You might mistakenly think that C<len> is the number of bytes to add to the
existing size, but instead it is the total size C<sv> should be.

	char *	SvGROW(SV* sv, STRLEN len)

=for hackers
Found in file sv.h

=item sv_grow
X<sv_grow>

Expands the character buffer in the SV.  If necessary, uses C<sv_unref> and
upgrades the SV to C<SVt_PV>.  Returns a pointer to the character buffer.
Use the C<SvGROW> wrapper instead.

	char*	sv_grow(SV *const sv, STRLEN newlen)

=for hackers
Found in file sv.c

=item sv_inc
X<sv_inc>

Auto-increment of the value in the SV, doing string to numeric conversion
if necessary.  Handles 'get' magic and operator overloading.

	void	sv_inc(SV *const sv)

=for hackers
Found in file sv.c

=item sv_inc_nomg
X<sv_inc_nomg>

Auto-increment of the value in the SV, doing string to numeric conversion
if necessary.  Handles operator overloading.  Skips handling 'get' magic.

	void	sv_inc_nomg(SV *const sv)

=for hackers
Found in file sv.c

=item sv_insert
X<sv_insert>

Inserts and/or replaces a string at the specified offset/length within the SV.
Similar to the Perl C<substr()> function, with C<littlelen> bytes starting at
C<little> replacing C<len> bytes of the string in C<bigstr> starting at
C<offset>.  Handles get magic.

	void	sv_insert(SV *const bigstr, const STRLEN offset,
		          const STRLEN len,
		          const char *const little,
		          const STRLEN littlelen)

=for hackers
Found in file sv.c

=item sv_insert_flags
X<sv_insert_flags>

Same as C<sv_insert>, but the extra C<flags> are passed to the
C<SvPV_force_flags> that applies to C<bigstr>.

	void	sv_insert_flags(SV *const bigstr,
		                const STRLEN offset,
		                const STRLEN len,
		                const char *little,
		                const STRLEN littlelen,
		                const U32 flags)

=for hackers
Found in file sv.c

=item SvIOK
X<SvIOK>

Returns a U32 value indicating whether the SV contains an integer.

	U32	SvIOK(SV* sv)

=for hackers
Found in file sv.h

=item SvIOK_notUV
X<SvIOK_notUV>

Returns a boolean indicating whether the SV contains a signed integer.

	bool	SvIOK_notUV(SV* sv)

=for hackers
Found in file sv.h

=item SvIOK_off
X<SvIOK_off>

Unsets the IV status of an SV.

	void	SvIOK_off(SV* sv)

=for hackers
Found in file sv.h

=item SvIOK_on
X<SvIOK_on>

Tells an SV that it is an integer.

	void	SvIOK_on(SV* sv)

=for hackers
Found in file sv.h

=item SvIOK_only
X<SvIOK_only>

Tells an SV that it is an integer and disables all other C<OK> bits.

	void	SvIOK_only(SV* sv)

=for hackers
Found in file sv.h

=item SvIOK_only_UV
X<SvIOK_only_UV>

Tells an SV that it is an unsigned integer and disables all other C<OK> bits.

	void	SvIOK_only_UV(SV* sv)

=for hackers
Found in file sv.h

=item SvIOKp
X<SvIOKp>

Returns a U32 value indicating whether the SV contains an integer.  Checks
the B<private> setting.  Use C<SvIOK> instead.

	U32	SvIOKp(SV* sv)

=for hackers
Found in file sv.h

=item SvIOK_UV
X<SvIOK_UV>

Returns a boolean indicating whether the SV contains an integer that must be
interpreted as unsigned.  A non-negative integer whose value is within the
range of both an IV and a UV may be flagged as either C<SvUOK> or C<SvIOK>.

	bool	SvIOK_UV(SV* sv)

=for hackers
Found in file sv.h

=item sv_isa
X<sv_isa>

Returns a boolean indicating whether the SV is blessed into the specified
class.

This does not check for subtypes or method overloading. Use C<sv_isa_sv> to
verify an inheritance relationship in the same way as the C<isa> operator by
respecting any C<isa()> method overloading; or C<sv_derived_from_sv> to test
directly on the actual object type.

	int	sv_isa(SV* sv, const char *const name)

=for hackers
Found in file sv.c

=item sv_isa_sv
X<sv_isa_sv>


NOTE: this function is experimental and may change or be
removed without notice.


Returns a boolean indicating whether the SV is an object reference and is
derived from the specified class, respecting any C<isa()> method overloading
it may have. Returns false if C<sv> is not a reference to an object, or is
not derived from the specified class.

This is the function used to implement the behaviour of the C<isa> operator.

Does not invoke magic on C<sv>.

Not to be confused with the older C<sv_isa> function, which does not use an
overloaded C<isa()> method, nor will check subclassing.

	bool	sv_isa_sv(SV* sv, SV* namesv)

=for hackers
Found in file universal.c

=item SvIsCOW
X<SvIsCOW>

Returns a U32 value indicating whether the SV is Copy-On-Write (either shared
hash key scalars, or full Copy On Write scalars if 5.9.0 is configured for
COW).

	U32	SvIsCOW(SV* sv)

=for hackers
Found in file sv.h

=item SvIsCOW_shared_hash
X<SvIsCOW_shared_hash>

Returns a boolean indicating whether the SV is Copy-On-Write shared hash key
scalar.

	bool	SvIsCOW_shared_hash(SV* sv)

=for hackers
Found in file sv.h

=item sv_isobject
X<sv_isobject>

Returns a boolean indicating whether the SV is an RV pointing to a blessed
object.  If the SV is not an RV, or if the object is not blessed, then this
will return false.

	int	sv_isobject(SV* sv)

=for hackers
Found in file sv.c

=item SvIV
X<SvIV>

Coerces the given SV to IV and returns it.  The returned value in many
circumstances will get stored in C<sv>'s IV slot, but not in all cases.  (Use
C<L</sv_setiv>> to make sure it does).

See C<L</SvIVx>> for a version which guarantees to evaluate C<sv> only once.

	IV	SvIV(SV* sv)

=for hackers
Found in file sv.h

=item SvIV_nomg
X<SvIV_nomg>

Like C<SvIV> but doesn't process magic.

	IV	SvIV_nomg(SV* sv)

=for hackers
Found in file sv.h

=item SvIV_set
X<SvIV_set>

Set the value of the IV pointer in sv to val.  It is possible to perform
the same function of this macro with an lvalue assignment to C<SvIVX>.
With future Perls, however, it will be more efficient to use 
C<SvIV_set> instead of the lvalue assignment to C<SvIVX>.

	void	SvIV_set(SV* sv, IV val)

=for hackers
Found in file sv.h

=item SvIVX
X<SvIVX>

Returns the raw value in the SV's IV slot, without checks or conversions.
Only use when you are sure C<SvIOK> is true.  See also C<L</SvIV>>.

	IV	SvIVX(SV* sv)

=for hackers
Found in file sv.h

=item SvIVx
X<SvIVx>

Coerces the given SV to IV and returns it.  The returned value in many
circumstances will get stored in C<sv>'s IV slot, but not in all cases.  (Use
C<L</sv_setiv>> to make sure it does).

This form guarantees to evaluate C<sv> only once.  Only use this if C<sv> is an
expression with side effects, otherwise use the more efficient C<SvIV>.

	IV	SvIVx(SV* sv)

=for hackers
Found in file sv.h

=item SvLEN
X<SvLEN>

Returns the size of the string buffer in the SV, not including any part
attributable to C<SvOOK>.  See C<L</SvCUR>>.

	STRLEN	SvLEN(SV* sv)

=for hackers
Found in file sv.h

=item sv_len
X<sv_len>

Returns the length of the string in the SV.  Handles magic and type
coercion and sets the UTF8 flag appropriately.  See also C<L</SvCUR>>, which
gives raw access to the C<xpv_cur> slot.

	STRLEN	sv_len(SV *const sv)

=for hackers
Found in file sv.c

=item SvLEN_set
X<SvLEN_set>

Set the size of the string buffer for the SV. See C<L</SvLEN>>.

	void	SvLEN_set(SV* sv, STRLEN len)

=for hackers
Found in file sv.h

=item sv_len_utf8
X<sv_len_utf8>

Returns the number of characters in the string in an SV, counting wide
UTF-8 bytes as a single character.  Handles magic and type coercion.

	STRLEN	sv_len_utf8(SV *const sv)

=for hackers
Found in file sv.c

=item sv_magic
X<sv_magic>

Adds magic to an SV.  First upgrades C<sv> to type C<SVt_PVMG> if
necessary, then adds a new magic item of type C<how> to the head of the
magic list.

See C<L</sv_magicext>> (which C<sv_magic> now calls) for a description of the
handling of the C<name> and C<namlen> arguments.

You need to use C<sv_magicext> to add magic to C<SvREADONLY> SVs and also
to add more than one instance of the same C<how>.

	void	sv_magic(SV *const sv, SV *const obj,
		         const int how, const char *const name,
		         const I32 namlen)

=for hackers
Found in file sv.c

=item sv_magicext
X<sv_magicext>

Adds magic to an SV, upgrading it if necessary.  Applies the
supplied C<vtable> and returns a pointer to the magic added.

Note that C<sv_magicext> will allow things that C<sv_magic> will not.
In particular, you can add magic to C<SvREADONLY> SVs, and add more than
one instance of the same C<how>.

If C<namlen> is greater than zero then a C<savepvn> I<copy> of C<name> is
stored, if C<namlen> is zero then C<name> is stored as-is and - as another
special case - if C<(name && namlen == HEf_SVKEY)> then C<name> is assumed
to contain an SV* and is stored as-is with its C<REFCNT> incremented.

(This is now used as a subroutine by C<sv_magic>.)

	MAGIC *	sv_magicext(SV *const sv, SV *const obj,
		            const int how,
		            const MGVTBL *const vtbl,
		            const char *const name,
		            const I32 namlen)

=for hackers
Found in file sv.c

=item SvMAGIC_set
X<SvMAGIC_set>

Set the value of the MAGIC pointer in C<sv> to val.  See C<L</SvIV_set>>.

	void	SvMAGIC_set(SV* sv, MAGIC* val)

=for hackers
Found in file sv.h

=item sv_mortalcopy
X<sv_mortalcopy>

Creates a new SV which is a copy of the original SV (using C<sv_setsv>).
The new SV is marked as mortal.  It will be destroyed "soon", either by an
explicit call to C<FREETMPS>, or by an implicit call at places such as
statement boundaries.  See also C<L</sv_newmortal>> and C<L</sv_2mortal>>.

	SV*	sv_mortalcopy(SV *const oldsv)

=for hackers
Found in file sv.c

=item sv_mortalcopy_flags
X<sv_mortalcopy_flags>

Like C<sv_mortalcopy>, but the extra C<flags> are passed to the
C<sv_setsv_flags>.

	SV*	sv_mortalcopy_flags(SV *const oldsv, U32 flags)

=for hackers
Found in file sv.c

=item sv_newmortal
X<sv_newmortal>

Creates a new null SV which is mortal.  The reference count of the SV is
set to 1.  It will be destroyed "soon", either by an explicit call to
C<FREETMPS>, or by an implicit call at places such as statement boundaries.
See also C<L</sv_mortalcopy>> and C<L</sv_2mortal>>.

	SV*	sv_newmortal()

=for hackers
Found in file sv.c

=item sv_newref
X<sv_newref>

Increment an SV's reference count.  Use the C<SvREFCNT_inc()> wrapper
instead.

	SV*	sv_newref(SV *const sv)

=for hackers
Found in file sv.c

=item SvNIOK
X<SvNIOK>

Returns a U32 value indicating whether the SV contains a number, integer or
double.

	U32	SvNIOK(SV* sv)

=for hackers
Found in file sv.h

=item SvNIOK_off
X<SvNIOK_off>

Unsets the NV/IV status of an SV.

	void	SvNIOK_off(SV* sv)

=for hackers
Found in file sv.h

=item SvNIOKp
X<SvNIOKp>

Returns a U32 value indicating whether the SV contains a number, integer or
double.  Checks the B<private> setting.  Use C<SvNIOK> instead.

	U32	SvNIOKp(SV* sv)

=for hackers
Found in file sv.h

=item SvNOK
X<SvNOK>

Returns a U32 value indicating whether the SV contains a double.

	U32	SvNOK(SV* sv)

=for hackers
Found in file sv.h

=item SvNOK_off
X<SvNOK_off>

Unsets the NV status of an SV.

	void	SvNOK_off(SV* sv)

=for hackers
Found in file sv.h

=item SvNOK_on
X<SvNOK_on>

Tells an SV that it is a double.

	void	SvNOK_on(SV* sv)

=for hackers
Found in file sv.h

=item SvNOK_only
X<SvNOK_only>

Tells an SV that it is a double and disables all other OK bits.

	void	SvNOK_only(SV* sv)

=for hackers
Found in file sv.h

=item SvNOKp
X<SvNOKp>

Returns a U32 value indicating whether the SV contains a double.  Checks the
B<private> setting.  Use C<SvNOK> instead.

	U32	SvNOKp(SV* sv)

=for hackers
Found in file sv.h

=item SvNV
X<SvNV>

Coerces the given SV to NV and returns it.  The returned value in many
circumstances will get stored in C<sv>'s NV slot, but not in all cases.  (Use
C<L</sv_setnv>> to make sure it does).

See C<L</SvNVx>> for a version which guarantees to evaluate C<sv> only once.

	NV	SvNV(SV* sv)

=for hackers
Found in file sv.h

=item SvNV_nomg
X<SvNV_nomg>

Like C<SvNV> but doesn't process magic.

	NV	SvNV_nomg(SV* sv)

=for hackers
Found in file sv.h

=item SvNV_set
X<SvNV_set>

Set the value of the NV pointer in C<sv> to val.  See C<L</SvIV_set>>.

	void	SvNV_set(SV* sv, NV val)

=for hackers
Found in file sv.h

=item SvNVX
X<SvNVX>

Returns the raw value in the SV's NV slot, without checks or conversions.
Only use when you are sure C<SvNOK> is true.  See also C<L</SvNV>>.

	NV	SvNVX(SV* sv)

=for hackers
Found in file sv.h

=item SvNVx
X<SvNVx>

Coerces the given SV to NV and returns it.  The returned value in many
circumstances will get stored in C<sv>'s NV slot, but not in all cases.  (Use
C<L</sv_setnv>> to make sure it does).

This form guarantees to evaluate C<sv> only once.  Only use this if C<sv> is an
expression with side effects, otherwise use the more efficient C<SvNV>.

	NV	SvNVx(SV* sv)

=for hackers
Found in file sv.h

=item SvOK
X<SvOK>

Returns a U32 value indicating whether the value is defined.  This is
only meaningful for scalars.

	U32	SvOK(SV* sv)

=for hackers
Found in file sv.h

=item SvOOK
X<SvOOK>

Returns a U32 indicating whether the pointer to the string buffer is offset.
This hack is used internally to speed up removal of characters from the
beginning of a C<SvPV>.  When C<SvOOK> is true, then the start of the
allocated string buffer is actually C<SvOOK_offset()> bytes before C<SvPVX>.
This offset used to be stored in C<SvIVX>, but is now stored within the spare
part of the buffer.

	U32	SvOOK(SV* sv)

=for hackers
Found in file sv.h

=item SvOOK_offset
X<SvOOK_offset>

Reads into C<len> the offset from C<SvPVX> back to the true start of the
allocated buffer, which will be non-zero if C<sv_chop> has been used to
efficiently remove characters from start of the buffer.  Implemented as a
macro, which takes the address of C<len>, which must be of type C<STRLEN>.
Evaluates C<sv> more than once.  Sets C<len> to 0 if C<SvOOK(sv)> is false.

	void	SvOOK_offset(SV*sv, STRLEN len)

=for hackers
Found in file sv.h

=item SvPOK
X<SvPOK>

Returns a U32 value indicating whether the SV contains a character
string.

	U32	SvPOK(SV* sv)

=for hackers
Found in file sv.h

=item SvPOK_off
X<SvPOK_off>

Unsets the PV status of an SV.

	void	SvPOK_off(SV* sv)

=for hackers
Found in file sv.h

=item SvPOK_on
X<SvPOK_on>

Tells an SV that it is a string.

	void	SvPOK_on(SV* sv)

=for hackers
Found in file sv.h

=item SvPOK_only
X<SvPOK_only>

Tells an SV that it is a string and disables all other C<OK> bits.
Will also turn off the UTF-8 status.

	void	SvPOK_only(SV* sv)

=for hackers
Found in file sv.h

=item SvPOK_only_UTF8
X<SvPOK_only_UTF8>

Tells an SV that it is a string and disables all other C<OK> bits,
and leaves the UTF-8 status as it was.

	void	SvPOK_only_UTF8(SV* sv)

=for hackers
Found in file sv.h

=item SvPOKp
X<SvPOKp>

Returns a U32 value indicating whether the SV contains a character string.
Checks the B<private> setting.  Use C<SvPOK> instead.

	U32	SvPOKp(SV* sv)

=for hackers
Found in file sv.h

=item sv_pos_b2u
X<sv_pos_b2u>

Converts the value pointed to by C<offsetp> from a count of bytes from the
start of the string, to a count of the equivalent number of UTF-8 chars.
Handles magic and type coercion.

Use C<sv_pos_b2u_flags> in preference, which correctly handles strings
longer than 2Gb.

	void	sv_pos_b2u(SV *const sv, I32 *const offsetp)

=for hackers
Found in file sv.c

=item sv_pos_b2u_flags
X<sv_pos_b2u_flags>

Converts C<offset> from a count of bytes from the start of the string, to
a count of the equivalent number of UTF-8 chars.  Handles type coercion.
C<flags> is passed to C<SvPV_flags>, and usually should be
C<SV_GMAGIC|SV_CONST_RETURN> to handle magic.

	STRLEN	sv_pos_b2u_flags(SV *const sv,
		                 STRLEN const offset, U32 flags)

=for hackers
Found in file sv.c

=item sv_pos_u2b
X<sv_pos_u2b>

Converts the value pointed to by C<offsetp> from a count of UTF-8 chars from
the start of the string, to a count of the equivalent number of bytes; if
C<lenp> is non-zero, it does the same to C<lenp>, but this time starting from
the offset, rather than from the start of the string.  Handles magic and
type coercion.

Use C<sv_pos_u2b_flags> in preference, which correctly handles strings longer
than 2Gb.

	void	sv_pos_u2b(SV *const sv, I32 *const offsetp,
		           I32 *const lenp)

=for hackers
Found in file sv.c

=item sv_pos_u2b_flags
X<sv_pos_u2b_flags>

Converts the offset from a count of UTF-8 chars from
the start of the string, to a count of the equivalent number of bytes; if
C<lenp> is non-zero, it does the same to C<lenp>, but this time starting from
C<offset>, rather than from the start
of the string.  Handles type coercion.
C<flags> is passed to C<SvPV_flags>, and usually should be
C<SV_GMAGIC|SV_CONST_RETURN> to handle magic.

	STRLEN	sv_pos_u2b_flags(SV *const sv, STRLEN uoffset,
		                 STRLEN *const lenp, U32 flags)

=for hackers
Found in file sv.c

=item SvPV
X<SvPV>

Returns a pointer to the string in the SV, or a stringified form of
the SV if the SV does not contain a string.  The SV may cache the
stringified version becoming C<SvPOK>.  Handles 'get' magic.  The
C<len> variable will be set to the length of the string (this is a macro, so
don't use C<&len>).  See also C<L</SvPVx>> for a version which guarantees to
evaluate C<sv> only once.

Note that there is no guarantee that the return value of C<SvPV()> is
equal to C<SvPVX(sv)>, or that C<SvPVX(sv)> contains valid data, or that
successive calls to C<SvPV(sv)> will return the same pointer value each
time.  This is due to the way that things like overloading and
Copy-On-Write are handled.  In these cases, the return value may point to
a temporary buffer or similar.  If you absolutely need the C<SvPVX> field to
be valid (for example, if you intend to write to it), then see
C<L</SvPV_force>>.

	char*	SvPV(SV* sv, STRLEN len)

=for hackers
Found in file sv.h

=item SvPVbyte
X<SvPVbyte>

Like C<SvPV>, but converts C<sv> to byte representation first if necessary.  If
the SV cannot be downgraded from UTF-8, this croaks.

	char*	SvPVbyte(SV* sv, STRLEN len)

=for hackers
Found in file sv.h

=item SvPVbyte_force
X<SvPVbyte_force>

Like C<SvPV_force>, but converts C<sv> to byte representation first if
necessary.  If the SV cannot be downgraded from UTF-8, this croaks.

	char*	SvPVbyte_force(SV* sv, STRLEN len)

=for hackers
Found in file sv.h

=item SvPVbyte_nolen
X<SvPVbyte_nolen>

Like C<SvPV_nolen>, but converts C<sv> to byte representation first if
necessary.  If the SV cannot be downgraded from UTF-8, this croaks.

	char*	SvPVbyte_nolen(SV* sv)

=for hackers
Found in file sv.h

=item SvPVbyte_nomg
X<SvPVbyte_nomg>

Like C<SvPVbyte>, but does not process get magic.

	char*	SvPVbyte_nomg(SV* sv, STRLEN len)

=for hackers
Found in file sv.h

=item sv_pvbyten_force
X<sv_pvbyten_force>

The backend for the C<SvPVbytex_force> macro.  Always use the macro
instead.  If the SV cannot be downgraded from UTF-8, this croaks.

	char*	sv_pvbyten_force(SV *const sv, STRLEN *const lp)

=for hackers
Found in file sv.c

=item SvPVbyte_or_null
X<SvPVbyte_or_null>

Like C<SvPVbyte>, but when C<sv> is undef, returns C<NULL>.

	char*	SvPVbyte_or_null(SV* sv, STRLEN len)

=for hackers
Found in file sv.h

=item SvPVbyte_or_null_nomg
X<SvPVbyte_or_null_nomg>

Like C<SvPVbyte_or_null>, but does not process get magic.

	char*	SvPVbyte_or_null_nomg(SV* sv, STRLEN len)

=for hackers
Found in file sv.h

=item SvPVbytex
X<SvPVbytex>

Like C<SvPV>, but converts C<sv> to byte representation first if necessary.
Guarantees to evaluate C<sv> only once; use the more efficient C<SvPVbyte>
otherwise.  If the SV cannot be downgraded from UTF-8, this croaks.

	char*	SvPVbytex(SV* sv, STRLEN len)

=for hackers
Found in file sv.h

=item SvPVbytex_force
X<SvPVbytex_force>

Like C<SvPV_force>, but converts C<sv> to byte representation first if necessary.
Guarantees to evaluate C<sv> only once; use the more efficient C<SvPVbyte_force>
otherwise.  If the SV cannot be downgraded from UTF-8, this croaks.

	char*	SvPVbytex_force(SV* sv, STRLEN len)

=for hackers
Found in file sv.h

=item SvPVCLEAR
X<SvPVCLEAR>

Ensures that sv is a SVt_PV and that its SvCUR is 0, and that it is
properly null terminated. Equivalent to sv_setpvs(""), but more efficient.

	char *	SvPVCLEAR(SV* sv)

=for hackers
Found in file sv.h

=item SvPV_force
X<SvPV_force>

Like C<SvPV> but will force the SV into containing a string (C<SvPOK>), and
only a string (C<SvPOK_only>), by hook or by crook.  You need force if you are
going to update the C<SvPVX> directly.  Processes get magic.

Note that coercing an arbitrary scalar into a plain PV will potentially
strip useful data from it.  For example if the SV was C<SvROK>, then the
referent will have its reference count decremented, and the SV itself may
be converted to an C<SvPOK> scalar with a string buffer containing a value
such as C<"ARRAY(0x1234)">.

	char*	SvPV_force(SV* sv, STRLEN len)

=for hackers
Found in file sv.h

=item SvPV_force_nomg
X<SvPV_force_nomg>

Like C<SvPV_force>, but doesn't process get magic.

	char*	SvPV_force_nomg(SV* sv, STRLEN len)

=for hackers
Found in file sv.h

=item SvPV_nolen
X<SvPV_nolen>

Like C<SvPV> but doesn't set a length variable.

	char*	SvPV_nolen(SV* sv)

=for hackers
Found in file sv.h

=item SvPV_nomg
X<SvPV_nomg>

Like C<SvPV> but doesn't process magic.

	char*	SvPV_nomg(SV* sv, STRLEN len)

=for hackers
Found in file sv.h

=item SvPV_nomg_nolen
X<SvPV_nomg_nolen>

Like C<SvPV_nolen> but doesn't process magic.

	char*	SvPV_nomg_nolen(SV* sv)

=for hackers
Found in file sv.h

=item sv_pvn_force
X<sv_pvn_force>

Get a sensible string out of the SV somehow.
A private implementation of the C<SvPV_force> macro for compilers which
can't cope with complex macro expressions.  Always use the macro instead.

	char*	sv_pvn_force(SV* sv, STRLEN* lp)

=for hackers
Found in file sv.c

=item sv_pvn_force_flags
X<sv_pvn_force_flags>

Get a sensible string out of the SV somehow.
If C<flags> has the C<SV_GMAGIC> bit set, will C<mg_get> on C<sv> if
appropriate, else not.  C<sv_pvn_force> and C<sv_pvn_force_nomg> are
implemented in terms of this function.
You normally want to use the various wrapper macros instead: see
C<L</SvPV_force>> and C<L</SvPV_force_nomg>>.

	char*	sv_pvn_force_flags(SV *const sv,
		                   STRLEN *const lp,
		                   const I32 flags)

=for hackers
Found in file sv.c

=item SvPV_set
X<SvPV_set>

This is probably not what you want to use, you probably wanted
L</sv_usepvn_flags> or L</sv_setpvn> or L</sv_setpvs>.

Set the value of the PV pointer in C<sv> to the Perl allocated
C<NUL>-terminated string C<val>.  See also C<L</SvIV_set>>.

Remember to free the previous PV buffer. There are many things to check.
Beware that the existing pointer may be involved in copy-on-write or other
mischief, so do C<SvOOK_off(sv)> and use C<sv_force_normal> or
C<SvPV_force> (or check the C<SvIsCOW> flag) first to make sure this
modification is safe. Then finally, if it is not a COW, call C<SvPV_free> to
free the previous PV buffer.

	void	SvPV_set(SV* sv, char* val)

=for hackers
Found in file sv.h

=item SvPVutf8
X<SvPVutf8>

Like C<SvPV>, but converts C<sv> to UTF-8 first if necessary.

	char*	SvPVutf8(SV* sv, STRLEN len)

=for hackers
Found in file sv.h

=item sv_pvutf8n_force
X<sv_pvutf8n_force>

The backend for the C<SvPVutf8x_force> macro.  Always use the macro
instead.

	char*	sv_pvutf8n_force(SV *const sv, STRLEN *const lp)

=for hackers
Found in file sv.c

=item SvPVutf8x
X<SvPVutf8x>

Like C<SvPV>, but converts C<sv> to UTF-8 first if necessary.
Guarantees to evaluate C<sv> only once; use the more efficient C<SvPVutf8>
otherwise.

	char*	SvPVutf8x(SV* sv, STRLEN len)

=for hackers
Found in file sv.h

=item SvPVutf8x_force
X<SvPVutf8x_force>

Like C<SvPV_force>, but converts C<sv> to UTF-8 first if necessary.
Guarantees to evaluate C<sv> only once; use the more efficient C<SvPVutf8_force>
otherwise.

	char*	SvPVutf8x_force(SV* sv, STRLEN len)

=for hackers
Found in file sv.h

=item SvPVutf8_force
X<SvPVutf8_force>

Like C<SvPV_force>, but converts C<sv> to UTF-8 first if necessary.

	char*	SvPVutf8_force(SV* sv, STRLEN len)

=for hackers
Found in file sv.h

=item SvPVutf8_nolen
X<SvPVutf8_nolen>

Like C<SvPV_nolen>, but converts C<sv> to UTF-8 first if necessary.

	char*	SvPVutf8_nolen(SV* sv)

=for hackers
Found in file sv.h

=item SvPVutf8_nomg
X<SvPVutf8_nomg>

Like C<SvPVutf8>, but does not process get magic.

	char*	SvPVutf8_nomg(SV* sv, STRLEN len)

=for hackers
Found in file sv.h

=item SvPVutf8_or_null
X<SvPVutf8_or_null>

Like C<SvPVutf8>, but when C<sv> is undef, returns C<NULL>.

	char*	SvPVutf8_or_null(SV* sv, STRLEN len)

=for hackers
Found in file sv.h

=item SvPVutf8_or_null_nomg
X<SvPVutf8_or_null_nomg>

Like C<SvPVutf8_or_null>, but does not process get magic.

	char*	SvPVutf8_or_null_nomg(SV* sv, STRLEN len)

=for hackers
Found in file sv.h

=item SvPVX
X<SvPVX>

Returns a pointer to the physical string in the SV.  The SV must contain a
string.  Prior to 5.9.3 it is not safe
to execute this macro unless the SV's
type >= C<SVt_PV>.

This is also used to store the name of an autoloaded subroutine in an XS
AUTOLOAD routine.  See L<perlguts/Autoloading with XSUBs>.

	char*	SvPVX(SV* sv)

=for hackers
Found in file sv.h

=item SvPVx
X<SvPVx>

A version of C<SvPV> which guarantees to evaluate C<sv> only once.
Only use this if C<sv> is an expression with side effects, otherwise use the
more efficient C<SvPV>.

	char*	SvPVx(SV* sv, STRLEN len)

=for hackers
Found in file sv.h

=item SvREADONLY
X<SvREADONLY>

Returns true if the argument is readonly, otherwise returns false.
Exposed to perl code via Internals::SvREADONLY().

	U32	SvREADONLY(SV* sv)

=for hackers
Found in file sv.h

=item SvREADONLY_off
X<SvREADONLY_off>

Mark an object as not-readonly. Exactly what this mean depends on the
object type. Exposed to perl code via Internals::SvREADONLY().

	U32	SvREADONLY_off(SV* sv)

=for hackers
Found in file sv.h

=item SvREADONLY_on
X<SvREADONLY_on>

Mark an object as readonly. Exactly what this means depends on the object
type. Exposed to perl code via Internals::SvREADONLY().

	U32	SvREADONLY_on(SV* sv)

=for hackers
Found in file sv.h

=item sv_ref
X<sv_ref>

Returns a SV describing what the SV passed in is a reference to.

dst can be a SV to be set to the description or NULL, in which case a
mortal SV is returned.

If ob is true and the SV is blessed, the description is the class
name, otherwise it is the type of the SV, "SCALAR", "ARRAY" etc.

	SV*	sv_ref(SV *dst, const SV *const sv,
		       const int ob)

=for hackers
Found in file sv.c

=item SvREFCNT
X<SvREFCNT>

Returns the value of the object's reference count. Exposed
to perl code via Internals::SvREFCNT().

	U32	SvREFCNT(SV* sv)

=for hackers
Found in file sv.h

=item SvREFCNT_dec
X<SvREFCNT_dec>

Decrements the reference count of the given SV.  C<sv> may be C<NULL>.

	void	SvREFCNT_dec(SV *sv)

=for hackers
Found in file sv.h

=item SvREFCNT_dec_NN
X<SvREFCNT_dec_NN>

Same as C<SvREFCNT_dec>, but can only be used if you know C<sv>
is not C<NULL>.  Since we don't have to check the NULLness, it's faster
and smaller.

	void	SvREFCNT_dec_NN(SV *sv)

=for hackers
Found in file sv.h

=item SvREFCNT_inc
X<SvREFCNT_inc>

Increments the reference count of the given SV, returning the SV.

All of the following C<SvREFCNT_inc>* are optimized versions of
C<SvREFCNT_inc>, and can be replaced with C<SvREFCNT_inc>.

	SV *	SvREFCNT_inc(SV *sv)

=for hackers
Found in file sv.h

=item SvREFCNT_inc_NN
X<SvREFCNT_inc_NN>

Same as C<SvREFCNT_inc>, but can only be used if you know C<sv>
is not C<NULL>.  Since we don't have to check the NULLness, it's faster
and smaller.

	SV *	SvREFCNT_inc_NN(SV *sv)

=for hackers
Found in file sv.h

=item SvREFCNT_inc_simple
X<SvREFCNT_inc_simple>

Same as C<SvREFCNT_inc>, but can only be used with expressions without side
effects.  Since we don't have to store a temporary value, it's faster.

	SV*	SvREFCNT_inc_simple(SV* sv)

=for hackers
Found in file sv.h

=item SvREFCNT_inc_simple_NN
X<SvREFCNT_inc_simple_NN>

Same as C<SvREFCNT_inc_simple>, but can only be used if you know C<sv>
is not C<NULL>.  Since we don't have to check the NULLness, it's faster
and smaller.

	SV*	SvREFCNT_inc_simple_NN(SV* sv)

=for hackers
Found in file sv.h

=item SvREFCNT_inc_simple_void
X<SvREFCNT_inc_simple_void>

Same as C<SvREFCNT_inc_simple>, but can only be used if you don't need the
return value.  The macro doesn't need to return a meaningful value.

	void	SvREFCNT_inc_simple_void(SV* sv)

=for hackers
Found in file sv.h

=item SvREFCNT_inc_simple_void_NN
X<SvREFCNT_inc_simple_void_NN>

Same as C<SvREFCNT_inc>, but can only be used if you don't need the return
value, and you know that C<sv> is not C<NULL>.  The macro doesn't need
to return a meaningful value, or check for NULLness, so it's smaller
and faster.

	void	SvREFCNT_inc_simple_void_NN(SV* sv)

=for hackers
Found in file sv.h

=item SvREFCNT_inc_void
X<SvREFCNT_inc_void>

Same as C<SvREFCNT_inc>, but can only be used if you don't need the
return value.  The macro doesn't need to return a meaningful value.

	void	SvREFCNT_inc_void(SV *sv)

=for hackers
Found in file sv.h

=item SvREFCNT_inc_void_NN
X<SvREFCNT_inc_void_NN>

Same as C<SvREFCNT_inc>, but can only be used if you don't need the return
value, and you know that C<sv> is not C<NULL>.  The macro doesn't need
to return a meaningful value, or check for NULLness, so it's smaller
and faster.

	void	SvREFCNT_inc_void_NN(SV* sv)

=for hackers
Found in file sv.h

=item sv_reftype
X<sv_reftype>

Returns a string describing what the SV is a reference to.

If ob is true and the SV is blessed, the string is the class name,
otherwise it is the type of the SV, "SCALAR", "ARRAY" etc.

	const char* sv_reftype(const SV *const sv, const int ob)

=for hackers
Found in file sv.c

=item sv_replace
X<sv_replace>

Make the first argument a copy of the second, then delete the original.
The target SV physically takes over ownership of the body of the source SV
and inherits its flags; however, the target keeps any magic it owns,
and any magic in the source is discarded.
Note that this is a rather specialist SV copying operation; most of the
time you'll want to use C<sv_setsv> or one of its many macro front-ends.

	void	sv_replace(SV *const sv, SV *const nsv)

=for hackers
Found in file sv.c

=item sv_report_used
X<sv_report_used>

Dump the contents of all SVs not yet freed (debugging aid).

	void	sv_report_used()

=for hackers
Found in file sv.c

=item sv_reset
X<sv_reset>

Underlying implementation for the C<reset> Perl function.
Note that the perl-level function is vaguely deprecated.

	void	sv_reset(const char* s, HV *const stash)

=for hackers
Found in file sv.c

=item SvROK
X<SvROK>

Tests if the SV is an RV.

	U32	SvROK(SV* sv)

=for hackers
Found in file sv.h

=item SvROK_off
X<SvROK_off>

Unsets the RV status of an SV.

	void	SvROK_off(SV* sv)

=for hackers
Found in file sv.h

=item SvROK_on
X<SvROK_on>

Tells an SV that it is an RV.

	void	SvROK_on(SV* sv)

=for hackers
Found in file sv.h

=item SvRV
X<SvRV>

Dereferences an RV to return the SV.

	SV*	SvRV(SV* sv)

=for hackers
Found in file sv.h

=item SvRV_set
X<SvRV_set>

Set the value of the RV pointer in C<sv> to val.  See C<L</SvIV_set>>.

	void	SvRV_set(SV* sv, SV* val)

=for hackers
Found in file sv.h

=item sv_rvunweaken
X<sv_rvunweaken>

Unweaken a reference: Clear the C<SvWEAKREF> flag on this RV; remove
the backreference to this RV from the array of backreferences
associated with the target SV, increment the refcount of the target.
Silently ignores C<undef> and warns on non-weak references.

	SV*	sv_rvunweaken(SV *const sv)

=for hackers
Found in file sv.c

=item sv_rvweaken
X<sv_rvweaken>

Weaken a reference: set the C<SvWEAKREF> flag on this RV; give the
referred-to SV C<PERL_MAGIC_backref> magic if it hasn't already; and
push a back-reference to this RV onto the array of backreferences
associated with that magic.  If the RV is magical, set magic will be
called after the RV is cleared.  Silently ignores C<undef> and warns
on already-weak references.

	SV*	sv_rvweaken(SV *const sv)

=for hackers
Found in file sv.c

=item sv_setiv
X<sv_setiv>

Copies an integer into the given SV, upgrading first if necessary.
Does not handle 'set' magic.  See also C<L</sv_setiv_mg>>.

	void	sv_setiv(SV *const sv, const IV num)

=for hackers
Found in file sv.c

=item sv_setiv_mg
X<sv_setiv_mg>

Like C<sv_setiv>, but also handles 'set' magic.

	void	sv_setiv_mg(SV *const sv, const IV i)

=for hackers
Found in file sv.c

=item sv_setnv
X<sv_setnv>

Copies a double into the given SV, upgrading first if necessary.
Does not handle 'set' magic.  See also C<L</sv_setnv_mg>>.

	void	sv_setnv(SV *const sv, const NV num)

=for hackers
Found in file sv.c

=item sv_setnv_mg
X<sv_setnv_mg>

Like C<sv_setnv>, but also handles 'set' magic.

	void	sv_setnv_mg(SV *const sv, const NV num)

=for hackers
Found in file sv.c

=item sv_setpv
X<sv_setpv>

Copies a string into an SV.  The string must be terminated with a C<NUL>
character, and not contain embeded C<NUL>'s.
Does not handle 'set' magic.  See C<L</sv_setpv_mg>>.

	void	sv_setpv(SV *const sv, const char *const ptr)

=for hackers
Found in file sv.c

=item sv_setpvf
X<sv_setpvf>

Works like C<sv_catpvf> but copies the text into the SV instead of
appending it.  Does not handle 'set' magic.  See C<L</sv_setpvf_mg>>.

	void	sv_setpvf(SV *const sv, const char *const pat,
		          ...)

=for hackers
Found in file sv.c

=item sv_setpvf_mg
X<sv_setpvf_mg>

Like C<sv_setpvf>, but also handles 'set' magic.

	void	sv_setpvf_mg(SV *const sv,
		             const char *const pat, ...)

=for hackers
Found in file sv.c

=item sv_setpviv
X<sv_setpviv>


DEPRECATED!  It is planned to remove this function from a
future release of Perl.  Do not use it for new code; remove it from
existing code.


Copies an integer into the given SV, also updating its string value.
Does not handle 'set' magic.  See C<L</sv_setpviv_mg>>.

	void	sv_setpviv(SV *const sv, const IV num)

=for hackers
Found in file sv.c

=item sv_setpviv_mg
X<sv_setpviv_mg>


DEPRECATED!  It is planned to remove this function from a
future release of Perl.  Do not use it for new code; remove it from
existing code.


Like C<sv_setpviv>, but also handles 'set' magic.

	void	sv_setpviv_mg(SV *const sv, const IV iv)

=for hackers
Found in file sv.c

=item sv_setpvn
X<sv_setpvn>

Copies a string (possibly containing embedded C<NUL> characters) into an SV.
The C<len> parameter indicates the number of
bytes to be copied.  If the C<ptr> argument is NULL the SV will become
undefined.  Does not handle 'set' magic.  See C<L</sv_setpvn_mg>>.

The UTF-8 flag is not changed by this function.  A terminating NUL byte is
guaranteed.

	void	sv_setpvn(SV *const sv, const char *const ptr,
		          const STRLEN len)

=for hackers
Found in file sv.c

=item sv_setpvn_mg
X<sv_setpvn_mg>

Like C<sv_setpvn>, but also handles 'set' magic.

	void	sv_setpvn_mg(SV *const sv,
		             const char *const ptr,
		             const STRLEN len)

=for hackers
Found in file sv.c

=item sv_setpvs
X<sv_setpvs>

Like C<sv_setpvn>, but takes a literal string instead of a
string/length pair.

	void	sv_setpvs(SV* sv, "literal string")

=for hackers
Found in file handy.h

=item sv_setpvs_mg
X<sv_setpvs_mg>

Like C<sv_setpvn_mg>, but takes a literal string instead of a
string/length pair.

	void	sv_setpvs_mg(SV* sv, "literal string")

=for hackers
Found in file handy.h

=item sv_setpv_bufsize
X<sv_setpv_bufsize>

Sets the SV to be a string of cur bytes length, with at least
len bytes available. Ensures that there is a null byte at SvEND.
Returns a char * pointer to the SvPV buffer.

	char  *	sv_setpv_bufsize(SV *const sv, const STRLEN cur,
		                 const STRLEN len)

=for hackers
Found in file sv.c

=item sv_setpv_mg
X<sv_setpv_mg>

Like C<sv_setpv>, but also handles 'set' magic.

	void	sv_setpv_mg(SV *const sv, const char *const ptr)

=for hackers
Found in file sv.c

=item sv_setref_iv
X<sv_setref_iv>

Copies an integer into a new SV, optionally blessing the SV.  The C<rv>
argument will be upgraded to an RV.  That RV will be modified to point to
the new SV.  The C<classname> argument indicates the package for the
blessing.  Set C<classname> to C<NULL> to avoid the blessing.  The new SV
will have a reference count of 1, and the RV will be returned.

	SV*	sv_setref_iv(SV *const rv,
		             const char *const classname,
		             const IV iv)

=for hackers
Found in file sv.c

=item sv_setref_nv
X<sv_setref_nv>

Copies a double into a new SV, optionally blessing the SV.  The C<rv>
argument will be upgraded to an RV.  That RV will be modified to point to
the new SV.  The C<classname> argument indicates the package for the
blessing.  Set C<classname> to C<NULL> to avoid the blessing.  The new SV
will have a reference count of 1, and the RV will be returned.

	SV*	sv_setref_nv(SV *const rv,
		             const char *const classname,
		             const NV nv)

=for hackers
Found in file sv.c

=item sv_setref_pv
X<sv_setref_pv>

Copies a pointer into a new SV, optionally blessing the SV.  The C<rv>
argument will be upgraded to an RV.  That RV will be modified to point to
the new SV.  If the C<pv> argument is C<NULL>, then C<PL_sv_undef> will be placed
into the SV.  The C<classname> argument indicates the package for the
blessing.  Set C<classname> to C<NULL> to avoid the blessing.  The new SV
will have a reference count of 1, and the RV will be returned.

Do not use with other Perl types such as HV, AV, SV, CV, because those
objects will become corrupted by the pointer copy process.

Note that C<sv_setref_pvn> copies the string while this copies the pointer.

	SV*	sv_setref_pv(SV *const rv,
		             const char *const classname,
		             void *const pv)

=for hackers
Found in file sv.c

=item sv_setref_pvn
X<sv_setref_pvn>

Copies a string into a new SV, optionally blessing the SV.  The length of the
string must be specified with C<n>.  The C<rv> argument will be upgraded to
an RV.  That RV will be modified to point to the new SV.  The C<classname>
argument indicates the package for the blessing.  Set C<classname> to
C<NULL> to avoid the blessing.  The new SV will have a reference count
of 1, and the RV will be returned.

Note that C<sv_setref_pv> copies the pointer while this copies the string.

	SV*	sv_setref_pvn(SV *const rv,
		              const char *const classname,
		              const char *const pv,
		              const STRLEN n)

=for hackers
Found in file sv.c

=item sv_setref_pvs
X<sv_setref_pvs>

Like C<sv_setref_pvn>, but takes a literal string instead of
a string/length pair.

	SV *	sv_setref_pvs(SV *const rv,
		              const char *const classname,
		              "literal string")

=for hackers
Found in file handy.h

=item sv_setref_uv
X<sv_setref_uv>

Copies an unsigned integer into a new SV, optionally blessing the SV.  The C<rv>
argument will be upgraded to an RV.  That RV will be modified to point to
the new SV.  The C<classname> argument indicates the package for the
blessing.  Set C<classname> to C<NULL> to avoid the blessing.  The new SV
will have a reference count of 1, and the RV will be returned.

	SV*	sv_setref_uv(SV *const rv,
		             const char *const classname,
		             const UV uv)

=for hackers
Found in file sv.c

=item sv_setsv
X<sv_setsv>

Copies the contents of the source SV C<ssv> into the destination SV
C<dsv>.  The source SV may be destroyed if it is mortal, so don't use this
function if the source SV needs to be reused.  Does not handle 'set' magic on
destination SV.  Calls 'get' magic on source SV.  Loosely speaking, it
performs a copy-by-value, obliterating any previous content of the
destination.

You probably want to use one of the assortment of wrappers, such as
C<SvSetSV>, C<SvSetSV_nosteal>, C<SvSetMagicSV> and
C<SvSetMagicSV_nosteal>.

	void	sv_setsv(SV *dstr, SV *sstr)

=for hackers
Found in file sv.c

=item sv_setsv_flags
X<sv_setsv_flags>

Copies the contents of the source SV C<ssv> into the destination SV
C<dsv>.  The source SV may be destroyed if it is mortal, so don't use this
function if the source SV needs to be reused.  Does not handle 'set' magic.
Loosely speaking, it performs a copy-by-value, obliterating any previous
content of the destination.
If the C<flags> parameter has the C<SV_GMAGIC> bit set, will C<mg_get> on
C<ssv> if appropriate, else not.  If the C<flags>
parameter has the C<SV_NOSTEAL> bit set then the
buffers of temps will not be stolen.  C<sv_setsv>
and C<sv_setsv_nomg> are implemented in terms of this function.

You probably want to use one of the assortment of wrappers, such as
C<SvSetSV>, C<SvSetSV_nosteal>, C<SvSetMagicSV> and
C<SvSetMagicSV_nosteal>.

This is the primary function for copying scalars, and most other
copy-ish functions and macros use this underneath.

	void	sv_setsv_flags(SV *dstr, SV *sstr,
		               const I32 flags)

=for hackers
Found in file sv.c

=item sv_setsv_mg
X<sv_setsv_mg>

Like C<sv_setsv>, but also handles 'set' magic.

	void	sv_setsv_mg(SV *const dstr, SV *const sstr)

=for hackers
Found in file sv.c

=item sv_setsv_nomg
X<sv_setsv_nomg>

Like C<sv_setsv> but doesn't process magic.

	void	sv_setsv_nomg(SV* dsv, SV* ssv)

=for hackers
Found in file sv.h

=item sv_setuv
X<sv_setuv>

Copies an unsigned integer into the given SV, upgrading first if necessary.
Does not handle 'set' magic.  See also C<L</sv_setuv_mg>>.

	void	sv_setuv(SV *const sv, const UV num)

=for hackers
Found in file sv.c

=item sv_setuv_mg
X<sv_setuv_mg>

Like C<sv_setuv>, but also handles 'set' magic.

	void	sv_setuv_mg(SV *const sv, const UV u)

=for hackers
Found in file sv.c

=item sv_set_undef
X<sv_set_undef>

Equivalent to C<sv_setsv(sv, &PL_sv_undef)>, but more efficient.
Doesn't handle set magic.

The perl equivalent is C<$sv = undef;>. Note that it doesn't free any string
buffer, unlike C<undef $sv>.

Introduced in perl 5.25.12.

	void	sv_set_undef(SV *sv)

=for hackers
Found in file sv.c

=item SvSTASH
X<SvSTASH>

Returns the stash of the SV.

	HV*	SvSTASH(SV* sv)

=for hackers
Found in file sv.h

=item SvSTASH_set
X<SvSTASH_set>

Set the value of the STASH pointer in C<sv> to val.  See C<L</SvIV_set>>.

	void	SvSTASH_set(SV* sv, HV* val)

=for hackers
Found in file sv.h

=item SvTAINT
X<SvTAINT>

Taints an SV if tainting is enabled, and if some input to the current
expression is tainted--usually a variable, but possibly also implicit
inputs such as locale settings.  C<SvTAINT> propagates that taintedness to
the outputs of an expression in a pessimistic fashion; i.e., without paying
attention to precisely which outputs are influenced by which inputs.

	void	SvTAINT(SV* sv)

=for hackers
Found in file sv.h

=item SvTAINTED
X<SvTAINTED>

Checks to see if an SV is tainted.  Returns TRUE if it is, FALSE if
not.

	bool	SvTAINTED(SV* sv)

=for hackers
Found in file sv.h

=item sv_tainted
X<sv_tainted>

Test an SV for taintedness.  Use C<SvTAINTED> instead.

	bool	sv_tainted(SV *const sv)

=for hackers
Found in file sv.c

=item SvTAINTED_off
X<SvTAINTED_off>

Untaints an SV.  Be I<very> careful with this routine, as it short-circuits
some of Perl's fundamental security features.  XS module authors should not
use this function unless they fully understand all the implications of
unconditionally untainting the value.  Untainting should be done in the
standard perl fashion, via a carefully crafted regexp, rather than directly
untainting variables.

	void	SvTAINTED_off(SV* sv)

=for hackers
Found in file sv.h

=item SvTAINTED_on
X<SvTAINTED_on>

Marks an SV as tainted if tainting is enabled.

	void	SvTAINTED_on(SV* sv)

=for hackers
Found in file sv.h

=item SvTRUE
X<SvTRUE>

Returns a boolean indicating whether Perl would evaluate the SV as true or
false.  See C<L</SvOK>> for a defined/undefined test.  Handles 'get' magic
unless the scalar is already C<SvPOK>, C<SvIOK> or C<SvNOK> (the public, not the
private flags).

See C<L</SvTRUEx>> for a version which guarantees to evaluate C<sv> only once.

	bool	SvTRUE(SV* sv)

=for hackers
Found in file sv.h

=item sv_true
X<sv_true>

Returns true if the SV has a true value by Perl's rules.
Use the C<SvTRUE> macro instead, which may call C<sv_true()> or may
instead use an in-line version.

	I32	sv_true(SV *const sv)

=for hackers
Found in file sv.c

=item SvTRUE_nomg
X<SvTRUE_nomg>

Returns a boolean indicating whether Perl would evaluate the SV as true or
false.  See C<L</SvOK>> for a defined/undefined test.  Does not handle 'get' magic.

	bool	SvTRUE_nomg(SV* sv)

=for hackers
Found in file sv.h

=item SvTRUEx
X<SvTRUEx>

Returns a boolean indicating whether Perl would evaluate the SV as true or
false.  See C<L</SvOK>> for a defined/undefined test.  Handles 'get' magic
unless the scalar is already C<SvPOK>, C<SvIOK> or C<SvNOK> (the public, not the
private flags).

This form guarantees to evaluate C<sv> only once.  Only use this if C<sv> is an
expression with side effects, otherwise use the more efficient C<SvTRUE>.

	bool	SvTRUEx(SV* sv)

=for hackers
Found in file sv.h

=item SvTYPE
X<SvTYPE>

Returns the type of the SV.  See C<L</svtype>>.

	svtype	SvTYPE(SV* sv)

=for hackers
Found in file sv.h

=item sv_unmagic
X<sv_unmagic>

Removes all magic of type C<type> from an SV.

	int	sv_unmagic(SV *const sv, const int type)

=for hackers
Found in file sv.c

=item sv_unmagicext
X<sv_unmagicext>

Removes all magic of type C<type> with the specified C<vtbl> from an SV.

	int	sv_unmagicext(SV *const sv, const int type,
		              MGVTBL *vtbl)

=for hackers
Found in file sv.c

=item sv_unref_flags
X<sv_unref_flags>

Unsets the RV status of the SV, and decrements the reference count of
whatever was being referenced by the RV.  This can almost be thought of
as a reversal of C<newSVrv>.  The C<cflags> argument can contain
C<SV_IMMEDIATE_UNREF> to force the reference count to be decremented
(otherwise the decrementing is conditional on the reference count being
different from one or the reference being a readonly SV).
See C<L</SvROK_off>>.

	void	sv_unref_flags(SV *const ref, const U32 flags)

=for hackers
Found in file sv.c

=item sv_untaint
X<sv_untaint>

Untaint an SV.  Use C<SvTAINTED_off> instead.

	void	sv_untaint(SV *const sv)

=for hackers
Found in file sv.c

=item SvUOK
X<SvUOK>

Returns a boolean indicating whether the SV contains an integer that must be
interpreted as unsigned.  A non-negative integer whose value is within the
range of both an IV and a UV may be flagged as either C<SvUOK> or C<SvIOK>.

	bool	SvUOK(SV* sv)

=for hackers
Found in file sv.h

=item SvUPGRADE
X<SvUPGRADE>

Used to upgrade an SV to a more complex form.  Uses C<sv_upgrade> to
perform the upgrade if necessary.  See C<L</svtype>>.

	void	SvUPGRADE(SV* sv, svtype type)

=for hackers
Found in file sv.h

=item sv_upgrade
X<sv_upgrade>

Upgrade an SV to a more complex form.  Generally adds a new body type to the
SV, then copies across as much information as possible from the old body.
It croaks if the SV is already in a more complex form than requested.  You
generally want to use the C<SvUPGRADE> macro wrapper, which checks the type
before calling C<sv_upgrade>, and hence does not croak.  See also
C<L</svtype>>.

	void	sv_upgrade(SV *const sv, svtype new_type)

=for hackers
Found in file sv.c

=item sv_usepvn_flags
X<sv_usepvn_flags>

Tells an SV to use C<ptr> to find its string value.  Normally the
string is stored inside the SV, but sv_usepvn allows the SV to use an
outside string.  C<ptr> should point to memory that was allocated
by L<C<Newx>|perlclib/Memory Management and String Handling>.  It must be
the start of a C<Newx>-ed block of memory, and not a pointer to the
middle of it (beware of L<C<OOK>|perlguts/Offsets> and copy-on-write),
and not be from a non-C<Newx> memory allocator like C<malloc>.  The
string length, C<len>, must be supplied.  By default this function
will C<Renew> (i.e. realloc, move) the memory pointed to by C<ptr>,
so that pointer should not be freed or used by the programmer after
giving it to C<sv_usepvn>, and neither should any pointers from "behind"
that pointer (e.g. ptr + 1) be used.

If S<C<flags & SV_SMAGIC>> is true, will call C<SvSETMAGIC>.  If
S<C<flags & SV_HAS_TRAILING_NUL>> is true, then C<ptr[len]> must be C<NUL>,
and the realloc
will be skipped (i.e. the buffer is actually at least 1 byte longer than
C<len>, and already meets the requirements for storing in C<SvPVX>).

	void	sv_usepvn_flags(SV *const sv, char* ptr,
		                const STRLEN len,
		                const U32 flags)

=for hackers
Found in file sv.c

=item SvUTF8
X<SvUTF8>

Returns a U32 value indicating the UTF-8 status of an SV.  If things are set-up
properly, this indicates whether or not the SV contains UTF-8 encoded data.
You should use this I<after> a call to C<SvPV()> or one of its variants, in
case any call to string overloading updates the internal flag.

If you want to take into account the L<bytes> pragma, use C<L</DO_UTF8>>
instead.

	U32	SvUTF8(SV* sv)

=for hackers
Found in file sv.h

=item sv_utf8_decode
X<sv_utf8_decode>

If the PV of the SV is an octet sequence in Perl's extended UTF-8
and contains a multiple-byte character, the C<SvUTF8> flag is turned on
so that it looks like a character.  If the PV contains only single-byte
characters, the C<SvUTF8> flag stays off.
Scans PV for validity and returns FALSE if the PV is invalid UTF-8.

	bool	sv_utf8_decode(SV *const sv)

=for hackers
Found in file sv.c

=item sv_utf8_downgrade
X<sv_utf8_downgrade>

Attempts to convert the PV of an SV from characters to bytes.
If the PV contains a character that cannot fit
in a byte, this conversion will fail;
in this case, either returns false or, if C<fail_ok> is not
true, croaks.

This is not a general purpose Unicode to byte encoding interface:
use the C<Encode> extension for that.

This function process get magic on C<sv>.

	bool	sv_utf8_downgrade(SV *const sv,
		                  const bool fail_ok)

=for hackers
Found in file sv.c

=item sv_utf8_downgrade_flags
X<sv_utf8_downgrade_flags>

Like C<sv_utf8_downgrade>, but with additional C<flags>.
If C<flags> has C<SV_GMAGIC> bit set, processes get magic on C<sv>.

	bool	sv_utf8_downgrade_flags(SV *const sv,
		                        const bool fail_ok,
		                        const U32 flags)

=for hackers
Found in file sv.c

=item sv_utf8_downgrade_nomg
X<sv_utf8_downgrade_nomg>

Like C<sv_utf8_downgrade>, but does not process get magic on C<sv>.

	bool	sv_utf8_downgrade_nomg(SV *const sv,
		                       const bool fail_ok)

=for hackers
Found in file sv.c

=item sv_utf8_encode
X<sv_utf8_encode>

Converts the PV of an SV to UTF-8, but then turns the C<SvUTF8>
flag off so that it looks like octets again.

	void	sv_utf8_encode(SV *const sv)

=for hackers
Found in file sv.c

=item sv_utf8_upgrade
X<sv_utf8_upgrade>

Converts the PV of an SV to its UTF-8-encoded form.
Forces the SV to string form if it is not already.
Will C<mg_get> on C<sv> if appropriate.
Always sets the C<SvUTF8> flag to avoid future validity checks even
if the whole string is the same in UTF-8 as not.
Returns the number of bytes in the converted string

This is not a general purpose byte encoding to Unicode interface:
use the Encode extension for that.

	STRLEN	sv_utf8_upgrade(SV *sv)

=for hackers
Found in file sv.c

=item sv_utf8_upgrade_flags
X<sv_utf8_upgrade_flags>

Converts the PV of an SV to its UTF-8-encoded form.
Forces the SV to string form if it is not already.
Always sets the SvUTF8 flag to avoid future validity checks even
if all the bytes are invariant in UTF-8.
If C<flags> has C<SV_GMAGIC> bit set,
will C<mg_get> on C<sv> if appropriate, else not.

The C<SV_FORCE_UTF8_UPGRADE> flag is now ignored.

Returns the number of bytes in the converted string.

This is not a general purpose byte encoding to Unicode interface:
use the Encode extension for that.

	STRLEN	sv_utf8_upgrade_flags(SV *const sv,
		                      const I32 flags)

=for hackers
Found in file sv.c

=item sv_utf8_upgrade_flags_grow
X<sv_utf8_upgrade_flags_grow>

Like C<sv_utf8_upgrade_flags>, but has an additional parameter C<extra>, which is
the number of unused bytes the string of C<sv> is guaranteed to have free after
it upon return.  This allows the caller to reserve extra space that it intends
to fill, to avoid extra grows.

C<sv_utf8_upgrade>, C<sv_utf8_upgrade_nomg>, and C<sv_utf8_upgrade_flags>
are implemented in terms of this function.

Returns the number of bytes in the converted string (not including the spares).

	STRLEN	sv_utf8_upgrade_flags_grow(SV *const sv,
		                           const I32 flags,
		                           STRLEN extra)

=for hackers
Found in file sv.c

=item sv_utf8_upgrade_nomg
X<sv_utf8_upgrade_nomg>

Like C<sv_utf8_upgrade>, but doesn't do magic on C<sv>.

	STRLEN	sv_utf8_upgrade_nomg(SV *sv)

=for hackers
Found in file sv.c

=item SvUTF8_off
X<SvUTF8_off>

Unsets the UTF-8 status of an SV (the data is not changed, just the flag).
Do not use frivolously.

	void	SvUTF8_off(SV *sv)

=for hackers
Found in file sv.h

=item SvUTF8_on
X<SvUTF8_on>

Turn on the UTF-8 status of an SV (the data is not changed, just the flag).
Do not use frivolously.

	void	SvUTF8_on(SV *sv)

=for hackers
Found in file sv.h

=item SvUV
X<SvUV>

Coerces the given SV to UV and returns it.  The returned value in many
circumstances will get stored in C<sv>'s UV slot, but not in all cases.  (Use
C<L</sv_setuv>> to make sure it does).

See C<L</SvUVx>> for a version which guarantees to evaluate C<sv> only once.

	UV	SvUV(SV* sv)

=for hackers
Found in file sv.h

=item SvUV_nomg
X<SvUV_nomg>

Like C<SvUV> but doesn't process magic.

	UV	SvUV_nomg(SV* sv)

=for hackers
Found in file sv.h

=item SvUV_set
X<SvUV_set>

Set the value of the UV pointer in C<sv> to val.  See C<L</SvIV_set>>.

	void	SvUV_set(SV* sv, UV val)

=for hackers
Found in file sv.h

=item SvUVX
X<SvUVX>

Returns the raw value in the SV's UV slot, without checks or conversions.
Only use when you are sure C<SvIOK> is true.  See also C<L</SvUV>>.

	UV	SvUVX(SV* sv)

=for hackers
Found in file sv.h

=item SvUVx
X<SvUVx>

Coerces the given SV to UV and returns it.  The returned value in many
circumstances will get stored in C<sv>'s UV slot, but not in all cases.  (Use
C<L</sv_setuv>> to make sure it does).

This form guarantees to evaluate C<sv> only once.  Only use this if C<sv> is an
expression with side effects, otherwise use the more efficient C<SvUV>.

	UV	SvUVx(SV* sv)

=for hackers
Found in file sv.h

=item SvUVXx
X<SvUVXx>


DEPRECATED!  It is planned to remove this function from a
future release of Perl.  Do not use it for new code; remove it from
existing code.


This is an unnecessary synonym for L</SvUVX>

	UV	SvUVXx(SV* sv)

=for hackers
Found in file sv.h

=item sv_vcatpvf
X<sv_vcatpvf>

Processes its arguments like C<sv_vcatpvfn> called with a non-null C-style
variable argument list, and appends the formatted output
to an SV.  Does not handle 'set' magic.  See C<L</sv_vcatpvf_mg>>.

Usually used via its frontend C<sv_catpvf>.

	void	sv_vcatpvf(SV *const sv, const char *const pat,
		           va_list *const args)

=for hackers
Found in file sv.c

=item sv_vcatpvfn
X<sv_vcatpvfn>

	void	sv_vcatpvfn(SV *const sv, const char *const pat,
		            const STRLEN patlen,
		            va_list *const args,
		            SV **const svargs,
		            const Size_t sv_count,
		            bool *const maybe_tainted)

=for hackers
Found in file sv.c

=item sv_vcatpvfn_flags
X<sv_vcatpvfn_flags>

Processes its arguments like C<vsprintf> and appends the formatted output
to an SV.  Uses an array of SVs if the C-style variable argument list is
missing (C<NULL>). Argument reordering (using format specifiers like C<%2$d>
or C<%*2$d>) is supported only when using an array of SVs; using a C-style
C<va_list> argument list with a format string that uses argument reordering
will yield an exception.

When running with taint checks enabled, indicates via
C<maybe_tainted> if results are untrustworthy (often due to the use of
locales).

If called as C<sv_vcatpvfn> or flags has the C<SV_GMAGIC> bit set, calls get magic.

It assumes that pat has the same utf8-ness as sv.  It's the caller's
responsibility to ensure that this is so.

Usually used via one of its frontends C<sv_vcatpvf> and C<sv_vcatpvf_mg>.

	void	sv_vcatpvfn_flags(SV *const sv,
		                  const char *const pat,
		                  const STRLEN patlen,
		                  va_list *const args,
		                  SV **const svargs,
		                  const Size_t sv_count,
		                  bool *const maybe_tainted,
		                  const U32 flags)

=for hackers
Found in file sv.c

=item sv_vcatpvf_mg
X<sv_vcatpvf_mg>

Like C<sv_vcatpvf>, but also handles 'set' magic.

Usually used via its frontend C<sv_catpvf_mg>.

	void	sv_vcatpvf_mg(SV *const sv,
		              const char *const pat,
		              va_list *const args)

=for hackers
Found in file sv.c

=item SvVOK
X<SvVOK>

Returns a boolean indicating whether the SV contains a v-string.

	bool	SvVOK(SV* sv)

=for hackers
Found in file sv.h

=item sv_vsetpvf
X<sv_vsetpvf>

Works like C<sv_vcatpvf> but copies the text into the SV instead of
appending it.  Does not handle 'set' magic.  See C<L</sv_vsetpvf_mg>>.

Usually used via its frontend C<sv_setpvf>.

	void	sv_vsetpvf(SV *const sv, const char *const pat,
		           va_list *const args)

=for hackers
Found in file sv.c

=item sv_vsetpvfn
X<sv_vsetpvfn>

Works like C<sv_vcatpvfn> but copies the text into the SV instead of
appending it.

Usually used via one of its frontends C<sv_vsetpvf> and C<sv_vsetpvf_mg>.

	void	sv_vsetpvfn(SV *const sv, const char *const pat,
		            const STRLEN patlen,
		            va_list *const args,
		            SV **const svargs,
		            const Size_t sv_count,
		            bool *const maybe_tainted)

=for hackers
Found in file sv.c

=item sv_vsetpvf_mg
X<sv_vsetpvf_mg>

Like C<sv_vsetpvf>, but also handles 'set' magic.

Usually used via its frontend C<sv_setpvf_mg>.

	void	sv_vsetpvf_mg(SV *const sv,
		              const char *const pat,
		              va_list *const args)

=for hackers
Found in file sv.c


=back

=head1 Unicode Support

L<perlguts/Unicode Support> has an introduction to this API.

See also L</Character classification>,
and L</Character case changing>.
Various functions outside this section also work specially with Unicode.
Search for the string "utf8" in this document.


=over 8

=item BOM_UTF8
X<BOM_UTF8>

This is a macro that evaluates to a string constant of the  UTF-8 bytes that
define the Unicode BYTE ORDER MARK (U+FEFF) for the platform that perl
is compiled on.  This allows code to use a mnemonic for this character that
works on both ASCII and EBCDIC platforms.
S<C<sizeof(BOM_UTF8) - 1>> can be used to get its length in
bytes.

=for hackers
Found in file unicode_constants.h

=item bytes_cmp_utf8
X<bytes_cmp_utf8>

Compares the sequence of characters (stored as octets) in C<b>, C<blen> with the
sequence of characters (stored as UTF-8)
in C<u>, C<ulen>.  Returns 0 if they are
equal, -1 or -2 if the first string is less than the second string, +1 or +2
if the first string is greater than the second string.

-1 or +1 is returned if the shorter string was identical to the start of the
longer string.  -2 or +2 is returned if
there was a difference between characters
within the strings.

	int	bytes_cmp_utf8(const U8 *b, STRLEN blen,
		               const U8 *u, STRLEN ulen)

=for hackers
Found in file utf8.c

=item bytes_from_utf8
X<bytes_from_utf8>


NOTE: this function is experimental and may change or be
removed without notice.


Converts a potentially UTF-8 encoded string C<s> of length C<*lenp> into native
byte encoding.  On input, the boolean C<*is_utf8p> gives whether or not C<s> is
actually encoded in UTF-8.

Unlike L</utf8_to_bytes> but like L</bytes_to_utf8>, this is non-destructive of
the input string.

Do nothing if C<*is_utf8p> is 0, or if there are code points in the string
not expressible in native byte encoding.  In these cases, C<*is_utf8p> and
C<*lenp> are unchanged, and the return value is the original C<s>.

Otherwise, C<*is_utf8p> is set to 0, and the return value is a pointer to a
newly created string containing a downgraded copy of C<s>, and whose length is
returned in C<*lenp>, updated.  The new string is C<NUL>-terminated.  The
caller is responsible for arranging for the memory used by this string to get
freed.

Upon successful return, the number of variants in the string can be computed by
having saved the value of C<*lenp> before the call, and subtracting the
after-call value of C<*lenp> from it.

	U8*	bytes_from_utf8(const U8 *s, STRLEN *lenp,
		                bool *is_utf8p)

=for hackers
Found in file utf8.c

=item bytes_to_utf8
X<bytes_to_utf8>


NOTE: this function is experimental and may change or be
removed without notice.


Converts a string C<s> of length C<*lenp> bytes from the native encoding into
UTF-8.
Returns a pointer to the newly-created string, and sets C<*lenp> to
reflect the new length in bytes.  The caller is responsible for arranging for
the memory used by this string to get freed.

Upon successful return, the number of variants in the string can be computed by
having saved the value of C<*lenp> before the call, and subtracting it from the
after-call value of C<*lenp>.

A C<NUL> character will be written after the end of the string.

If you want to convert to UTF-8 from encodings other than
the native (Latin1 or EBCDIC),
see L</sv_recode_to_utf8>().

	U8*	bytes_to_utf8(const U8 *s, STRLEN *lenp)

=for hackers
Found in file utf8.c

=item DO_UTF8
X<DO_UTF8>

Returns a bool giving whether or not the PV in C<sv> is to be treated as being
encoded in UTF-8.

You should use this I<after> a call to C<SvPV()> or one of its variants, in
case any call to string overloading updates the internal UTF-8 encoding flag.

	bool	DO_UTF8(SV* sv)

=for hackers
Found in file utf8.h

=item foldEQ_utf8
X<foldEQ_utf8>

Returns true if the leading portions of the strings C<s1> and C<s2> (either or
both of which may be in UTF-8) are the same case-insensitively; false
otherwise.  How far into the strings to compare is determined by other input
parameters.

If C<u1> is true, the string C<s1> is assumed to be in UTF-8-encoded Unicode;
otherwise it is assumed to be in native 8-bit encoding.  Correspondingly for
C<u2> with respect to C<s2>.

If the byte length C<l1> is non-zero, it says how far into C<s1> to check for
fold equality.  In other words, C<s1>+C<l1> will be used as a goal to reach.
The scan will not be considered to be a match unless the goal is reached, and
scanning won't continue past that goal.  Correspondingly for C<l2> with respect
to C<s2>.

If C<pe1> is non-C<NULL> and the pointer it points to is not C<NULL>, that
pointer is considered an end pointer to the position 1 byte past the maximum
point in C<s1> beyond which scanning will not continue under any circumstances.
(This routine assumes that UTF-8 encoded input strings are not malformed;
malformed input can cause it to read past C<pe1>).  This means that if both
C<l1> and C<pe1> are specified, and C<pe1> is less than C<s1>+C<l1>, the match
will never be successful because it can never
get as far as its goal (and in fact is asserted against).  Correspondingly for
C<pe2> with respect to C<s2>.

At least one of C<s1> and C<s2> must have a goal (at least one of C<l1> and
C<l2> must be non-zero), and if both do, both have to be
reached for a successful match.   Also, if the fold of a character is multiple
characters, all of them must be matched (see tr21 reference below for
'folding').

Upon a successful match, if C<pe1> is non-C<NULL>,
it will be set to point to the beginning of the I<next> character of C<s1>
beyond what was matched.  Correspondingly for C<pe2> and C<s2>.

For case-insensitiveness, the "casefolding" of Unicode is used
instead of upper/lowercasing both the characters, see
L<https://www.unicode.org/unicode/reports/tr21/> (Case Mappings).

	I32	foldEQ_utf8(const char *s1, char **pe1, UV l1,
		            bool u1, const char *s2, char **pe2,
		            UV l2, bool u2)

=for hackers
Found in file utf8.c

=item is_ascii_string
X<is_ascii_string>

This is a misleadingly-named synonym for L</is_utf8_invariant_string>.
On ASCII-ish platforms, the name isn't misleading: the ASCII-range characters
are exactly the UTF-8 invariants.  But EBCDIC machines have more invariants
than just the ASCII characters, so C<is_utf8_invariant_string> is preferred.

	bool	is_ascii_string(const U8* const s, STRLEN len)

=for hackers
Found in file utf8.h

=item is_c9strict_utf8_string
X<is_c9strict_utf8_string>

Returns TRUE if the first C<len> bytes of string C<s> form a valid
UTF-8-encoded string that conforms to
L<Unicode Corrigendum #9|http://www.unicode.org/versions/corrigendum9.html>;
otherwise it returns FALSE.  If C<len> is 0, it will be calculated using
C<strlen(s)> (which means if you use this option, that C<s> can't have embedded
C<NUL> characters and has to have a terminating C<NUL> byte).  Note that all
characters being ASCII constitute 'a valid UTF-8 string'.

This function returns FALSE for strings containing any code points above the
Unicode max of 0x10FFFF or surrogate code points, but accepts non-character
code points per
L<Corrigendum #9|http://www.unicode.org/versions/corrigendum9.html>.

See also
C<L</is_utf8_invariant_string>>,
C<L</is_utf8_invariant_string_loc>>,
C<L</is_utf8_string>>,
C<L</is_utf8_string_flags>>,
C<L</is_utf8_string_loc>>,
C<L</is_utf8_string_loc_flags>>,
C<L</is_utf8_string_loclen>>,
C<L</is_utf8_string_loclen_flags>>,
C<L</is_utf8_fixed_width_buf_flags>>,
C<L</is_utf8_fixed_width_buf_loc_flags>>,
C<L</is_utf8_fixed_width_buf_loclen_flags>>,
C<L</is_strict_utf8_string>>,
C<L</is_strict_utf8_string_loc>>,
C<L</is_strict_utf8_string_loclen>>,
C<L</is_c9strict_utf8_string_loc>>,
and
C<L</is_c9strict_utf8_string_loclen>>.

	bool	is_c9strict_utf8_string(const U8 *s, STRLEN len)

=for hackers
Found in file inline.h

=item is_c9strict_utf8_string_loc
X<is_c9strict_utf8_string_loc>

Like C<L</is_c9strict_utf8_string>> but stores the location of the failure (in
the case of "utf8ness failure") or the location C<s>+C<len> (in the case of
"utf8ness success") in the C<ep> pointer.

See also C<L</is_c9strict_utf8_string_loclen>>.

	bool	is_c9strict_utf8_string_loc(const U8 *s,
		                            STRLEN len,
		                            const U8 **ep)

=for hackers
Found in file inline.h

=item is_c9strict_utf8_string_loclen
X<is_c9strict_utf8_string_loclen>

Like C<L</is_c9strict_utf8_string>> but stores the location of the failure (in
the case of "utf8ness failure") or the location C<s>+C<len> (in the case of
"utf8ness success") in the C<ep> pointer, and the number of UTF-8 encoded
characters in the C<el> pointer.

See also C<L</is_c9strict_utf8_string_loc>>.

	bool	is_c9strict_utf8_string_loclen(const U8 *s,
		                               STRLEN len,
		                               const U8 **ep,
		                               STRLEN *el)

=for hackers
Found in file inline.h

=item isC9_STRICT_UTF8_CHAR
X<isC9_STRICT_UTF8_CHAR>

Evaluates to non-zero if the first few bytes of the string starting at C<s> and
looking no further than S<C<e - 1>> are well-formed UTF-8 that represents some
Unicode non-surrogate code point; otherwise it evaluates to 0.  If non-zero,
the value gives how many bytes starting at C<s> comprise the code point's
representation.  Any bytes remaining before C<e>, but beyond the ones needed to
form the first code point in C<s>, are not examined.

The largest acceptable code point is the Unicode maximum 0x10FFFF.  This
differs from C<L</isSTRICT_UTF8_CHAR>> only in that it accepts non-character
code points.  This corresponds to
L<Unicode Corrigendum #9|http://www.unicode.org/versions/corrigendum9.html>.
which said that non-character code points are merely discouraged rather than
completely forbidden in open interchange.  See
L<perlunicode/Noncharacter code points>.

Use C<L</isUTF8_CHAR>> to check for Perl's extended UTF-8; and
C<L</isUTF8_CHAR_flags>> for a more customized definition.

Use C<L</is_c9strict_utf8_string>>, C<L</is_c9strict_utf8_string_loc>>, and
C<L</is_c9strict_utf8_string_loclen>> to check entire strings.

	Size_t	isC9_STRICT_UTF8_CHAR(const U8 * const s0,
		                      const U8 * const e)

=for hackers
Found in file inline.h

=item is_invariant_string
X<is_invariant_string>

This is a somewhat misleadingly-named synonym for L</is_utf8_invariant_string>.
C<is_utf8_invariant_string> is preferred, as it indicates under what conditions
the string is invariant.

	bool	is_invariant_string(const U8* const s,
		                    STRLEN len)

=for hackers
Found in file utf8.h

=item isSTRICT_UTF8_CHAR
X<isSTRICT_UTF8_CHAR>

Evaluates to non-zero if the first few bytes of the string starting at C<s> and
looking no further than S<C<e - 1>> are well-formed UTF-8 that represents some
Unicode code point completely acceptable for open interchange between all
applications; otherwise it evaluates to 0.  If non-zero, the value gives how
many bytes starting at C<s> comprise the code point's representation.  Any
bytes remaining before C<e>, but beyond the ones needed to form the first code
point in C<s>, are not examined.

The largest acceptable code point is the Unicode maximum 0x10FFFF, and must not
be a surrogate nor a non-character code point.  Thus this excludes any code
point from Perl's extended UTF-8.

This is used to efficiently decide if the next few bytes in C<s> is
legal Unicode-acceptable UTF-8 for a single character.

Use C<L</isC9_STRICT_UTF8_CHAR>> to use the L<Unicode Corrigendum
#9|http://www.unicode.org/versions/corrigendum9.html> definition of allowable
code points; C<L</isUTF8_CHAR>> to check for Perl's extended UTF-8;
and C<L</isUTF8_CHAR_flags>> for a more customized definition.

Use C<L</is_strict_utf8_string>>, C<L</is_strict_utf8_string_loc>>, and
C<L</is_strict_utf8_string_loclen>> to check entire strings.

	Size_t	isSTRICT_UTF8_CHAR(const U8 * const s0,
		                   const U8 * const e)

=for hackers
Found in file inline.h

=item is_strict_utf8_string
X<is_strict_utf8_string>

Returns TRUE if the first C<len> bytes of string C<s> form a valid
UTF-8-encoded string that is fully interchangeable by any application using
Unicode rules; otherwise it returns FALSE.  If C<len> is 0, it will be
calculated using C<strlen(s)> (which means if you use this option, that C<s>
can't have embedded C<NUL> characters and has to have a terminating C<NUL>
byte).  Note that all characters being ASCII constitute 'a valid UTF-8 string'.

This function returns FALSE for strings containing any
code points above the Unicode max of 0x10FFFF, surrogate code points, or
non-character code points.

See also
C<L</is_utf8_invariant_string>>,
C<L</is_utf8_invariant_string_loc>>,
C<L</is_utf8_string>>,
C<L</is_utf8_string_flags>>,
C<L</is_utf8_string_loc>>,
C<L</is_utf8_string_loc_flags>>,
C<L</is_utf8_string_loclen>>,
C<L</is_utf8_string_loclen_flags>>,
C<L</is_utf8_fixed_width_buf_flags>>,
C<L</is_utf8_fixed_width_buf_loc_flags>>,
C<L</is_utf8_fixed_width_buf_loclen_flags>>,
C<L</is_strict_utf8_string_loc>>,
C<L</is_strict_utf8_string_loclen>>,
C<L</is_c9strict_utf8_string>>,
C<L</is_c9strict_utf8_string_loc>>,
and
C<L</is_c9strict_utf8_string_loclen>>.

	bool	is_strict_utf8_string(const U8 *s, STRLEN len)

=for hackers
Found in file inline.h

=item is_strict_utf8_string_loc
X<is_strict_utf8_string_loc>

Like C<L</is_strict_utf8_string>> but stores the location of the failure (in the
case of "utf8ness failure") or the location C<s>+C<len> (in the case of
"utf8ness success") in the C<ep> pointer.

See also C<L</is_strict_utf8_string_loclen>>.

	bool	is_strict_utf8_string_loc(const U8 *s,
		                          STRLEN len,
		                          const U8 **ep)

=for hackers
Found in file inline.h

=item is_strict_utf8_string_loclen
X<is_strict_utf8_string_loclen>

Like C<L</is_strict_utf8_string>> but stores the location of the failure (in the
case of "utf8ness failure") or the location C<s>+C<len> (in the case of
"utf8ness success") in the C<ep> pointer, and the number of UTF-8
encoded characters in the C<el> pointer.

See also C<L</is_strict_utf8_string_loc>>.

	bool	is_strict_utf8_string_loclen(const U8 *s,
		                             STRLEN len,
		                             const U8 **ep,
		                             STRLEN *el)

=for hackers
Found in file inline.h

=item is_utf8_fixed_width_buf_flags
X<is_utf8_fixed_width_buf_flags>

Returns TRUE if the fixed-width buffer starting at C<s> with length C<len>
is entirely valid UTF-8, subject to the restrictions given by C<flags>;
otherwise it returns FALSE.

If C<flags> is 0, any well-formed UTF-8, as extended by Perl, is accepted
without restriction.  If the final few bytes of the buffer do not form a
complete code point, this will return TRUE anyway, provided that
C<L</is_utf8_valid_partial_char_flags>> returns TRUE for them.

If C<flags> in non-zero, it can be any combination of the
C<UTF8_DISALLOW_I<foo>> flags accepted by C<L</utf8n_to_uvchr>>, and with the
same meanings.

This function differs from C<L</is_utf8_string_flags>> only in that the latter
returns FALSE if the final few bytes of the string don't form a complete code
point.

	bool	is_utf8_fixed_width_buf_flags(
		    const U8 * const s, STRLEN len,
		    const U32 flags
		)

=for hackers
Found in file inline.h

=item is_utf8_fixed_width_buf_loclen_flags
X<is_utf8_fixed_width_buf_loclen_flags>

Like C<L</is_utf8_fixed_width_buf_loc_flags>> but stores the number of
complete, valid characters found in the C<el> pointer.

	bool	is_utf8_fixed_width_buf_loclen_flags(
		    const U8 * const s, STRLEN len,
		    const U8 **ep, STRLEN *el, const U32 flags
		)

=for hackers
Found in file inline.h

=item is_utf8_fixed_width_buf_loc_flags
X<is_utf8_fixed_width_buf_loc_flags>

Like C<L</is_utf8_fixed_width_buf_flags>> but stores the location of the
failure in the C<ep> pointer.  If the function returns TRUE, C<*ep> will point
to the beginning of any partial character at the end of the buffer; if there is
no partial character C<*ep> will contain C<s>+C<len>.

See also C<L</is_utf8_fixed_width_buf_loclen_flags>>.

	bool	is_utf8_fixed_width_buf_loc_flags(
		    const U8 * const s, STRLEN len,
		    const U8 **ep, const U32 flags
		)

=for hackers
Found in file inline.h

=item is_utf8_invariant_string
X<is_utf8_invariant_string>

Returns TRUE if the first C<len> bytes of the string C<s> are the same
regardless of the UTF-8 encoding of the string (or UTF-EBCDIC encoding on
EBCDIC machines); otherwise it returns FALSE.  That is, it returns TRUE if they
are UTF-8 invariant.  On ASCII-ish machines, all the ASCII characters and only
the ASCII characters fit this definition.  On EBCDIC machines, the ASCII-range
characters are invariant, but so also are the C1 controls.

If C<len> is 0, it will be calculated using C<strlen(s)>, (which means if you
use this option, that C<s> can't have embedded C<NUL> characters and has to
have a terminating C<NUL> byte).

See also
C<L</is_utf8_string>>,
C<L</is_utf8_string_flags>>,
C<L</is_utf8_string_loc>>,
C<L</is_utf8_string_loc_flags>>,
C<L</is_utf8_string_loclen>>,
C<L</is_utf8_string_loclen_flags>>,
C<L</is_utf8_fixed_width_buf_flags>>,
C<L</is_utf8_fixed_width_buf_loc_flags>>,
C<L</is_utf8_fixed_width_buf_loclen_flags>>,
C<L</is_strict_utf8_string>>,
C<L</is_strict_utf8_string_loc>>,
C<L</is_strict_utf8_string_loclen>>,
C<L</is_c9strict_utf8_string>>,
C<L</is_c9strict_utf8_string_loc>>,
and
C<L</is_c9strict_utf8_string_loclen>>.

	bool	is_utf8_invariant_string(const U8* const s,
		                         STRLEN len)

=for hackers
Found in file inline.h

=item is_utf8_invariant_string_loc
X<is_utf8_invariant_string_loc>

Like C<L</is_utf8_invariant_string>> but upon failure, stores the location of
the first UTF-8 variant character in the C<ep> pointer; if all characters are
UTF-8 invariant, this function does not change the contents of C<*ep>.

	bool	is_utf8_invariant_string_loc(const U8* const s,
		                             STRLEN len,
		                             const U8 ** ep)

=for hackers
Found in file inline.h

=item is_utf8_string
X<is_utf8_string>

Returns TRUE if the first C<len> bytes of string C<s> form a valid
Perl-extended-UTF-8 string; returns FALSE otherwise.  If C<len> is 0, it will
be calculated using C<strlen(s)> (which means if you use this option, that C<s>
can't have embedded C<NUL> characters and has to have a terminating C<NUL>
byte).  Note that all characters being ASCII constitute 'a valid UTF-8 string'.

This function considers Perl's extended UTF-8 to be valid.  That means that
code points above Unicode, surrogates, and non-character code points are
considered valid by this function.  Use C<L</is_strict_utf8_string>>,
C<L</is_c9strict_utf8_string>>, or C<L</is_utf8_string_flags>> to restrict what
code points are considered valid.

See also
C<L</is_utf8_invariant_string>>,
C<L</is_utf8_invariant_string_loc>>,
C<L</is_utf8_string_loc>>,
C<L</is_utf8_string_loclen>>,
C<L</is_utf8_fixed_width_buf_flags>>,
C<L</is_utf8_fixed_width_buf_loc_flags>>,
C<L</is_utf8_fixed_width_buf_loclen_flags>>,

	bool	is_utf8_string(const U8 *s, STRLEN len)

=for hackers
Found in file inline.h

=item is_utf8_string_flags
X<is_utf8_string_flags>

Returns TRUE if the first C<len> bytes of string C<s> form a valid
UTF-8 string, subject to the restrictions imposed by C<flags>;
returns FALSE otherwise.  If C<len> is 0, it will be calculated
using C<strlen(s)> (which means if you use this option, that C<s> can't have
embedded C<NUL> characters and has to have a terminating C<NUL> byte).  Note
that all characters being ASCII constitute 'a valid UTF-8 string'.

If C<flags> is 0, this gives the same results as C<L</is_utf8_string>>; if
C<flags> is C<UTF8_DISALLOW_ILLEGAL_INTERCHANGE>, this gives the same results
as C<L</is_strict_utf8_string>>; and if C<flags> is
C<UTF8_DISALLOW_ILLEGAL_C9_INTERCHANGE>, this gives the same results as
C<L</is_c9strict_utf8_string>>.  Otherwise C<flags> may be any
combination of the C<UTF8_DISALLOW_I<foo>> flags understood by
C<L</utf8n_to_uvchr>>, with the same meanings.

See also
C<L</is_utf8_invariant_string>>,
C<L</is_utf8_invariant_string_loc>>,
C<L</is_utf8_string>>,
C<L</is_utf8_string_loc>>,
C<L</is_utf8_string_loc_flags>>,
C<L</is_utf8_string_loclen>>,
C<L</is_utf8_string_loclen_flags>>,
C<L</is_utf8_fixed_width_buf_flags>>,
C<L</is_utf8_fixed_width_buf_loc_flags>>,
C<L</is_utf8_fixed_width_buf_loclen_flags>>,
C<L</is_strict_utf8_string>>,
C<L</is_strict_utf8_string_loc>>,
C<L</is_strict_utf8_string_loclen>>,
C<L</is_c9strict_utf8_string>>,
C<L</is_c9strict_utf8_string_loc>>,
and
C<L</is_c9strict_utf8_string_loclen>>.

	bool	is_utf8_string_flags(const U8 *s, STRLEN len,
		                     const U32 flags)

=for hackers
Found in file inline.h

=item is_utf8_string_loc
X<is_utf8_string_loc>

Like C<L</is_utf8_string>> but stores the location of the failure (in the
case of "utf8ness failure") or the location C<s>+C<len> (in the case of
"utf8ness success") in the C<ep> pointer.

See also C<L</is_utf8_string_loclen>>.

	bool	is_utf8_string_loc(const U8 *s,
		                   const STRLEN len,
		                   const U8 **ep)

=for hackers
Found in file inline.h

=item is_utf8_string_loclen
X<is_utf8_string_loclen>

Like C<L</is_utf8_string>> but stores the location of the failure (in the
case of "utf8ness failure") or the location C<s>+C<len> (in the case of
"utf8ness success") in the C<ep> pointer, and the number of UTF-8
encoded characters in the C<el> pointer.

See also C<L</is_utf8_string_loc>>.

	bool	is_utf8_string_loclen(const U8 *s, STRLEN len,
		                      const U8 **ep, STRLEN *el)

=for hackers
Found in file inline.h

=item is_utf8_string_loclen_flags
X<is_utf8_string_loclen_flags>

Like C<L</is_utf8_string_flags>> but stores the location of the failure (in the
case of "utf8ness failure") or the location C<s>+C<len> (in the case of
"utf8ness success") in the C<ep> pointer, and the number of UTF-8
encoded characters in the C<el> pointer.

See also C<L</is_utf8_string_loc_flags>>.

	bool	is_utf8_string_loclen_flags(const U8 *s,
		                            STRLEN len,
		                            const U8 **ep,
		                            STRLEN *el,
		                            const U32 flags)

=for hackers
Found in file inline.h

=item is_utf8_string_loc_flags
X<is_utf8_string_loc_flags>

Like C<L</is_utf8_string_flags>> but stores the location of the failure (in the
case of "utf8ness failure") or the location C<s>+C<len> (in the case of
"utf8ness success") in the C<ep> pointer.

See also C<L</is_utf8_string_loclen_flags>>.

	bool	is_utf8_string_loc_flags(const U8 *s,
		                         STRLEN len,
		                         const U8 **ep,
		                         const U32 flags)

=for hackers
Found in file inline.h

=item is_utf8_valid_partial_char
X<is_utf8_valid_partial_char>

Returns 0 if the sequence of bytes starting at C<s> and looking no further than
S<C<e - 1>> is the UTF-8 encoding, as extended by Perl, for one or more code
points.  Otherwise, it returns 1 if there exists at least one non-empty
sequence of bytes that when appended to sequence C<s>, starting at position
C<e> causes the entire sequence to be the well-formed UTF-8 of some code point;
otherwise returns 0.

In other words this returns TRUE if C<s> points to a partial UTF-8-encoded code
point.

This is useful when a fixed-length buffer is being tested for being well-formed
UTF-8, but the final few bytes in it don't comprise a full character; that is,
it is split somewhere in the middle of the final code point's UTF-8
representation.  (Presumably when the buffer is refreshed with the next chunk
of data, the new first bytes will complete the partial code point.)   This
function is used to verify that the final bytes in the current buffer are in
fact the legal beginning of some code point, so that if they aren't, the
failure can be signalled without having to wait for the next read.

	bool	is_utf8_valid_partial_char(const U8 * const s,
		                           const U8 * const e)

=for hackers
Found in file inline.h

=item is_utf8_valid_partial_char_flags
X<is_utf8_valid_partial_char_flags>

Like C<L</is_utf8_valid_partial_char>>, it returns a boolean giving whether
or not the input is a valid UTF-8 encoded partial character, but it takes an
extra parameter, C<flags>, which can further restrict which code points are
considered valid.

If C<flags> is 0, this behaves identically to
C<L</is_utf8_valid_partial_char>>.  Otherwise C<flags> can be any combination
of the C<UTF8_DISALLOW_I<foo>> flags accepted by C<L</utf8n_to_uvchr>>.  If
there is any sequence of bytes that can complete the input partial character in
such a way that a non-prohibited character is formed, the function returns
TRUE; otherwise FALSE.  Non character code points cannot be determined based on
partial character input.  But many  of the other possible excluded types can be
determined from just the first one or two bytes.

	bool	is_utf8_valid_partial_char_flags(
		    const U8 * const s, const U8 * const e,
		    const U32 flags
		)

=for hackers
Found in file inline.h

=item isUTF8_CHAR
X<isUTF8_CHAR>

Evaluates to non-zero if the first few bytes of the string starting at C<s> and
looking no further than S<C<e - 1>> are well-formed UTF-8, as extended by Perl,
that represents some code point; otherwise it evaluates to 0.  If non-zero, the
value gives how many bytes starting at C<s> comprise the code point's
representation.  Any bytes remaining before C<e>, but beyond the ones needed to
form the first code point in C<s>, are not examined.

The code point can be any that will fit in an IV on this machine, using Perl's
extension to official UTF-8 to represent those higher than the Unicode maximum
of 0x10FFFF.  That means that this macro is used to efficiently decide if the
next few bytes in C<s> is legal UTF-8 for a single character.

Use C<L</isSTRICT_UTF8_CHAR>> to restrict the acceptable code points to those
defined by Unicode to be fully interchangeable across applications;
C<L</isC9_STRICT_UTF8_CHAR>> to use the L<Unicode Corrigendum
#9|http://www.unicode.org/versions/corrigendum9.html> definition of allowable
code points; and C<L</isUTF8_CHAR_flags>> for a more customized definition.

Use C<L</is_utf8_string>>, C<L</is_utf8_string_loc>>, and
C<L</is_utf8_string_loclen>> to check entire strings.

Note also that a UTF-8 "invariant" character (i.e. ASCII on non-EBCDIC
machines) is a valid UTF-8 character.

	Size_t	isUTF8_CHAR(const U8 * const s0,
		            const U8 * const e)

=for hackers
Found in file inline.h

=item isUTF8_CHAR_flags
X<isUTF8_CHAR_flags>

Evaluates to non-zero if the first few bytes of the string starting at C<s> and
looking no further than S<C<e - 1>> are well-formed UTF-8, as extended by Perl,
that represents some code point, subject to the restrictions given by C<flags>;
otherwise it evaluates to 0.  If non-zero, the value gives how many bytes
starting at C<s> comprise the code point's representation.  Any bytes remaining
before C<e>, but beyond the ones needed to form the first code point in C<s>,
are not examined.

If C<flags> is 0, this gives the same results as C<L</isUTF8_CHAR>>;
if C<flags> is C<UTF8_DISALLOW_ILLEGAL_INTERCHANGE>, this gives the same results
as C<L</isSTRICT_UTF8_CHAR>>;
and if C<flags> is C<UTF8_DISALLOW_ILLEGAL_C9_INTERCHANGE>, this gives
the same results as C<L</isC9_STRICT_UTF8_CHAR>>.
Otherwise C<flags> may be any combination of the C<UTF8_DISALLOW_I<foo>> flags
understood by C<L</utf8n_to_uvchr>>, with the same meanings.

The three alternative macros are for the most commonly needed validations; they
are likely to run somewhat faster than this more general one, as they can be
inlined into your code.

Use L</is_utf8_string_flags>, L</is_utf8_string_loc_flags>, and
L</is_utf8_string_loclen_flags> to check entire strings.

	STRLEN	isUTF8_CHAR_flags(const U8 *s, const U8 *e,
		                  const U32 flags)

=for hackers
Found in file utf8.h

=item LATIN1_TO_NATIVE
X<LATIN1_TO_NATIVE>

Returns the native  equivalent of the input Latin-1 code point (including ASCII
and control characters) given by C<ch>.  Thus, C<LATIN1_TO_NATIVE(66)> on
EBCDIC platforms returns 194.  These each represent the character C<"B"> on
their respective platforms.  On ASCII platforms no conversion is needed, so
this macro expands to just its input, adding no time nor space requirements to
the implementation.

For conversion of code points potentially larger than will fit in a character,
use L</UNI_TO_NATIVE>.

	U8	LATIN1_TO_NATIVE(U8 ch)

=for hackers
Found in file utf8.h

=item NATIVE_TO_LATIN1
X<NATIVE_TO_LATIN1>

Returns the Latin-1 (including ASCII and control characters) equivalent of the
input native code point given by C<ch>.  Thus, C<NATIVE_TO_LATIN1(193)> on
EBCDIC platforms returns 65.  These each represent the character C<"A"> on
their respective platforms.  On ASCII platforms no conversion is needed, so
this macro expands to just its input, adding no time nor space requirements to
the implementation.

For conversion of code points potentially larger than will fit in a character,
use L</NATIVE_TO_UNI>.

	U8	NATIVE_TO_LATIN1(U8 ch)

=for hackers
Found in file utf8.h

=item NATIVE_TO_UNI
X<NATIVE_TO_UNI>

Returns the Unicode  equivalent of the input native code point given by C<ch>.
Thus, C<NATIVE_TO_UNI(195)> on EBCDIC platforms returns 67.  These each
represent the character C<"C"> on their respective platforms.  On ASCII
platforms no conversion is needed, so this macro expands to just its input,
adding no time nor space requirements to the implementation.

	UV	NATIVE_TO_UNI(UV ch)

=for hackers
Found in file utf8.h

=item pv_uni_display
X<pv_uni_display>

Build to the scalar C<dsv> a displayable version of the UTF-8 encoded string
C<spv>, length C<len>, the displayable version being at most C<pvlim> bytes
long (if longer, the rest is truncated and C<"..."> will be appended).

The C<flags> argument can have C<UNI_DISPLAY_ISPRINT> set to display
C<isPRINT()>able characters as themselves, C<UNI_DISPLAY_BACKSLASH>
to display the C<\\[nrfta\\]> as the backslashed versions (like C<"\n">)
(C<UNI_DISPLAY_BACKSLASH> is preferred over C<UNI_DISPLAY_ISPRINT> for C<"\\">).
C<UNI_DISPLAY_QQ> (and its alias C<UNI_DISPLAY_REGEX>) have both
C<UNI_DISPLAY_BACKSLASH> and C<UNI_DISPLAY_ISPRINT> turned on.

Additionally, there is now C<UNI_DISPLAY_BACKSPACE> which allows C<\b> for a
backspace, but only when C<UNI_DISPLAY_BACKSLASH> also is set.

The pointer to the PV of the C<dsv> is returned.

See also L</sv_uni_display>.

	char*	pv_uni_display(SV *dsv, const U8 *spv,
		               STRLEN len, STRLEN pvlim,
		               UV flags)

=for hackers
Found in file utf8.c

=item REPLACEMENT_CHARACTER_UTF8
X<REPLACEMENT_CHARACTER_UTF8>

This is a macro that evaluates to a string constant of the  UTF-8 bytes that
define the Unicode REPLACEMENT CHARACTER (U+FFFD) for the platform that perl
is compiled on.  This allows code to use a mnemonic for this character that
works on both ASCII and EBCDIC platforms.
S<C<sizeof(REPLACEMENT_CHARACTER_UTF8) - 1>> can be used to get its length in
bytes.

=for hackers
Found in file unicode_constants.h

=item sv_cat_decode
X<sv_cat_decode>

C<encoding> is assumed to be an C<Encode> object, the PV of C<ssv> is
assumed to be octets in that encoding and decoding the input starts
from the position which S<C<(PV + *offset)>> pointed to.  C<dsv> will be
concatenated with the decoded UTF-8 string from C<ssv>.  Decoding will terminate
when the string C<tstr> appears in decoding output or the input ends on
the PV of C<ssv>.  The value which C<offset> points will be modified
to the last input position on C<ssv>.

Returns TRUE if the terminator was found, else returns FALSE.

	bool	sv_cat_decode(SV* dsv, SV *encoding, SV *ssv,
		              int *offset, char* tstr, int tlen)

=for hackers
Found in file sv.c

=item sv_recode_to_utf8
X<sv_recode_to_utf8>

C<encoding> is assumed to be an C<Encode> object, on entry the PV
of C<sv> is assumed to be octets in that encoding, and C<sv>
will be converted into Unicode (and UTF-8).

If C<sv> already is UTF-8 (or if it is not C<POK>), or if C<encoding>
is not a reference, nothing is done to C<sv>.  If C<encoding> is not
an C<Encode::XS> Encoding object, bad things will happen.
(See F<cpan/Encode/encoding.pm> and L<Encode>.)

The PV of C<sv> is returned.

	char*	sv_recode_to_utf8(SV* sv, SV *encoding)

=for hackers
Found in file sv.c

=item sv_uni_display
X<sv_uni_display>

Build to the scalar C<dsv> a displayable version of the scalar C<sv>,
the displayable version being at most C<pvlim> bytes long
(if longer, the rest is truncated and "..." will be appended).

The C<flags> argument is as in L</pv_uni_display>().

The pointer to the PV of the C<dsv> is returned.

	char*	sv_uni_display(SV *dsv, SV *ssv, STRLEN pvlim,
		               UV flags)

=for hackers
Found in file utf8.c

=item UNICODE_REPLACEMENT
X<UNICODE_REPLACEMENT>

Evaluates to 0xFFFD, the code point of the Unicode REPLACEMENT CHARACTER

=for hackers
Found in file utf8.h

=item UNI_TO_NATIVE
X<UNI_TO_NATIVE>

Returns the native  equivalent of the input Unicode code point  given by C<ch>.
Thus, C<UNI_TO_NATIVE(68)> on EBCDIC platforms returns 196.  These each
represent the character C<"D"> on their respective platforms.  On ASCII
platforms no conversion is needed, so this macro expands to just its input,
adding no time nor space requirements to the implementation.

	UV	UNI_TO_NATIVE(UV ch)

=for hackers
Found in file utf8.h

=item utf8n_to_uvchr
X<utf8n_to_uvchr>

THIS FUNCTION SHOULD BE USED IN ONLY VERY SPECIALIZED CIRCUMSTANCES.
Most code should use L</utf8_to_uvchr_buf>() rather than call this
directly.

Bottom level UTF-8 decode routine.
Returns the native code point value of the first character in the string C<s>,
which is assumed to be in UTF-8 (or UTF-EBCDIC) encoding, and no longer than
C<curlen> bytes; C<*retlen> (if C<retlen> isn't NULL) will be set to
the length, in bytes, of that character.

The value of C<flags> determines the behavior when C<s> does not point to a
well-formed UTF-8 character.  If C<flags> is 0, encountering a malformation
causes zero to be returned and C<*retlen> is set so that (S<C<s> + C<*retlen>>)
is the next possible position in C<s> that could begin a non-malformed
character.  Also, if UTF-8 warnings haven't been lexically disabled, a warning
is raised.  Some UTF-8 input sequences may contain multiple malformations.
This function tries to find every possible one in each call, so multiple
warnings can be raised for the same sequence.

Various ALLOW flags can be set in C<flags> to allow (and not warn on)
individual types of malformations, such as the sequence being overlong (that
is, when there is a shorter sequence that can express the same code point;
overlong sequences are expressly forbidden in the UTF-8 standard due to
potential security issues).  Another malformation example is the first byte of
a character not being a legal first byte.  See F<utf8.h> for the list of such
flags.  Even if allowed, this function generally returns the Unicode
REPLACEMENT CHARACTER when it encounters a malformation.  There are flags in
F<utf8.h> to override this behavior for the overlong malformations, but don't
do that except for very specialized purposes.

The C<UTF8_CHECK_ONLY> flag overrides the behavior when a non-allowed (by other
flags) malformation is found.  If this flag is set, the routine assumes that
the caller will raise a warning, and this function will silently just set
C<retlen> to C<-1> (cast to C<STRLEN>) and return zero.

Note that this API requires disambiguation between successful decoding a C<NUL>
character, and an error return (unless the C<UTF8_CHECK_ONLY> flag is set), as
in both cases, 0 is returned, and, depending on the malformation, C<retlen> may
be set to 1.  To disambiguate, upon a zero return, see if the first byte of
C<s> is 0 as well.  If so, the input was a C<NUL>; if not, the input had an
error.  Or you can use C<L</utf8n_to_uvchr_error>>.

Certain code points are considered problematic.  These are Unicode surrogates,
Unicode non-characters, and code points above the Unicode maximum of 0x10FFFF.
By default these are considered regular code points, but certain situations
warrant special handling for them, which can be specified using the C<flags>
parameter.  If C<flags> contains C<UTF8_DISALLOW_ILLEGAL_INTERCHANGE>, all
three classes are treated as malformations and handled as such.  The flags
C<UTF8_DISALLOW_SURROGATE>, C<UTF8_DISALLOW_NONCHAR>, and
C<UTF8_DISALLOW_SUPER> (meaning above the legal Unicode maximum) can be set to
disallow these categories individually.  C<UTF8_DISALLOW_ILLEGAL_INTERCHANGE>
restricts the allowed inputs to the strict UTF-8 traditionally defined by
Unicode.  Use C<UTF8_DISALLOW_ILLEGAL_C9_INTERCHANGE> to use the strictness
definition given by
L<Unicode Corrigendum #9|https://www.unicode.org/versions/corrigendum9.html>.
The difference between traditional strictness and C9 strictness is that the
latter does not forbid non-character code points.  (They are still discouraged,
however.)  For more discussion see L<perlunicode/Noncharacter code points>.

The flags C<UTF8_WARN_ILLEGAL_INTERCHANGE>,
C<UTF8_WARN_ILLEGAL_C9_INTERCHANGE>, C<UTF8_WARN_SURROGATE>,
C<UTF8_WARN_NONCHAR>, and C<UTF8_WARN_SUPER> will cause warning messages to be
raised for their respective categories, but otherwise the code points are
considered valid (not malformations).  To get a category to both be treated as
a malformation and raise a warning, specify both the WARN and DISALLOW flags.
(But note that warnings are not raised if lexically disabled nor if
C<UTF8_CHECK_ONLY> is also specified.)

Extremely high code points were never specified in any standard, and require an
extension to UTF-8 to express, which Perl does.  It is likely that programs
written in something other than Perl would not be able to read files that
contain these; nor would Perl understand files written by something that uses a
different extension.  For these reasons, there is a separate set of flags that
can warn and/or disallow these extremely high code points, even if other
above-Unicode ones are accepted.  They are the C<UTF8_WARN_PERL_EXTENDED> and
C<UTF8_DISALLOW_PERL_EXTENDED> flags.  For more information see
L</C<UTF8_GOT_PERL_EXTENDED>>.  Of course C<UTF8_DISALLOW_SUPER> will treat all
above-Unicode code points, including these, as malformations.
(Note that the Unicode standard considers anything above 0x10FFFF to be
illegal, but there are standards predating it that allow up to 0x7FFF_FFFF
(2**31 -1))

A somewhat misleadingly named synonym for C<UTF8_WARN_PERL_EXTENDED> is
retained for backward compatibility: C<UTF8_WARN_ABOVE_31_BIT>.  Similarly,
C<UTF8_DISALLOW_ABOVE_31_BIT> is usable instead of the more accurately named
C<UTF8_DISALLOW_PERL_EXTENDED>.  The names are misleading because these flags
can apply to code points that actually do fit in 31 bits.  This happens on
EBCDIC platforms, and sometimes when the L<overlong
malformation|/C<UTF8_GOT_LONG>> is also present.  The new names accurately
describe the situation in all cases.


All other code points corresponding to Unicode characters, including private
use and those yet to be assigned, are never considered malformed and never
warn.

	UV	utf8n_to_uvchr(const U8 *s, STRLEN curlen,
		               STRLEN *retlen, const U32 flags)

=for hackers
Found in file utf8.c

=item utf8n_to_uvchr_error
X<utf8n_to_uvchr_error>

THIS FUNCTION SHOULD BE USED IN ONLY VERY SPECIALIZED CIRCUMSTANCES.
Most code should use L</utf8_to_uvchr_buf>() rather than call this
directly.

This function is for code that needs to know what the precise malformation(s)
are when an error is found.  If you also need to know the generated warning
messages, use L</utf8n_to_uvchr_msgs>() instead.

It is like C<L</utf8n_to_uvchr>> but it takes an extra parameter placed after
all the others, C<errors>.  If this parameter is 0, this function behaves
identically to C<L</utf8n_to_uvchr>>.  Otherwise, C<errors> should be a pointer
to a C<U32> variable, which this function sets to indicate any errors found.
Upon return, if C<*errors> is 0, there were no errors found.  Otherwise,
C<*errors> is the bit-wise C<OR> of the bits described in the list below.  Some
of these bits will be set if a malformation is found, even if the input
C<flags> parameter indicates that the given malformation is allowed; those
exceptions are noted:

=over 4

=item C<UTF8_GOT_PERL_EXTENDED>

The input sequence is not standard UTF-8, but a Perl extension.  This bit is
set only if the input C<flags> parameter contains either the
C<UTF8_DISALLOW_PERL_EXTENDED> or the C<UTF8_WARN_PERL_EXTENDED> flags.

Code points above 0x7FFF_FFFF (2**31 - 1) were never specified in any standard,
and so some extension must be used to express them.  Perl uses a natural
extension to UTF-8 to represent the ones up to 2**36-1, and invented a further
extension to represent even higher ones, so that any code point that fits in a
64-bit word can be represented.  Text using these extensions is not likely to
be portable to non-Perl code.  We lump both of these extensions together and
refer to them as Perl extended UTF-8.  There exist other extensions that people
have invented, incompatible with Perl's.

On EBCDIC platforms starting in Perl v5.24, the Perl extension for representing
extremely high code points kicks in at 0x3FFF_FFFF (2**30 -1), which is lower
than on ASCII.  Prior to that, code points 2**31 and higher were simply
unrepresentable, and a different, incompatible method was used to represent
code points between 2**30 and 2**31 - 1.

On both platforms, ASCII and EBCDIC, C<UTF8_GOT_PERL_EXTENDED> is set if
Perl extended UTF-8 is used.

In earlier Perls, this bit was named C<UTF8_GOT_ABOVE_31_BIT>, which you still
may use for backward compatibility.  That name is misleading, as this flag may
be set when the code point actually does fit in 31 bits.  This happens on
EBCDIC platforms, and sometimes when the L<overlong
malformation|/C<UTF8_GOT_LONG>> is also present.  The new name accurately
describes the situation in all cases.

=item C<UTF8_GOT_CONTINUATION>

The input sequence was malformed in that the first byte was a UTF-8
continuation byte.

=item C<UTF8_GOT_EMPTY>

The input C<curlen> parameter was 0.

=item C<UTF8_GOT_LONG>

The input sequence was malformed in that there is some other sequence that
evaluates to the same code point, but that sequence is shorter than this one.

Until Unicode 3.1, it was legal for programs to accept this malformation, but
it was discovered that this created security issues.

=item C<UTF8_GOT_NONCHAR>

The code point represented by the input UTF-8 sequence is for a Unicode
non-character code point.
This bit is set only if the input C<flags> parameter contains either the
C<UTF8_DISALLOW_NONCHAR> or the C<UTF8_WARN_NONCHAR> flags.

=item C<UTF8_GOT_NON_CONTINUATION>

The input sequence was malformed in that a non-continuation type byte was found
in a position where only a continuation type one should be.  See also
L</C<UTF8_GOT_SHORT>>.

=item C<UTF8_GOT_OVERFLOW>

The input sequence was malformed in that it is for a code point that is not
representable in the number of bits available in an IV on the current platform.

=item C<UTF8_GOT_SHORT>

The input sequence was malformed in that C<curlen> is smaller than required for
a complete sequence.  In other words, the input is for a partial character
sequence.


C<UTF8_GOT_SHORT> and C<UTF8_GOT_NON_CONTINUATION> both indicate a too short
sequence.  The difference is that C<UTF8_GOT_NON_CONTINUATION> indicates always
that there is an error, while C<UTF8_GOT_SHORT> means that an incomplete
sequence was looked at.   If no other flags are present, it means that the
sequence was valid as far as it went.  Depending on the application, this could
mean one of three things:

=over

=item *

The C<curlen> length parameter passed in was too small, and the function was
prevented from examining all the necessary bytes.

=item *

The buffer being looked at is based on reading data, and the data received so
far stopped in the middle of a character, so that the next read will
read the remainder of this character.  (It is up to the caller to deal with the
split bytes somehow.)

=item *

This is a real error, and the partial sequence is all we're going to get.

=back

=item C<UTF8_GOT_SUPER>

The input sequence was malformed in that it is for a non-Unicode code point;
that is, one above the legal Unicode maximum.
This bit is set only if the input C<flags> parameter contains either the
C<UTF8_DISALLOW_SUPER> or the C<UTF8_WARN_SUPER> flags.

=item C<UTF8_GOT_SURROGATE>

The input sequence was malformed in that it is for a -Unicode UTF-16 surrogate
code point.
This bit is set only if the input C<flags> parameter contains either the
C<UTF8_DISALLOW_SURROGATE> or the C<UTF8_WARN_SURROGATE> flags.

=back

To do your own error handling, call this function with the C<UTF8_CHECK_ONLY>
flag to suppress any warnings, and then examine the C<*errors> return.

	UV	utf8n_to_uvchr_error(const U8 *s, STRLEN curlen,
		                     STRLEN *retlen,
		                     const U32 flags,
		                     U32 * errors)

=for hackers
Found in file utf8.c

=item utf8n_to_uvchr_msgs
X<utf8n_to_uvchr_msgs>


NOTE: this function is experimental and may change or be
removed without notice.


THIS FUNCTION SHOULD BE USED IN ONLY VERY SPECIALIZED CIRCUMSTANCES.
Most code should use L</utf8_to_uvchr_buf>() rather than call this
directly.

This function is for code that needs to know what the precise malformation(s)
are when an error is found, and wants the corresponding warning and/or error
messages to be returned to the caller rather than be displayed.  All messages
that would have been displayed if all lexcial warnings are enabled will be
returned.

It is just like C<L</utf8n_to_uvchr_error>> but it takes an extra parameter
placed after all the others, C<msgs>.  If this parameter is 0, this function
behaves identically to C<L</utf8n_to_uvchr_error>>.  Otherwise, C<msgs> should
be a pointer to an C<AV *> variable, in which this function creates a new AV to
contain any appropriate messages.  The elements of the array are ordered so
that the first message that would have been displayed is in the 0th element,
and so on.  Each element is a hash with three key-value pairs, as follows:

=over 4

=item C<text>

The text of the message as a C<SVpv>.

=item C<warn_categories>

The warning category (or categories) packed into a C<SVuv>.

=item C<flag>

A single flag bit associated with this message, in a C<SVuv>.
The bit corresponds to some bit in the C<*errors> return value,
such as C<UTF8_GOT_LONG>.

=back

It's important to note that specifying this parameter as non-null will cause
any warnings this function would otherwise generate to be suppressed, and
instead be placed in C<*msgs>.  The caller can check the lexical warnings state
(or not) when choosing what to do with the returned messages.

If the flag C<UTF8_CHECK_ONLY> is passed, no warnings are generated, and hence
no AV is created.

The caller, of course, is responsible for freeing any returned AV.

	UV	utf8n_to_uvchr_msgs(const U8 *s, STRLEN curlen,
		                    STRLEN *retlen,
		                    const U32 flags,
		                    U32 * errors, AV ** msgs)

=for hackers
Found in file utf8.c

=item UTF8SKIP
X<UTF8SKIP>

returns the number of bytes a non-malformed UTF-8 encoded character whose first
(perhaps only) byte is pointed to by C<s>.

If there is a possibility of malformed input, use instead:

=over

=item L</C<UTF8_SAFE_SKIP>> if you know the maximum ending pointer in the
buffer pointed to by C<s>; or

=item L</C<UTF8_CHK_SKIP>> if you don't know it.

=back

It is better to restructure your code so the end pointer is passed down so that
you know what it actually is at the point of this call, but if that isn't
possible, L</C<UTF8_CHK_SKIP>> can minimize the chance of accessing beyond the end
of the input buffer.

	STRLEN	UTF8SKIP(char* s)

=for hackers
Found in file utf8.h

=item UTF8_CHK_SKIP
X<UTF8_CHK_SKIP>

This is a safer version of L</C<UTF8SKIP>>, but still not as safe as
L</C<UTF8_SAFE_SKIP>>.  This version doesn't blindly assume that the input
string pointed to by C<s> is well-formed, but verifies that there isn't a NUL
terminating character before the expected end of the next character in C<s>.
The length C<UTF8_CHK_SKIP> returns stops just before any such NUL.

Perl tends to add NULs, as an insurance policy, after the end of strings in
SV's, so it is likely that using this macro will prevent inadvertent reading
beyond the end of the input buffer, even if it is malformed UTF-8.

This macro is intended to be used by XS modules where the inputs could be
malformed, and it isn't feasible to restructure to use the safer
L</C<UTF8_SAFE_SKIP>>, for example when interfacing with a C library.

	STRLEN	UTF8_CHK_SKIP(char* s)

=for hackers
Found in file utf8.h

=item utf8_distance
X<utf8_distance>

Returns the number of UTF-8 characters between the UTF-8 pointers C<a>
and C<b>.

WARNING: use only if you *know* that the pointers point inside the
same UTF-8 buffer.

	IV	utf8_distance(const U8 *a, const U8 *b)

=for hackers
Found in file inline.h

=item utf8_hop
X<utf8_hop>

Return the UTF-8 pointer C<s> displaced by C<off> characters, either
forward or backward.

WARNING: do not use the following unless you *know* C<off> is within
the UTF-8 data pointed to by C<s> *and* that on entry C<s> is aligned
on the first byte of character or just after the last byte of a character.

	U8*	utf8_hop(const U8 *s, SSize_t off)

=for hackers
Found in file inline.h

=item utf8_hop_back
X<utf8_hop_back>

Return the UTF-8 pointer C<s> displaced by up to C<off> characters,
backward.

C<off> must be non-positive.

C<s> must be after or equal to C<start>.

When moving backward it will not move before C<start>.

Will not exceed this limit even if the string is not valid "UTF-8".

	U8*	utf8_hop_back(const U8 *s, SSize_t off,
		              const U8 *start)

=for hackers
Found in file inline.h

=item utf8_hop_forward
X<utf8_hop_forward>

Return the UTF-8 pointer C<s> displaced by up to C<off> characters,
forward.

C<off> must be non-negative.

C<s> must be before or equal to C<end>.

When moving forward it will not move beyond C<end>.

Will not exceed this limit even if the string is not valid "UTF-8".

	U8*	utf8_hop_forward(const U8 *s, SSize_t off,
		                 const U8 *end)

=for hackers
Found in file inline.h

=item utf8_hop_safe
X<utf8_hop_safe>

Return the UTF-8 pointer C<s> displaced by up to C<off> characters,
either forward or backward.

When moving backward it will not move before C<start>.

When moving forward it will not move beyond C<end>.

Will not exceed those limits even if the string is not valid "UTF-8".

	U8*	utf8_hop_safe(const U8 *s, SSize_t off,
		              const U8 *start, const U8 *end)

=for hackers
Found in file inline.h

=item UTF8_IS_INVARIANT
X<UTF8_IS_INVARIANT>

Evaluates to 1 if the byte C<c> represents the same character when encoded in
UTF-8 as when not; otherwise evaluates to 0.  UTF-8 invariant characters can be
copied as-is when converting to/from UTF-8, saving time.

In spite of the name, this macro gives the correct result if the input string
from which C<c> comes is not encoded in UTF-8.

See C<L</UVCHR_IS_INVARIANT>> for checking if a UV is invariant.

	bool	UTF8_IS_INVARIANT(char c)

=for hackers
Found in file utf8.h

=item UTF8_IS_NONCHAR
X<UTF8_IS_NONCHAR>

Evaluates to non-zero if the first few bytes of the string starting at C<s> and
looking no further than S<C<e - 1>> are well-formed UTF-8 that represents one
of the Unicode non-character code points; otherwise it evaluates to 0.  If
non-zero, the value gives how many bytes starting at C<s> comprise the code
point's representation.

	bool	UTF8_IS_NONCHAR(const U8 *s, const U8 *e)

=for hackers
Found in file utf8.h

=item UTF8_IS_SUPER
X<UTF8_IS_SUPER>

Recall that Perl recognizes an extension to UTF-8 that can encode code
points larger than the ones defined by Unicode, which are 0..0x10FFFF.

This macro evaluates to non-zero if the first few bytes of the string starting
at C<s> and looking no further than S<C<e - 1>> are from this UTF-8 extension;
otherwise it evaluates to 0.  If non-zero, the value gives how many bytes
starting at C<s> comprise the code point's representation.

0 is returned if the bytes are not well-formed extended UTF-8, or if they
represent a code point that cannot fit in a UV on the current platform.  Hence
this macro can give different results when run on a 64-bit word machine than on
one with a 32-bit word size.

Note that it is illegal to have code points that are larger than what can
fit in an IV on the current machine.

	bool	UTF8_IS_SUPER(const U8 *s, const U8 *e)

=for hackers
Found in file utf8.h

=item UTF8_IS_SURROGATE
X<UTF8_IS_SURROGATE>

Evaluates to non-zero if the first few bytes of the string starting at C<s> and
looking no further than S<C<e - 1>> are well-formed UTF-8 that represents one
of the Unicode surrogate code points; otherwise it evaluates to 0.  If
non-zero, the value gives how many bytes starting at C<s> comprise the code
point's representation.

	bool	UTF8_IS_SURROGATE(const U8 *s, const U8 *e)

=for hackers
Found in file utf8.h

=item utf8_length
X<utf8_length>

Returns the number of characters in the sequence of UTF-8-encoded bytes starting
at C<s> and ending at the byte just before C<e>.  If <s> and <e> point to the
same place, it returns 0 with no warning raised.

If C<e E<lt> s> or if the scan would end up past C<e>, it raises a UTF8 warning
and returns the number of valid characters.

	STRLEN	utf8_length(const U8* s, const U8 *e)

=for hackers
Found in file utf8.c

=item UTF8_MAXBYTES
X<UTF8_MAXBYTES>

The maximum width of a single UTF-8 encoded character, in bytes.

NOTE: Strictly speaking Perl's UTF-8 should not be called UTF-8 since UTF-8
is an encoding of Unicode, and Unicode's upper limit, 0x10FFFF, can be
expressed with 4 bytes.  However, Perl thinks of UTF-8 as a way to encode
non-negative integers in a binary format, even those above Unicode.

=for hackers
Found in file utf8.h

=item UTF8_MAXBYTES_CASE
X<UTF8_MAXBYTES_CASE>

The maximum number of UTF-8 bytes a single Unicode character can
uppercase/lowercase/titlecase/fold into.

=for hackers
Found in file utf8.h

=item UTF8_SAFE_SKIP
X<UTF8_SAFE_SKIP>

returns 0 if S<C<s E<gt>= e>>; otherwise returns the number of bytes in the
UTF-8 encoded character whose first  byte is pointed to by C<s>.  But it never
returns beyond C<e>.  On DEBUGGING builds, it asserts that S<C<s E<lt>= e>>.

	STRLEN	UTF8_SAFE_SKIP(char* s, char* e)

=for hackers
Found in file utf8.h

=item UTF8_SKIP
X<UTF8_SKIP>

This is a synonym for L</C<UTF8SKIP>>

	STRLEN	UTF8_SKIP(char* s)

=for hackers
Found in file utf8.h

=item utf8_to_bytes
X<utf8_to_bytes>


NOTE: this function is experimental and may change or be
removed without notice.


Converts a string C<"s"> of length C<*lenp> from UTF-8 into native byte encoding.
Unlike L</bytes_to_utf8>, this over-writes the original string, and
updates C<*lenp> to contain the new length.
Returns zero on failure (leaving C<"s"> unchanged) setting C<*lenp> to -1.

Upon successful return, the number of variants in the string can be computed by
having saved the value of C<*lenp> before the call, and subtracting the
after-call value of C<*lenp> from it.

If you need a copy of the string, see L</bytes_from_utf8>.

	U8*	utf8_to_bytes(U8 *s, STRLEN *lenp)

=for hackers
Found in file utf8.c

=item utf8_to_uvchr_buf
X<utf8_to_uvchr_buf>

Returns the native code point of the first character in the string C<s> which
is assumed to be in UTF-8 encoding; C<send> points to 1 beyond the end of C<s>.
C<*retlen> will be set to the length, in bytes, of that character.

If C<s> does not point to a well-formed UTF-8 character and UTF8 warnings are
enabled, zero is returned and C<*retlen> is set (if C<retlen> isn't
C<NULL>) to -1.  If those warnings are off, the computed value, if well-defined
(or the Unicode REPLACEMENT CHARACTER if not), is silently returned, and
C<*retlen> is set (if C<retlen> isn't C<NULL>) so that (S<C<s> + C<*retlen>>) is
the next possible position in C<s> that could begin a non-malformed character.
See L</utf8n_to_uvchr> for details on when the REPLACEMENT CHARACTER is
returned.

	UV	utf8_to_uvchr_buf(const U8 *s, const U8 *send,
		                  STRLEN *retlen)

=for hackers
Found in file utf8.c

=item UVCHR_IS_INVARIANT
X<UVCHR_IS_INVARIANT>

Evaluates to 1 if the representation of code point C<cp> is the same whether or
not it is encoded in UTF-8; otherwise evaluates to 0.  UTF-8 invariant
characters can be copied as-is when converting to/from UTF-8, saving time.
C<cp> is Unicode if above 255; otherwise is platform-native.

	bool	UVCHR_IS_INVARIANT(UV cp)

=for hackers
Found in file utf8.h

=item UVCHR_SKIP
X<UVCHR_SKIP>

returns the number of bytes required to represent the code point C<cp> when
encoded as UTF-8.  C<cp> is a native (ASCII or EBCDIC) code point if less than
255; a Unicode code point otherwise.

	STRLEN	UVCHR_SKIP(UV cp)

=for hackers
Found in file utf8.h

=item uvchr_to_utf8
X<uvchr_to_utf8>

Adds the UTF-8 representation of the native code point C<uv> to the end
of the string C<d>; C<d> should have at least C<UVCHR_SKIP(uv)+1> (up to
C<UTF8_MAXBYTES+1>) free bytes available.  The return value is the pointer to
the byte after the end of the new character.  In other words,

    d = uvchr_to_utf8(d, uv);

is the recommended wide native character-aware way of saying

    *(d++) = uv;

This function accepts any code point from 0..C<IV_MAX> as input.
C<IV_MAX> is typically 0x7FFF_FFFF in a 32-bit word.

It is possible to forbid or warn on non-Unicode code points, or those that may
be problematic by using L</uvchr_to_utf8_flags>.

	U8*	uvchr_to_utf8(U8 *d, UV uv)

=for hackers
Found in file utf8.c

=item uvchr_to_utf8_flags
X<uvchr_to_utf8_flags>

Adds the UTF-8 representation of the native code point C<uv> to the end
of the string C<d>; C<d> should have at least C<UVCHR_SKIP(uv)+1> (up to
C<UTF8_MAXBYTES+1>) free bytes available.  The return value is the pointer to
the byte after the end of the new character.  In other words,

    d = uvchr_to_utf8_flags(d, uv, flags);

or, in most cases,

    d = uvchr_to_utf8_flags(d, uv, 0);

This is the Unicode-aware way of saying

    *(d++) = uv;

If C<flags> is 0, this function accepts any code point from 0..C<IV_MAX> as
input.  C<IV_MAX> is typically 0x7FFF_FFFF in a 32-bit word.

Specifying C<flags> can further restrict what is allowed and not warned on, as
follows:

If C<uv> is a Unicode surrogate code point and C<UNICODE_WARN_SURROGATE> is set,
the function will raise a warning, provided UTF8 warnings are enabled.  If
instead C<UNICODE_DISALLOW_SURROGATE> is set, the function will fail and return
NULL.  If both flags are set, the function will both warn and return NULL.

Similarly, the C<UNICODE_WARN_NONCHAR> and C<UNICODE_DISALLOW_NONCHAR> flags
affect how the function handles a Unicode non-character.

And likewise, the C<UNICODE_WARN_SUPER> and C<UNICODE_DISALLOW_SUPER> flags
affect the handling of code points that are above the Unicode maximum of
0x10FFFF.  Languages other than Perl may not be able to accept files that
contain these.

The flag C<UNICODE_WARN_ILLEGAL_INTERCHANGE> selects all three of
the above WARN flags; and C<UNICODE_DISALLOW_ILLEGAL_INTERCHANGE> selects all
three DISALLOW flags.  C<UNICODE_DISALLOW_ILLEGAL_INTERCHANGE> restricts the
allowed inputs to the strict UTF-8 traditionally defined by Unicode.
Similarly, C<UNICODE_WARN_ILLEGAL_C9_INTERCHANGE> and
C<UNICODE_DISALLOW_ILLEGAL_C9_INTERCHANGE> are shortcuts to select the
above-Unicode and surrogate flags, but not the non-character ones, as
defined in
L<Unicode Corrigendum #9|https://www.unicode.org/versions/corrigendum9.html>.
See L<perlunicode/Noncharacter code points>.

Extremely high code points were never specified in any standard, and require an
extension to UTF-8 to express, which Perl does.  It is likely that programs
written in something other than Perl would not be able to read files that
contain these; nor would Perl understand files written by something that uses a
different extension.  For these reasons, there is a separate set of flags that
can warn and/or disallow these extremely high code points, even if other
above-Unicode ones are accepted.  They are the C<UNICODE_WARN_PERL_EXTENDED>
and C<UNICODE_DISALLOW_PERL_EXTENDED> flags.  For more information see
L</C<UTF8_GOT_PERL_EXTENDED>>.  Of course C<UNICODE_DISALLOW_SUPER> will
treat all above-Unicode code points, including these, as malformations.  (Note
that the Unicode standard considers anything above 0x10FFFF to be illegal, but
there are standards predating it that allow up to 0x7FFF_FFFF (2**31 -1))

A somewhat misleadingly named synonym for C<UNICODE_WARN_PERL_EXTENDED> is
retained for backward compatibility: C<UNICODE_WARN_ABOVE_31_BIT>.  Similarly,
C<UNICODE_DISALLOW_ABOVE_31_BIT> is usable instead of the more accurately named
C<UNICODE_DISALLOW_PERL_EXTENDED>.  The names are misleading because on EBCDIC
platforms,these flags can apply to code points that actually do fit in 31 bits.
The new names accurately describe the situation in all cases.

	U8*	uvchr_to_utf8_flags(U8 *d, UV uv, UV flags)

=for hackers
Found in file utf8.c

=item uvchr_to_utf8_flags_msgs
X<uvchr_to_utf8_flags_msgs>


NOTE: this function is experimental and may change or be
removed without notice.


THIS FUNCTION SHOULD BE USED IN ONLY VERY SPECIALIZED CIRCUMSTANCES.

Most code should use C<L</uvchr_to_utf8_flags>()> rather than call this directly.

This function is for code that wants any warning and/or error messages to be
returned to the caller rather than be displayed.  All messages that would have
been displayed if all lexical warnings are enabled will be returned.

It is just like C<L</uvchr_to_utf8_flags>> but it takes an extra parameter
placed after all the others, C<msgs>.  If this parameter is 0, this function
behaves identically to C<L</uvchr_to_utf8_flags>>.  Otherwise, C<msgs> should
be a pointer to an C<HV *> variable, in which this function creates a new HV to
contain any appropriate messages.  The hash has three key-value pairs, as
follows:

=over 4

=item C<text>

The text of the message as a C<SVpv>.

=item C<warn_categories>

The warning category (or categories) packed into a C<SVuv>.

=item C<flag>

A single flag bit associated with this message, in a C<SVuv>.
The bit corresponds to some bit in the C<*errors> return value,
such as C<UNICODE_GOT_SURROGATE>.

=back

It's important to note that specifying this parameter as non-null will cause
any warnings this function would otherwise generate to be suppressed, and
instead be placed in C<*msgs>.  The caller can check the lexical warnings state
(or not) when choosing what to do with the returned messages.

The caller, of course, is responsible for freeing any returned HV.

	U8*	uvchr_to_utf8_flags_msgs(U8 *d, UV uv, UV flags,
		                         HV ** msgs)

=for hackers
Found in file utf8.c


=back

=head1 Variables created by C<xsubpp> and C<xsubpp> internal functions

=over 8

=item newXSproto
X<newXSproto>

Used by C<xsubpp> to hook up XSUBs as Perl subs.  Adds Perl prototypes to
the subs.

=for hackers
Found in file XSUB.h

=item XS_APIVERSION_BOOTCHECK
X<XS_APIVERSION_BOOTCHECK>

Macro to verify that the perl api version an XS module has been compiled against
matches the api version of the perl interpreter it's being loaded into.

		XS_APIVERSION_BOOTCHECK;

=for hackers
Found in file XSUB.h

=item XS_VERSION
X<XS_VERSION>

The version identifier for an XS module.  This is usually
handled automatically by C<ExtUtils::MakeMaker>.  See
C<L</XS_VERSION_BOOTCHECK>>.

=for hackers
Found in file XSUB.h

=item XS_VERSION_BOOTCHECK
X<XS_VERSION_BOOTCHECK>

Macro to verify that a PM module's C<$VERSION> variable matches the XS
module's C<XS_VERSION> variable.  This is usually handled automatically by
C<xsubpp>.  See L<perlxs/"The VERSIONCHECK: Keyword">.

		XS_VERSION_BOOTCHECK;

=for hackers
Found in file XSUB.h


=back

=head1 Warning and Dieing

In all these calls, the C<U32 wI<n>> parameters are warning category
constants.  You can see the ones currently available in
L<warnings/Category Hierarchy>, just capitalize all letters in the names
and prefix them by C<WARN_>.  So, for example, the category C<void> used in a
perl program becomes C<WARN_VOID> when used in XS code and passed to one of
the calls below.


=over 8

=item ckWARN
X<ckWARN>

Returns a boolean as to whether or not warnings are enabled for the warning
category C<w>.  If the category is by default enabled even if not within the
scope of S<C<use warnings>>, instead use the L</ckWARN_d> macro.

	bool	ckWARN(U32 w)

=for hackers
Found in file warnings.h

=item ckWARN2
X<ckWARN2>

Like C<L</ckWARN>>, but takes two warnings categories as input, and returns
TRUE if either is enabled.  If either category is by default enabled even if
not within the scope of S<C<use warnings>>, instead use the L</ckWARN2_d>
macro.  The categories must be completely independent, one may not be
subclassed from the other.

	bool	ckWARN2(U32 w1, U32 w2)

=for hackers
Found in file warnings.h

=item ckWARN3
X<ckWARN3>

Like C<L</ckWARN2>>, but takes three warnings categories as input, and returns
TRUE if any is enabled.  If any of the categories is by default enabled even
if not within the scope of S<C<use warnings>>, instead use the L</ckWARN3_d>
macro.  The categories must be completely independent, one may not be
subclassed from any other.

	bool	ckWARN3(U32 w1, U32 w2, U32 w3)

=for hackers
Found in file warnings.h

=item ckWARN4
X<ckWARN4>

Like C<L</ckWARN3>>, but takes four warnings categories as input, and returns
TRUE if any is enabled.  If any of the categories is by default enabled even
if not within the scope of S<C<use warnings>>, instead use the L</ckWARN4_d>
macro.  The categories must be completely independent, one may not be
subclassed from any other.

	bool	ckWARN4(U32 w1, U32 w2, U32 w3, U32 w4)

=for hackers
Found in file warnings.h

=item ckWARN_d
X<ckWARN_d>

Like C<L</ckWARN>>, but for use if and only if the warning category is by
default enabled even if not within the scope of S<C<use warnings>>.

	bool	ckWARN_d(U32 w)

=for hackers
Found in file warnings.h

=item ckWARN2_d
X<ckWARN2_d>

Like C<L</ckWARN2>>, but for use if and only if either warning category is by
default enabled even if not within the scope of S<C<use warnings>>.

	bool	ckWARN2_d(U32 w1, U32 w2)

=for hackers
Found in file warnings.h

=item ckWARN3_d
X<ckWARN3_d>

Like C<L</ckWARN3>>, but for use if and only if any of the warning categories
is by default enabled even if not within the scope of S<C<use warnings>>.

	bool	ckWARN3_d(U32 w1, U32 w2, U32 w3)

=for hackers
Found in file warnings.h

=item ckWARN4_d
X<ckWARN4_d>

Like C<L</ckWARN4>>, but for use if and only if any of the warning categories
is by default enabled even if not within the scope of S<C<use warnings>>.

	bool	ckWARN4_d(U32 w1, U32 w2, U32 w3, U32 w4)

=for hackers
Found in file warnings.h

=item CLEAR_ERRSV
X<CLEAR_ERRSV>

Clear the contents of C<$@>, setting it to the empty string.

This replaces any read-only SV with a fresh SV and removes any magic.

	void	CLEAR_ERRSV()

=for hackers
Found in file perl.h

=item croak
X<croak>

This is an XS interface to Perl's C<die> function.

Take a sprintf-style format pattern and argument list.  These are used to
generate a string message.  If the message does not end with a newline,
then it will be extended with some indication of the current location
in the code, as described for L</mess_sv>.

The error message will be used as an exception, by default
returning control to the nearest enclosing C<eval>, but subject to
modification by a C<$SIG{__DIE__}> handler.  In any case, the C<croak>
function never returns normally.

For historical reasons, if C<pat> is null then the contents of C<ERRSV>
(C<$@>) will be used as an error message or object instead of building an
error message from arguments.  If you want to throw a non-string object,
or build an error message in an SV yourself, it is preferable to use
the L</croak_sv> function, which does not involve clobbering C<ERRSV>.

	void	croak(const char* pat, ...)

=for hackers
Found in file util.c

=item croak_no_modify
X<croak_no_modify>

Exactly equivalent to C<Perl_croak(aTHX_ "%s", PL_no_modify)>, but generates
terser object code than using C<Perl_croak>.  Less code used on exception code
paths reduces CPU cache pressure.

	void	croak_no_modify()

=for hackers
Found in file util.c

=item croak_sv
X<croak_sv>

This is an XS interface to Perl's C<die> function.

C<baseex> is the error message or object.  If it is a reference, it
will be used as-is.  Otherwise it is used as a string, and if it does
not end with a newline then it will be extended with some indication of
the current location in the code, as described for L</mess_sv>.

The error message or object will be used as an exception, by default
returning control to the nearest enclosing C<eval>, but subject to
modification by a C<$SIG{__DIE__}> handler.  In any case, the C<croak_sv>
function never returns normally.

To die with a simple string message, the L</croak> function may be
more convenient.

	void	croak_sv(SV *baseex)

=for hackers
Found in file util.c

=item die
X<die>

Behaves the same as L</croak>, except for the return type.
It should be used only where the C<OP *> return type is required.
The function never actually returns.

	OP*	die(const char* pat, ...)

=for hackers
Found in file util.c

=item die_sv
X<die_sv>

Behaves the same as L</croak_sv>, except for the return type.
It should be used only where the C<OP *> return type is required.
The function never actually returns.

	OP*	die_sv(SV *baseex)

=for hackers
Found in file util.c

=item ERRSV
X<ERRSV>

Returns the SV for C<$@>, creating it if needed.

	SV *	ERRSV

=for hackers
Found in file perl.h

=item my_setenv
X<my_setenv>

A wrapper for the C library L<setenv(3)>.  Don't use the latter, as the perl
version has desirable safeguards

	void	my_setenv(const char* nam, const char* val)

=for hackers
Found in file util.c

=item rsignal
X<rsignal>

A wrapper for the C library L<signal(2)>.  Don't use the latter, as the Perl
version knows things that interact with the rest of the perl interpreter.

	Sighandler_t rsignal(int i, Sighandler_t t)

=for hackers
Found in file util.c

=item SANE_ERRSV
X<SANE_ERRSV>

Clean up ERRSV so we can safely set it.

This replaces any read-only SV with a fresh writable copy and removes
any magic.

	void	SANE_ERRSV()

=for hackers
Found in file perl.h

=item vcroak
X<vcroak>

This is an XS interface to Perl's C<die> function.

C<pat> and C<args> are a sprintf-style format pattern and encapsulated
argument list.  These are used to generate a string message.  If the
message does not end with a newline, then it will be extended with
some indication of the current location in the code, as described for
L</mess_sv>.

The error message will be used as an exception, by default
returning control to the nearest enclosing C<eval>, but subject to
modification by a C<$SIG{__DIE__}> handler.  In any case, the C<croak>
function never returns normally.

For historical reasons, if C<pat> is null then the contents of C<ERRSV>
(C<$@>) will be used as an error message or object instead of building an
error message from arguments.  If you want to throw a non-string object,
or build an error message in an SV yourself, it is preferable to use
the L</croak_sv> function, which does not involve clobbering C<ERRSV>.

	void	vcroak(const char* pat, va_list* args)

=for hackers
Found in file util.c

=item vwarn
X<vwarn>

This is an XS interface to Perl's C<warn> function.

C<pat> and C<args> are a sprintf-style format pattern and encapsulated
argument list.  These are used to generate a string message.  If the
message does not end with a newline, then it will be extended with
some indication of the current location in the code, as described for
L</mess_sv>.

The error message or object will by default be written to standard error,
but this is subject to modification by a C<$SIG{__WARN__}> handler.

Unlike with L</vcroak>, C<pat> is not permitted to be null.

	void	vwarn(const char* pat, va_list* args)

=for hackers
Found in file util.c

=item warn
X<warn>

This is an XS interface to Perl's C<warn> function.

Take a sprintf-style format pattern and argument list.  These are used to
generate a string message.  If the message does not end with a newline,
then it will be extended with some indication of the current location
in the code, as described for L</mess_sv>.

The error message or object will by default be written to standard error,
but this is subject to modification by a C<$SIG{__WARN__}> handler.

Unlike with L</croak>, C<pat> is not permitted to be null.

	void	warn(const char* pat, ...)

=for hackers
Found in file util.c

=item warn_sv
X<warn_sv>

This is an XS interface to Perl's C<warn> function.

C<baseex> is the error message or object.  If it is a reference, it
will be used as-is.  Otherwise it is used as a string, and if it does
not end with a newline then it will be extended with some indication of
the current location in the code, as described for L</mess_sv>.

The error message or object will by default be written to standard error,
but this is subject to modification by a C<$SIG{__WARN__}> handler.

To warn with a simple string message, the L</warn> function may be
more convenient.

	void	warn_sv(SV *baseex)

=for hackers
Found in file util.c


=back

=head1 Undocumented functions

The following functions have been flagged as part of the public API,
but are currently undocumented.  Use them at your own risk, as the
interfaces are subject to change.  Functions that are not listed in this
document are not intended for public use, and should NOT be used under any
circumstances.

If you feel you need to use one of these functions, first send email to
L<perl5-porters@perl.org|mailto:perl5-porters@perl.org>.  It may be
that there is a good reason for the function not being documented, and it
should be removed from this list; or it may just be that no one has gotten
around to documenting it.  In the latter case, you will be asked to submit a
patch to document the function.  Once your patch is accepted, it will indicate
that the interface is stable (unless it is explicitly marked otherwise) and
usable by you.

=over

=item CvDEPTH
X<CvDEPTH>

=item CvGV
X<CvGV>

=item GetVars
X<GetVars>

=item Gv_AMupdate
X<Gv_AMupdate>

=item PerlIO_close
X<PerlIO_close>

=item PerlIO_context_layers
X<PerlIO_context_layers>

=item PerlIO_error
X<PerlIO_error>

=item PerlIO_fill
X<PerlIO_fill>

=item PerlIO_flush
X<PerlIO_flush>

=item PerlIO_get_bufsiz
X<PerlIO_get_bufsiz>

=item PerlIO_get_ptr
X<PerlIO_get_ptr>

=item PerlIO_read
X<PerlIO_read>

=item PerlIO_seek
X<PerlIO_seek>

=item PerlIO_set_cnt
X<PerlIO_set_cnt>

=item PerlIO_setlinebuf
X<PerlIO_setlinebuf>

=item PerlIO_stdout
X<PerlIO_stdout>

=item PerlIO_unread
X<PerlIO_unread>

=item SvAMAGIC_off
X<SvAMAGIC_off>

=item SvAMAGIC_on
X<SvAMAGIC_on>

=item amagic_call
X<amagic_call>

=item amagic_deref_call
X<amagic_deref_call>

=item any_dup
X<any_dup>

=item atfork_lock
X<atfork_lock>

=item atfork_unlock
X<atfork_unlock>

=item av_arylen_p
X<av_arylen_p>

=item av_iter_p
X<av_iter_p>

=item block_gimme
X<block_gimme>

=item call_atexit
X<call_atexit>

=item call_list
X<call_list>

=item calloc
X<calloc>

=item cast_i32
X<cast_i32>

=item cast_iv
X<cast_iv>

=item cast_ulong
X<cast_ulong>

=item cast_uv
X<cast_uv>

=item ck_warner
X<ck_warner>

=item ck_warner_d
X<ck_warner_d>

=item ckwarn
X<ckwarn>

=item ckwarn_d
X<ckwarn_d>

=item clear_defarray
X<clear_defarray>

=item clone_params_del
X<clone_params_del>

=item clone_params_new
X<clone_params_new>

=item croak_nocontext
X<croak_nocontext>

=item csighandler
X<csighandler>

=item csighandler1
X<csighandler1>

=item csighandler3
X<csighandler3>

=item cx_dump
X<cx_dump>

=item cx_dup
X<cx_dup>

=item cxinc
X<cxinc>

=item deb
X<deb>

=item deb_nocontext
X<deb_nocontext>

=item debop
X<debop>

=item debprofdump
X<debprofdump>

=item debstack
X<debstack>

=item debstackptrs
X<debstackptrs>

=item delimcpy
X<delimcpy>

=item despatch_signals
X<despatch_signals>

=item die_nocontext
X<die_nocontext>

=item dirp_dup
X<dirp_dup>

=item do_aspawn
X<do_aspawn>

=item do_close
X<do_close>

=item do_gv_dump
X<do_gv_dump>

=item do_gvgv_dump
X<do_gvgv_dump>

=item do_hv_dump
X<do_hv_dump>

=item do_join
X<do_join>

=item do_magic_dump
X<do_magic_dump>

=item do_op_dump
X<do_op_dump>

=item do_open
X<do_open>

=item do_openn
X<do_openn>

=item do_pmop_dump
X<do_pmop_dump>

=item do_spawn
X<do_spawn>

=item do_spawn_nowait
X<do_spawn_nowait>

=item do_sprintf
X<do_sprintf>

=item do_sv_dump
X<do_sv_dump>

=item doing_taint
X<doing_taint>

=item doref
X<doref>

=item dounwind
X<dounwind>

=item dowantarray
X<dowantarray>

=item dump_eval
X<dump_eval>

=item dump_form
X<dump_form>

=item dump_indent
X<dump_indent>

=item dump_mstats
X<dump_mstats>

=item dump_sub
X<dump_sub>

=item dump_vindent
X<dump_vindent>

=item filter_del
X<filter_del>

=item filter_read
X<filter_read>

=item foldEQ_latin1
X<foldEQ_latin1>

=item form_nocontext
X<form_nocontext>

=item fp_dup
X<fp_dup>

=item free_global_struct
X<free_global_struct>

=item free_tmps
X<free_tmps>

=item get_context
X<get_context>

=item get_mstats
X<get_mstats>

=item get_op_descs
X<get_op_descs>

=item get_op_names
X<get_op_names>

=item get_ppaddr
X<get_ppaddr>

=item get_vtbl
X<get_vtbl>

=item gp_dup
X<gp_dup>

=item gp_free
X<gp_free>

=item gp_ref
X<gp_ref>

=item gv_AVadd
X<gv_AVadd>

=item gv_HVadd
X<gv_HVadd>

=item gv_IOadd
X<gv_IOadd>

=item gv_SVadd
X<gv_SVadd>

=item gv_add_by_type
X<gv_add_by_type>

=item gv_autoload4
X<gv_autoload4>

=item gv_autoload_pv
X<gv_autoload_pv>

=item gv_autoload_pvn
X<gv_autoload_pvn>

=item gv_autoload_sv
X<gv_autoload_sv>

=item gv_check
X<gv_check>

=item gv_dump
X<gv_dump>

=item gv_efullname3
X<gv_efullname3>

=item gv_efullname4
X<gv_efullname4>

=item gv_fetchfile
X<gv_fetchfile>

=item gv_fetchfile_flags
X<gv_fetchfile_flags>

=item gv_fetchpv
X<gv_fetchpv>

=item gv_fetchpvn_flags
X<gv_fetchpvn_flags>

=item gv_fetchsv
X<gv_fetchsv>

=item gv_fullname3
X<gv_fullname3>

=item gv_fullname4
X<gv_fullname4>

=item gv_handler
X<gv_handler>

=item gv_name_set
X<gv_name_set>

=item he_dup
X<he_dup>

=item hek_dup
X<hek_dup>

=item hv_common
X<hv_common>

=item hv_common_key_len
X<hv_common_key_len>

=item hv_delayfree_ent
X<hv_delayfree_ent>

=item hv_eiter_p
X<hv_eiter_p>

=item hv_eiter_set
X<hv_eiter_set>

=item hv_free_ent
X<hv_free_ent>

=item hv_ksplit
X<hv_ksplit>

=item hv_name_set
X<hv_name_set>

=item hv_placeholders_get
X<hv_placeholders_get>

=item hv_placeholders_set
X<hv_placeholders_set>

=item hv_rand_set
X<hv_rand_set>

=item hv_riter_p
X<hv_riter_p>

=item hv_riter_set
X<hv_riter_set>

=item ibcmp_utf8
X<ibcmp_utf8>

=item init_global_struct
X<init_global_struct>

=item init_stacks
X<init_stacks>

=item init_tm
X<init_tm>

=item is_lvalue_sub
X<is_lvalue_sub>

=item leave_scope
X<leave_scope>

=item load_module_nocontext
X<load_module_nocontext>

=item magic_dump
X<magic_dump>

=item markstack_grow
X<markstack_grow>

=item mess_nocontext
X<mess_nocontext>

=item mfree
X<mfree>

=item mg_dup
X<mg_dup>

=item mg_size
X<mg_size>

=item mini_mktime
X<mini_mktime>

=item moreswitches
X<moreswitches>

=item mro_get_from_name
X<mro_get_from_name>

=item mro_set_mro
X<mro_set_mro>

=item mro_set_private_data
X<mro_set_private_data>

=item my_atof
X<my_atof>

=item my_chsize
X<my_chsize>

=item my_cxt_index
X<my_cxt_index>

=item my_cxt_init
X<my_cxt_init>

=item my_dirfd
X<my_dirfd>

=item my_failure_exit
X<my_failure_exit>

=item my_fflush_all
X<my_fflush_all>

=item my_fork
X<my_fork>

=item my_lstat
X<my_lstat>

=item my_pclose
X<my_pclose>

=item my_popen
X<my_popen>

=item my_popen_list
X<my_popen_list>

=item my_socketpair
X<my_socketpair>

=item my_stat
X<my_stat>

=item my_strftime
X<my_strftime>

=item newANONATTRSUB
X<newANONATTRSUB>

=item newANONHASH
X<newANONHASH>

=item newANONLIST
X<newANONLIST>

=item newANONSUB
X<newANONSUB>

=item newATTRSUB
X<newATTRSUB>

=item newAVREF
X<newAVREF>

=item newCVREF
X<newCVREF>

=item newFORM
X<newFORM>

=item newGVREF
X<newGVREF>

=item newGVgen
X<newGVgen>

=item newGVgen_flags
X<newGVgen_flags>

=item newHVREF
X<newHVREF>

=item newHVhv
X<newHVhv>

=item newIO
X<newIO>

=item newMYSUB
X<newMYSUB>

=item newPROG
X<newPROG>

=item newRV
X<newRV>

=item newSUB
X<newSUB>

=item newSVREF
X<newSVREF>

=item newSVpvf_nocontext
X<newSVpvf_nocontext>

=item newSVsv_flags
X<newSVsv_flags>

=item new_stackinfo
X<new_stackinfo>

=item op_refcnt_lock
X<op_refcnt_lock>

=item op_refcnt_unlock
X<op_refcnt_unlock>

=item parser_dup
X<parser_dup>

=item perl_alloc_using
X<perl_alloc_using>

=item perl_clone_using
X<perl_clone_using>

=item perly_sighandler
X<perly_sighandler>

=item pmop_dump
X<pmop_dump>

=item pop_scope
X<pop_scope>

=item pregcomp
X<pregcomp>

=item pregexec
X<pregexec>

=item pregfree
X<pregfree>

=item pregfree2
X<pregfree2>

=item ptr_table_fetch
X<ptr_table_fetch>

=item ptr_table_free
X<ptr_table_free>

=item ptr_table_new
X<ptr_table_new>

=item ptr_table_split
X<ptr_table_split>

=item ptr_table_store
X<ptr_table_store>

=item push_scope
X<push_scope>

=item re_compile
X<re_compile>

=item re_dup_guts
X<re_dup_guts>

=item reentrant_free
X<reentrant_free>

=item reentrant_init
X<reentrant_init>

=item reentrant_retry
X<reentrant_retry>

=item reentrant_size
X<reentrant_size>

=item ref
X<ref>

=item reg_named_buff_all
X<reg_named_buff_all>

=item reg_named_buff_exists
X<reg_named_buff_exists>

=item reg_named_buff_fetch
X<reg_named_buff_fetch>

=item reg_named_buff_firstkey
X<reg_named_buff_firstkey>

=item reg_named_buff_nextkey
X<reg_named_buff_nextkey>

=item reg_named_buff_scalar
X<reg_named_buff_scalar>

=item regdump
X<regdump>

=item regdupe_internal
X<regdupe_internal>

=item regexec_flags
X<regexec_flags>

=item regfree_internal
X<regfree_internal>

=item reginitcolors
X<reginitcolors>

=item regnext
X<regnext>

=item repeatcpy
X<repeatcpy>

=item rsignal_state
X<rsignal_state>

=item runops_debug
X<runops_debug>

=item runops_standard
X<runops_standard>

=item rvpv_dup
X<rvpv_dup>

=item safesyscalloc
X<safesyscalloc>

=item safesysfree
X<safesysfree>

=item safesysmalloc
X<safesysmalloc>

=item safesysrealloc
X<safesysrealloc>

=item save_I16
X<save_I16>

=item save_I32
X<save_I32>

=item save_I8
X<save_I8>

=item save_adelete
X<save_adelete>

=item save_aelem
X<save_aelem>

=item save_aelem_flags
X<save_aelem_flags>

=item save_alloc
X<save_alloc>

=item save_ary
X<save_ary>

=item save_bool
X<save_bool>

=item save_clearsv
X<save_clearsv>

=item save_delete
X<save_delete>

=item save_destructor
X<save_destructor>

=item save_destructor_x
X<save_destructor_x>

=item save_freeop
X<save_freeop>

=item save_freepv
X<save_freepv>

=item save_freesv
X<save_freesv>

=item save_generic_pvref
X<save_generic_pvref>

=item save_generic_svref
X<save_generic_svref>

=item save_hdelete
X<save_hdelete>

=item save_helem
X<save_helem>

=item save_helem_flags
X<save_helem_flags>

=item save_hints
X<save_hints>

=item save_hptr
X<save_hptr>

=item save_int
X<save_int>

=item save_item
X<save_item>

=item save_iv
X<save_iv>

=item save_mortalizesv
X<save_mortalizesv>

=item save_op
X<save_op>

=item save_padsv_and_mortalize
X<save_padsv_and_mortalize>

=item save_pptr
X<save_pptr>

=item save_pushi32ptr
X<save_pushi32ptr>

=item save_pushptr
X<save_pushptr>

=item save_pushptrptr
X<save_pushptrptr>

=item save_re_context
X<save_re_context>

=item save_set_svflags
X<save_set_svflags>

=item save_shared_pvref
X<save_shared_pvref>

=item save_sptr
X<save_sptr>

=item save_svref
X<save_svref>

=item save_vptr
X<save_vptr>

=item savestack_grow
X<savestack_grow>

=item savestack_grow_cnt
X<savestack_grow_cnt>

=item scan_num
X<scan_num>

=item scan_vstring
X<scan_vstring>

=item seed
X<seed>

=item set_context
X<set_context>

=item share_hek
X<share_hek>

=item si_dup
X<si_dup>

=item ss_dup
X<ss_dup>

=item stack_grow
X<stack_grow>

=item start_subparse
X<start_subparse>

=item str_to_version
X<str_to_version>

=item sv_2iv
X<sv_2iv>

=item sv_2pv
X<sv_2pv>

=item sv_2pvbyte_flags
X<sv_2pvbyte_flags>

=item sv_2pvutf8_flags
X<sv_2pvutf8_flags>

=item sv_2uv
X<sv_2uv>

=item sv_catpvf_mg_nocontext
X<sv_catpvf_mg_nocontext>

=item sv_catpvf_nocontext
X<sv_catpvf_nocontext>

=item sv_dup
X<sv_dup>

=item sv_dup_inc
X<sv_dup_inc>

=item sv_peek
X<sv_peek>

=item sv_setpvf_mg_nocontext
X<sv_setpvf_mg_nocontext>

=item sv_setpvf_nocontext
X<sv_setpvf_nocontext>

=item sys_init
X<sys_init>

=item sys_init3
X<sys_init3>

=item sys_intern_clear
X<sys_intern_clear>

=item sys_intern_dup
X<sys_intern_dup>

=item sys_intern_init
X<sys_intern_init>

=item sys_term
X<sys_term>

=item taint_env
X<taint_env>

=item taint_proper
X<taint_proper>

=item unlnk
X<unlnk>

=item unsharepvn
X<unsharepvn>

=item vdeb
X<vdeb>

=item vform
X<vform>

=item vload_module
X<vload_module>

=item vnewSVpvf
X<vnewSVpvf>

=item vwarner
X<vwarner>

=item warn_nocontext
X<warn_nocontext>

=item warner
X<warner>

=item warner_nocontext
X<warner_nocontext>

=item whichsig
X<whichsig>

=item whichsig_pv
X<whichsig_pv>

=item whichsig_pvn
X<whichsig_pvn>

=item whichsig_sv
X<whichsig_sv>

=back


=head1 AUTHORS

Until May 1997, this document was maintained by Jeff Okamoto
<okamoto@corp.hp.com>.  It is now maintained as part of Perl itself.

With lots of help and suggestions from Dean Roehrich, Malcolm Beattie,
Andreas Koenig, Paul Hudson, Ilya Zakharevich, Paul Marquess, Neil
Bowers, Matthew Green, Tim Bunce, Spider Boardman, Ulrich Pfeifer,
Stephen McCamant, and Gurusamy Sarathy.

API Listing originally by Dean Roehrich <roehrich@cray.com>.

Updated to be autogenerated from comments in the source by Benjamin Stuhl.

=head1 SEE ALSO

F<config.h> L<perlapio> L<perlcall> L<perlclib> L<perlfilter> L<perlguts> L<perlintern> L<perlmroapi> L<perlxs> L<perlxstut> L<warnings>
=cut

ex: set ro:
