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# perlapi

Perl 5 version 10.1 documentation
Go to top • Show page index • Download PDF

# perlapi

- NAME
- DESCRIPTION
- "Gimme" Values
- Array Manipulation Functions
- Callback Functions
- Character classes
- Cloning an interpreter
- CV Manipulation Functions
- Embedding Functions
- Functions in file dump.c
- Functions in file mathoms.c
- Functions in file perl.h
- Functions in file pp_ctl.c
- Functions in file pp_pack.c
- GV Functions
- Handy Values
- Hash Manipulation Functions
- Magical Functions
- Memory Management
- Miscellaneous Functions
- MRO Functions
- Multicall Functions
- Numeric functions
- Optree Manipulation Functions
- Pad Data Structures
- Per-Interpreter Variables
- REGEXP Functions
- Simple Exception Handling Macros
- Stack Manipulation Macros
- SV Flags
- SV Manipulation Functions
- SV-Body Allocation
- Unicode Support
- Variables created by xsubpp and xsubpp internal functions
- Warning and Dieing
- AUTHORS
- SEE ALSO

# NAME

perlapi - autogenerated documentation for the perl public API

# DESCRIPTION

This file contains the documentation of the perl public API generated by embed.pl, specifically a listing of functions, macros, flags, and variables that may be used by extension writers. The interfaces of any functions that are not listed here are subject to change without notice. For this reason, blindly using functions listed in proto.h is to be avoided when writing extensions.

Note that all Perl API global variables must be referenced with the `PL_` prefix. 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.

Note that Perl can be compiled and run under EBCDIC (See perlebcdic) or ASCII. 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 `utf8` (and variants of that name, including in function names), it also (essentially transparently) means `UTF-EBCDIC` . But the ordinals of characters differ between ASCII, EBCDIC, and the UTF- encodings, and a string encoded in UTF-EBCDIC may occupy more bytes than in UTF-8.

Also, on some EBCDIC machines, functions that are documented as operating on US-ASCII (or Basic Latin in Unicode terminology) may in fact operate on all 256 characters in the EBCDIC range, not just the subset corresponding to US-ASCII.

The listing below is alphabetical, case insensitive.

# "Gimme" Values

- GIMME

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

      	U32	GIMME

- GIMME_V

  The XSUB-writer's equivalent to Perl's `wantarray`. Returns `G_VOID` , `G_SCALAR` or `G_ARRAY` for void, scalar or list context, respectively.

      	U32	GIMME_V

- G_ARRAY

  Used to indicate list context. See `GIMME_V` , `GIMME` and perlcall.

- G_DISCARD

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

- G_EVAL

  Used to force a Perl `eval` wrapper around a callback. See perlcall.

- G_NOARGS

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

- G_SCALAR

  Used to indicate scalar context. See `GIMME_V` , `GIMME` , and perlcall.

- G_VOID

  Used to indicate void context. See `GIMME_V` and perlcall.

# Array Manipulation Functions

- AvFILL

  Same as `av_len()` . Deprecated, use `av_len()` instead.

      	int	AvFILL(AV* av)

- av_clear

  Clears an array, making it empty. Does not free the memory used by the array itself.

      	void	av_clear(AV *av)

- av_create_and_push

  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 is experimental and may change or be removed without notice.

      	void	av_create_and_push(AV **const avp, SV *const val)

- av_create_and_unshift_one

  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 is experimental and may change or be removed without notice.

      	SV**	av_create_and_unshift_one(AV **const avp, SV *const val)

- av_delete

  Deletes the element indexed by `key` from the array. Returns the deleted element. If `flags` equals `G_DISCARD` , the element is freed and null is returned.

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

- av_exists

  Returns true if the element indexed by `key` has been initialized.

  This relies on the fact that uninitialized array elements are set to `&PL_sv_undef` .

      	bool	av_exists(AV *av, I32 key)

- av_extend

  Pre-extend an array. The `key` is the index to which the array should be extended.

      	void	av_extend(AV *av, I32 key)

- av_fetch

  Returns the SV at the specified index in the array. The `key` is the index. If `lval` is set then the fetch will be part of a store. Check that the return value is non-null before dereferencing it to a `SV*` .

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

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

- av_fill

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

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

      	void	av_fill(AV *av, I32 fill)

- av_len

  Returns the highest index in the array. The number of elements in the array is `av_len(av) + 1` . Returns -1 if the array is empty.

      	I32	av_len(const AV *av)

- 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 av_make. The new AV will have a reference count of 1.

      	AV*	av_make(I32 size, SV **strp)

- av_pop

  Pops an SV off the end of the array. Returns `&PL_sv_undef` if the array is empty.

      	SV*	av_pop(AV *av)

- av_push

  Pushes an SV onto the end of the array. The array will grow automatically to accommodate the addition. Like `av_store` , this takes ownership of one reference count.

      	void	av_push(AV *av, SV *val)

- av_shift

  Shifts an SV off the beginning of the array. Returns `&PL_sv_undef` if the array is empty.

      	SV*	av_shift(AV *av)

- av_store

  Stores an SV in an array. The array index is specified as `key` . The return value will be 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 original `SV*` . Note that the caller is responsible for suitably incrementing the reference count of `val` before the call, and decrementing it if the function returned NULL.

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

      	SV**	av_store(AV *av, I32 key, SV *val)

- av_undef

  Undefines the array. Frees the memory used by the array itself.

      	void	av_undef(AV *av)

- av_unshift

  Unshift the given number of `undef` values onto the beginning of the array. The array will grow automatically to accommodate the addition. You must then use `av_store` to assign values to these new elements.

      	void	av_unshift(AV *av, I32 num)

- get_av

  Returns the AV of the specified Perl array. `flags` are passed to `gv_fetchpv` . If `GV_ADD` is set and the Perl variable does not exist then it will be created. If `flags` is zero and the variable does not exist then NULL is returned.

  NOTE: the perl_ form of this function is deprecated.

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

- newAV

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

      	AV*	newAV()

- sortsv

  Sort an array. Here is an example:

          sortsv(AvARRAY(av), av_len(av)+1, Perl_sv_cmp_locale);

  Currently this always uses mergesort. See sortsv_flags for a more flexible routine.

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

- sortsv_flags

  Sort an array, with various options.

      	void	sortsv_flags(SV** array, size_t num_elts, SVCOMPARE_t cmp, U32 flags)

# Callback Functions

- call_argv

  Performs a callback to the specified Perl sub. See perlcall.

  NOTE: the perl_ form of this function is deprecated.

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

- call_method

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

  NOTE: the perl_ form of this function is deprecated.

      	I32	call_method(const char* methname, I32 flags)

- call_pv

  Performs a callback to the specified Perl sub. See perlcall.

  NOTE: the perl_ form of this function is deprecated.

      	I32	call_pv(const char* sub_name, I32 flags)

- call_sv

  Performs a callback to the Perl sub whose name is in the SV. See perlcall.

  NOTE: the perl_ form of this function is deprecated.

      	I32	call_sv(SV* sv, VOL I32 flags)

- ENTER

  Opening bracket on a callback. See `LEAVE` and perlcall.

      		ENTER;

- eval_pv

  Tells Perl to `eval` the given string and return an SV* result.

  NOTE: the perl_ form of this function is deprecated.

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

- eval_sv

  Tells Perl to `eval` the string in the SV.

  NOTE: the perl_ form of this function is deprecated.

      	I32	eval_sv(SV* sv, I32 flags)

- FREETMPS

  Closing bracket for temporaries on a callback. See `SAVETMPS` and perlcall.

      		FREETMPS;

- LEAVE

  Closing bracket on a callback. See `ENTER` and perlcall.

      		LEAVE;

- SAVETMPS

  Opening bracket for temporaries on a callback. See `FREETMPS` and perlcall.

      		SAVETMPS;

# Character classes

- isALNUM

  Returns a boolean indicating whether the C `char` is a US-ASCII (Basic Latin) alphanumeric character (including underscore) or digit.

      	bool	isALNUM(char ch)

- isALPHA

  Returns a boolean indicating whether the C `char` is a US-ASCII (Basic Latin) alphabetic character.

      	bool	isALPHA(char ch)

- isDIGIT

  Returns a boolean indicating whether the C `char` is a US-ASCII (Basic Latin) digit.

      	bool	isDIGIT(char ch)

- isLOWER

  Returns a boolean indicating whether the C `char` is a US-ASCII (Basic Latin) lowercase character.

      	bool	isLOWER(char ch)

- isSPACE

  Returns a boolean indicating whether the C `char` is a US-ASCII (Basic Latin) whitespace.

      	bool	isSPACE(char ch)

- isUPPER

  Returns a boolean indicating whether the C `char` is a US-ASCII (Basic Latin) uppercase character.

      	bool	isUPPER(char ch)

- toLOWER

  Converts the specified character to lowercase. Characters outside the US-ASCII (Basic Latin) range are viewed as not having any case.

      	char	toLOWER(char ch)

- toUPPER

  Converts the specified character to uppercase. Characters outside the US-ASCII (Basic Latin) range are viewed as not having any case.

      	char	toUPPER(char ch)

# Cloning an interpreter

- perl_clone

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

  perl_clone takes these flags as parameters:

  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 COPY_STACKS while the threads->create doesn't.

  CLONEf_KEEP_PTR_TABLE 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 KEEP_PTR_TABLE is not set then perl_clone will kill the ptr_table using the function `ptr_table_free(PL_ptr_table); PL_ptr_table = NULL;` , reason to keep it around is if you want to dup some of your own variable who are outside the graph perl scans, example of this code is in threads.xs create

  CLONEf_CLONE_HOST This is a win32 thing, it is ignored on unix, it tells perls 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)

# CV Manipulation Functions

- CvSTASH

  Returns the stash of the CV.

      	HV*	CvSTASH(CV* cv)

- get_cv

  Uses `strlen` to get the length of `name` , then calls `get_cvn_flags` .

  NOTE: the perl_ form of this function is deprecated.

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

- get_cvn_flags

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

  NOTE: the perl_ form of this function is deprecated.

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

# Embedding Functions

- cv_undef

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

      	void	cv_undef(CV* cv)

- load_module

  Loads the module whose name is pointed to by the string part of name. Note that the actual module name, not its filename, should be given. Eg, "Foo::Bar" instead of "Foo/Bar.pm". flags can be any of PERL_LOADMOD_DENY, PERL_LOADMOD_NOIMPORT, or PERL_LOADMOD_IMPORT_OPS (or 0 for no flags). ver, if specified, provides version semantics similar to `use Foo::Bar VERSION` . The optional trailing SV* arguments can be used to specify arguments to the module's import() method, similar to `use Foo::Bar VERSION LIST` . They must be terminated with a final NULL pointer. Note that this list can only be omitted when the PERL_LOADMOD_NOIMPORT flag has been used. Otherwise at least a single NULL pointer to designate the default import list is required.

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

- nothreadhook

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

      	int	nothreadhook()

- perl_alloc

  Allocates a new Perl interpreter. See perlembed.

      	PerlInterpreter*	perl_alloc()

- perl_construct

  Initializes a new Perl interpreter. See perlembed.

      	void	perl_construct(PerlInterpreter *my_perl)

- perl_destruct

  Shuts down a Perl interpreter. See perlembed.

      	int	perl_destruct(PerlInterpreter *my_perl)

- perl_free

  Releases a Perl interpreter. See perlembed.

      	void	perl_free(PerlInterpreter *my_perl)

- perl_parse

  Tells a Perl interpreter to parse a Perl script. See perlembed.

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

- perl_run

  Tells a Perl interpreter to run. See perlembed.

      	int	perl_run(PerlInterpreter *my_perl)

- require_pv

  Tells Perl to `require` the file named by the string argument. It is analogous to the Perl code `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)

# Functions in file dump.c

- 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)

- pv_escape

  Escapes at most the first "count" chars of pv and puts the results into dsv such that the size of the escaped string will not exceed "max" chars and will not contain any incomplete escape sequences.

  If flags contains 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 PERL_PV_ESCAPE_NOCLEAR is set this will not occur.

  If PERL_PV_ESCAPE_UNI is set then the input string is treated as Unicode, if PERL_PV_ESCAPE_UNI_DETECT is set then the input string is scanned using `is_utf8_string()` to determine if it is Unicode.

  If PERL_PV_ESCAPE_ALL is set then all input chars will be output using `\x01F1` style escapes, otherwise only chars above 255 will be escaped using this style, other non printable chars will use octal or common escaped patterns like `\n` . If PERL_PV_ESCAPE_NOBACKSLASH then all chars below 255 will be treated as printable and will be output as literals.

  If PERL_PV_ESCAPE_FIRSTCHAR is set then only the first char of the string will be escaped, regardles of max. If the string is utf8 and the chars value is >255 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 `\n` or a 3 or more digit hex value.

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

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

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

- pv_pretty

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

  If the 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 PERL_PV_PRETTY_LTGT flag is set then the result be wrapped in angle brackets.

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

  If start_color is non-null then it will be inserted after the opening quote (if there is one) but before the escaped text. If 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 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)

# Functions in file mathoms.c

- gv_fetchmethod

  See gv_fetchmethod_autoload.

      	GV*	gv_fetchmethod(HV* stash, const char* name)

- pack_cat

  The engine implementing pack() Perl function. Note: parameters next_in_list and flags are not used. This call should not be used; use packlist instead.

      	void	pack_cat(SV *cat, const char *pat, const char *patend, SV **beglist, SV **endlist, SV ***next_in_list, U32 flags)

- 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 `SvPVbyte_nolen` macro.

      	char*	sv_2pvbyte_nolen(SV* sv)

- 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 `SvPVutf8_nolen` macro.

      	char*	sv_2pvutf8_nolen(SV* sv)

- sv_2pv_nolen

  Like `sv_2pv()` , but doesn't return the length too. You should usually use the macro wrapper `SvPV_nolen(sv)` instead. char* sv_2pv_nolen(SV* sv)

- sv_catpvn_mg

  Like `sv_catpvn` , but also handles 'set' magic.

      	void	sv_catpvn_mg(SV *sv, const char *ptr, STRLEN len)

- sv_catsv_mg

  Like `sv_catsv` , but also handles 'set' magic.

      	void	sv_catsv_mg(SV *dsv, SV *ssv)

- 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 xpvmg. See also `sv_force_normal_flags` .

      	void	sv_force_normal(SV *sv)

- sv_iv

  A private implementation of the `SvIVx` macro for compilers which can't cope with complex macro expressions. Always use the macro instead.

      	IV	sv_iv(SV* sv)

- sv_nolocking

  Dummy routine which "locks" an SV when there is no locking module present. Exists to avoid test for a NULL function pointer and because it could potentially warn under some level of strict-ness.

  "Superseded" by sv_nosharing().

      	void	sv_nolocking(SV *sv)

- sv_nounlocking

  Dummy routine which "unlocks" an SV when there is no locking module present. Exists to avoid test for a NULL function pointer and because it could potentially warn under some level of strict-ness.

  "Superseded" by sv_nosharing().

      	void	sv_nounlocking(SV *sv)

- sv_nv

  A private implementation of the `SvNVx` macro for compilers which can't cope with complex macro expressions. Always use the macro instead.

      	NV	sv_nv(SV* sv)

- sv_pv

  Use the `SvPV_nolen` macro instead

      	char*	sv_pv(SV *sv)

- sv_pvbyte

  Use `SvPVbyte_nolen` instead.

      	char*	sv_pvbyte(SV *sv)

- sv_pvbyten

  A private implementation of the `SvPVbyte` macro for compilers which can't cope with complex macro expressions. Always use the macro instead.

      	char*	sv_pvbyten(SV *sv, STRLEN *lp)

- sv_pvn

  A private implementation of the `SvPV` macro for compilers which can't cope with complex macro expressions. Always use the macro instead.

      	char*	sv_pvn(SV *sv, STRLEN *lp)

- sv_pvutf8

  Use the `SvPVutf8_nolen` macro instead

      	char*	sv_pvutf8(SV *sv)

- sv_pvutf8n

  A private implementation of the `SvPVutf8` macro for compilers which can't cope with complex macro expressions. Always use the macro instead.

      	char*	sv_pvutf8n(SV *sv, STRLEN *lp)

- sv_taint

  Taint an SV. Use `SvTAINTED_on` instead. void sv_taint(SV* sv)

- 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 `newSVrv` . This is `sv_unref_flags` with the `flag` being zero. See `SvROK_off` .

      	void	sv_unref(SV* sv)

- sv_usepvn

  Tells an SV to use `ptr` to find its string value. Implemented by calling `sv_usepvn_flags` with `flags` of 0, hence does not handle 'set' magic. See `sv_usepvn_flags` .

      	void	sv_usepvn(SV* sv, char* ptr, STRLEN len)

- sv_usepvn_mg

  Like `sv_usepvn` , but also handles 'set' magic.

      	void	sv_usepvn_mg(SV *sv, char *ptr, STRLEN len)

- sv_uv

  A private implementation of the `SvUVx` macro for compilers which can't cope with complex macro expressions. Always use the macro instead.

      	UV	sv_uv(SV* sv)

- unpack_str

  The engine implementing unpack() Perl function. Note: parameters strbeg, new_s and ocnt are not used. This call should not be used, use unpackstring instead.

      	I32	unpack_str(const char *pat, const char *patend, const char *s, const char *strbeg, const char *strend, char **new_s, I32 ocnt, U32 flags)

# Functions in file perl.h

- 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)

- 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)

- 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()

# Functions in file pp_ctl.c

- find_runcv

  Locate the CV corresponding to the currently executing sub or eval. If db_seqp is non_null, skip CVs that are in the DB package and populate *db_seqp with the cop sequence number at the point that the DB:: code was entered. (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)

# Functions in file pp_pack.c

- packlist

  The engine implementing pack() Perl function.

      	void	packlist(SV *cat, const char *pat, const char *patend, SV **beglist, SV **endlist)

- unpackstring

  The engine implementing unpack() Perl function. `unpackstring` puts the extracted list items on the stack and returns the number of elements. Issue `PUTBACK` before and `SPAGAIN` after the call to this function.

      	I32	unpackstring(const char *pat, const char *patend, const char *s, const char *strend, U32 flags)

# GV Functions

- GvSV

  Return the SV from the GV.

      	SV*	GvSV(GV* gv)

- gv_const_sv

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

      	SV*	gv_const_sv(GV* gv)

- gv_fetchmeth

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

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

  This function grants `"SUPER"` token as a postfix of the stash name. The GV returned from `gv_fetchmeth` may be a method cache entry, which is not visible to Perl code. So when calling `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 `GvCV` macro.

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

- gv_fetchmethod_autoload

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

  The third parameter of `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 `gv_fetchmethod` is equivalent to calling `gv_fetchmethod_autoload` with a non-zero `autoload` parameter.

  These functions grant `"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 $AUTOLOAD changing its value. Use the glob created via a side effect to do this.

  These functions have the same side-effects and as `gv_fetchmeth` with `level==0` . `name` should be writable if contains `':'` or `' ''`. The warning against passing the GV returned by `gv_fetchmeth` to `call_sv` apply equally to these functions.

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

- gv_fetchmeth_autoload

  Same as gv_fetchmeth(), 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 `level < 0` . For an autoloaded subroutine without a stub, GvCV() of the result may be zero.

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

- gv_stashpv

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

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

- gv_stashpvn

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

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

- gv_stashpvs

  Like `gv_stashpvn` , but takes a literal string instead of a string/length pair.

      	HV*	gv_stashpvs(const char* name, I32 create)

- gv_stashsv

  Returns a pointer to the stash for a specified package. See `gv_stashpvn` .

      	HV*	gv_stashsv(SV* sv, I32 flags)

# Handy Values

- Nullav

  Null AV pointer.

- Nullch

  Null character pointer.

- Nullcv

  Null CV pointer.

- Nullhv

  Null HV pointer.

- Nullsv

  Null SV pointer.

# Hash Manipulation Functions

- get_hv

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

  NOTE: the perl_ form of this function is deprecated.

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

- HEf_SVKEY

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

- HeHASH

  Returns the computed hash stored in the hash entry.

      	U32	HeHASH(HE* he)

- HeKEY

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

      	void*	HeKEY(HE* he)

- HeKLEN

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

      	STRLEN	HeKLEN(HE* he)

- HePV

  Returns the key slot of the hash entry as a `char*` value, doing any necessary dereferencing of possibly `SV*` keys. The length of the string is placed in `len` (this is a macro, so do not use `&len` ). If you do not care about what the length of the key is, you may use the global variable `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 `strlen()` or similar is not a good way to find the length of hash keys. This is very similar to the `SvPV()` macro described elsewhere in this document. See also `HeUTF8` .

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

      	char*	HePV(HE* he, STRLEN len)

- HeSVKEY

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

      	SV*	HeSVKEY(HE* he)

- HeSVKEY_force

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

      	SV*	HeSVKEY_force(HE* he)

- HeSVKEY_set

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

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

- HeUTF8

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

      	char*	HeUTF8(HE* he, STRLEN len)

- HeVAL

  Returns the value slot (type `SV*` ) stored in the hash entry.

      	SV*	HeVAL(HE* he)

- HvNAME

  Returns the package name of a stash, or NULL if `stash` isn't a stash. See `SvSTASH` , `CvSTASH` .

      	char*	HvNAME(HV* stash)

- hv_assert

  Check that a hash is in an internally consistent state.

      	void	hv_assert(HV *hv)

- hv_clear

  Clears a hash, making it empty.

      	void	hv_clear(HV* hv)

- 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 &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 Hash::Util::lock_keys() for an example of its use.

      	void	hv_clear_placeholders(HV *hv)

- hv_delete

  Deletes a key/value pair in the hash. The value SV is removed from the hash and returned to the caller. The `klen` is the length of the key. The `flags` value will normally be zero; if set to G_DISCARD then NULL will be returned.

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

- hv_delete_ent

  Deletes a key/value pair in the hash. The value SV is removed from the hash and returned to the caller. The `flags` value will normally be zero; if set to G_DISCARD then NULL will be returned. `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)

- hv_exists

  Returns a boolean indicating whether the specified hash key exists. The `klen` is the length of the key.

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

- hv_exists_ent

  Returns a boolean indicating whether the specified hash key exists. `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)

- hv_fetch

  Returns the SV which corresponds to the specified key in the hash. The `klen` is the length of the key. If `lval` is set then the fetch will be part of a store. Check that the return value is non-null before dereferencing it to an `SV*` .

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

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

- hv_fetchs

  Like `hv_fetch` , but takes a literal string instead of a string/length pair.

      	SV**	hv_fetchs(HV* tb, const char* key, I32 lval)

- hv_fetch_ent

  Returns the hash entry which corresponds to the specified key in the hash. `hash` must be a valid precomputed hash number for the given `key` , or 0 if you want the function to compute it. IF `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 `tb` 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 "Understanding the Magic of Tied Hashes and Arrays" in perlguts for more information on how to use this function on tied hashes.

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

- hv_iterinit

  Prepares a starting point to traverse a hash table. Returns the number of keys in the hash (i.e. the same as `HvKEYS(tb)` ). The return value is currently only meaningful for hashes without tie magic.

  NOTE: Before version 5.004_65, `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 `HvFILL(tb)` .

      	I32	hv_iterinit(HV *hv)

- hv_iterkey

  Returns the key from the current position of the hash iterator. See `hv_iterinit` .

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

- hv_iterkeysv

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

      	SV*	hv_iterkeysv(HE* entry)

- hv_iternext

  Returns entries from a hash iterator. See `hv_iterinit` .

  You may call `hv_delete` or `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 `hv_iternext` , so you must not discard your iterator immediately else the entry will leak - call `hv_iternext` to trigger the resource deallocation.

      	HE*	hv_iternext(HV *hv)

- hv_iternextsv

  Performs an `hv_iternext` , `hv_iterkey` , and `hv_iterval` in one operation.

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

- hv_iternext_flags

  Returns entries from a hash iterator. See `hv_iterinit` and `hv_iternext` . The `flags` value will normally be zero; if 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 `&Perl_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.

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

      	HE*	hv_iternext_flags(HV *hv, I32 flags)

- hv_iterval

  Returns the value from the current position of the hash iterator. See `hv_iterkey` .

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

- hv_magic

  Adds magic to a hash. See `sv_magic` .

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

- hv_scalar

  Evaluates the hash in scalar context and returns the result. Handles magic when the hash is tied.

      	SV*	hv_scalar(HV *hv)

- hv_store

  Stores an SV in a hash. The hash key is specified as `key` and `klen` is the length of the key. The `hash` parameter is the precomputed hash value; if it is zero then Perl will compute it. The return value will be 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 `SV*` . Note that the caller is responsible for suitably incrementing the reference count of `val` before the call, and decrementing it if the function returned NULL. Effectively a successful hv_store takes ownership of one reference to `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, hv_store will own the only reference to the new SV, and your code doesn't need to do anything further to tidy up. hv_store is not implemented as a call to 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 hv_store in preference to hv_store_ent.

  See "Understanding the Magic of Tied Hashes and Arrays" in perlguts 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)

- hv_stores

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

      	SV**	hv_stores(HV* tb, const char* key, NULLOK SV* val)

- hv_store_ent

  Stores `val` in a hash. The hash key is specified as `key` . The `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 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 `He?` macros described here. Note that the caller is responsible for suitably incrementing the reference count of `val` before the call, and decrementing it if the function returned NULL. Effectively a successful hv_store_ent takes ownership of one reference to `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, 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 hv_store_ent only reads the `key` ; unlike `val` it does not take ownership of it, so maintaining the correct reference count on `key` is entirely the caller's responsibility. hv_store is not implemented as a call to 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 hv_store in preference to hv_store_ent.

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

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

- hv_undef

  Undefines the hash.

      	void	hv_undef(HV *hv)

- newHV

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

      	HV*	newHV()

# Magical Functions

- mg_clear

  Clear something magical that the SV represents. See `sv_magic` .

      	int	mg_clear(SV* sv)

- mg_copy

  Copies the magic from one SV to another. See `sv_magic` .

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

- mg_find

  Finds the magic pointer for type matching the SV. See `sv_magic` .

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

- mg_free

  Free any magic storage used by the SV. See `sv_magic` .

      	int	mg_free(SV* sv)

- mg_get

  Do magic after a value is retrieved from the SV. See `sv_magic` .

      	int	mg_get(SV* sv)

- mg_length

  Report on the SV's length. See `sv_magic` .

      	U32	mg_length(SV* sv)

- mg_magical

  Turns on the magical status of an SV. See `sv_magic` .

      	void	mg_magical(SV* sv)

- mg_set

  Do magic after a value is assigned to the SV. See `sv_magic` .

      	int	mg_set(SV* sv)

- SvGETMAGIC

  Invokes `mg_get` on an SV if it has 'get' magic. This macro evaluates its argument more than once.

      	void	SvGETMAGIC(SV* sv)

- SvLOCK

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

      	void	SvLOCK(SV* sv)

- SvSETMAGIC

  Invokes `mg_set` on an SV if it has 'set' magic. This macro evaluates its argument more than once.

      	void	SvSETMAGIC(SV* sv)

- SvSetMagicSV

  Like `SvSetSV` , but does any set magic required afterwards.

      	void	SvSetMagicSV(SV* dsb, SV* ssv)

- SvSetMagicSV_nosteal

  Like `SvSetSV_nosteal` , but does any set magic required afterwards.

      	void	SvSetMagicSV_nosteal(SV* dsv, SV* ssv)

- SvSetSV

  Calls `sv_setsv` if dsv is not the same as ssv. May evaluate arguments more than once.

      	void	SvSetSV(SV* dsb, SV* ssv)

- SvSetSV_nosteal

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

      	void	SvSetSV_nosteal(SV* dsv, SV* ssv)

- SvSHARE

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

      	void	SvSHARE(SV* sv)

- SvUNLOCK

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

      	void	SvUNLOCK(SV* sv)

# Memory Management

- Copy

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

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

- CopyD

  Like `Copy` but returns dest. Useful for encouraging compilers to tail-call optimise.

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

- Move

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

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

- MoveD

  Like `Move` but returns dest. Useful for encouraging compilers to tail-call optimise.

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

- Newx

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

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

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

- Newxc

  The XSUB-writer's interface to the C `malloc` function, with cast. See also `Newx` .

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

- Newxz

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

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

- Poison

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

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

- PoisonFree

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

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

- PoisonNew

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

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

- 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)

- Renew

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

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

- Renewc

  The XSUB-writer's interface to the C `realloc` function, with cast.

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

- Safefree

  The XSUB-writer's interface to the C `free` function.

      	void	Safefree(void* ptr)

- savepv

  Perl's version of `strdup()` . Returns a pointer to a newly allocated string which is a duplicate of `pv` . The size of the string is determined by `strlen()` . The memory allocated for the new string can be freed with the `Safefree()` function.

      	char*	savepv(const char* pv)

- savepvn

  Perl's version of what `strndup()` would be if it existed. Returns a pointer to a newly allocated string which is a duplicate of the first `len` bytes from `pv` , plus a trailing NUL byte. The memory allocated for the new string can be freed with the `Safefree()` function.

      	char*	savepvn(const char* pv, I32 len)

- savepvs

  Like `savepvn` , but takes a literal string instead of a string/length pair.

      	char*	savepvs(const char* s)

- savesharedpv

  A version of `savepv()` which allocates the duplicate string in memory which is shared between threads.

      	char*	savesharedpv(const char* pv)

- savesharedpvn

  A version of `savepvn()` which allocates the duplicate string in memory which is shared between threads. (With the specific difference that a NULL pointer is not acceptable)

      	char*	savesharedpvn(const char *const pv, const STRLEN len)

- savesvpv

  A version of `savepv()` /`savepvn()` which gets the string to duplicate from the passed in SV using `SvPV()`

      	char*	savesvpv(SV* sv)

- StructCopy

  This is an architecture-independent macro to copy one structure to another.

      	void	StructCopy(type src, type dest, type)

- Zero

  The XSUB-writer's interface to the C `memzero` function. The `dest` is the destination, `nitems` is the number of items, and `type` is the type.

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

- ZeroD

  Like `Zero` but returns dest. Useful for encouraging compilers to tail-call optimise.

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

# Miscellaneous Functions

- fbm_compile

  Analyses the string in order to make fast searches on it using fbm_instr() -- the Boyer-Moore algorithm.

      	void	fbm_compile(SV* sv, U32 flags)

- fbm_instr

  Returns the location of the SV in the string delimited by `str` and `strend` . It returns `NULL` if the string can't be found. The `sv` does not have to be fbm_compiled, but the search will not be as fast then.

      	char*	fbm_instr(unsigned char* big, unsigned char* bigend, SV* littlestr, U32 flags)

- 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, ...)

- getcwd_sv

  Fill the sv with current working directory

      	int	getcwd_sv(SV* sv)

- my_snprintf

  The C library `snprintf` functionality, if available and standards-compliant (uses `vsnprintf` , actually). However, if the `vsnprintf` is not available, will unfortunately use the unsafe `vsprintf` which can overrun the buffer (there is an overrun check, but that may be too late). Consider using `sv_vcatpvf` instead, or getting `vsnprintf` .

      	int	my_snprintf(char *buffer, const Size_t len, const char *format, ...)

- my_sprintf

  The C library `sprintf`, wrapped if necessary, to ensure that it will return the length of the string written to the buffer. Only rare pre-ANSI systems need the wrapper function - usually this is a direct call to `sprintf`.

      	int	my_sprintf(char *buffer, const char *pat, ...)

- my_vsnprintf

  The C library `vsnprintf` if available and standards-compliant. However, if if the `vsnprintf` is not available, will unfortunately use the unsafe `vsprintf` which can overrun the buffer (there is an overrun check, but that may be too late). Consider using `sv_vcatpvf` instead, or getting `vsnprintf` .

      	int	my_vsnprintf(char *buffer, const Size_t len, const char *format, va_list ap)

- 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)

- 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)

- strEQ

  Test two strings to see if they are equal. Returns true or false.

      	bool	strEQ(char* s1, char* s2)

- strGE

  Test two strings to see if the first, `s1` , is greater than or equal to the second, `s2` . Returns true or false.

      	bool	strGE(char* s1, char* s2)

- strGT

  Test two strings to see if the first, `s1` , is greater than the second, `s2` . Returns true or false.

      	bool	strGT(char* s1, char* s2)

- strLE

  Test two strings to see if the first, `s1` , is less than or equal to the second, `s2` . Returns true or false.

      	bool	strLE(char* s1, char* s2)

- strLT

  Test two strings to see if the first, `s1` , is less than the second, `s2` . Returns true or false.

      	bool	strLT(char* s1, char* s2)

- strNE

  Test two strings to see if they are different. Returns true or false.

      	bool	strNE(char* s1, char* s2)

- strnEQ

  Test two strings to see if they are equal. The `len` parameter indicates the number of bytes to compare. Returns true or false. (A wrapper for `strncmp` ).

      	bool	strnEQ(char* s1, char* s2, STRLEN len)

- strnNE

  Test two strings to see if they are different. The `len` parameter indicates the number of bytes to compare. Returns true or false. (A wrapper for `strncmp` ).

      	bool	strnNE(char* s1, char* s2, STRLEN len)

- 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 NULL function pointer and because it could potentially warn under some level of strict-ness.

      	bool	sv_destroyable(SV *sv)

- 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 NULL function pointer and because it could potentially warn under some level of strict-ness.

      	void	sv_nosharing(SV *sv)

- 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)

- vcmp

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

      	int	vcmp(SV *lhv, SV *rhv)

- 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.

      	SV*	vnormal(SV *vs)

- 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.

      	SV*	vnumify(SV *vs)

- 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

      	SV*	vstringify(SV *vs)

- vverify

  Validates that the SV contains a valid version object.

          bool vverify(SV *vobj);

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

      	bool	vverify(SV *vs)

# MRO Functions

- mro_get_linear_isa

  Returns either `mro_get_linear_isa_c3` or `mro_get_linear_isa_dfs` for the given stash, dependant upon which MRO is in effect for that stash. The return value is a read-only AV*.

  You are responsible for `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)

- 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 `PL_sub_generation++` in perl source outside of `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 constant.pm does).

  This same method is available from pure perl via, `mro::method_changed_in(classname)` .

      	void	mro_method_changed_in(HV* stash)

# Multicall Functions

- dMULTICALL

  Declare local variables for a multicall. See "Lightweight Callbacks" in perlcall.

      		dMULTICALL;

- MULTICALL

  Make a lightweight callback. See "Lightweight Callbacks" in perlcall.

      		MULTICALL;

- POP_MULTICALL

  Closing bracket for a lightweight callback. See "Lightweight Callbacks" in perlcall.

      		POP_MULTICALL;

- PUSH_MULTICALL

  Opening bracket for a lightweight callback. See "Lightweight Callbacks" in perlcall.

      		PUSH_MULTICALL;

# Numeric functions

- grok_bin

  converts a string representing a binary number to numeric form.

  On entry start and *len give the string to scan, *flags gives conversion flags, and result should be NULL or a pointer to an NV. The scan stops at the end of the string, or the first invalid character. Unless `PERL_SCAN_SILENT_ILLDIGIT` is set in *flags, encountering an invalid character will also trigger a warning. On return *len is set to the length of the scanned string, and *flags gives output flags.

  If the value is <= `UV_MAX` it is returned as a UV, the output flags are clear, and nothing is written to *result. If the value is > UV_MAX `grok_bin` returns UV_MAX, sets `PERL_SCAN_GREATER_THAN_UV_MAX` in the output flags, and writes the value to *result (or the value is discarded if result is NULL).

  The binary number may optionally be prefixed with "0b" or "b" unless `PERL_SCAN_DISALLOW_PREFIX` is set in *flags on entry. If `PERL_SCAN_ALLOW_UNDERSCORES` is set in *flags then the binary number may use '_' characters to separate digits.

      	UV	grok_bin(const char* start, STRLEN* len_p, I32* flags, NV *result)

- grok_hex

  converts a string representing a hex number to numeric form.

  On entry start and *len give the string to scan, *flags gives conversion flags, and result should be NULL or a pointer to an NV. The scan stops at the end of the string, or the first invalid character. Unless `PERL_SCAN_SILENT_ILLDIGIT` is set in *flags, encountering an invalid character will also trigger a warning. On return *len is set to the length of the scanned string, and *flags gives output flags.

  If the value is <= UV_MAX it is returned as a UV, the output flags are clear, and nothing is written to *result. If the value is > UV_MAX `grok_hex` returns UV_MAX, sets `PERL_SCAN_GREATER_THAN_UV_MAX` in the output flags, and writes the value to *result (or the value is discarded if result is NULL).

  The hex number may optionally be prefixed with "0x" or "x" unless `PERL_SCAN_DISALLOW_PREFIX` is set in *flags on entry. If `PERL_SCAN_ALLOW_UNDERSCORES` is set in *flags then the hex number may use '_' characters to separate digits.

      	UV	grok_hex(const char* start, STRLEN* len_p, I32* flags, NV *result)

- grok_number

  Recognise (or not) a number. The type of the number is returned (0 if unrecognised), otherwise it is a bit-ORed combination of IS_NUMBER_IN_UV, IS_NUMBER_GREATER_THAN_UV_MAX, IS_NUMBER_NOT_INT, IS_NUMBER_NEG, IS_NUMBER_INFINITY, IS_NUMBER_NAN (defined in perl.h).

  If the value of the number can fit an in UV, it is returned in the *valuep IS_NUMBER_IN_UV will be set to indicate that *valuep is valid, IS_NUMBER_IN_UV will never be set unless *valuep is valid, but *valuep may have been assigned to during processing even though IS_NUMBER_IN_UV is not set on return. If valuep is NULL, IS_NUMBER_IN_UV will be set for the same cases as when valuep is non-NULL, but no actual assignment (or SEGV) will occur.

  IS_NUMBER_NOT_INT will be set with IS_NUMBER_IN_UV if trailing decimals were seen (in which case *valuep gives the true value truncated to an integer), and IS_NUMBER_NEG if the number is negative (in which case *valuep holds the absolute value). IS_NUMBER_IN_UV is not set if e notation was used or the number is larger than a UV.

      	int	grok_number(const char *pv, STRLEN len, UV *valuep)

- grok_numeric_radix

  Scan and skip for a numeric decimal separator (radix).

      	bool	grok_numeric_radix(const char **sp, const char *send)

- grok_oct

  converts a string representing an octal number to numeric form.

  On entry start and *len give the string to scan, *flags gives conversion flags, and result should be NULL or a pointer to an NV. The scan stops at the end of the string, or the first invalid character. Unless `PERL_SCAN_SILENT_ILLDIGIT` is set in *flags, encountering an invalid character will also trigger a warning. On return *len is set to the length of the scanned string, and *flags gives output flags.

  If the value is <= UV_MAX it is returned as a UV, the output flags are clear, and nothing is written to *result. If the value is > UV_MAX `grok_oct` returns UV_MAX, sets `PERL_SCAN_GREATER_THAN_UV_MAX` in the output flags, and writes the value to *result (or the value is discarded if result is NULL).

  If `PERL_SCAN_ALLOW_UNDERSCORES` is set in *flags then the octal number may use '_' characters to separate digits.

      	UV	grok_oct(const char* start, STRLEN* len_p, I32* flags, NV *result)

- Perl_signbit

  Return a non-zero integer if the sign bit on an NV is set, and 0 if it is not.

  If Configure detects this system has a signbit() that will work with our NVs, then we just use it via the #define in perl.h. Otherwise, fall back on this implementation. As a first pass, this gets everything right except -0.0. Alas, catching -0.0 is the main use for this function, so this is not too helpful yet. Still, at least we have the scaffolding in place to support other systems, should that prove useful.

  Configure notes: This function is called 'Perl_signbit' instead of a plain 'signbit' because it is easy to imagine a system having a signbit() function or macro that doesn't happen to work with our particular choice of NVs. We shouldn't just re-#define signbit as Perl_signbit and expect the standard system headers to be happy. Also, this is a no-context function (no pTHX_) because Perl_signbit() is usually re-#defined in perl.h as a simple macro call to the system's signbit(). Users should just always call Perl_signbit().

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

      	int	Perl_signbit(NV f)

- scan_bin

  For backwards compatibility. Use `grok_bin` instead.

      	NV	scan_bin(const char* start, STRLEN len, STRLEN* retlen)

- scan_hex

  For backwards compatibility. Use `grok_hex` instead.

      	NV	scan_hex(const char* start, STRLEN len, STRLEN* retlen)

- scan_oct

  For backwards compatibility. Use `grok_oct` instead.

      	NV	scan_oct(const char* start, STRLEN len, STRLEN* retlen)

# Optree Manipulation Functions

- cv_const_sv

  If `cv` is a constant sub eligible for inlining. returns the constant value returned by the sub. Otherwise, returns NULL.

  Constant subs can be created with `newCONSTSUB` or as described in "Constant Functions" in perlsub.

      	SV*	cv_const_sv(CV* cv)

- newCONSTSUB

  Creates a constant sub equivalent to Perl `sub FOO () { 123 }` which is eligible for inlining at compile-time.

      	CV*	newCONSTSUB(HV* stash, const char* name, SV* sv)

- newXS

  Used by `xsubpp` to hook up XSUBs as Perl subs. filename needs to be static storage, as it is used directly as CvFILE(), without a copy being made.

# Pad Data Structures

- pad_sv

  Get the value at offset po in the current pad. Use macro PAD_SV instead of calling this function directly.

      	SV*	pad_sv(PADOFFSET po)

# Per-Interpreter Variables

- PL_modglobal

  `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

- PL_na

  A convenience variable which is typically used with `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 `SvPV_nolen` macro.

      	STRLEN	PL_na

- PL_sv_no

  This is the `false` SV. See `PL_sv_yes` . Always refer to this as `&PL_sv_no` .

      	SV	PL_sv_no

- PL_sv_undef

  This is the `undef` SV. Always refer to this as `&PL_sv_undef` .

      	SV	PL_sv_undef

- PL_sv_yes

  This is the `true` SV. See `PL_sv_no` . Always refer to this as `&PL_sv_yes` .

      	SV	PL_sv_yes

# REGEXP Functions

- 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) &&        (tmpsv = (SV*)SvRV(sv)) &&        SvTYPE(tmpsv) == SVt_PVMG &&        (tmpmg = mg_find(tmpsv, PERL_MAGIC_qr)))    {        return (REGEXP *)tmpmg->mg_obj;    }

  NULL will be returned if a REGEXP* is not found.

      	REGEXP *	SvRX(SV *sv)

- SvRXOK

  Returns a boolean indicating whether the SV contains qr magic (PERL_MAGIC_qr).

  If you want to do something with the REGEXP* later use SvRX instead and check for NULL.

      	bool	SvRXOK(SV* sv)

# Simple Exception Handling Macros

- dXCPT

  Set up necessary local variables for exception handling. See "Exception Handling" in perlguts.

      		dXCPT;

- XCPT_CATCH

  Introduces a catch block. See "Exception Handling" in perlguts.

- XCPT_RETHROW

  Rethrows a previously caught exception. See "Exception Handling" in perlguts.

      		XCPT_RETHROW;

- XCPT_TRY_END

  Ends a try block. See "Exception Handling" in perlguts.

- XCPT_TRY_START

  Starts a try block. See "Exception Handling" in perlguts.

# Stack Manipulation Macros

- dMARK

  Declare a stack marker variable, `mark` , for the XSUB. See `MARK` and `dORIGMARK` .

      		dMARK;

- dORIGMARK

  Saves the original stack mark for the XSUB. See `ORIGMARK` .

      		dORIGMARK;

- dSP

  Declares a local copy of perl's stack pointer for the XSUB, available via the `SP` macro. See `SP` .

      		dSP;

- EXTEND

  Used to extend the argument stack for an XSUB's return values. Once used, guarantees that there is room for at least `nitems` to be pushed onto the stack.

      	void	EXTEND(SP, int nitems)

- MARK

  Stack marker variable for the XSUB. See `dMARK` .

- mPUSHi

  Push an integer onto the stack. The stack must have room for this element. Does not use `TARG` . See also `PUSHi` , `mXPUSHi` and `XPUSHi` .

      	void	mPUSHi(IV iv)

- mPUSHn

  Push a double onto the stack. The stack must have room for this element. Does not use `TARG` . See also `PUSHn` , `mXPUSHn` and `XPUSHn` .

      	void	mPUSHn(NV nv)

- mPUSHp

  Push a string onto the stack. The stack must have room for this element. The `len` indicates the length of the string. Does not use `TARG` . See also `PUSHp` , `mXPUSHp` and `XPUSHp` .

      	void	mPUSHp(char* str, STRLEN len)

- mPUSHs

  Push an SV onto the stack and mortalizes the SV. The stack must have room for this element. Does not use `TARG` . See also `PUSHs` and `mXPUSHs` .

      	void	mPUSHs(SV* sv)

- mPUSHu

  Push an unsigned integer onto the stack. The stack must have room for this element. Does not use `TARG` . See also `PUSHu` , `mXPUSHu` and `XPUSHu` .

      	void	mPUSHu(UV uv)

- mXPUSHi

  Push an integer onto the stack, extending the stack if necessary. Does not use `TARG` . See also `XPUSHi` , `mPUSHi` and `PUSHi` .

      	void	mXPUSHi(IV iv)

- mXPUSHn

  Push a double onto the stack, extending the stack if necessary. Does not use `TARG` . See also `XPUSHn` , `mPUSHn` and `PUSHn` .

      	void	mXPUSHn(NV nv)

- mXPUSHp

  Push a string onto the stack, extending the stack if necessary. The `len` indicates the length of the string. Does not use `TARG` . See also `XPUSHp` , `mPUSHp` and `PUSHp` .

      	void	mXPUSHp(char* str, STRLEN len)

- mXPUSHs

  Push an SV onto the stack, extending the stack if necessary and mortalizes the SV. Does not use `TARG` . See also `XPUSHs` and `mPUSHs` .

      	void	mXPUSHs(SV* sv)

- mXPUSHu

  Push an unsigned integer onto the stack, extending the stack if necessary. Does not use `TARG` . See also `XPUSHu` , `mPUSHu` and `PUSHu` .

      	void	mXPUSHu(UV uv)

- ORIGMARK

  The original stack mark for the XSUB. See `dORIGMARK` .

- POPi

  Pops an integer off the stack.

      	IV	POPi

- POPl

  Pops a long off the stack.

      	long	POPl

- POPn

  Pops a double off the stack.

      	NV	POPn

- POPp

  Pops a string off the stack. Deprecated. New code should use POPpx.

      	char*	POPp

- POPpbytex

  Pops a string off the stack which must consist of bytes i.e. characters < 256.

      	char*	POPpbytex

- POPpx

  Pops a string off the stack.

      	char*	POPpx

- POPs

  Pops an SV off the stack.

      	SV*	POPs

- PUSHi

  Push an integer onto the stack. The stack must have room for this element. Handles 'set' magic. Uses `TARG` , so `dTARGET` or `dXSTARG` should be called to declare it. Do not call multiple `TARG` -oriented macros to return lists from XSUB's - see `mPUSHi` instead. See also `XPUSHi` and `mXPUSHi` .

      	void	PUSHi(IV iv)

- PUSHMARK

  Opening bracket for arguments on a callback. See `PUTBACK` and perlcall.

      	void	PUSHMARK(SP)

- PUSHmortal

  Push a new mortal SV onto the stack. The stack must have room for this element. Does not use `TARG` . See also `PUSHs` , `XPUSHmortal` and `XPUSHs` .

      	void	PUSHmortal()

- PUSHn

  Push a double onto the stack. The stack must have room for this element. Handles 'set' magic. Uses `TARG` , so `dTARGET` or `dXSTARG` should be called to declare it. Do not call multiple `TARG` -oriented macros to return lists from XSUB's - see `mPUSHn` instead. See also `XPUSHn` and `mXPUSHn` .

      	void	PUSHn(NV nv)

- PUSHp

  Push a string onto the stack. The stack must have room for this element. The `len` indicates the length of the string. Handles 'set' magic. Uses `TARG` , so `dTARGET` or `dXSTARG` should be called to declare it. Do not call multiple `TARG` -oriented macros to return lists from XSUB's - see `mPUSHp` instead. See also `XPUSHp` and `mXPUSHp` .

      	void	PUSHp(char* str, STRLEN len)

- PUSHs

  Push an SV onto the stack. The stack must have room for this element. Does not handle 'set' magic. Does not use `TARG` . See also `PUSHmortal` , `XPUSHs` and `XPUSHmortal` .

      	void	PUSHs(SV* sv)

- PUSHu

  Push an unsigned integer onto the stack. The stack must have room for this element. Handles 'set' magic. Uses `TARG` , so `dTARGET` or `dXSTARG` should be called to declare it. Do not call multiple `TARG` -oriented macros to return lists from XSUB's - see `mPUSHu` instead. See also `XPUSHu` and `mXPUSHu` .

      	void	PUSHu(UV uv)

- PUTBACK

  Closing bracket for XSUB arguments. This is usually handled by `xsubpp` . See `PUSHMARK` and perlcall for other uses.

      		PUTBACK;

- SP

  Stack pointer. This is usually handled by `xsubpp` . See `dSP` and `SPAGAIN` .

- SPAGAIN

  Refetch the stack pointer. Used after a callback. See perlcall.

      		SPAGAIN;

- XPUSHi

  Push an integer onto the stack, extending the stack if necessary. Handles 'set' magic. Uses `TARG` , so `dTARGET` or `dXSTARG` should be called to declare it. Do not call multiple `TARG` -oriented macros to return lists from XSUB's - see `mXPUSHi` instead. See also `PUSHi` and `mPUSHi` .

      	void	XPUSHi(IV iv)

- XPUSHmortal

  Push a new mortal SV onto the stack, extending the stack if necessary. Does not use `TARG` . See also `XPUSHs` , `PUSHmortal` and `PUSHs` .

      	void	XPUSHmortal()

- XPUSHn

  Push a double onto the stack, extending the stack if necessary. Handles 'set' magic. Uses `TARG` , so `dTARGET` or `dXSTARG` should be called to declare it. Do not call multiple `TARG` -oriented macros to return lists from XSUB's - see `mXPUSHn` instead. See also `PUSHn` and `mPUSHn` .

      	void	XPUSHn(NV nv)

- XPUSHp

  Push a string onto the stack, extending the stack if necessary. The `len` indicates the length of the string. Handles 'set' magic. Uses `TARG` , so `dTARGET` or `dXSTARG` should be called to declare it. Do not call multiple `TARG` -oriented macros to return lists from XSUB's - see `mXPUSHp` instead. See also `PUSHp` and `mPUSHp` .

      	void	XPUSHp(char* str, STRLEN len)

- XPUSHs

  Push an SV onto the stack, extending the stack if necessary. Does not handle 'set' magic. Does not use `TARG` . See also `XPUSHmortal` , `PUSHs` and `PUSHmortal` .

      	void	XPUSHs(SV* sv)

- XPUSHu

  Push an unsigned integer onto the stack, extending the stack if necessary. Handles 'set' magic. Uses `TARG` , so `dTARGET` or `dXSTARG` should be called to declare it. Do not call multiple `TARG` -oriented macros to return lists from XSUB's - see `mXPUSHu` instead. See also `PUSHu` and `mPUSHu` .

      	void	XPUSHu(UV uv)

- XSRETURN

  Return from XSUB, indicating number of items on the stack. This is usually handled by `xsubpp` .

      	void	XSRETURN(int nitems)

- XSRETURN_EMPTY

  Return an empty list from an XSUB immediately.

      		XSRETURN_EMPTY;

- XSRETURN_IV

  Return an integer from an XSUB immediately. Uses `XST_mIV` .

      	void	XSRETURN_IV(IV iv)

- XSRETURN_NO

  Return `&PL_sv_no` from an XSUB immediately. Uses `XST_mNO` .

      		XSRETURN_NO;

- XSRETURN_NV

  Return a double from an XSUB immediately. Uses `XST_mNV` .

      	void	XSRETURN_NV(NV nv)

- XSRETURN_PV

  Return a copy of a string from an XSUB immediately. Uses `XST_mPV` .

      	void	XSRETURN_PV(char* str)

- XSRETURN_UNDEF

  Return `&PL_sv_undef` from an XSUB immediately. Uses `XST_mUNDEF` .

      		XSRETURN_UNDEF;

- XSRETURN_UV

  Return an integer from an XSUB immediately. Uses `XST_mUV` .

      	void	XSRETURN_UV(IV uv)

- XSRETURN_YES

  Return `&PL_sv_yes` from an XSUB immediately. Uses `XST_mYES` .

      		XSRETURN_YES;

- XST_mIV

  Place an integer into the specified position `pos` on the stack. The value is stored in a new mortal SV.

      	void	XST_mIV(int pos, IV iv)

- XST_mNO

  Place `&PL_sv_no` into the specified position `pos` on the stack.

      	void	XST_mNO(int pos)

- XST_mNV

  Place a double into the specified position `pos` on the stack. The value is stored in a new mortal SV.

      	void	XST_mNV(int pos, NV nv)

- XST_mPV

  Place a copy of a string into the specified position `pos` on the stack. The value is stored in a new mortal SV.

      	void	XST_mPV(int pos, char* str)

- XST_mUNDEF

  Place `&PL_sv_undef` into the specified position `pos` on the stack.

      	void	XST_mUNDEF(int pos)

- XST_mYES

  Place `&PL_sv_yes` into the specified position `pos` on the stack.

      	void	XST_mYES(int pos)

# SV Flags

- svtype

  An enum of flags for Perl types. These are found in the file sv.h in the `svtype` enum. Test these flags with the `SvTYPE` macro.

- SVt_IV

  Integer type flag for scalars. See `svtype` .

- SVt_NV

  Double type flag for scalars. See `svtype` .

- SVt_PV

  Pointer type flag for scalars. See `svtype` .

- SVt_PVAV

  Type flag for arrays. See `svtype` .

- SVt_PVCV

  Type flag for code refs. See `svtype` .

- SVt_PVHV

  Type flag for hashes. See `svtype` .

- SVt_PVMG

  Type flag for blessed scalars. See `svtype` .

# SV Manipulation Functions

- croak_xs_usage

  A specialised variant of `croak()` for emitting the usage message for xsubs

          croak_xs_usage(cv, "eee_yow");

  works out the package name and subroutine name from `cv` , and then calls `croak()` . Hence if `cv` is `&ouch::awk` , it would call `croak` as:

          Perl_croak(aTHX_ "Usage %s::%s(%s)", "ouch" "awk", "eee_yow");	void	croak_xs_usage(const CV *const cv, const char *const params)

- get_sv

  Returns the SV of the specified Perl scalar. `flags` are passed to `gv_fetchpv` . If `GV_ADD` is set and the Perl variable does not exist then it will be created. If `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)

- newRV_inc

  Creates an RV wrapper for an SV. The reference count for the original SV is incremented.

      	SV*	newRV_inc(SV* sv)

- newSVpvn_utf8

  Creates a new SV and copies a string into it. If utf8 is true, calls `SvUTF8_on` on the new SV. Implemented as a wrapper around `newSVpvn_flags` .

      	SV*	newSVpvn_utf8(NULLOK const char* s, STRLEN len, U32 utf8)

- SvCUR

  Returns the length of the string which is in the SV. See `SvLEN` .

      	STRLEN	SvCUR(SV* sv)

- SvCUR_set

  Set the current length of the string which is in the SV. See `SvCUR` and `SvIV_set` .

      	void	SvCUR_set(SV* sv, STRLEN len)

- SvEND

  Returns a pointer to the last character in the string which is in the SV. See `SvCUR` . Access the character as *(SvEND(sv)).

      	char*	SvEND(SV* sv)

- 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)

- 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 NUL character). Calls `sv_grow` to perform the expansion if necessary. Returns a pointer to the character buffer.

      	char *	SvGROW(SV* sv, STRLEN len)

- SvIOK

  Returns a U32 value indicating whether the SV contains an integer.

      	U32	SvIOK(SV* sv)

- SvIOKp

  Returns a U32 value indicating whether the SV contains an integer. Checks the private setting. Use `SvIOK` instead.

      	U32	SvIOKp(SV* sv)

- SvIOK_notUV

  Returns a boolean indicating whether the SV contains a signed integer.

      	bool	SvIOK_notUV(SV* sv)

- SvIOK_off

  Unsets the IV status of an SV.

      	void	SvIOK_off(SV* sv)

- SvIOK_on

  Tells an SV that it is an integer.

      	void	SvIOK_on(SV* sv)

- SvIOK_only

  Tells an SV that it is an integer and disables all other OK bits.

      	void	SvIOK_only(SV* sv)

- SvIOK_only_UV

  Tells and SV that it is an unsigned integer and disables all other OK bits.

      	void	SvIOK_only_UV(SV* sv)

- SvIOK_UV

  Returns a boolean indicating whether the SV contains an unsigned integer.

      	bool	SvIOK_UV(SV* sv)

- SvIsCOW

  Returns a boolean 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)

      	bool	SvIsCOW(SV* sv)

- SvIsCOW_shared_hash

  Returns a boolean indicating whether the SV is Copy-On-Write shared hash key scalar.

      	bool	SvIsCOW_shared_hash(SV* sv)

- SvIV

  Coerces the given SV to an integer and returns it. See `SvIVx` for a version which guarantees to evaluate sv only once.

      	IV	SvIV(SV* sv)

- SvIVX

  Returns the raw value in the SV's IV slot, without checks or conversions. Only use when you are sure SvIOK is true. See also `SvIV()` .

      	IV	SvIVX(SV* sv)

- SvIVx

  Coerces the given SV to an integer and returns it. Guarantees to evaluate `sv` only once. Only use this if `sv` is an expression with side effects, otherwise use the more efficient `SvIV` .

      	IV	SvIVx(SV* sv)

- SvIV_nomg

  Like `SvIV` but doesn't process magic.

      	IV	SvIV_nomg(SV* sv)

- 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 `SvIVX` . With future Perls, however, it will be more efficient to use `SvIV_set` instead of the lvalue assignment to `SvIVX` .

      	void	SvIV_set(SV* sv, IV val)

- SvLEN

  Returns the size of the string buffer in the SV, not including any part attributable to `SvOOK` . See `SvCUR` .

      	STRLEN	SvLEN(SV* sv)

- SvLEN_set

  Set the actual length of the string which is in the SV. See `SvIV_set` .

      	void	SvLEN_set(SV* sv, STRLEN len)

- SvMAGIC_set

  Set the value of the MAGIC pointer in sv to val. See `SvIV_set` .

      	void	SvMAGIC_set(SV* sv, MAGIC* val)

- SvNIOK

  Returns a U32 value indicating whether the SV contains a number, integer or double.

      	U32	SvNIOK(SV* sv)

- SvNIOKp

  Returns a U32 value indicating whether the SV contains a number, integer or double. Checks the private setting. Use `SvNIOK` instead.

      	U32	SvNIOKp(SV* sv)

- SvNIOK_off

  Unsets the NV/IV status of an SV.

      	void	SvNIOK_off(SV* sv)

- SvNOK

  Returns a U32 value indicating whether the SV contains a double.

      	U32	SvNOK(SV* sv)

- SvNOKp

  Returns a U32 value indicating whether the SV contains a double. Checks the private setting. Use `SvNOK` instead.

      	U32	SvNOKp(SV* sv)

- SvNOK_off

  Unsets the NV status of an SV.

      	void	SvNOK_off(SV* sv)

- SvNOK_on

  Tells an SV that it is a double.

      	void	SvNOK_on(SV* sv)

- SvNOK_only

  Tells an SV that it is a double and disables all other OK bits.

      	void	SvNOK_only(SV* sv)

- SvNV

  Coerce the given SV to a double and return it. See `SvNVx` for a version which guarantees to evaluate sv only once.

      	NV	SvNV(SV* sv)

- SvNVX

  Returns the raw value in the SV's NV slot, without checks or conversions. Only use when you are sure SvNOK is true. See also `SvNV()` .

      	NV	SvNVX(SV* sv)

- SvNVx

  Coerces the given SV to a double and returns it. Guarantees to evaluate `sv` only once. Only use this if `sv` is an expression with side effects, otherwise use the more efficient `SvNV` .

      	NV	SvNVx(SV* sv)

- SvNV_set

  Set the value of the NV pointer in sv to val. See `SvIV_set` .

      	void	SvNV_set(SV* sv, NV val)

- SvOK

  Returns a U32 value indicating whether the value is defined. This is only meaningful for scalars.

      	U32	SvOK(SV* sv)

- SvOOK

  Returns a U32 indicating whether the SvIVX is a valid offset value for the SvPVX. This hack is used internally to speed up removal of characters from the beginning of a SvPV. When SvOOK is true, then the start of the allocated string buffer is really (SvPVX - SvIVX).

      	U32	SvOOK(SV* sv)

- SvPOK

  Returns a U32 value indicating whether the SV contains a character string.

      	U32	SvPOK(SV* sv)

- SvPOKp

  Returns a U32 value indicating whether the SV contains a character string. Checks the private setting. Use `SvPOK` instead.

      	U32	SvPOKp(SV* sv)

- SvPOK_off

  Unsets the PV status of an SV.

      	void	SvPOK_off(SV* sv)

- SvPOK_on

  Tells an SV that it is a string.

      	void	SvPOK_on(SV* sv)

- SvPOK_only

  Tells an SV that it is a string and disables all other OK bits. Will also turn off the UTF-8 status.

      	void	SvPOK_only(SV* sv)

- SvPOK_only_UTF8

  Tells an SV that it is a string and disables all other OK bits, and leaves the UTF-8 status as it was.

      	void	SvPOK_only_UTF8(SV* sv)

- 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 `SvPOK` . Handles 'get' magic. See also `SvPVx` for a version which guarantees to evaluate sv only once.

      	char*	SvPV(SV* sv, STRLEN len)

- SvPVbyte

  Like `SvPV` , but converts sv to byte representation first if necessary.

      	char*	SvPVbyte(SV* sv, STRLEN len)

- SvPVbytex

  Like `SvPV` , but converts sv to byte representation first if necessary. Guarantees to evaluate sv only once; use the more efficient `SvPVbyte` otherwise.

      	char*	SvPVbytex(SV* sv, STRLEN len)

- SvPVbytex_force

  Like `SvPV_force` , but converts sv to byte representation first if necessary. Guarantees to evaluate sv only once; use the more efficient `SvPVbyte_force` otherwise.

      	char*	SvPVbytex_force(SV* sv, STRLEN len)

- SvPVbyte_force

  Like `SvPV_force` , but converts sv to byte representation first if necessary.

      	char*	SvPVbyte_force(SV* sv, STRLEN len)

- SvPVbyte_nolen

  Like `SvPV_nolen` , but converts sv to byte representation first if necessary.

      	char*	SvPVbyte_nolen(SV* sv)

- SvPVutf8

  Like `SvPV` , but converts sv to utf8 first if necessary.

      	char*	SvPVutf8(SV* sv, STRLEN len)

- SvPVutf8x

  Like `SvPV` , but converts sv to utf8 first if necessary. Guarantees to evaluate sv only once; use the more efficient `SvPVutf8` otherwise.

      	char*	SvPVutf8x(SV* sv, STRLEN len)

- SvPVutf8x_force

  Like `SvPV_force` , but converts sv to utf8 first if necessary. Guarantees to evaluate sv only once; use the more efficient `SvPVutf8_force` otherwise.

      	char*	SvPVutf8x_force(SV* sv, STRLEN len)

- SvPVutf8_force

  Like `SvPV_force` , but converts sv to utf8 first if necessary.

      	char*	SvPVutf8_force(SV* sv, STRLEN len)

- SvPVutf8_nolen

  Like `SvPV_nolen` , but converts sv to utf8 first if necessary.

      	char*	SvPVutf8_nolen(SV* sv)

- SvPVX

  Returns a pointer to the physical string in the SV. The SV must contain a string.

      	char*	SvPVX(SV* sv)

- SvPVx

  A version of `SvPV` which guarantees to evaluate `sv` only once. Only use this if `sv` is an expression with side effects, otherwise use the more efficient `SvPVX` .

      	char*	SvPVx(SV* sv, STRLEN len)

- SvPV_force

  Like `SvPV` but will force the SV into containing just a string (`SvPOK_only` ). You want force if you are going to update the `SvPVX` directly.

      	char*	SvPV_force(SV* sv, STRLEN len)

- SvPV_force_nomg

  Like `SvPV` but will force the SV into containing just a string (`SvPOK_only` ). You want force if you are going to update the `SvPVX` directly. Doesn't process magic.

      	char*	SvPV_force_nomg(SV* sv, STRLEN len)

- SvPV_nolen

  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 form becoming `SvPOK` . Handles 'get' magic.

      	char*	SvPV_nolen(SV* sv)

- SvPV_nomg

  Like `SvPV` but doesn't process magic.

      	char*	SvPV_nomg(SV* sv, STRLEN len)

- SvPV_set

  Set the value of the PV pointer in sv to val. See `SvIV_set` .

      	void	SvPV_set(SV* sv, char* val)

- SvREFCNT

  Returns the value of the object's reference count.

      	U32	SvREFCNT(SV* sv)

- SvREFCNT_dec

  Decrements the reference count of the given SV.

      	void	SvREFCNT_dec(SV* sv)

- SvREFCNT_inc

  Increments the reference count of the given SV.

  All of the following SvREFCNT_inc* macros are optimized versions of SvREFCNT_inc, and can be replaced with SvREFCNT_inc.

      	SV*	SvREFCNT_inc(SV* sv)

- SvREFCNT_inc_NN

  Same as SvREFCNT_inc, but can only be used if you know sv is not NULL. Since we don't have to check the NULLness, it's faster and smaller.

      	SV*	SvREFCNT_inc_NN(SV* sv)

- SvREFCNT_inc_simple

  Same as 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)

- SvREFCNT_inc_simple_NN

  Same as SvREFCNT_inc_simple, but can only be used if you know sv is not NULL. Since we don't have to check the NULLness, it's faster and smaller.

      	SV*	SvREFCNT_inc_simple_NN(SV* sv)

- SvREFCNT_inc_simple_void

  Same as 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)

- SvREFCNT_inc_simple_void_NN

  Same as SvREFCNT_inc, but can only be used if you don't need the return value, and you know that sv is not 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)

- SvREFCNT_inc_void

  Same as 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)

- SvREFCNT_inc_void_NN

  Same as SvREFCNT_inc, but can only be used if you don't need the return value, and you know that sv is not 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)

- SvROK

  Tests if the SV is an RV.

      	U32	SvROK(SV* sv)

- SvROK_off

  Unsets the RV status of an SV.

      	void	SvROK_off(SV* sv)

- SvROK_on

  Tells an SV that it is an RV.

      	void	SvROK_on(SV* sv)

- SvRV

  Dereferences an RV to return the SV.

      	SV*	SvRV(SV* sv)

- SvRV_set

  Set the value of the RV pointer in sv to val. See `SvIV_set` .

      	void	SvRV_set(SV* sv, SV* val)

- SvSTASH

  Returns the stash of the SV.

      	HV*	SvSTASH(SV* sv)

- SvSTASH_set

  Set the value of the STASH pointer in sv to val. See `SvIV_set` .

      	void	SvSTASH_set(SV* sv, HV* val)

- SvTAINT

  Taints an SV if tainting is enabled.

      	void	SvTAINT(SV* sv)

- SvTAINTED

  Checks to see if an SV is tainted. Returns TRUE if it is, FALSE if not.

      	bool	SvTAINTED(SV* sv)

- SvTAINTED_off

  Untaints an SV. Be 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)

- SvTAINTED_on

  Marks an SV as tainted if tainting is enabled.

      	void	SvTAINTED_on(SV* sv)

- SvTRUE

  Returns a boolean indicating whether Perl would evaluate the SV as true or false. See SvOK() for a defined/undefined test. Does not handle 'get' magic.

      	bool	SvTRUE(SV* sv)

- SvTYPE

  Returns the type of the SV. See `svtype` .

      	svtype	SvTYPE(SV* sv)

- SvUOK

  Returns a boolean indicating whether the SV contains an unsigned integer.

      	bool	SvUOK(SV* sv)

- SvUPGRADE

  Used to upgrade an SV to a more complex form. Uses `sv_upgrade` to perform the upgrade if necessary. See `svtype` .

      	void	SvUPGRADE(SV* sv, svtype type)

- SvUTF8

  Returns a U32 value indicating whether the SV contains UTF-8 encoded data. Call this after SvPV() in case any call to string overloading updates the internal flag.

      	U32	SvUTF8(SV* sv)

- SvUTF8_off

  Unsets the UTF-8 status of an SV.

      	void	SvUTF8_off(SV *sv)

- 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)

- SvUV

  Coerces the given SV to an unsigned integer and returns it. See `SvUVx` for a version which guarantees to evaluate sv only once.

      	UV	SvUV(SV* sv)

- SvUVX

  Returns the raw value in the SV's UV slot, without checks or conversions. Only use when you are sure SvIOK is true. See also `SvUV()` .

      	UV	SvUVX(SV* sv)

- SvUVx

  Coerces the given SV to an unsigned integer and returns it. Guarantees to `sv` only once. Only use this if `sv` is an expression with side effects, otherwise use the more efficient `SvUV` .

      	UV	SvUVx(SV* sv)

- SvUV_nomg

  Like `SvUV` but doesn't process magic.

      	UV	SvUV_nomg(SV* sv)

- SvUV_set

  Set the value of the UV pointer in sv to val. See `SvIV_set` .

      	void	SvUV_set(SV* sv, UV val)

- SvVOK

  Returns a boolean indicating whether the SV contains a v-string.

      	bool	SvVOK(SV* sv)

- sv_catpvn_nomg

  Like `sv_catpvn` but doesn't process magic.

      	void	sv_catpvn_nomg(SV* sv, const char* ptr, STRLEN len)

- sv_catsv_nomg

  Like `sv_catsv` but doesn't process magic.

      	void	sv_catsv_nomg(SV* dsv, SV* ssv)

- sv_derived_from

  Returns a boolean indicating whether the SV is derived from the specified class at the C level. To check derivation at the Perl level, call `isa()` as a normal Perl method.

      	bool	sv_derived_from(SV* sv, const char* name)

- sv_does

  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, const char* name)

- sv_report_used

  Dump the contents of all SVs not yet freed. (Debugging aid).

      	void	sv_report_used()

- sv_setsv_nomg

  Like `sv_setsv` but doesn't process magic.

      	void	sv_setsv_nomg(SV* dsv, SV* ssv)

- sv_utf8_upgrade_nomg

  Like sv_utf8_upgrade, but doesn't do magic on `sv`

      	STRLEN	sv_utf8_upgrade_nomg(NN SV *sv)

# SV-Body Allocation

- looks_like_number

  Test if the content of an SV looks like a number (or is a number). `Inf` and `Infinity` are treated as numbers (so will not issue a non-numeric warning), even if your atof() doesn't grok them.

      	I32	looks_like_number(SV* sv)

- newRV_noinc

  Creates an RV wrapper for an SV. The reference count for the original SV is not incremented.

      	SV*	newRV_noinc(SV* sv)

- newSV

  Creates a new SV. A non-zero `len` parameter indicates the number of bytes of preallocated string space the SV should have. An extra byte for a trailing NUL is also reserved. (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, newSV() replaces the older NEWSV() API, and drops the first parameter, x, a debug aid which allowed callers to identify themselves. This aid has been superseded by a new build option, PERL_MEM_LOG (see "PERL_MEM_LOG" in perlhack). The older API is still there for use in XS modules supporting older perls.

      	SV*	newSV(STRLEN len)

- 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 the hek is NULL.

      	SV*	newSVhek(const HEK *hek)

- newSViv

  Creates a new SV and copies an integer into it. The reference count for the SV is set to 1.

      	SV*	newSViv(IV i)

- 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(NV n)

- newSVpv

  Creates a new SV and copies a string into it. The reference count for the SV is set to 1. If `len` is zero, Perl will compute the length using strlen(). For efficiency, consider using `newSVpvn` instead.

      	SV*	newSVpv(const char* s, STRLEN len)

- newSVpvf

  Creates a new SV and initializes it with the string formatted like `sprintf`.

      	SV*	newSVpvf(const char* pat, ...)

- newSVpvn

  Creates a new SV and copies a string into it. The reference count for the SV is set to 1. Note that if `len` is zero, Perl will create a zero length string. You are responsible for ensuring that the source string is at least `len` bytes long. If the `s` argument is NULL the new SV will be undefined.

      	SV*	newSVpvn(const char* s, STRLEN len)

- newSVpvn_flags

  Creates a new SV and copies a string into it. The reference count for the SV is set to 1. Note that if `len` is zero, Perl will create a zero length string. You are responsible for ensuring that the source string is at least `len` bytes long. If the `s` argument is NULL the new SV will be undefined. Currently the only flag bits accepted are `SVf_UTF8` and `SVs_TEMP` . If `SVs_TEMP` is set, then `sv2mortal()` is called on the result before returning. If `SVf_UTF8` is set, then it will be set on the new SV. `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* s, STRLEN len, U32 flags)

- newSVpvn_share

  Creates a new SV with its 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 READONLY and FAKE. If the `hash` parameter is non-zero, that value is used; otherwise the hash is computed. The string's hash can be later be retrieved from the SV with the `SvSHARED_HASH()` macro. The idea here is that as the string table is used for shared hash keys these strings will have SvPVX_const == HeKEY and hash lookup will avoid string compare.

      	SV*	newSVpvn_share(const char* s, I32 len, U32 hash)

- newSVpvs

  Like `newSVpvn` , but takes a literal string instead of a string/length pair.

      	SV*	newSVpvs(const char* s)

- newSVpvs_flags

  Like `newSVpvn_flags` , but takes a literal string instead of a string/length pair.

      	SV*	newSVpvs_flags(const char* s, U32 flags)

- newSVpvs_share

  Like `newSVpvn_share` , but takes a literal string instead of a string/length pair and omits the hash parameter.

      	SV*	newSVpvs_share(const char* s)

- newSVrv

  Creates a new SV for the RV, `rv` , to point to. If `rv` is not an RV then it will be upgraded to one. If `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.

      	SV*	newSVrv(SV* rv, const char* classname)

- newSVsv

  Creates a new SV which is an exact duplicate of the original SV. (Uses `sv_setsv` ).

      	SV*	newSVsv(SV* old)

- newSVuv

  Creates a new SV and copies an unsigned integer into it. The reference count for the SV is set to 1.

      	SV*	newSVuv(UV u)

- newSV_type

  Creates a new SV, of the type specified. The reference count for the new SV is set to 1.

      	SV*	newSV_type(svtype type)

- sv_2bool

  This function is only called on magical items, and is only used by sv_true() or its macro equivalent.

      	bool	sv_2bool(SV* sv)

- sv_2cv

  Using various gambits, try to get a CV from an SV; in addition, try if possible to set `*st` and `*gvp` to the stash and GV associated with it. The flags in `lref` are passed to sv_fetchsv.

      	CV*	sv_2cv(SV* sv, HV** st, GV** gvp, I32 lref)

- 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.

      	IO*	sv_2io(SV* sv)

- sv_2iv_flags

  Return the integer value of an SV, doing any necessary string conversion. If flags includes SV_GMAGIC, does an mg_get() first. Normally used via the `SvIV(sv)` and `SvIVx(sv)` macros.

      	IV	sv_2iv_flags(SV* sv, I32 flags)

- sv_2mortal

  Marks an existing SV as mortal. The SV will be destroyed "soon", either by an explicit call to FREETMPS, or by an implicit call at places such as statement boundaries. SvTEMP() is turned on which means that the SV's string buffer can be "stolen" if this SV is copied. See also `sv_newmortal` and `sv_mortalcopy` .

      	SV*	sv_2mortal(SV* sv)

- sv_2nv

  Return the num value of an SV, doing any necessary string or integer conversion, magic etc. Normally used via the `SvNV(sv)` and `SvNVx(sv)` macros.

      	NV	sv_2nv(SV* sv)

- sv_2pvbyte

  Return a pointer to the byte-encoded representation of the SV, and set *lp to its length. May cause the SV to be downgraded from UTF-8 as a side-effect.

  Usually accessed via the `SvPVbyte` macro.

      	char*	sv_2pvbyte(SV* sv, STRLEN* lp)

- sv_2pvutf8

  Return a pointer to the UTF-8-encoded representation of the SV, and set *lp to its length. May cause the SV to be upgraded to UTF-8 as a side-effect.

  Usually accessed via the `SvPVutf8` macro.

      	char*	sv_2pvutf8(SV* sv, STRLEN* lp)

- sv_2pv_flags

  Returns a pointer to the string value of an SV, and sets *lp to its length. If flags includes SV_GMAGIC, does an mg_get() first. Coerces sv to a string if necessary. Normally invoked via the `SvPV_flags` macro. `sv_2pv()` and `sv_2pv_nomg` usually end up here too.

      	char*	sv_2pv_flags(SV* sv, STRLEN* lp, I32 flags)

- sv_2uv_flags

  Return the unsigned integer value of an SV, doing any necessary string conversion. If flags includes SV_GMAGIC, does an mg_get() first. Normally used via the `SvUV(sv)` and `SvUVx(sv)` macros.

      	UV	sv_2uv_flags(SV* sv, I32 flags)

- sv_backoff

  Remove any string offset. You should normally use the `SvOOK_off` macro wrapper instead.

      	int	sv_backoff(SV* sv)

- sv_bless

  Blesses an SV into a specified package. The SV must be an RV. The package must be designated by its stash (see `gv_stashpv()` ). The reference count of the SV is unaffected.

      	SV*	sv_bless(SV* sv, HV* stash)

- sv_catpv

  Concatenates the 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 `sv_catpv_mg` .

      	void	sv_catpv(SV* sv, const char* ptr)

- sv_catpvf

  Processes its arguments like `sprintf` and appends the formatted output to an SV. If the appended data contains "wide" characters (including, but not limited to, SVs with a UTF-8 PV formatted with %s, and characters >255 formatted with %c), the original SV might get upgraded to UTF-8. Handles 'get' magic, but not 'set' magic. See `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* sv, const char* pat, ...)

- sv_catpvf_mg

  Like `sv_catpvf` , but also handles 'set' magic.

      	void	sv_catpvf_mg(SV *sv, const char* pat, ...)

- sv_catpvn

  Concatenates the string onto the end of the string which is in the SV. The `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 `sv_catpvn_mg` .

      	void	sv_catpvn(SV *dsv, const char *sstr, STRLEN len)

- sv_catpvn_flags

  Concatenates the string onto the end of the string which is in the SV. The `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. If `flags` has `SV_GMAGIC` bit set, will `mg_get` on `dsv` if appropriate, else not. `sv_catpvn` and `sv_catpvn_nomg` are implemented in terms of this function.

      	void	sv_catpvn_flags(SV *dstr, const char *sstr, STRLEN len, I32 flags)

- sv_catpvs

  Like `sv_catpvn` , but takes a literal string instead of a string/length pair.

      	void	sv_catpvs(SV* sv, const char* s)

- sv_catpv_mg

  Like `sv_catpv` , but also handles 'set' magic.

      	void	sv_catpv_mg(SV *sv, const char *ptr)

- sv_catsv

  Concatenates the string from SV `ssv` onto the end of the string in SV `dsv` . Modifies `dsv` but not `ssv` . Handles 'get' magic, but not 'set' magic. See `sv_catsv_mg` .

      	void	sv_catsv(SV *dstr, SV *sstr)

- sv_catsv_flags

  Concatenates the string from SV `ssv` onto the end of the string in SV `dsv` . Modifies `dsv` but not `ssv` . If `flags` has `SV_GMAGIC` bit set, will `mg_get` on the SVs if appropriate, else not. `sv_catsv` and `sv_catsv_nomg` are implemented in terms of this function.

      	void	sv_catsv_flags(SV* dsv, SV* ssv, I32 flags)

- sv_chop

  Efficient removal of characters from the beginning of the string buffer. SvPOK(sv) must be true and the `ptr` must be a pointer to somewhere inside the string buffer. The `ptr` becomes the first character of the adjusted string. Uses the "OOK hack". Beware: after this function returns, `ptr` and SvPVX_const(sv) may no longer refer to the same chunk of data.

      	void	sv_chop(SV* sv, const char* ptr)

- 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 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 REFCNT is zero. Most of the time you'll want to call `sv_free()` (or its macro wrapper `SvREFCNT_dec` ) instead.

      	void	sv_clear(SV* sv)

- sv_cmp

  Compares the strings in two SVs. Returns -1, 0, or 1 indicating whether the string in `sv1` is less than, equal to, or greater than the string in `sv2` . Is UTF-8 and 'use bytes' aware, handles get magic, and will coerce its args to strings if necessary. See also `sv_cmp_locale` .

      	I32	sv_cmp(SV* sv1, SV* sv2)

- sv_cmp_locale

  Compares the strings in two SVs in a locale-aware manner. Is UTF-8 and 'use bytes' aware, handles get magic, and will coerce its args to strings if necessary. See also `sv_cmp` .

      	I32	sv_cmp_locale(SV* sv1, SV* sv2)

- sv_collxfrm

  Add Collate Transform magic to an SV if it doesn't already have it.

  Any scalar variable may carry 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(SV* sv, STRLEN* nxp)

- sv_copypv

  Copies a stringified representation of the source SV into the destination SV. Automatically performs any necessary mg_get and coercion of numeric values into strings. Guaranteed to preserve UTF8 flag even from overloaded objects. Similar in nature to sv_2pv[_flags] but operates directly on an SV instead of just the string. Mostly uses sv_2pv_flags to do its work, except when that would lose the UTF-8'ness of the PV.

      	void	sv_copypv(SV* dsv, SV* ssv)

- sv_dec

  Auto-decrement of the value in the SV, doing string to numeric conversion if necessary. Handles 'get' magic.

      	void	sv_dec(SV* sv)

- sv_eq

  Returns a boolean indicating whether the strings in the two SVs are identical. Is UTF-8 and 'use bytes' aware, handles get magic, and will coerce its args to strings if necessary.

      	I32	sv_eq(SV* sv1, SV* sv2)

- sv_force_normal_flags

  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 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 `SV_COW_DROP_PV` is set then a copy-on-write scalar drops its PV buffer (if any) and becomes SvPOK_off rather than making a copy. (Used where this scalar is about to be set to some other value.) In addition, the `flags` parameter gets passed to `sv_unref_flags()` when unrefing. `sv_force_normal` calls this function with flags set to 0.

      	void	sv_force_normal_flags(SV *sv, U32 flags)

- sv_free

  Decrement an SV's reference count, and if it drops to zero, call `sv_clear` to invoke destructors and free up any memory used by the body; finally, deallocate the SV's head itself. Normally called via a wrapper macro `SvREFCNT_dec` .

      	void	sv_free(SV* sv)

- sv_gets

  Get a line from the filehandle and store it into the SV, optionally appending to the currently-stored string.

      	char*	sv_gets(SV* sv, PerlIO* fp, I32 append)

- sv_grow

  Expands the character buffer in the SV. If necessary, uses `sv_unref` and upgrades the SV to `SVt_PV` . Returns a pointer to the character buffer. Use the `SvGROW` wrapper instead.

      	char*	sv_grow(SV* sv, STRLEN newlen)

- sv_inc

  Auto-increment of the value in the SV, doing string to numeric conversion if necessary. Handles 'get' magic.

      	void	sv_inc(SV* sv)

- sv_insert

  Inserts a string at the specified offset/length within the SV. Similar to the Perl substr() function. Handles get magic.

      	void	sv_insert(SV *bigstr, STRLEN offset, STRLEN len, const char *little, STRLEN littlelen)

- sv_insert_flags

  Same as `sv_insert` , but the extra `flags` are passed the `SvPV_force_flags` that applies to `bigstr` .

      	void	sv_insert_flags(SV *const bigstr, const STRLEN offset, const STRLEN len, const char *const little, const STRLEN littlelen, const U32 flags)

- sv_isa

  Returns a boolean indicating whether the SV is blessed into the specified class. This does not check for subtypes; use `sv_derived_from` to verify an inheritance relationship.

      	int	sv_isa(SV* sv, const char* name)

- 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)

- sv_len

  Returns the length of the string in the SV. Handles magic and type coercion. See also `SvCUR` , which gives raw access to the xpv_cur slot.

      	STRLEN	sv_len(SV* sv)

- 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* sv)

- sv_magic

  Adds magic to an SV. First upgrades `sv` to type `SVt_PVMG` if necessary, then adds a new magic item of type `how` to the head of the magic list.

  See `sv_magicext` (which `sv_magic` now calls) for a description of the handling of the `name` and `namlen` arguments.

  You need to use `sv_magicext` to add magic to SvREADONLY SVs and also to add more than one instance of the same 'how'.

      	void	sv_magic(SV* sv, SV* obj, int how, const char* name, I32 namlen)

- sv_magicext

  Adds magic to an SV, upgrading it if necessary. Applies the supplied vtable and returns a pointer to the magic added.

  Note that `sv_magicext` will allow things that `sv_magic` will not. In particular, you can add magic to SvREADONLY SVs, and add more than one instance of the same 'how'.

  If `namlen` is greater than zero then a `savepvn` copy of `name` is stored, if `namlen` is zero then `name` is stored as-is and - as another special case - if `(name && namlen == HEf_SVKEY)` then `name` is assumed to contain an `SV*` and is stored as-is with its REFCNT incremented.

  (This is now used as a subroutine by `sv_magic` .)

      	MAGIC *	sv_magicext(SV* sv, SV* obj, int how, const MGVTBL *vtbl, const char* name, I32 namlen)

- sv_mortalcopy

  Creates a new SV which is a copy of the original SV (using `sv_setsv` ). The new SV is marked as mortal. It will be destroyed "soon", either by an explicit call to FREETMPS, or by an implicit call at places such as statement boundaries. See also `sv_newmortal` and `sv_2mortal` .

      	SV*	sv_mortalcopy(SV* oldsv)

- 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 FREETMPS, or by an implicit call at places such as statement boundaries. See also `sv_mortalcopy` and `sv_2mortal` .

      	SV*	sv_newmortal()

- sv_newref

  Increment an SV's reference count. Use the `SvREFCNT_inc()` wrapper instead.

      	SV*	sv_newref(SV* sv)

- sv_pos_b2u

  Converts the value pointed to by 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.

      	void	sv_pos_b2u(SV* sv, I32* offsetp)

- sv_pos_u2b

  Converts the value pointed to by offsetp from a count of UTF-8 chars from the start of the string, to a count of the equivalent number of bytes; if lenp is non-zero, it does the same to lenp, but this time starting from the offset, rather than from the start of the string. Handles magic and type coercion.

      	void	sv_pos_u2b(SV* sv, I32* offsetp, I32* lenp)

- sv_pvbyten_force

  The backend for the `SvPVbytex_force` macro. Always use the macro instead.

      	char*	sv_pvbyten_force(SV* sv, STRLEN* lp)

- sv_pvn_force

  Get a sensible string out of the SV somehow. A private implementation of the `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)

- sv_pvn_force_flags

  Get a sensible string out of the SV somehow. If `flags` has `SV_GMAGIC` bit set, will `mg_get` on `sv` if appropriate, else not. `sv_pvn_force` and `sv_pvn_force_nomg` are implemented in terms of this function. You normally want to use the various wrapper macros instead: see `SvPV_force` and `SvPV_force_nomg`

      	char*	sv_pvn_force_flags(SV* sv, STRLEN* lp, I32 flags)

- sv_pvutf8n_force

  The backend for the `SvPVutf8x_force` macro. Always use the macro instead.

      	char*	sv_pvutf8n_force(SV* sv, STRLEN* lp)

- sv_reftype

  Returns a string describing what the SV is a reference to.

      	const char*	sv_reftype(const SV* sv, int ob)

- 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 `sv_setsv` or one of its many macro front-ends.

      	void	sv_replace(SV* sv, SV* nsv)

- sv_reset

  Underlying implementation for the `reset` Perl function. Note that the perl-level function is vaguely deprecated.

      	void	sv_reset(const char* s, HV* stash)

- sv_rvweaken

  Weaken a reference: set the `SvWEAKREF` flag on this RV; give the referred-to SV `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.

      	SV*	sv_rvweaken(SV *sv)

- sv_setiv

  Copies an integer into the given SV, upgrading first if necessary. Does not handle 'set' magic. See also `sv_setiv_mg` .

      	void	sv_setiv(SV* sv, IV num)

- sv_setiv_mg

  Like `sv_setiv` , but also handles 'set' magic.

      	void	sv_setiv_mg(SV *sv, IV i)

- sv_setnv

  Copies a double into the given SV, upgrading first if necessary. Does not handle 'set' magic. See also `sv_setnv_mg` .

      	void	sv_setnv(SV* sv, NV num)

- sv_setnv_mg

  Like `sv_setnv` , but also handles 'set' magic.

      	void	sv_setnv_mg(SV *sv, NV num)

- sv_setpv

  Copies a string into an SV. The string must be null-terminated. Does not handle 'set' magic. See `sv_setpv_mg` .

      	void	sv_setpv(SV* sv, const char* ptr)

- sv_setpvf

  Works like `sv_catpvf` but copies the text into the SV instead of appending it. Does not handle 'set' magic. See `sv_setpvf_mg` .

      	void	sv_setpvf(SV* sv, const char* pat, ...)

- sv_setpvf_mg

  Like `sv_setpvf` , but also handles 'set' magic.

      	void	sv_setpvf_mg(SV *sv, const char* pat, ...)

- sv_setpviv

  Copies an integer into the given SV, also updating its string value. Does not handle 'set' magic. See `sv_setpviv_mg` .

      	void	sv_setpviv(SV* sv, IV num)

- sv_setpviv_mg

  Like `sv_setpviv` , but also handles 'set' magic.

      	void	sv_setpviv_mg(SV *sv, IV iv)

- sv_setpvn

  Copies a string into an SV. The `len` parameter indicates the number of bytes to be copied. If the `ptr` argument is NULL the SV will become undefined. Does not handle 'set' magic. See `sv_setpvn_mg` .

      	void	sv_setpvn(SV* sv, const char* ptr, STRLEN len)

- sv_setpvn_mg

  Like `sv_setpvn` , but also handles 'set' magic.

      	void	sv_setpvn_mg(SV *sv, const char *ptr, STRLEN len)

- sv_setpvs

  Like `sv_setpvn` , but takes a literal string instead of a string/length pair.

      	void	sv_setpvs(SV* sv, const char* s)

- sv_setpv_mg

  Like `sv_setpv` , but also handles 'set' magic.

      	void	sv_setpv_mg(SV *sv, const char *ptr)

- sv_setref_iv

  Copies an integer into a new SV, optionally blessing the SV. The `rv` argument will be upgraded to an RV. That RV will be modified to point to the new SV. The `classname` argument indicates the package for the blessing. Set `classname` to `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* rv, const char* classname, IV iv)

- sv_setref_nv

  Copies a double into a new SV, optionally blessing the SV. The `rv` argument will be upgraded to an RV. That RV will be modified to point to the new SV. The `classname` argument indicates the package for the blessing. Set `classname` to `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* rv, const char* classname, NV nv)

- sv_setref_pv

  Copies a pointer into a new SV, optionally blessing the SV. The `rv` argument will be upgraded to an RV. That RV will be modified to point to the new SV. If the `pv` argument is NULL then `PL_sv_undef` will be placed into the SV. The `classname` argument indicates the package for the blessing. Set `classname` to `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 `sv_setref_pvn` copies the string while this copies the pointer.

      	SV*	sv_setref_pv(SV* rv, const char* classname, void* pv)

- sv_setref_pvn

  Copies a string into a new SV, optionally blessing the SV. The length of the string must be specified with `n` . The `rv` argument will be upgraded to an RV. That RV will be modified to point to the new SV. The `classname` argument indicates the package for the blessing. Set `classname` to `NULL` to avoid the blessing. The new SV will have a reference count of 1, and the RV will be returned.

  Note that `sv_setref_pv` copies the pointer while this copies the string.

      	SV*	sv_setref_pvn(SV* rv, const char* classname, const char* pv, STRLEN n)

- sv_setref_uv

  Copies an unsigned integer into a new SV, optionally blessing the SV. The `rv` argument will be upgraded to an RV. That RV will be modified to point to the new SV. The `classname` argument indicates the package for the blessing. Set `classname` to `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* rv, const char* classname, UV uv)

- sv_setsv

  Copies the contents of the source SV `ssv` into the destination SV `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.

  You probably want to use one of the assortment of wrappers, such as `SvSetSV` , `SvSetSV_nosteal` , `SvSetMagicSV` and `SvSetMagicSV_nosteal` .

      	void	sv_setsv(SV *dstr, SV *sstr)

- sv_setsv_flags

  Copies the contents of the source SV `ssv` into the destination SV `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 `flags` parameter has the `SV_GMAGIC` bit set, will `mg_get` on `ssv` if appropriate, else not. If the `flags` parameter has the `NOSTEAL` bit set then the buffers of temps will not be stolen. <sv_setsv> and `sv_setsv_nomg` are implemented in terms of this function.

  You probably want to use one of the assortment of wrappers, such as `SvSetSV` , `SvSetSV_nosteal` , `SvSetMagicSV` and `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, I32 flags)

- sv_setsv_mg

  Like `sv_setsv` , but also handles 'set' magic.

      	void	sv_setsv_mg(SV *dstr, SV *sstr)

- sv_setuv

  Copies an unsigned integer into the given SV, upgrading first if necessary. Does not handle 'set' magic. See also `sv_setuv_mg` .

      	void	sv_setuv(SV* sv, UV num)

- sv_setuv_mg

  Like `sv_setuv` , but also handles 'set' magic.

      	void	sv_setuv_mg(SV *sv, UV u)

- sv_tainted

  Test an SV for taintedness. Use `SvTAINTED` instead. bool sv_tainted(SV* sv)

- sv_true

  Returns true if the SV has a true value by Perl's rules. Use the `SvTRUE` macro instead, which may call `sv_true()` or may instead use an in-line version.

      	I32	sv_true(SV *sv)

- sv_unmagic

  Removes all magic of type `type` from an SV.

      	int	sv_unmagic(SV* sv, int type)

- 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 `newSVrv` . The `cflags` argument can contain `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 `SvROK_off` .

      	void	sv_unref_flags(SV *ref, U32 flags)

- sv_untaint

  Untaint an SV. Use `SvTAINTED_off` instead. void sv_untaint(SV* sv)

- 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. You generally want to use the `SvUPGRADE` macro wrapper. See also `svtype` .

      	void	sv_upgrade(SV* sv, svtype new_type)

- sv_usepvn_flags

  Tells an SV to use `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. The `ptr` should point to memory that was allocated by `malloc` . The string length, `len` , must be supplied. By default this function will realloc (i.e. move) the memory pointed to by `ptr` , so that pointer should not be freed or used by the programmer after giving it to sv_usepvn, and neither should any pointers from "behind" that pointer (e.g. ptr + 1) be used.

  If `flags` & SV_SMAGIC is true, will call SvSETMAGIC. If `flags` & SV_HAS_TRAILING_NUL is true, then `ptr[len]` must be NUL, and the realloc will be skipped. (i.e. the buffer is actually at least 1 byte longer than `len` , and already meets the requirements for storing in `SvPVX` )

      	void	sv_usepvn_flags(SV* sv, char* ptr, STRLEN len, U32 flags)

- sv_utf8_decode

  If the PV of the SV is an octet sequence in UTF-8 and contains a multiple-byte character, the `SvUTF8` flag is turned on so that it looks like a character. If the PV contains only single-byte characters, the `SvUTF8` flag stays being off. Scans PV for validity and returns false if the PV is invalid UTF-8.

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

      	bool	sv_utf8_decode(SV *sv)

- 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 `fail_ok` is not true, croaks.

  This is not as a general purpose Unicode to byte encoding interface: use the Encode extension for that.

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

      	bool	sv_utf8_downgrade(SV *sv, bool fail_ok)

- sv_utf8_encode

  Converts the PV of an SV to UTF-8, but then turns the `SvUTF8` flag off so that it looks like octets again.

      	void	sv_utf8_encode(SV *sv)

- 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 `mg_get` on `sv` if appropriate. Always sets the 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 as a general purpose byte encoding to Unicode interface: use the Encode extension for that.

      	STRLEN	sv_utf8_upgrade(SV *sv)

- 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 `flags` has `SV_GMAGIC` bit set, will `mg_get` on `sv` if appropriate, else not. Returns the number of bytes in the converted string `sv_utf8_upgrade` and `sv_utf8_upgrade_nomg` are implemented in terms of this function.

  This is not as a general purpose byte encoding to Unicode interface: use the Encode extension for that.

      	STRLEN	sv_utf8_upgrade_flags(SV *sv, I32 flags)

- sv_utf8_upgrade_nomg

  Like sv_utf8_upgrade, but doesn't do magic on `sv`

      	STRLEN	sv_utf8_upgrade_nomg(SV *sv)

- sv_vcatpvf

  Processes its arguments like `vsprintf` and appends the formatted output to an SV. Does not handle 'set' magic. See `sv_vcatpvf_mg` .

  Usually used via its frontend `sv_catpvf` .

      	void	sv_vcatpvf(SV* sv, const char* pat, va_list* args)

- sv_vcatpvfn

  Processes its arguments like `vsprintf` and appends the formatted output to an SV. Uses an array of SVs if the C style variable argument list is missing (NULL). When running with taint checks enabled, indicates via `maybe_tainted` if results are untrustworthy (often due to the use of locales).

  Usually used via one of its frontends `sv_vcatpvf` and `sv_vcatpvf_mg` .

      	void	sv_vcatpvfn(SV* sv, const char* pat, STRLEN patlen, va_list* args, SV** svargs, I32 svmax, bool *maybe_tainted)

- sv_vcatpvf_mg

  Like `sv_vcatpvf` , but also handles 'set' magic.

  Usually used via its frontend `sv_catpvf_mg` .

      	void	sv_vcatpvf_mg(SV* sv, const char* pat, va_list* args)

- sv_vsetpvf

  Works like `sv_vcatpvf` but copies the text into the SV instead of appending it. Does not handle 'set' magic. See `sv_vsetpvf_mg` .

  Usually used via its frontend `sv_setpvf` .

      	void	sv_vsetpvf(SV* sv, const char* pat, va_list* args)

- sv_vsetpvfn

  Works like `sv_vcatpvfn` but copies the text into the SV instead of appending it.

  Usually used via one of its frontends `sv_vsetpvf` and `sv_vsetpvf_mg` .

      	void	sv_vsetpvfn(SV* sv, const char* pat, STRLEN patlen, va_list* args, SV** svargs, I32 svmax, bool *maybe_tainted)

- sv_vsetpvf_mg

  Like `sv_vsetpvf` , but also handles 'set' magic.

  Usually used via its frontend `sv_setpvf_mg` .

      	void	sv_vsetpvf_mg(SV* sv, const char* pat, va_list* args)

# Unicode Support

- bytes_from_utf8

  Converts a string `s` of length `len` from UTF-8 into native byte encoding. Unlike `utf8_to_bytes` but like `bytes_to_utf8` , returns a pointer to the newly-created string, and updates `len` to contain the new length. Returns the original string if no conversion occurs, `len` is unchanged. Do nothing if `is_utf8` points to 0. Sets `is_utf8` to 0 if `s` is converted or consisted entirely of characters that are invariant in utf8 (i.e., US-ASCII on non-EBCDIC machines).

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

      	U8*	bytes_from_utf8(const U8 *s, STRLEN *len, bool *is_utf8)

- bytes_to_utf8

  Converts a string `s` of length `len` from the native encoding into UTF-8. Returns a pointer to the newly-created string, and sets `len` to reflect the new length.

  A 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 sv_recode_to_utf8().

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

      	U8*	bytes_to_utf8(const U8 *s, STRLEN *len)

- ibcmp_utf8

  Return true if the strings s1 and s2 differ case-insensitively, false if not (if they are equal case-insensitively). If u1 is true, the string s1 is assumed to be in UTF-8-encoded Unicode. If u2 is true, the string s2 is assumed to be in UTF-8-encoded Unicode. If u1 or u2 are false, the respective string is assumed to be in native 8-bit encoding.

  If the pe1 and pe2 are non-NULL, the scanning pointers will be copied in there (they will point at the beginning of the next character). If the pointers behind pe1 or pe2 are non-NULL, they are the end pointers beyond which scanning will not continue under any circumstances. If the byte lengths l1 and l2 are non-zero, s1+l1 and s2+l2 will be used as goal end pointers that will also stop the scan, and which qualify towards defining a successful match: all the scans that define an explicit length must reach their goal pointers for a match to succeed).

  For case-insensitiveness, the "casefolding" of Unicode is used instead of upper/lowercasing both the characters, see http://www.unicode.org/unicode/reports/tr21/ (Case Mappings).

      	I32	ibcmp_utf8(const char *s1, char **pe1, UV l1, bool u1, const char *s2, char **pe2, UV l2, bool u2)

- is_utf8_char

  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.

      	STRLEN	is_utf8_char(const U8 *s)

- is_utf8_string

  Returns true if first `len` bytes of the given string form a valid UTF-8 string, false otherwise. Note that 'a valid UTF-8 string' does not mean 'a string that contains code points above 0x7F encoded in UTF-8' because a valid ASCII string is a valid UTF-8 string.

  See also is_utf8_string_loclen() and is_utf8_string_loc().

      	bool	is_utf8_string(const U8 *s, STRLEN len)

- is_utf8_string_loc

  Like is_utf8_string() but stores the location of the failure (in the case of "utf8ness failure") or the location s+len (in the case of "utf8ness success") in the `ep` .

  See also is_utf8_string_loclen() and is_utf8_string().

      	bool	is_utf8_string_loc(const U8 *s, STRLEN len, const U8 **p)

- is_utf8_string_loclen

  Like is_utf8_string() but stores the location of the failure (in the case of "utf8ness failure") or the location s+len (in the case of "utf8ness success") in the `ep` , and the number of UTF-8 encoded characters in the `el` .

  See also is_utf8_string_loc() and is_utf8_string().

      	bool	is_utf8_string_loclen(const U8 *s, STRLEN len, const U8 **ep, STRLEN *el)

- pv_uni_display

  Build to the scalar dsv a displayable version of the string spv, length len, the displayable version being at most pvlim bytes long (if longer, the rest is truncated and "..." will be appended).

  The flags argument can have UNI_DISPLAY_ISPRINT set to display isPRINT()able characters as themselves, UNI_DISPLAY_BACKSLASH to display the \\[nrfta\\] as the backslashed versions (like '\n') (UNI_DISPLAY_BACKSLASH is preferred over UNI_DISPLAY_ISPRINT for \\). UNI_DISPLAY_QQ (and its alias UNI_DISPLAY_REGEX) have both UNI_DISPLAY_BACKSLASH and UNI_DISPLAY_ISPRINT turned on.

  The pointer to the PV of the dsv is returned.

      	char*	pv_uni_display(SV *dsv, const U8 *spv, STRLEN len, STRLEN pvlim, UV flags)

- sv_cat_decode

  The encoding is assumed to be an Encode object, the PV of the ssv is assumed to be octets in that encoding and decoding the input starts from the position which (PV + *offset) pointed to. The dsv will be concatenated the decoded UTF-8 string from ssv. Decoding will terminate when the string tstr appears in decoding output or the input ends on the PV of the ssv. The value which the offset points will be modified to the last input position on the 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)

- sv_recode_to_utf8

  The encoding is assumed to be an Encode object, on entry the PV of the sv is assumed to be octets in that encoding, and the sv will be converted into Unicode (and UTF-8).

  If the sv already is UTF-8 (or if it is not POK), or if the encoding is not a reference, nothing is done to the sv. If the encoding is not an `Encode::XS` Encoding object, bad things will happen. (See lib/encoding.pm and Encode).

  The PV of the sv is returned.

      	char*	sv_recode_to_utf8(SV* sv, SV *encoding)

- sv_uni_display

  Build to the scalar dsv a displayable version of the scalar sv, the displayable version being at most pvlim bytes long (if longer, the rest is truncated and "..." will be appended).

  The flags argument is as in pv_uni_display().

  The pointer to the PV of the dsv is returned.

      	char*	sv_uni_display(SV *dsv, SV *ssv, STRLEN pvlim, UV flags)

- to_utf8_case

  The "p" contains the pointer to the UTF-8 string encoding the character that is being converted.

  The "ustrp" is a pointer to the character buffer to put the conversion result to. The "lenp" is a pointer to the length of the result.

  The "swashp" is a pointer to the swash to use.

  Both the special and normal mappings are stored lib/unicore/To/Foo.pl, and loaded by SWASHNEW, using lib/utf8_heavy.pl. The special (usually, but not always, a multicharacter mapping), is tried first.

  The "special" is a string like "utf8::ToSpecLower", which means the hash %utf8::ToSpecLower. The access to the hash is through Perl_to_utf8_case().

  The "normal" is a string like "ToLower" which means the swash %utf8::ToLower.

      	UV	to_utf8_case(const U8 *p, U8* ustrp, STRLEN *lenp, SV **swashp, const char *normal, const char *special)

- to_utf8_fold

  Convert the UTF-8 encoded character at p to its foldcase version and store that in UTF-8 in ustrp and its length in bytes in lenp. Note that the ustrp needs to be at least UTF8_MAXBYTES_CASE+1 bytes since the foldcase version may be longer than the original character (up to three characters).

  The first character of the foldcased version is returned (but note, as explained above, that there may be more.)

      	UV	to_utf8_fold(const U8 *p, U8* ustrp, STRLEN *lenp)

- to_utf8_lower

  Convert the UTF-8 encoded character at p to its lowercase version and store that in UTF-8 in ustrp and its length in bytes in lenp. Note that the ustrp needs to be at least UTF8_MAXBYTES_CASE+1 bytes since the lowercase version may be longer than the original character.

  The first character of the lowercased version is returned (but note, as explained above, that there may be more.)

      	UV	to_utf8_lower(const U8 *p, U8* ustrp, STRLEN *lenp)

- to_utf8_title

  Convert the UTF-8 encoded character at p to its titlecase version and store that in UTF-8 in ustrp and its length in bytes in lenp. Note that the ustrp needs to be at least UTF8_MAXBYTES_CASE+1 bytes since the titlecase version may be longer than the original character.

  The first character of the titlecased version is returned (but note, as explained above, that there may be more.)

      	UV	to_utf8_title(const U8 *p, U8* ustrp, STRLEN *lenp)

- to_utf8_upper

  Convert the UTF-8 encoded character at p to its uppercase version and store that in UTF-8 in ustrp and its length in bytes in lenp. Note that the ustrp needs to be at least UTF8_MAXBYTES_CASE+1 bytes since the uppercase version may be longer than the original character.

  The first character of the uppercased version is returned (but note, as explained above, that there may be more.)

      	UV	to_utf8_upper(const U8 *p, U8* ustrp, STRLEN *lenp)

- utf8n_to_uvchr

  flags

  Returns the native character value of the first character in the string `s` which is assumed to be in UTF-8 encoding; `retlen` will be set to the length, in bytes, of that character.

  Allows length and flags to be passed to low level routine.

      	UV	utf8n_to_uvchr(const U8 *s, STRLEN curlen, STRLEN *retlen, U32 flags)

- utf8n_to_uvuni

  Bottom level UTF-8 decode routine. Returns the Unicode code point value of the first character in the string `s` which is assumed to be in UTF-8 encoding and no longer than `curlen` ; `retlen` will be set to the length, in bytes, of that character.

  If `s` does not point to a well-formed UTF-8 character, the behaviour is dependent on the value of `flags` : if it contains UTF8_CHECK_ONLY, it is assumed that the caller will raise a warning, and this function will silently just set `retlen` to `-1` and return zero. If the `flags` does not contain UTF8_CHECK_ONLY, warnings about malformations will be given, `retlen` will be set to the expected length of the UTF-8 character in bytes, and zero will be returned.

  The `flags` can also contain various flags to allow deviations from the strict UTF-8 encoding (see utf8.h).

  Most code should use utf8_to_uvchr() rather than call this directly.

      	UV	utf8n_to_uvuni(const U8 *s, STRLEN curlen, STRLEN *retlen, U32 flags)

- utf8_distance

  Returns the number of UTF-8 characters between the UTF-8 pointers `a` and `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)

- utf8_hop

  Return the UTF-8 pointer `s` displaced by `off` characters, either forward or backward.

  WARNING: do not use the following unless you *know* `off` is within the UTF-8 data pointed to by `s` *and* that on entry `s` is aligned on the first byte of character or just after the last byte of a character.

      	U8*	utf8_hop(const U8 *s, I32 off)

- utf8_length

  Return the length of the UTF-8 char encoded string `s` in characters. Stops at `e` (inclusive). If `e < s` or if the scan would end up past `e` , croaks.

      	STRLEN	utf8_length(const U8* s, const U8 *e)

- utf8_to_bytes

  Converts a string `s` of length `len` from UTF-8 into native byte encoding. Unlike `bytes_to_utf8` , this over-writes the original string, and updates len to contain the new length. Returns zero on failure, setting `len` to -1.

  If you need a copy of the string, see `bytes_from_utf8` .

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

      	U8*	utf8_to_bytes(U8 *s, STRLEN *len)

- utf8_to_uvchr

  Returns the native character value of the first character in the string `s` which is assumed to be in UTF-8 encoding; `retlen` will be set to the length, in bytes, of that character.

  If `s` does not point to a well-formed UTF-8 character, zero is returned and retlen is set, if possible, to -1.

      	UV	utf8_to_uvchr(const U8 *s, STRLEN *retlen)

- utf8_to_uvuni

  Returns the Unicode code point of the first character in the string `s` which is assumed to be in UTF-8 encoding; `retlen` will be set to the length, in bytes, of that character.

  This function should only be used when the returned UV is considered an index into the Unicode semantic tables (e.g. swashes).

  If `s` does not point to a well-formed UTF-8 character, zero is returned and retlen is set, if possible, to -1.

      	UV	utf8_to_uvuni(const U8 *s, STRLEN *retlen)

- uvchr_to_utf8

  Adds the UTF-8 representation of the Native codepoint `uv` to the end of the string `d` ; `d` should be have at least `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;	U8*	uvchr_to_utf8(U8 *d, UV uv)

- uvuni_to_utf8_flags

  Adds the UTF-8 representation of the Unicode codepoint `uv` to the end of the string `d` ; `d` should be have at least `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 = uvuni_to_utf8_flags(d, uv, flags);

  or, in most cases,

          d = uvuni_to_utf8(d, uv);

  (which is equivalent to)

          d = uvuni_to_utf8_flags(d, uv, 0);

  is the recommended Unicode-aware way of saying

          *(d++) = uv;	U8*	uvuni_to_utf8_flags(U8 *d, UV uv, UV flags)

# Variables created by `xsubpp` and `xsubpp` internal functions

- ax

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

      	I32	ax

- CLASS

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

      	char*	CLASS

- dAX

  Sets up the `ax` variable. This is usually handled automatically by `xsubpp` by calling `dXSARGS` .

      		dAX;

- dAXMARK

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

      		dAXMARK;

- dITEMS

  Sets up the `items` variable. This is usually handled automatically by `xsubpp` by calling `dXSARGS` .

      		dITEMS;

- dUNDERBAR

  Sets up the `padoff_du` variable for an XSUB that wishes to use `UNDERBAR` .

      		dUNDERBAR;

- dXSARGS

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

      		dXSARGS;

- dXSI32

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

      		dXSI32;

- items

  Variable which is setup by `xsubpp` to indicate the number of items on the stack. See "Variable-length Parameter Lists" in perlxs.

      	I32	items

- ix

  Variable which is setup by `xsubpp` to indicate which of an XSUB's aliases was used to invoke it. See "The ALIAS: Keyword" in perlxs.

      	I32	ix

- newXSproto

  Used by `xsubpp` to hook up XSUBs as Perl subs. Adds Perl prototypes to the subs.

- RETVAL

  Variable which is setup by `xsubpp` to hold the return value for an XSUB. This is always the proper type for the XSUB. See "The RETVAL Variable" in perlxs.

      	(whatever)	RETVAL

- ST

  Used to access elements on the XSUB's stack.

      	SV*	ST(int ix)

- THIS

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

      	(whatever)	THIS

- UNDERBAR

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

- XS

  Macro to declare an XSUB and its C parameter list. This is handled by `xsubpp` .

- XS_VERSION

  The version identifier for an XS module. This is usually handled automatically by `ExtUtils::MakeMaker` . See `XS_VERSION_BOOTCHECK` .

- XS_VERSION_BOOTCHECK

  Macro to verify that a PM module's $VERSION variable matches the XS module's `XS_VERSION` variable. This is usually handled automatically by `xsubpp` . See "The VERSIONCHECK: Keyword" in perlxs.

      		XS_VERSION_BOOTCHECK;

# Warning and Dieing

- croak

  This is the XSUB-writer's interface to Perl's `die` function. Normally call this function the same way you call the C `printf` function. Calling `croak` returns control directly to Perl, sidestepping the normal C order of execution. See `warn`.

  If you want to throw an exception object, assign the object to `$@` and then pass `NULL` to croak():

         errsv = get_sv("@", GV_ADD);   sv_setsv(errsv, exception_object);   croak(NULL);	void	croak(const char* pat, ...)

- warn

  This is the XSUB-writer's interface to Perl's `warn` function. Call this function the same way you call the C `printf` function. See `croak` .

      	void	warn(const char* pat, ...)

# 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.

# SEE ALSO

perlguts(1), perlxs(1), perlxstut(1), perlintern(1)

Page index

- NAME
- DESCRIPTION
- "Gimme" Values
- Array Manipulation Functions
- Callback Functions
- Character classes
- Cloning an interpreter
- CV Manipulation Functions
- Embedding Functions
- Functions in file dump.c
- Functions in file mathoms.c
- Functions in file perl.h
- Functions in file pp_ctl.c
- Functions in file pp_pack.c
- GV Functions
- Handy Values
- Hash Manipulation Functions
- Magical Functions
- Memory Management
- Miscellaneous Functions
- MRO Functions
- Multicall Functions
- Numeric functions
- Optree Manipulation Functions
- Pad Data Structures
- Per-Interpreter Variables
- REGEXP Functions
- Simple Exception Handling Macros
- Stack Manipulation Macros
- SV Flags
- SV Manipulation Functions
- SV-Body Allocation
- Unicode Support
- Variables created by xsubpp and xsubpp internal functions
- Warning and Dieing
- AUTHORS
- SEE ALSO

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