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PERLAPI(1) Perl Programmers Reference Guide PERLAPI(1)

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. At the end is a list of functions which have yet to be documented. The interfaces of those are subject to change without notice. Any functions not listed here are not part of the public API, and should not be used by extension writers at all. For these reasons, blindly using functions listed in proto.h is to be avoided when writing extensions.

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

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

        U32     GIMME_V
Used to indicate list context. See "GIMME_V", "GIMME" and perlcall.
Indicates that arguments returned from a callback should be discarded. See perlcall.
Used to force a Perl "eval" wrapper around a callback. See perlcall.
Indicates that no arguments are being sent to a callback. See perlcall.
Used to indicate scalar context. See "GIMME_V", "GIMME", and perlcall.
Used to indicate void context. See "GIMME_V" and perlcall.

Array Manipulation Functions

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

        int     AvFILL(AV* av)
Clears an array, making it empty. Does not free the memory the av uses to store its list of scalars. If any destructors are triggered as a result, the av itself may be freed when this function returns.

Perl equivalent: "@myarray = ();".

        void    av_clear(AV *av)
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)
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)
Deletes the element indexed by "key" from the array, makes the element mortal, and returns it. If "flags" equals "G_DISCARD", the element is freed and null is returned. Perl equivalent: "my $elem = delete($myarray[$idx]);" for the non-"G_DISCARD" version and a void-context "delete($myarray[$idx]);" for the "G_DISCARD" version. 

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

Perl equivalent: "exists($myarray[$key])".

        bool    av_exists(AV *av, I32 key)
Pre-extend an array. The "key" is the index to which the array should be extended. 

        void    av_extend(AV *av, I32 key)
Returns the SV at the specified index in the array. The "key" is the index. If lval is true, you are guaranteed to get a real SV back (in case it wasn't real before), which you can then modify. Check that the return value is non-null before dereferencing it to a "SV*".

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

The rough perl equivalent is $myarray[$idx].

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

The Perl equivalent for this is $#myarray.

        I32     av_len(AV *av)
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.

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

        AV*     av_make(I32 size, SV **strp)
Pops an SV off the end of the array. Returns &PL_sv_undef if the array is empty.

Perl equivalent: "pop(@myarray);"

        SV*     av_pop(AV *av)
Pushes an SV onto the end of the array. The array will grow automatically to accommodate the addition. This takes ownership of one reference count.

Perl equivalent: "push @myarray, $elem;".

        void    av_push(AV *av, SV *val)
Shifts an SV off the beginning of the array. Returns &PL_sv_undef if the array is empty.

Perl equivalent: "shift(@myarray);"

        SV*     av_shift(AV *av)
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 "SV*" that was stored there (= "val")).

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.

Approximate Perl equivalent: "$myarray[$key] = $val;".

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)
Undefines the array. Frees the memory used by the av to store its list of scalars. If any destructors are triggered as a result, the av itself may be freed. 

        void    av_undef(AV *av)
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.

Perl equivalent: "unshift @myarray, ( (undef) x $n );"

        void    av_unshift(AV *av, I32 num)
Returns the AV of the specified Perl global or package array with the given name (so it won't work on lexical variables). "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.

Perl equivalent: "@{"$name"}".

NOTE: the perl_ form of this function is deprecated.

        AV*     get_av(const char *name, I32 flags)
Creates a new AV. The reference count is set to 1.

Perl equivalent: "my @array;".

        AV*     newAV()
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)
Sort an array, with various options. 

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

Callback Functions

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

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

NOTE: the perl_ form of this function is deprecated.

        I32     call_argv(const char* sub_name, I32 flags,
                          char** argv)
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)
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)
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)
Opening bracket on a callback. See "LEAVE" and perlcall. 

                ENTER;
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)
Tells Perl to "eval" the string in the SV. It supports the same flags as "call_sv", with the obvious exception of G_EVAL. See perlcall.

NOTE: the perl_ form of this function is deprecated.

        I32     eval_sv(SV* sv, I32 flags)
Closing bracket for temporaries on a callback. See "SAVETMPS" and perlcall. 

                FREETMPS;
Closing bracket on a callback. See "ENTER" and perlcall. 

                LEAVE;
Opening bracket for temporaries on a callback. See "FREETMPS" and perlcall. 

                SAVETMPS;

Character case changing

Converts the specified character to lowercase in the platform's native character set, if possible; otherwise returns the input character itself. 

        char    toLOWER(char ch)
Converts the specified character to uppercase in the platform's native character set, if possible; otherwise returns the input character itself. 

        char    toUPPER(char ch)

Character classes

There are three variants for all the functions in this section. The base ones operate using the character set of the platform Perl is running on. The ones with an "_A" suffix operate on the ASCII character set, and the ones with an "_L1" suffix operate on the full Latin1 character set. All are unaffected by locale and by "use bytes".

For ASCII platforms, the base function with no suffix and the one with the "_A" suffix are identical. The function with the "_L1" suffix imposes the Latin-1 character set onto the platform. That is, the code points that are ASCII are unaffected, since ASCII is a subset of Latin-1. But the non-ASCII code points are treated as if they are Latin-1 characters. For example, "isSPACE_L1()" will return true when called with the code point 0xA0, which is the Latin-1 NO-BREAK SPACE.

For EBCDIC platforms, the base function with no suffix and the one with the "_L1" suffix should be identical, since, as of this writing, the EBCDIC code pages that Perl knows about all are equivalent to Latin-1. The function that ends in an "_A" suffix will not return true unless the specified character also has an ASCII equivalent.

Returns a boolean indicating whether the specified character is an alphabetic character in the platform's native character set. See the top of this section for an explanation of variants "isALPHA_A" and "isALPHA_L1". 

        bool    isALPHA(char ch)
Returns a boolean indicating whether the specified character is one of the 128 characters in the ASCII character set. On non-ASCII platforms, it is if this character corresponds to an ASCII character. Variants "isASCII_A()" and "isASCII_L1()" are identical to "isASCII()". 

        bool    isASCII(char ch)
Returns a boolean indicating whether the specified character is a digit in the platform's native character set. Variants "isDIGIT_A" and "isDIGIT_L1" are identical to "isDIGIT". 

        bool    isDIGIT(char ch)
Returns a boolean indicating whether the specified character is a lowercase character in the platform's native character set. See the top of this section for an explanation of variants "isLOWER_A" and "isLOWER_L1". 

        bool    isLOWER(char ch)
Returns a boolean indicating whether the specified character is an octal digit, [0-7] in the platform's native character set. Variants "isOCTAL_A" and "isOCTAL_L1" are identical to "isOCTAL". 

        bool    isOCTAL(char ch)
Returns a boolean indicating whether the specified character is a whitespace character in the platform's native character set. This is the same as what "\s" matches in a regular expression. See the top of this section for an explanation of variants "isSPACE_A" and "isSPACE_L1". 

        bool    isSPACE(char ch)
Returns a boolean indicating whether the specified character is an uppercase character in the platform's native character set. See the top of this section for an explanation of variants "isUPPER_A" and "isUPPER_L1". 

        bool    isUPPER(char ch)
Returns a boolean indicating whether the specified character is a character that is any of: alphabetic, numeric, or an underscore. This is the same as what "\w" matches in a regular expression. "isALNUM()" is a synonym provided for backward compatibility. Note that it does not have the standard C language meaning of alphanumeric, since it matches an underscore and the standard meaning does not. See the top of this section for an explanation of variants "isWORDCHAR_A" and "isWORDCHAR_L1". 

        bool    isWORDCHAR(char ch)
Returns a boolean indicating whether the specified character is a hexadecimal digit, [0-9A-Fa-f]. Variants "isXDIGIT_A()" and "isXDIGIT_L1()" are identical to "isXDIGIT()". 

        bool    isXDIGIT(char ch)

Cloning an interpreter

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
                         )

Compile-time scope hooks

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

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

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

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

        void    BhkENABLE(BHK *hk, which)
Set an entry in the BHK structure, and set the flags to indicate it is valid. which is a preprocessing token indicating which entry to set. The type of ptr depends on the entry.

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

        void    BhkENTRY_set(BHK *hk, which, void *ptr)
Register a set of hooks to be called when the Perl lexical scope changes at compile time. See "Compile-time scope hooks" in perlguts.

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

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

        void    Perl_blockhook_register(pTHX_ BHK *hk)

COP Hint Hashes

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

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

        HV *    cophh_2hv(const COPHH *cophh, U32 flags)
Make and return a complete copy of the cop hints hash cophh.

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

        COPHH * cophh_copy(COPHH *cophh)
Like "cophh_delete_pvn", but takes a nul-terminated string instead of a string/length pair.

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

        COPHH * cophh_delete_pv(const COPHH *cophh,
                                const char *key, U32 hash,
                                U32 flags)
Delete a key and its associated value from the cop hints hash cophh, and returns the modified hash. The returned hash pointer is in general not the same as the hash pointer that was passed in. The input hash is consumed by the function, and the pointer to it must not be subsequently used. Use "cophh_copy" if you need both hashes.

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

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

        COPHH * cophh_delete_pvn(COPHH *cophh,
                                 const char *keypv,
                                 STRLEN keylen, U32 hash,
                                 U32 flags)
Like "cophh_delete_pvn", but takes a literal string instead of a string/length pair, and no precomputed hash.

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

        COPHH * cophh_delete_pvs(const COPHH *cophh,
                                 const char *key, U32 flags)
Like "cophh_delete_pvn", but takes a Perl scalar instead of a string/length pair.

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

        COPHH * cophh_delete_sv(const COPHH *cophh, SV *key,
                                U32 hash, U32 flags)
Like "cophh_fetch_pvn", but takes a nul-terminated string instead of a string/length pair.

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

        SV *    cophh_fetch_pv(const COPHH *cophh,
                               const char *key, U32 hash,
                               U32 flags)
Look up the entry in the cop hints hash cophh with the key specified by keypv and keylen. If flags has the "COPHH_KEY_UTF8" bit set, the key octets are interpreted as UTF-8, otherwise they are interpreted as Latin-1. hash is a precomputed hash of the key string, or zero if it has not been precomputed. Returns a mortal scalar copy of the value associated with the key, or &PL_sv_placeholder if there is no value associated with the key.

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

        SV *    cophh_fetch_pvn(const COPHH *cophh,
                                const char *keypv,
                                STRLEN keylen, U32 hash,
                                U32 flags)
Like "cophh_fetch_pvn", but takes a literal string instead of a string/length pair, and no precomputed hash.

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

        SV *    cophh_fetch_pvs(const COPHH *cophh,
                                const char *key, U32 flags)
Like "cophh_fetch_pvn", but takes a Perl scalar instead of a string/length pair.

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

        SV *    cophh_fetch_sv(const COPHH *cophh, SV *key,
                               U32 hash, U32 flags)
Discard the cop hints hash cophh, freeing all resources associated with it.

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

        void    cophh_free(COPHH *cophh)
Generate and return a fresh cop hints hash containing no entries.

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

        COPHH * cophh_new_empty()
Like "cophh_store_pvn", but takes a nul-terminated string instead of a string/length pair.

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

        COPHH * cophh_store_pv(const COPHH *cophh,
                               const char *key, U32 hash,
                               SV *value, U32 flags)
Stores a value, associated with a key, in the cop hints hash cophh, and returns the modified hash. The returned hash pointer is in general not the same as the hash pointer that was passed in. The input hash is consumed by the function, and the pointer to it must not be subsequently used. Use "cophh_copy" if you need both hashes.

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

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

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

        COPHH * cophh_store_pvn(COPHH *cophh, const char *keypv,
                                STRLEN keylen, U32 hash,
                                SV *value, U32 flags)
Like "cophh_store_pvn", but takes a literal string instead of a string/length pair, and no precomputed hash.

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

        COPHH * cophh_store_pvs(const COPHH *cophh,
                                const char *key, SV *value,
                                U32 flags)
Like "cophh_store_pvn", but takes a Perl scalar instead of a string/length pair.

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

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

COP Hint Reading

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

        HV *    cop_hints_2hv(const COP *cop, U32 flags)
Like "cop_hints_fetch_pvn", but takes a nul-terminated string instead of a string/length pair. 

        SV *    cop_hints_fetch_pv(const COP *cop,
                                   const char *key, U32 hash,
                                   U32 flags)
Look up the hint entry in the cop cop with the key specified by keypv and keylen. If flags has the "COPHH_KEY_UTF8" bit set, the key octets are interpreted as UTF-8, otherwise they are interpreted as Latin-1. hash is a precomputed hash of the key string, or zero if it has not been precomputed. Returns a mortal scalar copy of the value associated with the key, or &PL_sv_placeholder if there is no value associated with the key. 

        SV *    cop_hints_fetch_pvn(const COP *cop,
                                    const char *keypv,
                                    STRLEN keylen, U32 hash,
                                    U32 flags)
Like "cop_hints_fetch_pvn", but takes a literal string instead of a string/length pair, and no precomputed hash. 

        SV *    cop_hints_fetch_pvs(const COP *cop,
                                    const char *key, U32 flags)
Like "cop_hints_fetch_pvn", but takes a Perl scalar instead of a string/length pair. 

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

Custom Operators

Register a custom op. See "Custom Operators" in perlguts.

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

        void    Perl_custom_op_register(pTHX_ 
                                        Perl_ppaddr_t ppaddr,
                                        const XOP *xop)
Return the XOP structure for a given custom op. This function should be considered internal to OP_NAME and the other access macros: use them instead.

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

        const XOP * Perl_custom_op_xop(pTHX_ const OP *o)
Temporarily disable a member of the XOP, by clearing the appropriate flag. 

        void    XopDISABLE(XOP *xop, which)
Reenable a member of the XOP which has been disabled. 

        void    XopENABLE(XOP *xop, which)
Return a member of the XOP structure. which is a cpp token indicating which entry to return. If the member is not set this will return a default value. The return type depends on which. 

                XopENTRY(XOP *xop, which)
Set a member of the XOP structure. which is a cpp token indicating which entry to set. See "Custom Operators" in perlguts for details about the available members and how they are used. 

        void    XopENTRY_set(XOP *xop, which, value)
Return the XOP's flags. 

        U32     XopFLAGS(XOP *xop)

CV Manipulation Functions

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

This also has a special use with XS AUTOLOAD subs. See "Autoloading with XSUBs" in perlguts.

        HV*     CvSTASH(CV* 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)
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

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

        CV *    cv_clone(CV *proto)
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)
Find and return the variable that is named $_ in the lexical scope of the currently-executing function. This may be a lexical $_, or will otherwise be the global one. 

        SV *    find_rundefsv()
Find the position of the lexical $_ in the pad of the currently-executing function. Returns the offset in the current pad, or "NOT_IN_PAD" if there is no lexical $_ in scope (in which case the global one should be used instead). "find_rundefsv" is likely to be more convenient.

NOTE: the perl_ form of this function is deprecated.

        PADOFFSET find_rundefsvoffset()
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 and not NULL, 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.

The reference count for each specified "SV*" parameter is decremented.

        void    load_module(U32 flags, SV* name, SV* ver, ...)
Stub that provides thread hook for perl_destruct when there are no threads. 

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

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

        PADOFFSET pad_add_anon(CV *func, I32 optype)
Exactly like "pad_add_name_pvn", but takes a nul-terminated string instead of a string/length pair. 

        PADOFFSET pad_add_name_pv(const char *name, U32 flags,
                                  HV *typestash, HV *ourstash)
Allocates a place in the currently-compiling pad for a named lexical variable. Stores the name and other metadata in the name part of the pad, and makes preparations to manage the variable's lexical scoping. Returns the offset of the allocated pad slot.

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

    padadd_OUR          redundantly specifies if it's a package var
    padadd_STATE        variable will retain value persistently
    padadd_NO_DUP_CHECK skip check for lexical shadowing
        PADOFFSET pad_add_name_pvn(const char *namepv,
                                   STRLEN namelen, U32 flags,
                                   HV *typestash, HV *ourstash)
Exactly like "pad_add_name_pvn", but takes the name string in the form of an SV instead of a string/length pair. 

        PADOFFSET pad_add_name_sv(SV *name, U32 flags,
                                  HV *typestash, HV *ourstash)
Allocates a place in the currently-compiling pad, returning the offset of the allocated pad slot. No name is initially attached to the pad slot. tmptype is a set of flags indicating the kind of pad entry required, which will be set in the value SV for the allocated pad entry: 

    SVs_PADMY    named lexical variable ("my", "our", "state")
    SVs_PADTMP   unnamed temporary store

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

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

        PADOFFSET pad_alloc(I32 optype, U32 tmptype)
Looks up the type of the lexical variable at position po in the currently-compiling pad. If the variable is typed, the stash of the class to which it is typed is returned. If not, "NULL" is returned. 

        HV *    pad_compname_type(PADOFFSET po)
Exactly like "pad_findmy_pvn", but takes a nul-terminated string instead of a string/length pair. 

        PADOFFSET pad_findmy_pv(const char *name, U32 flags)
Given the name of a lexical variable, find its position in the currently-compiling pad. namepv/namelen specify the variable's name, including leading sigil. flags is reserved and must be zero. If it is not in the current pad but appears in the pad of any lexically enclosing scope, then a pseudo-entry for it is added in the current pad. Returns the offset in the current pad, or "NOT_IN_PAD" if no such lexical is in scope. 

        PADOFFSET pad_findmy_pvn(const char *namepv,
                                 STRLEN namelen, U32 flags)
Exactly like "pad_findmy_pvn", but takes the name string in the form of an SV instead of a string/length pair. 

        PADOFFSET pad_findmy_sv(SV *name, U32 flags)
Set the value at offset po in the current (compiling or executing) pad. Use the macro PAD_SETSV() rather than calling this function directly. 

        void    pad_setsv(PADOFFSET po, SV *sv)
Get the value at offset po in the current (compiling or executing) pad. Use macro PAD_SV instead of calling this function directly. 

        SV *    pad_sv(PADOFFSET po)
Tidy up a pad at the end of compilation of the code to which it belongs. Jobs performed here are: remove most stuff from the pads of anonsub prototypes; give it a @_; mark temporaries as such. type indicates the kind of subroutine: 

    padtidy_SUB        ordinary subroutine
    padtidy_SUBCLONE   prototype for lexical closure
    padtidy_FORMAT     format

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

        void    pad_tidy(padtidy_type type)
Allocates a new Perl interpreter. See perlembed. 

        PerlInterpreter* perl_alloc()
Initializes a new Perl interpreter. See perlembed. 

        void    perl_construct(PerlInterpreter *my_perl)
Shuts down a Perl interpreter. See perlembed. 

        int     perl_destruct(PerlInterpreter *my_perl)
Releases a Perl interpreter. See perlembed. 

        void    perl_free(PerlInterpreter *my_perl)
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)
Tells a Perl interpreter to run. See perlembed. 

        int     perl_run(PerlInterpreter *my_perl)
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

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)
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 if PERL_PV_ESCAPE_NONASCII is set, only chars above 127 will be escaped using this style; otherwise, only chars above 255 will be so escaped; other non printable chars will use octal or common escaped patterns like "\n". Otherwise, 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, regardless of max. If the output is to be in hex, then it will be returned as a plain hex sequence. Thus the output will either be a single char, an octal escape sequence, a special escape like "\n" or a 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)
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

Return the description of a given custom op. This was once used by the OP_DESC macro, but is no longer: it has only been kept for compatibility, and should not be used. 

        const char * custom_op_desc(const OP *o)
Return the name for a given custom op. This was once used by the OP_NAME macro, but is no longer: it has only been kept for compatibility, and should not be used. 

        const char * custom_op_name(const OP *o)
See "gv_fetchmethod_autoload". 

        GV*     gv_fetchmethod(HV* stash, const char* name)
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)
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)
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)
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)
Like "sv_catpvn", but also handles 'set' magic. 

        void    sv_catpvn_mg(SV *sv, const char *ptr,
                             STRLEN len)
Like "sv_catsv", but also handles 'set' magic. 

        void    sv_catsv_mg(SV *dsv, SV *ssv)
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)
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)
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)
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)
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)
Use the "SvPV_nolen" macro instead 

        char*   sv_pv(SV *sv)
Use "SvPVbyte_nolen" instead. 

        char*   sv_pvbyte(SV *sv)
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)
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)
Use the "SvPVutf8_nolen" macro instead 

        char*   sv_pvutf8(SV *sv)
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)
Taint an SV. Use "SvTAINTED_on" instead. 

        void    sv_taint(SV* sv)
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)
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)
Like "sv_usepvn", but also handles 'set' magic. 

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

Applies a syntactic context to an op tree representing an expression. o is the op tree, and context must be "G_SCALAR", "G_ARRAY", or "G_VOID" to specify the context to apply. The modified op tree is returned. 

        OP *    op_contextualize(OP *o, I32 context)

Functions in file perl.h

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)
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)
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

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

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

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

The engine implementing pack() Perl function. 

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

Functions in file pp_sys.c

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

        void    setdefout(GV* gv)

Functions in file utf8.h

This is a synonym for (! foldEQ_utf8()) 

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

Functions in file util.h

This is a synonym for (! foldEQ()) 

        I32     ibcmp(const char* a, const char* b, I32 len)
This is a synonym for (! foldEQ_locale()) 

        I32     ibcmp_locale(const char* a, const char* b,
                             I32 len)

Global Variables

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

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

For thread safety, modules should not write directly to this array. Instead, use the function "wrap_op_checker".

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

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

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

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

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

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

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

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

GV Functions

Return the SV from the GV. 

        SV*     GvSV(GV* gv)
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)
Like "gv_fetchmeth_pvn", but lacks a flags parameter. 

        GV*     gv_fetchmeth(HV* stash, const char* name,
                             STRLEN len, I32 level)
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)
This is the old form of "gv_fetchmeth_pvn_autoload", which has no flags parameter. 

        GV*     gv_fetchmeth_autoload(HV* stash,
                                      const char* name,
                                      STRLEN len, I32 level)
Exactly like "gv_fetchmeth_pvn", but takes a nul-terminated string instead of a string/length pair. 

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

Currently, the only significant value for "flags" is SVf_UTF8.

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_pvn(HV* stash, const char* name,
                                 STRLEN len, I32 level,
                                 U32 flags)
Same as gv_fetchmeth_pvn(), but looks for autoloaded subroutines too. Returns a glob for the subroutine.

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

Currently, the only significant value for "flags" is SVf_UTF8.

        GV*     gv_fetchmeth_pvn_autoload(HV* stash,
                                          const char* name,
                                          STRLEN len, I32 level,
                                          U32 flags)
Exactly like "gv_fetchmeth_pvn_autoload", but takes a nul-terminated string instead of a string/length pair. 

        GV*     gv_fetchmeth_pv_autoload(HV* stash,
                                         const char* name,
                                         I32 level, U32 flags)
Exactly like "gv_fetchmeth_pvn", but takes the name string in the form of an SV instead of a string/length pair. 

        GV*     gv_fetchmeth_sv(HV* stash, SV* namesv,
                                I32 level, U32 flags)
Exactly like "gv_fetchmeth_pvn_autoload", but takes the name string in the form of an SV instead of a string/length pair. 

        GV*     gv_fetchmeth_sv_autoload(HV* stash, SV* namesv,
                                         I32 level, U32 flags)
The old form of gv_init_pvn(). It does not work with UTF8 strings, as it has no flags parameter. If the "multi" parameter is set, the GV_ADDMULTI flag will be passed to gv_init_pvn(). 

        void    gv_init(GV* gv, HV* stash, const char* name,
                        STRLEN len, int multi)
Same as gv_init_pvn(), but takes a nul-terminated string for the name instead of separate char * and length parameters. 

        void    gv_init_pv(GV* gv, HV* stash, const char* name,
                           U32 flags)
Converts a scalar into a typeglob. This is an incoercible typeglob; assigning a reference to it will assign to one of its slots, instead of overwriting it as happens with typeglobs created by SvSetSV. Converting any scalar that is SvOK() may produce unpredictable results and is reserved for perl's internal use.

"gv" is the scalar to be converted.

"stash" is the parent stash/package, if any.

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

"flags" can be set to SVf_UTF8 if "name" is a UTF8 string, or the return value of SvUTF8(sv). It can also take the GV_ADDMULTI flag, which means to pretend that the GV has been seen before (i.e., suppress "Used once" warnings).

        void    gv_init_pvn(GV* gv, HV* stash, const char* name,
                            STRLEN len, U32 flags)
Same as gv_init_pvn(), but takes an SV * for the name instead of separate char * and length parameters. "flags" is currently unused. 

        void    gv_init_sv(GV* gv, HV* stash, SV* namesv,
                           U32 flags)
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)
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)
Like "gv_stashpvn", but takes a literal string instead of a string/length pair. 

        HV*     gv_stashpvs(const char* name, I32 create)
Returns a pointer to the stash for a specified package. See "gv_stashpvn". 

        HV*     gv_stashsv(SV* sv, I32 flags)

Handy Values

Null AV pointer.

(deprecated - use "(AV *)NULL" instead)

Null character pointer. (No longer available when "PERL_CORE" is defined.)
Null CV pointer.

(deprecated - use "(CV *)NULL" instead)

Null HV pointer.

(deprecated - use "(HV *)NULL" instead)

Null SV pointer. (No longer available when "PERL_CORE" is defined.)

Hash Manipulation Functions

Returns the label attached to a cop. The flags pointer may be set to "SVf_UTF8" or 0.

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

        const char * cop_fetch_label(COP *const cop,
                                     STRLEN *len, U32 *flags)
Save a label into a "cop_hints_hash". You need to set flags to "SVf_UTF8" for a utf-8 label.

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

        void    cop_store_label(COP *const cop,
                                const char *label, STRLEN len,
                                U32 flags)
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)
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).
Returns the computed hash stored in the hash entry. 

        U32     HeHASH(HE* he)
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)
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)
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)
Returns the key as an "SV*", or "NULL" if the hash entry does not contain an "SV*" key. 

        SV*     HeSVKEY(HE* he)
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)
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)
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)
Returns the value slot (type "SV*") stored in the hash entry. 

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

        char*   HvENAME(HV* stash)
Returns the length of the stash's effective name. 

        STRLEN  HvENAMELEN(HV *stash)
Returns true if the effective name is in UTF8 encoding. 

        unsigned char HvENAMEUTF8(HV *stash)
Returns the package name of a stash, or NULL if "stash" isn't a stash. See "SvSTASH", "CvSTASH". 

        char*   HvNAME(HV* stash)
Returns the length of the stash's name. 

        STRLEN  HvNAMELEN(HV *stash)
Returns true if the name is in UTF8 encoding. 

        unsigned char HvNAMEUTF8(HV *stash)
Check that a hash is in an internally consistent state. 

        void    hv_assert(HV *hv)
Frees the all the elements of a hash, leaving it empty. The XS equivalent of "%hash = ()". See also "hv_undef".

If any destructors are triggered as a result, the hv itself may be freed.

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

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

        SV*     hv_delete(HV *hv, const char *key, I32 klen,
                          I32 flags)
Deletes a key/value pair in the hash. The value SV is removed from the hash, made mortal, and returned to the caller. The "flags" value will normally be zero; if set to G_DISCARD then NULL will be returned. NULL will also be returned if the key is not found. "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)
Returns a boolean indicating whether the specified hash key exists. The absolute value of "klen" is the length of the key. If "klen" is negative the key is assumed to be in UTF-8-encoded Unicode. 

        bool    hv_exists(HV *hv, const char *key, I32 klen)
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)
Returns the SV which corresponds to the specified key in the hash. The absolute value of "klen" is the length of the key. If "klen" is negative the key is assumed to be in UTF-8-encoded Unicode. 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)
Like "hv_fetch", but takes a literal string instead of a string/length pair. 

        SV**    hv_fetchs(HV* tb, const char* key, I32 lval)
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 "hv" is a tied hash is a pointer to a static location, so be sure to make a copy of the structure if you need to store it somewhere.

See "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)
Returns the number of hash buckets that happen to be in use. This function is wrapped by the macro "HvFILL".

Previously this value was stored in the HV structure, rather than being calculated on demand.

        STRLEN  hv_fill(HV const *const hv)
Prepares a starting point to traverse a hash table. Returns the number of keys in the hash (i.e. the same as "HvUSEDKEYS(hv)"). 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(hv)".

        I32     hv_iterinit(HV *hv)
Returns the key from the current position of the hash iterator. See "hv_iterinit". 

        char*   hv_iterkey(HE* entry, I32* retlen)
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)
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)
Performs an "hv_iternext", "hv_iterkey", and "hv_iterval" in one operation. 

        SV*     hv_iternextsv(HV *hv, char **key, I32 *retlen)
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 &PL_sv_placeholder. Note that the implementation of placeholders and restricted hashes may change, and the implementation currently is insufficiently abstracted for any change to be tidy.

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

        HE*     hv_iternext_flags(HV *hv, I32 flags)
Returns the value from the current position of the hash iterator. See "hv_iterkey". 

        SV*     hv_iterval(HV *hv, HE *entry)
Adds magic to a hash. See "sv_magic". 

        void    hv_magic(HV *hv, GV *gv, int how)
Evaluates the hash in scalar context and returns the result. Handles magic when the hash is tied. 

        SV*     hv_scalar(HV *hv)
Stores an SV in a hash. The hash key is specified as "key" and the absolute value of "klen" is the length of the key. If "klen" is negative the key is assumed to be in UTF-8-encoded Unicode. 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)
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)
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)
Undefines the hash. The XS equivalent of "undef(%hash)".

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

If any destructors are triggered as a result, the hv itself may be freed.

See also "hv_clear".

        void    hv_undef(HV *hv)
Creates a new HV. The reference count is set to 1. 

        HV*     newHV()

Hook manipulation

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

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

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

If you want to influence compilation of calls to a specific subroutine, then use "cv_set_call_checker" rather than hooking checking of all "entersub" ops.

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

Lexer interface

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

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

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

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

        bool    lex_bufutf8()
Discards the first part of the "PL_parser->linestr" buffer, up to ptr. The remaining content of the buffer will be moved, and all pointers into the buffer updated appropriately. ptr must not be later in the buffer than the position of "PL_parser->bufptr": it is not permitted to discard text that has yet to be lexed.

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

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

        void    lex_discard_to(char *ptr)
Reallocates the lexer buffer ("PL_parser->linestr") to accommodate at least len octets (including terminating NUL). Returns a pointer to the reallocated buffer. This is necessary before making any direct modification of the buffer that would increase its length. "lex_stuff_pvn" provides a more convenient way to insert text into the buffer.

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

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

        char *  lex_grow_linestr(STRLEN len)
Reads in the next chunk of text to be lexed, appending it to "PL_parser->linestr". This should be called when lexing code has looked to the end of the current chunk and wants to know more. It is usual, but not necessary, for lexing to have consumed the entirety of the current chunk at this time.

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

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

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

        bool    lex_next_chunk(U32 flags)
Looks ahead one (Unicode) character in the text currently being lexed. Returns the codepoint (unsigned integer value) of the next character, or -1 if lexing has reached the end of the input text. To consume the peeked character, use "lex_read_unichar".

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

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

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

        I32     lex_peek_unichar(U32 flags)
Reads optional spaces, in Perl style, in the text currently being lexed. The spaces may include ordinary whitespace characters and Perl-style comments. "#line" directives are processed if encountered. "PL_parser->bufptr" is moved past the spaces, so that it points at a non-space character (or the end of the input text).

If spaces extend into the next chunk of input text, the next chunk will be read in. Normally the current chunk will be discarded at the same time, but if flags includes "LEX_KEEP_PREVIOUS" then the current chunk will not be discarded.

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

        void    lex_read_space(U32 flags)
Consume text in the lexer buffer, from "PL_parser->bufptr" up to ptr. This advances "PL_parser->bufptr" to match ptr, performing the correct bookkeeping whenever a newline character is passed. This is the normal way to consume lexed text.

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

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

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

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

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

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

        I32     lex_read_unichar(U32 flags)
Creates and initialises a new lexer/parser state object, supplying a context in which to lex and parse from a new source of Perl code. A pointer to the new state object is placed in "PL_parser". An entry is made on the save stack so that upon unwinding the new state object will be destroyed and the former value of "PL_parser" will be restored. Nothing else need be done to clean up the parsing context.

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

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

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

        void    lex_start(SV *line, PerlIO *rsfp, U32 flags)
Insert characters into the lexer buffer ("PL_parser->linestr"), immediately after the current lexing point ("PL_parser->bufptr"), reallocating the buffer if necessary. This means that lexing code that runs later will see the characters as if they had appeared in the input. It is not recommended to do this as part of normal parsing, and most uses of this facility run the risk of the inserted characters being interpreted in an unintended manner.

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

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

        void    lex_stuff_pv(const char *pv, U32 flags)
Insert characters into the lexer buffer ("PL_parser->linestr"), immediately after the current lexing point ("PL_parser->bufptr"), reallocating the buffer if necessary. This means that lexing code that runs later will see the characters as if they had appeared in the input. It is not recommended to do this as part of normal parsing, and most uses of this facility run the risk of the inserted characters being interpreted in an unintended manner.

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

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

        void    lex_stuff_pvn(const char *pv, STRLEN len,
                              U32 flags)
Like "lex_stuff_pvn", but takes a literal string instead of a string/length pair.

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

        void    lex_stuff_pvs(const char *pv, U32 flags)
Insert characters into the lexer buffer ("PL_parser->linestr"), immediately after the current lexing point ("PL_parser->bufptr"), reallocating the buffer if necessary. This means that lexing code that runs later will see the characters as if they had appeared in the input. It is not recommended to do this as part of normal parsing, and most uses of this facility run the risk of the inserted characters being interpreted in an unintended manner.

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

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

        void    lex_stuff_sv(SV *sv, U32 flags)
Discards text about to be lexed, from "PL_parser->bufptr" up to ptr. Text following ptr will be moved, and the buffer shortened. This hides the discarded text from any lexing code that runs later, as if the text had never appeared.

This is not the normal way to consume lexed text. For that, use "lex_read_to".

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

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

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

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

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

        OP *    parse_arithexpr(U32 flags)
Parse a single unadorned Perl statement. This may be a normal imperative statement or a declaration that has compile-time effect. It does not include any label or other affixture. It is up to the caller to ensure that the dynamic parser state ("PL_parser" et al) is correctly set to reflect the source of the code to be parsed and the lexical context for the statement.

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

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

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

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

        OP *    parse_barestmt(U32 flags)
Parse a single complete Perl code block. This consists of an opening brace, a sequence of statements, and a closing brace. The block constitutes a lexical scope, so "my" variables and various compile-time effects can be contained within it. It is up to the caller to ensure that the dynamic parser state ("PL_parser" et al) is correctly set to reflect the source of the code to be parsed and the lexical context for the statement.

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

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

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

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

        OP *    parse_block(U32 flags)
Parse a single complete Perl expression. This allows the full expression grammar, including the lowest-precedence operators such as "or". The expression must be followed (and thus terminated) by a token that an expression would normally be terminated by: end-of-file, closing bracketing punctuation, semicolon, or one of the keywords that signals a postfix expression-statement modifier. If flags includes "PARSE_OPTIONAL" then the expression is optional, otherwise it is mandatory. It is up to the caller to ensure that the dynamic parser state ("PL_parser" et al) is correctly set to reflect the source of the code to be parsed and the lexical context for the expression.

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

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

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

        OP *    parse_fullexpr(U32 flags)
Parse a single complete Perl statement. This may be a normal imperative statement or a declaration that has compile-time effect, and may include optional labels. It is up to the caller to ensure that the dynamic parser state ("PL_parser" et al) is correctly set to reflect the source of the code to be parsed and the lexical context for the statement.

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

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

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

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

        OP *    parse_fullstmt(U32 flags)
Parse a single label, possibly optional, of the type that may prefix a Perl statement. It is up to the caller to ensure that the dynamic parser state ("PL_parser" et al) is correctly set to reflect the source of the code to be parsed. If flags includes "PARSE_OPTIONAL" then the label is optional, otherwise it is mandatory.

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

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

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

        SV *    parse_label(U32 flags)
Parse a Perl list expression. This may contain operators of precedence down to the comma operator. The expression must be followed (and thus terminated) either by a low-precedence logic operator such as "or" or by something that would normally terminate an expression such as semicolon. If flags includes "PARSE_OPTIONAL" then the expression is optional, otherwise it is mandatory. It is up to the caller to ensure that the dynamic parser state ("PL_parser" et al) is correctly set to reflect the source of the code to be parsed and the lexical context for the expression.

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

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

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

        OP *    parse_listexpr(U32 flags)
Parse a sequence of zero or more Perl statements. These may be normal imperative statements, including optional labels, or declarations that have compile-time effect, or any mixture thereof. The statement sequence ends when a closing brace or end-of-file is encountered in a place where a new statement could have validly started. It is up to the caller to ensure that the dynamic parser state ("PL_parser" et al) is correctly set to reflect the source of the code to be parsed and the lexical context for the statements.

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

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

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

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

        OP *    parse_stmtseq(U32 flags)
Parse a Perl term expression. This may contain operators of precedence down to the assignment operators. The expression must be followed (and thus terminated) either by a comma or lower-precedence operator or by something that would normally terminate an expression such as semicolon. If flags includes "PARSE_OPTIONAL" then the expression is optional, otherwise it is mandatory. It is up to the caller to ensure that the dynamic parser state ("PL_parser" et al) is correctly set to reflect the source of the code to be parsed and the lexical context for the expression.

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

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

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

        OP *    parse_termexpr(U32 flags)
Pointer to a structure encapsulating the state of the parsing operation currently in progress. The pointer can be locally changed to perform a nested parse without interfering with the state of an outer parse. Individual members of "PL_parser" have their own documentation.
PL_parser->bufend
Direct pointer to the end of the chunk of text currently being lexed, the end of the lexer buffer. This is equal to "SvPVX(PL_parser->linestr) + SvCUR(PL_parser->linestr)". A NUL character (zero octet) is always located at the end of the buffer, and does not count as part of the buffer's contents.

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

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

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

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

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

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

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

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

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

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

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

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

Magical Functions

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

        int     mg_clear(SV* sv)
Copies the magic from one SV to another. See "sv_magic". 

        int     mg_copy(SV *sv, SV *nsv, const char *key,
                        I32 klen)
Finds the magic pointer for type matching the SV. See "sv_magic". 

        MAGIC*  mg_find(const SV* sv, int type)
Finds the magic pointer of "type" with the given "vtbl" for the "SV". See "sv_magicext". 

        MAGIC*  mg_findext(const SV* sv, int type,
                           const MGVTBL *vtbl)
Free any magic storage used by the SV. See "sv_magic". 

        int     mg_free(SV* sv)
Remove any magic of type how from the SV sv. See "sv_magic". 

        void    mg_free_type(SV *sv, int how)
Do magic before a value is retrieved from the SV. See "sv_magic". 

        int     mg_get(SV* sv)
Report on the SV's length. See "sv_magic". 

        U32     mg_length(SV* sv)
Turns on the magical status of an SV. See "sv_magic". 

        void    mg_magical(SV* sv)
Do magic after a value is assigned to the SV. See "sv_magic". 

        int     mg_set(SV* sv)
Invokes "mg_get" on an SV if it has 'get' magic. This macro evaluates its argument more than once. 

        void    SvGETMAGIC(SV* sv)
Arranges for a mutual exclusion lock to be obtained on sv if a suitable module has been loaded. 

        void    SvLOCK(SV* sv)
Invokes "mg_set" on an SV if it has 'set' magic. This macro evaluates its argument more than once. 

        void    SvSETMAGIC(SV* sv)
Like "SvSetSV", but does any set magic required afterwards. 

        void    SvSetMagicSV(SV* dsb, SV* ssv)
Like "SvSetSV_nosteal", but does any set magic required afterwards. 

        void    SvSetMagicSV_nosteal(SV* dsv, SV* ssv)
Calls "sv_setsv" if dsv is not the same as ssv. May evaluate arguments more than once. 

        void    SvSetSV(SV* dsb, SV* ssv)
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)
Arranges for sv to be shared between threads if a suitable module has been loaded. 

        void    SvSHARE(SV* sv)
Releases a mutual exclusion lock on sv if a suitable module has been loaded. 

        void    SvUNLOCK(SV* sv)

Memory Management

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

        void *  CopyD(void* src, void* dest, int nitems, type)
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)
Like "Move" but returns dest. Useful for encouraging compilers to tail-call optimise. 

        void *  MoveD(void* src, void* dest, int nitems, type)
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 perlhacktips). The older API is still there for use in XS modules supporting older perls.

        void    Newx(void* ptr, int nitems, type)
The XSUB-writer's interface to the C "malloc" function, with cast. See also "Newx". 

        void    Newxc(void* ptr, int nitems, type, cast)
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)
PoisonWith(0xEF) for catching access to freed memory. 

        void    Poison(void* dest, int nitems, type)
PoisonWith(0xEF) for catching access to freed memory. 

        void    PoisonFree(void* dest, int nitems, type)
PoisonWith(0xAB) for catching access to allocated but uninitialized memory. 

        void    PoisonNew(void* dest, int nitems, type)
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)
The XSUB-writer's interface to the C "realloc" function. 

        void    Renew(void* ptr, int nitems, type)
The XSUB-writer's interface to the C "realloc" function, with cast. 

        void    Renewc(void* ptr, int nitems, type, cast)
The XSUB-writer's interface to the C "free" function. 

        void    Safefree(void* ptr)
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)
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)
Like "savepvn", but takes a literal string instead of a string/length pair. 

        char*   savepvs(const char* s)
A version of "savepv()" which allocates the duplicate string in memory which is shared between threads. 

        char*   savesharedpv(const char* pv)
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)
A version of "savepvs()" which allocates the duplicate string in memory which is shared between threads. 

        char*   savesharedpvs(const char* s)
A version of "savesharedpv()" which allocates the duplicate string in memory which is shared between threads. 

        char*   savesharedsvpv(SV *sv)
A version of "savepv()"/"savepvn()" which gets the string to duplicate from the passed in SV using "SvPV()" 

        char*   savesvpv(SV* sv)
This is an architecture-independent macro to copy one structure to another. 

        void    StructCopy(type src, type dest, type)
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)
Like "Zero" but returns dest. Useful for encouraging compilers to tail-call optimise. 

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

Miscellaneous Functions

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)
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)
Returns true if the leading len bytes of the strings s1 and s2 are the same case-insensitively; false otherwise. Uppercase and lowercase ASCII range bytes match themselves and their opposite case counterparts. Non-cased and non-ASCII range bytes match only themselves. 

        I32     foldEQ(const char* a, const char* b, I32 len)
Returns true if the leading len bytes of the strings s1 and s2 are the same case-insensitively in the current locale; false otherwise. 

        I32     foldEQ_locale(const char* a, const char* b,
                              I32 len)
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, ...)
Fill the sv with current working directory 

        int     getcwd_sv(SV* sv)
Take a sprintf-style format pattern and argument list. These are used to generate a string message. If the message does not end with a newline, then it will be extended with some indication of the current location in the code, as described for "mess_sv".

Normally, the resulting message is returned in a new mortal SV. During global destruction a single SV may be shared between uses of this function.

        SV *    mess(const char *pat, ...)
Expands a message, intended for the user, to include an indication of the current location in the code, if the message does not already appear to be complete.

"basemsg" is the initial message or object. If it is a reference, it will be used as-is and will be the result of this function. Otherwise it is used as a string, and if it already ends with a newline, it is taken to be complete, and the result of this function will be the same string. If the message does not end with a newline, then a segment such as "at foo.pl line 37" will be appended, and possibly other clauses indicating the current state of execution. The resulting message will end with a dot and a newline.

Normally, the resulting message is returned in a new mortal SV. During global destruction a single SV may be shared between uses of this function. If "consume" is true, then the function is permitted (but not required) to modify and return "basemsg" instead of allocating a new SV.

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

        const char* prescan_version(const char *s, bool strict,
                                    const char** errstr,
                                    bool *sqv,
                                    int *ssaw_decimal,
                                    int *swidth, bool *salpha)
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)
Test two strings to see if they are equal. Returns true or false. 

        bool    strEQ(char* s1, char* s2)
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)
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)
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)
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)
Test two strings to see if they are different. Returns true or false. 

        bool    strNE(char* s1, char* s2)
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)
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)
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)
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)
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)
Version object aware cmp. Both operands must already have been converted into version objects. 

        int     vcmp(SV *lhv, SV *rhv)
"pat" and "args" are a sprintf-style format pattern and encapsulated argument list. These are used to generate a string message. If the message does not end with a newline, then it will be extended with some indication of the current location in the code, as described for "mess_sv".

Normally, the resulting message is returned in a new mortal SV. During global destruction a single SV may be shared between uses of this function.

        SV *    vmess(const char *pat, va_list *args)
Accepts a version object and returns the normalized string representation. Call like: 

    sv = vnormal(rv);

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

The SV returned has a refcount of 1.

        SV*     vnormal(SV *vs)
Accepts a version object and returns the normalized floating point representation. Call like: 

    sv = vnumify(rv);

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

The SV returned has a refcount of 1.

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

The SV returned has a refcount of 1.

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

    SV *hv = vverify(sv);

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

        SV*     vverify(SV *vs)

MRO Functions

Returns the mro linearisation for the given stash. By default, this will be whatever "mro_get_linear_isa_dfs" returns unless some other MRO is in effect for the stash. The return value is a read-only AV*.

You are responsible for "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)
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)
Registers a custom mro plugin. See perlmroapi for details. 

        void    mro_register(const struct mro_alg *mro)

Multicall Functions

Declare local variables for a multicall. See "LIGHTWEIGHT CALLBACKS" in perlcall. 

                dMULTICALL;
Make a lightweight callback. See "LIGHTWEIGHT CALLBACKS" in perlcall. 

                MULTICALL;
Closing bracket for a lightweight callback. See "LIGHTWEIGHT CALLBACKS" in perlcall. 

                POP_MULTICALL;
Opening bracket for a lightweight callback. See "LIGHTWEIGHT CALLBACKS" in perlcall. 

                PUSH_MULTICALL;

Numeric functions

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

        bool    grok_numeric_radix(const char **sp,
                                   const char *send)
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 8 or 9 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)
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)
For backwards compatibility. Use "grok_bin" instead. 

        NV      scan_bin(const char* start, STRLEN len,
                         STRLEN* retlen)
For backwards compatibility. Use "grok_hex" instead. 

        NV      scan_hex(const char* start, STRLEN len,
                         STRLEN* retlen)
For backwards compatibility. Use "grok_oct" instead. 

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

Optree construction

Constructs, checks, and returns an assignment op. left and right supply the parameters of the assignment; they are consumed by this function and become part of the constructed op tree.

If optype is "OP_ANDASSIGN", "OP_ORASSIGN", or "OP_DORASSIGN", then a suitable conditional optree is constructed. If optype is the opcode of a binary operator, such as "OP_BIT_OR", then an op is constructed that performs the binary operation and assigns the result to the left argument. Either way, if optype is non-zero then flags has no effect.

If optype is zero, then a plain scalar or list assignment is constructed. Which type of assignment it is is automatically determined. flags gives the eight bits of "op_flags", except that "OPf_KIDS" will be set automatically, and, shifted up eight bits, the eight bits of "op_private", except that the bit with value 1 or 2 is automatically set as required.

        OP *    newASSIGNOP(I32 flags, OP *left, I32 optype,
                            OP *right)
Constructs, checks, and returns an op of any binary type. type is the opcode. flags gives the eight bits of "op_flags", except that "OPf_KIDS" will be set automatically, and, shifted up eight bits, the eight bits of "op_private", except that the bit with value 1 or 2 is automatically set as required. first and last supply up to two ops to be the direct children of the binary op; they are consumed by this function and become part of the constructed op tree. 

        OP *    newBINOP(I32 type, I32 flags, OP *first,
                         OP *last)
Constructs, checks, and returns a conditional-expression ("cond_expr") op. flags gives the eight bits of "op_flags", except that "OPf_KIDS" will be set automatically, and, shifted up eight bits, the eight bits of "op_private", except that the bit with value 1 is automatically set. first supplies the expression selecting between the two branches, and trueop and falseop supply the branches; they are consumed by this function and become part of the constructed op tree. 

        OP *    newCONDOP(I32 flags, OP *first, OP *trueop,
                          OP *falseop)
Constructs, checks, and returns an op tree expressing a "foreach" loop (iteration through a list of values). This is a heavyweight loop, with structure that allows exiting the loop by "last" and suchlike.

sv optionally supplies the variable that will be aliased to each item in turn; if null, it defaults to $_ (either lexical or global). expr supplies the list of values to iterate over. block supplies the main body of the loop, and cont optionally supplies a "continue" block that operates as a second half of the body. All of these optree inputs are consumed by this function and become part of the constructed op tree.

flags gives the eight bits of "op_flags" for the "leaveloop" op and, shifted up eight bits, the eight bits of "op_private" for the "leaveloop" op, except that (in both cases) some bits will be set automatically.

        OP *    newFOROP(I32 flags, OP *sv, OP *expr, OP *block,
                         OP *cont)
Constructs, checks, and returns an op tree expressing a "given" block. cond supplies the expression that will be locally assigned to a lexical variable, and block supplies the body of the "given" construct; they are consumed by this function and become part of the constructed op tree. defsv_off is the pad offset of the scalar lexical variable that will be affected. 

        OP *    newGIVENOP(OP *cond, OP *block,
                           PADOFFSET defsv_off)
Constructs, checks, and returns an op of any type that involves an embedded reference to a GV. type is the opcode. flags gives the eight bits of "op_flags". gv identifies the GV that the op should reference; calling this function does not transfer ownership of any reference to it. 

        OP *    newGVOP(I32 type, I32 flags, GV *gv)
Constructs, checks, and returns an op of any list type. type is the opcode. flags gives the eight bits of "op_flags", except that "OPf_KIDS" will be set automatically if required. first and last supply up to two ops to be direct children of the list op; they are consumed by this function and become part of the constructed op tree. 

        OP *    newLISTOP(I32 type, I32 flags, OP *first,
                          OP *last)
Constructs, checks, and returns a logical (flow control) op. type is the opcode. flags gives the eight bits of "op_flags", except that "OPf_KIDS" will be set automatically, and, shifted up eight bits, the eight bits of "op_private", except that the bit with value 1 is automatically set. first supplies the expression controlling the flow, and other supplies the side (alternate) chain of ops; they are consumed by this function and become part of the constructed op tree. 

        OP *    newLOGOP(I32 type, I32 flags, OP *first,
                         OP *other)
Constructs, checks, and returns a loop-exiting op (such as "goto" or "last"). type is the opcode. label supplies the parameter determining the target of the op; it is consumed by this function and become part of the constructed op tree. 

        OP *    newLOOPEX(I32 type, OP *label)
Constructs, checks, and returns an op tree expressing a loop. This is only a loop in the control flow through the op tree; it does not have the heavyweight loop structure that allows exiting the loop by "last" and suchlike. flags gives the eight bits of "op_flags" for the top-level op, except that some bits will be set automatically as required. expr supplies the expression controlling loop iteration, and block supplies the body of the loop; they are consumed by this function and become part of the constructed op tree. debuggable is currently unused and should always be 1. 

        OP *    newLOOPOP(I32 flags, I32 debuggable, OP *expr,
                          OP *block)
Constructs, checks, and returns a new "stub" op, which represents an empty list expression. 

        OP *    newNULLLIST()
Constructs, checks, and returns an op of any base type (any type that has no extra fields). type is the opcode. flags gives the eight bits of "op_flags", and, shifted up eight bits, the eight bits of "op_private". 

        OP *    newOP(I32 type, I32 flags)
Constructs, checks, and returns an op of any type that involves a reference to a pad element. type is the opcode. flags gives the eight bits of "op_flags". A pad slot is automatically allocated, and is populated with sv; this function takes ownership of one reference to it.

This function only exists if Perl has been compiled to use ithreads.

        OP *    newPADOP(I32 type, I32 flags, SV *sv)
Constructs, checks, and returns an op of any pattern matching type. type is the opcode. flags gives the eight bits of "op_flags" and, shifted up eight bits, the eight bits of "op_private". 

        OP *    newPMOP(I32 type, I32 flags)
Constructs, checks, and returns an op of any type that involves an embedded C-level pointer (PV). type is the opcode. flags gives the eight bits of "op_flags". pv supplies the C-level pointer, which must have been allocated using "PerlMemShared_malloc"; the memory will be freed when the op is destroyed. 

        OP *    newPVOP(I32 type, I32 flags, char *pv)
Constructs and returns a "range" op, with subordinate "flip" and "flop" ops. flags gives the eight bits of "op_flags" for the "flip" op and, shifted up eight bits, the eight bits of "op_private" for both the "flip" and "range" ops, except that the bit with value 1 is automatically set. left and right supply the expressions controlling the endpoints of the range; they are consumed by this function and become part of the constructed op tree. 

        OP *    newRANGE(I32 flags, OP *left, OP *right)
Constructs, checks, and returns an "lslice" (list slice) op. flags gives the eight bits of "op_flags", except that "OPf_KIDS" will be set automatically, and, shifted up eight bits, the eight bits of "op_private", except that the bit with value 1 or 2 is automatically set as required. listval and subscript supply the parameters of the slice; they are consumed by this function and become part of the constructed op tree. 

        OP *    newSLICEOP(I32 flags, OP *subscript,
                           OP *listval)
Constructs a state op (COP). The state op is normally a "nextstate" op, but will be a "dbstate" op if debugging is enabled for currently-compiled code. The state op is populated from "PL_curcop" (or "PL_compiling"). If label is non-null, it supplies the name of a label to attach to the state op; this function takes ownership of the memory pointed at by label, and will free it. flags gives the eight bits of "op_flags" for the state op.

If o is null, the state op is returned. Otherwise the state op is combined with o into a "lineseq" list op, which is returned. o is consumed by this function and becomes part of the returned op tree.

        OP *    newSTATEOP(I32 flags, char *label, OP *o)
Constructs, checks, and returns an op of any type that involves an embedded SV. type is the opcode. flags gives the eight bits of "op_flags". sv gives the SV to embed in the op; this function takes ownership of one reference to it. 

        OP *    newSVOP(I32 type, I32 flags, SV *sv)
Constructs, checks, and returns an op of any unary type. type is the opcode. flags gives the eight bits of "op_flags", except that "OPf_KIDS" will be set automatically if required, and, shifted up eight bits, the eight bits of "op_private", except that the bit with value 1 is automatically set. first supplies an optional op to be the direct child of the unary op; it is consumed by this function and become part of the constructed op tree. 

        OP *    newUNOP(I32 type, I32 flags, OP *first)
Constructs, checks, and returns an op tree expressing a "when" block. cond supplies the test expression, and block supplies the block that will be executed if the test evaluates to true; they are consumed by this function and become part of the constructed op tree. cond will be interpreted DWIMically, often as a comparison against $_, and may be null to generate a "default" block. 

        OP *    newWHENOP(OP *cond, OP *block)
Constructs, checks, and returns an op tree expressing a "while" loop. This is a heavyweight loop, with structure that allows exiting the loop by "last" and suchlike.

loop is an optional preconstructed "enterloop" op to use in the loop; if it is null then a suitable op will be constructed automatically. expr supplies the loop's controlling expression. block supplies the main body of the loop, and cont optionally supplies a "continue" block that operates as a second half of the body. All of these optree inputs are consumed by this function and become part of the constructed op tree.

flags gives the eight bits of "op_flags" for the "leaveloop" op and, shifted up eight bits, the eight bits of "op_private" for the "leaveloop" op, except that (in both cases) some bits will be set automatically. debuggable is currently unused and should always be 1. has_my can be supplied as true to force the loop body to be enclosed in its own scope.

        OP *    newWHILEOP(I32 flags, I32 debuggable,
                           LOOP *loop, OP *expr, OP *block,
                           OP *cont, I32 has_my)

Optree Manipulation Functions

Performs the default fixup of the arguments part of an "entersub" op tree. This consists of applying list context to each of the argument ops. This is the standard treatment used on a call marked with "&", or a method call, or a call through a subroutine reference, or any other call where the callee can't be identified at compile time, or a call where the callee has no prototype. 

        OP *    ck_entersub_args_list(OP *entersubop)
Performs the fixup of the arguments part of an "entersub" op tree based on a subroutine prototype. This makes various modifications to the argument ops, from applying context up to inserting "refgen" ops, and checking the number and syntactic types of arguments, as directed by the prototype. This is the standard treatment used on a subroutine call, not marked with "&", where the callee can be identified at compile time and has a prototype.

protosv supplies the subroutine prototype to be applied to the call. It may be a normal defined scalar, of which the string value will be used. Alternatively, for convenience, it may be a subroutine object (a "CV*" that has been cast to "SV*") which has a prototype. The prototype supplied, in whichever form, does not need to match the actual callee referenced by the op tree.

If the argument ops disagree with the prototype, for example by having an unacceptable number of arguments, a valid op tree is returned anyway. The error is reflected in the parser state, normally resulting in a single exception at the top level of parsing which covers all the compilation errors that occurred. In the error message, the callee is referred to by the name defined by the namegv parameter.

        OP *    ck_entersub_args_proto(OP *entersubop,
                                       GV *namegv, SV *protosv)
Performs the fixup of the arguments part of an "entersub" op tree either based on a subroutine prototype or using default list-context processing. This is the standard treatment used on a subroutine call, not marked with "&", where the callee can be identified at compile time.

protosv supplies the subroutine prototype to be applied to the call, or indicates that there is no prototype. It may be a normal scalar, in which case if it is defined then the string value will be used as a prototype, and if it is undefined then there is no prototype. Alternatively, for convenience, it may be a subroutine object (a "CV*" that has been cast to "SV*"), of which the prototype will be used if it has one. The prototype (or lack thereof) supplied, in whichever form, does not need to match the actual callee referenced by the op tree.

If the argument ops disagree with the prototype, for example by having an unacceptable number of arguments, a valid op tree is returned anyway. The error is reflected in the parser state, normally resulting in a single exception at the top level of parsing which covers all the compilation errors that occurred. In the error message, the callee is referred to by the name defined by the namegv parameter.

        OP *    ck_entersub_args_proto_or_list(OP *entersubop,
                                               GV *namegv,
                                               SV *protosv)
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(const CV *const cv)
Retrieves the function that will be used to fix up a call to cv. Specifically, the function is applied to an "entersub" op tree for a subroutine call, not marked with "&", where the callee can be identified at compile time as cv.

The C-level function pointer is returned in *ckfun_p, and an SV argument for it is returned in *ckobj_p. The function is intended to be called in this manner:

    entersubop = (*ckfun_p)(aTHX_ entersubop, namegv, (*ckobj_p));

In this call, entersubop is a pointer to the "entersub" op, which may be replaced by the check function, and namegv is a GV supplying the name that should be used by the check function to refer to the callee of the "entersub" op if it needs to emit any diagnostics. It is permitted to apply the check function in non-standard situations, such as to a call to a different subroutine or to a method call.

By default, the function is Perl_ck_entersub_args_proto_or_list, and the SV parameter is cv itself. This implements standard prototype processing. It can be changed, for a particular subroutine, by "cv_set_call_checker".

        void    cv_get_call_checker(CV *cv,
                                    Perl_call_checker *ckfun_p,
                                    SV **ckobj_p)
Sets the function that will be used to fix up a call to cv. Specifically, the function is applied to an "entersub" op tree for a subroutine call, not marked with "&", where the callee can be identified at compile time as cv.

The C-level function pointer is supplied in ckfun, and an SV argument for it is supplied in ckobj. The function is intended to be called in this manner:

    entersubop = ckfun(aTHX_ entersubop, namegv, ckobj);

In this call, entersubop is a pointer to the "entersub" op, which may be replaced by the check function, and namegv is a GV supplying the name that should be used by the check function to refer to the callee of the "entersub" op if it needs to emit any diagnostics. It is permitted to apply the check function in non-standard situations, such as to a call to a different subroutine or to a method call.

The current setting for a particular CV can be retrieved by "cv_get_call_checker".

        void    cv_set_call_checker(CV *cv,
                                    Perl_call_checker ckfun,
                                    SV *ckobj)
Given the root of an optree, link the tree in execution order using the "op_next" pointers and return the first op executed. If this has already been done, it will not be redone, and "o->op_next" will be returned. If "o->op_next" is not already set, o should be at least an "UNOP". 

        OP*     LINKLIST(OP *o)
See "newCONSTSUB_flags". 

        CV*     newCONSTSUB(HV* stash, const char* name, SV* sv)
Creates a constant sub equivalent to Perl "sub FOO () { 123 }" which is eligible for inlining at compile-time.

Currently, the only useful value for "flags" is SVf_UTF8.

Passing NULL for SV creates a constant sub equivalent to "sub BAR () {}", which won't be called if used as a destructor, but will suppress the overhead of a call to "AUTOLOAD". (This form, however, isn't eligible for inlining at compile time.)

        CV*     newCONSTSUB_flags(HV* stash, const char* name,
                                  STRLEN len, U32 flags, SV* sv)
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.
Append an item to the list of ops contained directly within a list-type op, returning the lengthened list. first is the list-type op, and last is the op to append to the list. optype specifies the intended opcode for the list. If first is not already a list of the right type, it will be upgraded into one. If either first or last is null, the other is returned unchanged. 

        OP *    op_append_elem(I32 optype, OP *first, OP *last)
Concatenate the lists of ops contained directly within two list-type ops, returning the combined list. first and last are the list-type ops to concatenate. optype specifies the intended opcode for the list. If either first or last is not already a list of the right type, it will be upgraded into one. If either first or last is null, the other is returned unchanged. 

        OP *    op_append_list(I32 optype, OP *first, OP *last)
Return the class of the provided OP: that is, which of the *OP structures it uses. For core ops this currently gets the information out of PL_opargs, which does not always accurately reflect the type used. For custom ops the type is returned from the registration, and it is up to the registree to ensure it is accurate. The value returned will be one of the OA_* constants from op.h. 

        U32     OP_CLASS(OP *o)
Return a short description of the provided OP. 

        const char * OP_DESC(OP *o)
This function is the implementation of the "LINKLIST" macro. It should not be called directly. 

        OP*     op_linklist(OP *o)
Propagate lvalue ("modifiable") context to an op and its children. type represents the context type, roughly based on the type of op that would do the modifying, although "local()" is represented by OP_NULL, because it has no op type of its own (it is signalled by a flag on the lvalue op).

This function detects things that can't be modified, such as "$x+1", and generates errors for them. For example, "$x+1 = 2" would cause it to be called with an op of type OP_ADD and a "type" argument of OP_SASSIGN.

It also flags things that need to behave specially in an lvalue context, such as "$$x = 5" which might have to vivify a reference in $x.

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

        OP *    op_lvalue(OP *o, I32 type)
Return the name of the provided OP. For core ops this looks up the name from the op_type; for custom ops from the op_ppaddr. 

        const char * OP_NAME(OP *o)
Prepend an item to the list of ops contained directly within a list-type op, returning the lengthened list. first is the op to prepend to the list, and last is the list-type op. optype specifies the intended opcode for the list. If last is not already a list of the right type, it will be upgraded into one. If either first or last is null, the other is returned unchanged. 

        OP *    op_prepend_elem(I32 optype, OP *first, OP *last)
Wraps up an op tree with some additional ops so that at runtime a dynamic scope will be created. The original ops run in the new dynamic scope, and then, provided that they exit normally, the scope will be unwound. The additional ops used to create and unwind the dynamic scope will normally be an "enter"/"leave" pair, but a "scope" op may be used instead if the ops are simple enough to not need the full dynamic scope structure.

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

        OP *    op_scope(OP *o)
Examines an op, which is expected to identify a subroutine at runtime, and attempts to determine at compile time which subroutine it identifies. This is normally used during Perl compilation to determine whether a prototype can be applied to a function call. cvop is the op being considered, normally an "rv2cv" op. A pointer to the identified subroutine is returned, if it could be determined statically, and a null pointer is returned if it was not possible to determine statically.

Currently, the subroutine can be identified statically if the RV that the "rv2cv" is to operate on is provided by a suitable "gv" or "const" op. A "gv" op is suitable if the GV's CV slot is populated. A "const" op is suitable if the constant value must be an RV pointing to a CV. Details of this process may change in future versions of Perl. If the "rv2cv" op has the "OPpENTERSUB_AMPER" flag set then no attempt is made to identify the subroutine statically: this flag is used to suppress compile-time magic on a subroutine call, forcing it to use default runtime behaviour.

If flags has the bit "RV2CVOPCV_MARK_EARLY" set, then the handling of a GV reference is modified. If a GV was examined and its CV slot was found to be empty, then the "gv" op has the "OPpEARLY_CV" flag set. If the op is not optimised away, and the CV slot is later populated with a subroutine having a prototype, that flag eventually triggers the warning "called too early to check prototype".

If flags has the bit "RV2CVOPCV_RETURN_NAME_GV" set, then instead of returning a pointer to the subroutine it returns a pointer to the GV giving the most appropriate name for the subroutine in this context. Normally this is just the "CvGV" of the subroutine, but for an anonymous ("CvANON") subroutine that is referenced through a GV it will be the referencing GV. The resulting "GV*" is cast to "CV*" to be returned. A null pointer is returned as usual if there is no statically-determinable subroutine.

        CV *    rv2cv_op_cv(OP *cvop, U32 flags)

Pad Data Structures

CV's can have CvPADLIST(cv) set to point to an AV. This is the CV's scratchpad, which stores lexical variables and opcode temporary and per-thread values.

For these purposes "forms" are a kind-of CV, eval""s are too (except they're not callable at will and are always thrown away after the eval"" is done executing). Require'd files are simply evals without any outer lexical scope.

XSUBs don't have CvPADLIST set - dXSTARG fetches values from PL_curpad, but that is really the callers pad (a slot of which is allocated by every entersub).

The CvPADLIST AV has the REFCNT of its component items managed "manually" (mostly in pad.c) rather than by normal av.c rules. So we turn off AvREAL just before freeing it, to let av.c know not to touch the entries. The items in the AV are not SVs as for a normal AV, but other AVs:

0'th Entry of the CvPADLIST is an AV which represents the "names" or rather the "static type information" for lexicals.

The CvDEPTH'th entry of CvPADLIST AV is an AV which is the stack frame at that depth of recursion into the CV. The 0'th slot of a frame AV is an AV which is @_. other entries are storage for variables and op targets.

Iterating over the names AV iterates over all possible pad items. Pad slots that are SVs_PADTMP (targets/GVs/constants) end up having &PL_sv_undef "names" (see pad_alloc()).

Only my/our variable (SVs_PADMY/SVs_PADOUR) slots get valid names. The rest are op targets/GVs/constants which are statically allocated or resolved at compile time. These don't have names by which they can be looked up from Perl code at run time through eval"" like my/our variables can be. Since they can't be looked up by "name" but only by their index allocated at compile time (which is usually in PL_op->op_targ), wasting a name SV for them doesn't make sense.

The SVs in the names AV have their PV being the name of the variable. xlow+1..xhigh inclusive in the NV union is a range of cop_seq numbers for which the name is valid (accessed through the macros COP_SEQ_RANGE_LOW and _HIGH). During compilation, these fields may hold the special value PERL_PADSEQ_INTRO to indicate various stages:

   COP_SEQ_RANGE_LOW        _HIGH
   -----------------        -----
   PERL_PADSEQ_INTRO            0   variable not yet introduced:   { my ($x
   valid-seq#   PERL_PADSEQ_INTRO   variable in scope:             { my ($x)
   valid-seq#          valid-seq#   compilation of scope complete: { my ($x) }

For typed lexicals name SV is SVt_PVMG and SvSTASH points at the type. For "our" lexicals, the type is also SVt_PVMG, with the SvOURSTASH slot pointing at the stash of the associated global (so that duplicate "our" declarations in the same package can be detected). SvUVX is sometimes hijacked to store the generation number during compilation.

If SvFAKE is set on the name SV, then that slot in the frame AV is a REFCNT'ed reference to a lexical from "outside". In this case, the name SV does not use xlow and xhigh to store a cop_seq range, since it is in scope throughout. Instead xhigh stores some flags containing info about the real lexical (is it declared in an anon, and is it capable of being instantiated multiple times?), and for fake ANONs, xlow contains the index within the parent's pad where the lexical's value is stored, to make cloning quicker.

If the 'name' is '&' the corresponding entry in frame AV is a CV representing a possible closure. (SvFAKE and name of '&' is not a meaningful combination currently but could become so if "my sub foo {}" is implemented.)

Note that formats are treated as anon subs, and are cloned each time write is called (if necessary).

The flag SVs_PADSTALE is cleared on lexicals each time the my() is executed, and set on scope exit. This allows the 'Variable $x is not available' warning to be generated in evals, such as

    { my $x = 1; sub f { eval '$x'} } f();

For state vars, SVs_PADSTALE is overloaded to mean 'not yet initialised'

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

        PADLIST * CvPADLIST(CV *cv)
Exactly like "pad_add_name_pvn", but takes a literal string instead of a string/length pair. 

        PADOFFSET pad_add_name_pvs(const char *name, U32 flags,
                                   HV *typestash, HV *ourstash)
Exactly like "pad_findmy_pvn", but takes a literal string instead of a string/length pair. 

        PADOFFSET pad_findmy_pvs(const char *name, U32 flags)
Create a new padlist, updating the global variables for the currently-compiling padlist to point to the new padlist. The following flags can be OR'ed together: 

    padnew_CLONE        this pad is for a cloned CV
    padnew_SAVE         save old globals on the save stack
    padnew_SAVESUB      also save extra stuff for start of sub
        PADLIST * pad_new(int flags)
During compilation, this points to the array containing the values part of the pad for the currently-compiling code. (At runtime a CV may have many such value arrays; at compile time just one is constructed.) At runtime, this points to the array containing the currently-relevant values for the pad for the currently-executing code.

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

During compilation, this points to the array containing the names part of the pad for the currently-compiling code.

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

Points directly to the body of the "PL_comppad" array. (I.e., this is "AvARRAY(PL_comppad)".)

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

Per-Interpreter Variables

"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
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
When non-"NULL", the function pointed by this variable will be called each time an OP is freed with the corresponding OP as the argument. This allows extensions to free any extra attribute they have locally attached to an OP. It is also assured to first fire for the parent OP and then for its kids.

When you replace this variable, it is considered a good practice to store the possibly previously installed hook and that you recall it inside your own.

        Perl_ophook_t   PL_opfreehook
Pointer to the per-subroutine peephole optimiser. This is a function that gets called at the end of compilation of a Perl subroutine (or equivalently independent piece of Perl code) to perform fixups of some ops and to perform small-scale optimisations. The function is called once for each subroutine that is compiled, and is passed, as sole parameter, a pointer to the op that is the entry point to the subroutine. It modifies the op tree in place.

The peephole optimiser should never be completely replaced. Rather, add code to it by wrapping the existing optimiser. The basic way to do this can be seen in "Compile pass 3: peephole optimization" in perlguts. If the new code wishes to operate on ops throughout the subroutine's structure, rather than just at the top level, it is likely to be more convenient to wrap the "PL_rpeepp" hook.

        peep_t  PL_peepp
Pointer to the recursive peephole optimiser. This is a function that gets called at the end of compilation of a Perl subroutine (or equivalently independent piece of Perl code) to perform fixups of some ops and to perform small-scale optimisations. The function is called once for each chain of ops linked through their "op_next" fields; it is recursively called to handle each side chain. It is passed, as sole parameter, a pointer to the op that is at the head of the chain. It modifies the op tree in place.

The peephole optimiser should never be completely replaced. Rather, add code to it by wrapping the existing optimiser. The basic way to do this can be seen in "Compile pass 3: peephole optimization" in perlguts. If the new code wishes to operate only on ops at a subroutine's top level, rather than throughout the structure, it is likely to be more convenient to wrap the "PL_peepp" hook.

        peep_t  PL_rpeepp
This is the "false" SV. See "PL_sv_yes". Always refer to this as &PL_sv_no. 

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

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

        SV      PL_sv_yes

REGEXP Functions

Convenience macro to get the REGEXP from a SV. This is approximately equivalent to the following snippet: 

    if (SvMAGICAL(sv))
        mg_get(sv);
    if (SvROK(sv))
        sv = MUTABLE_SV(SvRV(sv));
    if (SvTYPE(sv) == SVt_REGEXP)
        return (REGEXP*) sv;

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

        REGEXP * SvRX(SV *sv)
Returns a boolean indicating whether the SV (or the one it references) is a REGEXP.

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

        bool    SvRXOK(SV* sv)

Simple Exception Handling Macros

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

                dXCPT;
Introduces a catch block. See "Exception Handling" in perlguts.
Rethrows a previously caught exception. See "Exception Handling" in perlguts. 

                XCPT_RETHROW;
Ends a try block. See "Exception Handling" in perlguts.
Starts a try block. See "Exception Handling" in perlguts.

Stack Manipulation Macros

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

                dMARK;
Saves the original stack mark for the XSUB. See "ORIGMARK". 

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

                dSP;
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)
Stack marker variable for the XSUB. See "dMARK".
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)
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)
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)
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)
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)
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)
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)
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)
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)
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)
The original stack mark for the XSUB. See "dORIGMARK".
Pops an integer off the stack. 

        IV      POPi
Pops a long off the stack. 

        long    POPl
Pops a double off the stack. 

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

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

        char*   POPpbytex
Pops a string off the stack. 

        char*   POPpx
Pops an SV off the stack. 

        SV*     POPs
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)
Opening bracket for arguments on a callback. See "PUTBACK" and perlcall. 

        void    PUSHMARK(SP)
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()
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)
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)
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)
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)
Closing bracket for XSUB arguments. This is usually handled by "xsubpp". See "PUSHMARK" and perlcall for other uses. 

                PUTBACK;
Stack pointer. This is usually handled by "xsubpp". See "dSP" and "SPAGAIN".
Refetch the stack pointer. Used after a callback. See perlcall. 

                SPAGAIN;
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)
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()
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)
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)
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)
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)
Return from XSUB, indicating number of items on the stack. This is usually handled by "xsubpp". 

        void    XSRETURN(int nitems)
Return an empty list from an XSUB immediately. 

                XSRETURN_EMPTY;
Return an integer from an XSUB immediately. Uses "XST_mIV". 

        void    XSRETURN_IV(IV iv)
Return &PL_sv_no from an XSUB immediately. Uses "XST_mNO". 

                XSRETURN_NO;
Return a double from an XSUB immediately. Uses "XST_mNV". 

        void    XSRETURN_NV(NV nv)
Return a copy of a string from an XSUB immediately. Uses "XST_mPV". 

        void    XSRETURN_PV(char* str)
Return &PL_sv_undef from an XSUB immediately. Uses "XST_mUNDEF". 

                XSRETURN_UNDEF;
Return an integer from an XSUB immediately. Uses "XST_mUV". 

        void    XSRETURN_UV(IV uv)
Return &PL_sv_yes from an XSUB immediately. Uses "XST_mYES". 

                XSRETURN_YES;
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)
Place &PL_sv_no into the specified position "pos" on the stack. 

        void    XST_mNO(int pos)
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)
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)
Place &PL_sv_undef into the specified position "pos" on the stack. 

        void    XST_mUNDEF(int pos)
Place &PL_sv_yes into the specified position "pos" on the stack. 

        void    XST_mYES(int pos)

SV Flags

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.
Integer type flag for scalars. See "svtype".
Double type flag for scalars. See "svtype".
Pointer type flag for scalars. See "svtype".
Type flag for arrays. See "svtype".
Type flag for code refs. See "svtype".
Type flag for hashes. See "svtype".
Type flag for blessed scalars. See "svtype".

SV Manipulation Functions

Returns a true SV if "b" is a true value, or a false SV if "b" is 0.

See also "PL_sv_yes" and "PL_sv_no".

        SV *    boolSV(bool b)
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: %"SVf"::%"SVf"(%s)", "ouch" "awk", "eee_yow");
        void    croak_xs_usage(const CV *const cv,
                               const char *const params)
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)
Creates an RV wrapper for an SV. The reference count for the original SV is incremented. 

        SV*     newRV_inc(SV* sv)
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)
Returns the length of the string which is in the SV. See "SvLEN". 

        STRLEN  SvCUR(SV* sv)
Set the current length of the string which is in the SV. See "SvCUR" and "SvIV_set". 

        void    SvCUR_set(SV* sv, STRLEN len)
Returns a pointer to the spot just after the last character in the string which is in the SV, where there is usually a trailing null (even though Perl scalars do not strictly require it). See "SvCUR". Access the character as *(SvEND(sv)).

Warning: If "SvCUR" is equal to "SvLEN", then "SvEND" points to unallocated memory.

        char*   SvEND(SV* sv)
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)
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)
Returns a U32 value indicating whether the SV contains an integer. 

        U32     SvIOK(SV* sv)
Returns a U32 value indicating whether the SV contains an integer. Checks the private setting. Use "SvIOK" instead. 

        U32     SvIOKp(SV* sv)
Returns a boolean indicating whether the SV contains a signed integer. 

        bool    SvIOK_notUV(SV* sv)
Unsets the IV status of an SV. 

        void    SvIOK_off(SV* sv)
Tells an SV that it is an integer. 

        void    SvIOK_on(SV* sv)
Tells an SV that it is an integer and disables all other OK bits. 

        void    SvIOK_only(SV* sv)
Tells and SV that it is an unsigned integer and disables all other OK bits. 

        void    SvIOK_only_UV(SV* sv)
Returns a boolean indicating whether the SV contains an unsigned integer. 

        bool    SvIOK_UV(SV* sv)
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)
Returns a boolean indicating whether the SV is Copy-On-Write shared hash key scalar. 

        bool    SvIsCOW_shared_hash(SV* sv)
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)
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)
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)
Like "SvIV" but doesn't process magic. 

        IV      SvIV_nomg(SV* sv)
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)
Returns the size of the string buffer in the SV, not including any part attributable to "SvOOK". See "SvCUR". 

        STRLEN  SvLEN(SV* sv)
Set the actual length of the string which is in the SV. See "SvIV_set". 

        void    SvLEN_set(SV* sv, STRLEN len)
Set the value of the MAGIC pointer in sv to val. See "SvIV_set". 

        void    SvMAGIC_set(SV* sv, MAGIC* val)
Returns a U32 value indicating whether the SV contains a number, integer or double. 

        U32     SvNIOK(SV* sv)
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)
Unsets the NV/IV status of an SV. 

        void    SvNIOK_off(SV* sv)
Returns a U32 value indicating whether the SV contains a double. 

        U32     SvNOK(SV* sv)
Returns a U32 value indicating whether the SV contains a double. Checks the private setting. Use "SvNOK" instead. 

        U32     SvNOKp(SV* sv)
Unsets the NV status of an SV. 

        void    SvNOK_off(SV* sv)
Tells an SV that it is a double. 

        void    SvNOK_on(SV* sv)
Tells an SV that it is a double and disables all other OK bits. 

        void    SvNOK_only(SV* sv)
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)
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)
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)
Like "SvNV" but doesn't process magic. 

        NV      SvNV_nomg(SV* sv)
Set the value of the NV pointer in sv to val. See "SvIV_set". 

        void    SvNV_set(SV* sv, NV val)
Returns a U32 value indicating whether the value is defined. This is only meaningful for scalars. 

        U32     SvOK(SV* sv)
Returns a U32 indicating whether the pointer to the string buffer is offset. This hack is used internally to speed up removal of characters from the beginning of a SvPV. When SvOOK is true, then the start of the allocated string buffer is actually "SvOOK_offset()" bytes before SvPVX. This offset used to be stored in SvIVX, but is now stored within the spare part of the buffer. 

        U32     SvOOK(SV* sv)
Reads into len the offset from SvPVX back to the true start of the allocated buffer, which will be non-zero if "sv_chop" has been used to efficiently remove characters from start of the buffer. Implemented as a macro, which takes the address of len, which must be of type "STRLEN". Evaluates sv more than once. Sets len to 0 if "SvOOK(sv)" is false. 

        void    SvOOK_offset(NN SV*sv, STRLEN len)
Returns a U32 value indicating whether the SV contains a character string. 

        U32     SvPOK(SV* sv)
Returns a U32 value indicating whether the SV contains a character string. Checks the private setting. Use "SvPOK" instead. 

        U32     SvPOKp(SV* sv)
Unsets the PV status of an SV. 

        void    SvPOK_off(SV* sv)
Tells an SV that it is a string. 

        void    SvPOK_on(SV* sv)
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)
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)
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)
Like "SvPV", but converts sv to byte representation first if necessary. 

        char*   SvPVbyte(SV* sv, STRLEN len)
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)
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)
Like "SvPV_force", but converts sv to byte representation first if necessary. 

        char*   SvPVbyte_force(SV* sv, STRLEN len)
Like "SvPV_nolen", but converts sv to byte representation first if necessary. 

        char*   SvPVbyte_nolen(SV* sv)
Like "SvPV", but converts sv to utf8 first if necessary. 

        char*   SvPVutf8(SV* sv, STRLEN len)
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)
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)
Like "SvPV_force", but converts sv to utf8 first if necessary. 

        char*   SvPVutf8_force(SV* sv, STRLEN len)
Like "SvPV_nolen", but converts sv to utf8 first if necessary. 

        char*   SvPVutf8_nolen(SV* sv)
Returns a pointer to the physical string in the SV. The SV must contain a string.

This is also used to store the name of an autoloaded subroutine in an XS AUTOLOAD routine. See "Autoloading with XSUBs" in perlguts.

        char*   SvPVX(SV* sv)
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 "SvPV". 

        char*   SvPVx(SV* sv, STRLEN len)
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)
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)
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)
Like "SvPV" but doesn't process magic. 

        char*   SvPV_nomg(SV* sv, STRLEN len)
Like "SvPV_nolen" but doesn't process magic. 

        char*   SvPV_nomg_nolen(SV* sv)
Set the value of the PV pointer in sv to val. See "SvIV_set". 

        void    SvPV_set(SV* sv, char* val)
Returns the value of the object's reference count. 

        U32     SvREFCNT(SV* sv)
Decrements the reference count of the given SV. 

        void    SvREFCNT_dec(SV* sv)
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)
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)
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)
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)
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)
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)
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)
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)
Tests if the SV is an RV. 

        U32     SvROK(SV* sv)
Unsets the RV status of an SV. 

        void    SvROK_off(SV* sv)
Tells an SV that it is an RV. 

        void    SvROK_on(SV* sv)
Dereferences an RV to return the SV. 

        SV*     SvRV(SV* sv)
Set the value of the RV pointer in sv to val. See "SvIV_set". 

        void    SvRV_set(SV* sv, SV* val)
Returns the stash of the SV. 

        HV*     SvSTASH(SV* sv)
Set the value of the STASH pointer in sv to val. See "SvIV_set". 

        void    SvSTASH_set(SV* sv, HV* val)
Taints an SV if tainting is enabled, and if some input to the current expression is tainted--usually a variable, but possibly also implicit inputs such as locale settings. "SvTAINT" propagates that taintedness to the outputs of an expression in a pessimistic fashion; i.e., without paying attention to precisely which outputs are influenced by which inputs. 

        void    SvTAINT(SV* sv)
Checks to see if an SV is tainted. Returns TRUE if it is, FALSE if not. 

        bool    SvTAINTED(SV* sv)
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)
Marks an SV as tainted if tainting is enabled. 

        void    SvTAINTED_on(SV* sv)
Returns a boolean indicating whether Perl would evaluate the SV as true or false. See SvOK() for a defined/undefined test. Handles 'get' magic unless the scalar is already SvPOK, SvIOK or SvNOK (the public, not the private flags). 

        bool    SvTRUE(SV* sv)
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_nomg(SV* sv)
Returns the type of the SV. See "svtype". 

        svtype  SvTYPE(SV* sv)
Returns a boolean indicating whether the SV contains an unsigned integer. 

        bool    SvUOK(SV* sv)
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)
Returns a U32 value indicating the UTF-8 status of an SV. If things are set-up properly, this indicates whether or not the SV contains UTF-8 encoded data. Call this after SvPV() in case any call to string overloading updates the internal flag. 

        U32     SvUTF8(SV* sv)
Unsets the UTF-8 status of an SV (the data is not changed, just the flag). Do not use frivolously. 

        void    SvUTF8_off(SV *sv)
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)
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)
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)
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)
Like "SvUV" but doesn't process magic. 

        UV      SvUV_nomg(SV* sv)
Set the value of the UV pointer in sv to val. See "SvIV_set". 

        void    SvUV_set(SV* sv, UV val)
Returns a boolean indicating whether the SV contains a v-string. 

        bool    SvVOK(SV* sv)
Like "sv_catpvn" but doesn't process magic. 

        void    sv_catpvn_nomg(SV* sv, const char* ptr,
                               STRLEN len)
Like "sv_catpv" but doesn't process magic. 

        void    sv_catpv_nomg(SV* sv, const char* ptr)
Like "sv_catsv" but doesn't process magic. 

        void    sv_catsv_nomg(SV* dsv, SV* ssv)
Exactly like "sv_derived_from_pv", but doesn't take a "flags" parameter. 

        bool    sv_derived_from(SV* sv, const char *const name)
Exactly like "sv_derived_from_pvn", but takes a nul-terminated string instead of a string/length pair. 

        bool    sv_derived_from_pv(SV* sv,
                                   const char *const name,
                                   U32 flags)
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.

Currently, the only significant value for "flags" is SVf_UTF8.

        bool    sv_derived_from_pvn(SV* sv,
                                    const char *const name,
                                    const STRLEN len, U32 flags)
Exactly like "sv_derived_from_pvn", but takes the name string in the form of an SV instead of a string/length pair. 

        bool    sv_derived_from_sv(SV* sv, SV *namesv,
                                   U32 flags)
Like "sv_does_pv", but doesn't take a "flags" parameter. 

        bool    sv_does(SV* sv, const char *const name)
Like "sv_does_sv", but takes a nul-terminated string instead of an SV. 

        bool    sv_does_pv(SV* sv, const char *const name,
                           U32 flags)
Like "sv_does_sv", but takes a string/length pair instead of an SV. 

        bool    sv_does_pvn(SV* sv, const char *const name,
                            const STRLEN len, U32 flags)
Returns a boolean indicating whether the SV performs a specific, named role. The SV can be a Perl object or the name of a Perl class. 

        bool    sv_does_sv(SV* sv, SV* namesv, U32 flags)
Dump the contents of all SVs not yet freed (debugging aid). 

        void    sv_report_used()
Like "sv_setsv" but doesn't process magic. 

        void    sv_setsv_nomg(SV* dsv, SV* ssv)
Like sv_utf8_upgrade, but doesn't do magic on "sv". 

        STRLEN  sv_utf8_upgrade_nomg(NN SV *sv)

SV-Body Allocation

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. Get-magic is ignored. 

        I32     looks_like_number(SV *const sv)
Creates an RV wrapper for an SV. The reference count for the original SV is not incremented. 

        SV*     newRV_noinc(SV *const sv)
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 perlhacktips). The older API is still there for use in XS modules supporting older perls.

        SV*     newSV(const STRLEN len)
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 *const hek)
Creates a new SV and copies an integer into it. The reference count for the SV is set to 1. 

        SV*     newSViv(const IV i)
Creates a new SV and copies a floating point value into it. The reference count for the SV is set to 1. 

        SV*     newSVnv(const NV n)
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 *const s, const STRLEN len)
Creates a new SV and initializes it with the string formatted like "sprintf". 

        SV*     newSVpvf(const char *const pat, ...)
Creates a new SV and copies a buffer into it, which may contain NUL characters ("\0") and other binary data. The reference count for the SV is set to 1. Note that if "len" is zero, Perl will create a zero length (Perl) string. You are responsible for ensuring that the source buffer is at least "len" bytes long. If the "buffer" argument is NULL the new SV will be undefined. 

        SV*     newSVpvn(const char *const s, const STRLEN len)
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 "sv_2mortal()" is called on the result before returning. If "SVf_UTF8" is set, "s" is considered to be in UTF-8 and the "SVf_UTF8" flag 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 *const s,
                               const STRLEN len,
                               const U32 flags)
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 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)
Like "newSVpvn", but takes a literal string instead of a string/length pair. 

        SV*     newSVpvs(const char* s)
Like "newSVpvn_flags", but takes a literal string instead of a string/length pair. 

        SV*     newSVpvs_flags(const char* s, U32 flags)
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)
Like "newSVpvn_share", but takes a nul-terminated string instead of a string/length pair. 

        SV*     newSVpv_share(const char* s, U32 hash)
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 *const rv,
                        const char *const classname)
Creates a new SV which is an exact duplicate of the original SV. (Uses "sv_setsv".) 

        SV*     newSVsv(SV *const old)
Creates a new SV and copies an unsigned integer into it. The reference count for the SV is set to 1. 

        SV*     newSVuv(const UV u)
Creates a new SV, of the type specified. The reference count for the new SV is set to 1. 

        SV*     newSV_type(const svtype type)
This macro is only used by sv_true() or its macro equivalent, and only if the latter's argument is neither SvPOK, SvIOK nor SvNOK. It calls sv_2bool_flags with the SV_GMAGIC flag. 

        bool    sv_2bool(SV *const sv)
This function is only used by sv_true() and friends, and only if the latter's argument is neither SvPOK, SvIOK nor SvNOK. If the flags contain SV_GMAGIC, then it does an mg_get() first. 

        bool    sv_2bool_flags(SV *const sv, const I32 flags)
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 gv_fetchsv. 

        CV*     sv_2cv(SV* sv, HV **const st, GV **const gvp,
                       const I32 lref)
Using various gambits, try to get an IO from an SV: the IO slot if its a GV; or the recursive result if we're an RV; or the IO slot of the symbol named after the PV if we're a string.

'Get' magic is ignored on the sv passed in, but will be called on "SvRV(sv)" if sv is an RV.

        IO*     sv_2io(SV *const sv)
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 *const sv, const I32 flags)
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 *const sv)
Return the num value of an SV, doing any necessary string or integer conversion. If flags includes SV_GMAGIC, does an mg_get() first. Normally used via the "SvNV(sv)" and "SvNVx(sv)" macros. 

        NV      sv_2nv_flags(SV *const sv, const I32 flags)
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 *const lp)
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 *const lp)
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 *const sv, STRLEN *const lp,
                             const I32 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 *const sv, const I32 flags)
Remove any string offset. You should normally use the "SvOOK_off" macro wrapper instead. 

        int     sv_backoff(SV *const sv)
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 *const sv, HV *const stash)
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 *const sv, const char* ptr)
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 *const sv, const char *const pat,
                          ...)
Like "sv_catpvf", but also handles 'set' magic. 

        void    sv_catpvf_mg(SV *const sv,
                             const char *const pat, ...)
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)
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 the "SV_SMAGIC" bit set, will "mg_set" on "dsv" afterwards if appropriate. "sv_catpvn" and "sv_catpvn_nomg" are implemented in terms of this function. 

        void    sv_catpvn_flags(SV *const dstr,
                                const char *sstr,
                                const STRLEN len,
                                const I32 flags)
Like "sv_catpvn", but takes a literal string instead of a string/length pair. 

        void    sv_catpvs(SV* sv, const char* s)
Like "sv_catpvn_flags", but takes a literal string instead of a string/length pair. 

        void    sv_catpvs_flags(SV* sv, const char* s,
                                I32 flags)
Like "sv_catpvn_mg", but takes a literal string instead of a string/length pair. 

        void    sv_catpvs_mg(SV* sv, const char* s)
Like "sv_catpvn_nomg", but takes a literal string instead of a string/length pair. 

        void    sv_catpvs_nomg(SV* sv, const char* s)
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. If "flags" has the "SV_SMAGIC" bit set, will "mg_set" on the modified SV if appropriate. 

        void    sv_catpv_flags(SV *dstr, const char *sstr,
                               const I32 flags)
Like "sv_catpv", but also handles 'set' magic. 

        void    sv_catpv_mg(SV *const sv, const char *const ptr)
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)
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 "ssv", if appropriate, before reading it. If the "flags" contain "SV_SMAGIC", "mg_set" will be called on the modified SV afterward, if appropriate. "sv_catsv" and "sv_catsv_nomg" are implemented in terms of this function. 

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

The unfortunate similarity of this function's name to that of Perl's "chop" operator is strictly coincidental. This function works from the left; "chop" works from the right.

        void    sv_chop(SV *const sv, const char *const ptr)
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 *const orig_sv)
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 *const sv1, SV *const sv2)
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 and will coerce its args to strings if necessary. If the flags include SV_GMAGIC, it handles get magic. See also "sv_cmp_locale_flags". 

        I32     sv_cmp_flags(SV *const sv1, SV *const sv2,
                             const U32 flags)
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 *const sv1, SV *const sv2)
Compares the strings in two SVs in a locale-aware manner. Is UTF-8 and 'use bytes' aware and will coerce its args to strings if necessary. If the flags contain SV_GMAGIC, it handles get magic. See also "sv_cmp_flags". 

        I32     sv_cmp_locale_flags(SV *const sv1,
                                    SV *const sv2,
                                    const U32 flags)
This calls "sv_collxfrm_flags" with the SV_GMAGIC flag. See "sv_collxfrm_flags". 

        char*   sv_collxfrm(SV *const sv, STRLEN *const nxp)
Add Collate Transform magic to an SV if it doesn't already have it. If the flags contain SV_GMAGIC, it handles get-magic.

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_flags(SV *const sv,
                                  STRLEN *const nxp,
                                  I32 const flags)
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 *const dsv, SV *const ssv)
Auto-decrement of the value in the SV, doing string to numeric conversion if necessary. Handles 'get' magic and operator overloading. 

        void    sv_dec(SV *const sv)
Auto-decrement of the value in the SV, doing string to numeric conversion if necessary. Handles operator overloading. Skips handling 'get' magic. 

        void    sv_dec_nomg(SV *const sv)
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)
Returns a boolean indicating whether the strings in the two SVs are identical. Is UTF-8 and 'use bytes' aware and coerces its args to strings if necessary. If the flags include SV_GMAGIC, it handles get-magic, too. 

        I32     sv_eq_flags(SV* sv1, SV* sv2, const U32 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 unreffing. "sv_force_normal" calls this function with flags set to 0. 

        void    sv_force_normal_flags(SV *const sv,
                                      const U32 flags)
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 *const sv)
Get a line from the filehandle and store it into the SV, optionally appending to the currently-stored string. 

        char*   sv_gets(SV *const sv, PerlIO *const fp,
                        I32 append)
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 *const sv, STRLEN newlen)
Auto-increment of the value in the SV, doing string to numeric conversion if necessary. Handles 'get' magic and operator overloading. 

        void    sv_inc(SV *const sv)
Auto-increment of the value in the SV, doing string to numeric conversion if necessary. Handles operator overloading. Skips handling 'get' magic. 

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

        void    sv_insert(SV *const bigstr, const STRLEN offset,
                          const STRLEN len,
                          const char *const little,
                          const STRLEN littlelen)
Same as "sv_insert", but the extra "flags" are passed to 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)
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 *const name)
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)
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 *const sv)
Returns the number of characters in the string in an SV, counting wide UTF-8 bytes as a single character. Handles magic and type coercion. 

        STRLEN  sv_len_utf8(SV *const sv)
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 *const sv, SV *const obj,
                         const int how, const char *const name,
                         const I32 namlen)
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 *const sv, SV *const obj,
                            const int how,
                            const MGVTBL *const vtbl,
                            const char *const name,
                            const I32 namlen)
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 *const oldsv)
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()
Increment an SV's reference count. Use the "SvREFCNT_inc()" wrapper instead. 

        SV*     sv_newref(SV *const sv)
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 *const sv, I32 *const offsetp)
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.

Use "sv_pos_u2b_flags" in preference, which correctly handles strings longer than 2Gb.

        void    sv_pos_u2b(SV *const sv, I32 *const offsetp,
                           I32 *const lenp)
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 type coercion. flags is passed to "SvPV_flags", and usually should be "SV_GMAGIC|SV_CONST_RETURN" to handle magic. 

        STRLEN  sv_pos_u2b_flags(SV *const sv, STRLEN uoffset,
                                 STRLEN *const lenp, U32 flags)
The backend for the "SvPVbytex_force" macro. Always use the macro instead. 

        char*   sv_pvbyten_force(SV *const sv, STRLEN *const lp)
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)
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 *const sv,
                                   STRLEN *const lp,
                                   const I32 flags)
The backend for the "SvPVutf8x_force" macro. Always use the macro instead. 

        char*   sv_pvutf8n_force(SV *const sv, STRLEN *const lp)
Returns a string describing what the SV is a reference to. 

        const char* sv_reftype(const SV *const sv, const int ob)
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 *const sv, SV *const nsv)
Underlying implementation for the "reset" Perl function. Note that the perl-level function is vaguely deprecated. 

        void    sv_reset(const char* s, HV *const stash)
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 *const sv)
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 *const sv, const IV num)
Like "sv_setiv", but also handles 'set' magic. 

        void    sv_setiv_mg(SV *const sv, const IV i)
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 *const sv, const NV num)
Like "sv_setnv", but also handles 'set' magic. 

        void    sv_setnv_mg(SV *const sv, const NV num)
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 *const sv, const char *const ptr)
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 *const sv, const char *const pat,
                          ...)
Like "sv_setpvf", but also handles 'set' magic. 

        void    sv_setpvf_mg(SV *const sv,
                             const char *const pat, ...)
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 *const sv, const IV num)
Like "sv_setpviv", but also handles 'set' magic. 

        void    sv_setpviv_mg(SV *const sv, const IV iv)
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 *const sv, const char *const ptr,
                          const STRLEN len)
Like "sv_setpvn", but also handles 'set' magic. 

        void    sv_setpvn_mg(SV *const sv,
                             const char *const ptr,
                             const STRLEN len)
Like "sv_setpvn", but takes a literal string instead of a string/length pair. 

        void    sv_setpvs(SV* sv, const char* s)
Like "sv_setpvn_mg", but takes a literal string instead of a string/length pair. 

        void    sv_setpvs_mg(SV* sv, const char* s)
Like "sv_setpv", but also handles 'set' magic. 

        void    sv_setpv_mg(SV *const sv, const char *const ptr)
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 *const rv,
                             const char *const classname,
                             const IV iv)
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 *const rv,
                             const char *const classname,
                             const NV nv)
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 *const rv,
                             const char *const classname,
                             void *const pv)
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 *const rv,
                              const char *const classname,
                              const char *const pv,
                              const STRLEN n)
Like "sv_setref_pvn", but takes a literal string instead of a string/length pair. 

        SV *    sv_setref_pvs(const char* s)
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 *const rv,
                             const char *const classname,
                             const UV uv)
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)
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,
                               const I32 flags)
Like "sv_setsv", but also handles 'set' magic. 

        void    sv_setsv_mg(SV *const dstr, SV *const sstr)
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 *const sv, const UV num)
Like "sv_setuv", but also handles 'set' magic. 

        void    sv_setuv_mg(SV *const sv, const UV u)
Test an SV for taintedness. Use "SvTAINTED" instead. 

        bool    sv_tainted(SV *const sv)
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 *const sv)
Removes all magic of type "type" from an SV. 

        int     sv_unmagic(SV *const sv, const int type)
Removes all magic of type "type" with the specified "vtbl" from an SV. 

        int     sv_unmagicext(SV *const sv, const int type,
                              MGVTBL *vtbl)
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 *const ref, const U32 flags)
Untaint an SV. Use "SvTAINTED_off" instead. 

        void    sv_untaint(SV *const sv)
Upgrade an SV to a more complex form. Generally adds a new body type to the SV, then copies across as much information as possible from the old body. It croaks if the SV is already in a more complex form than requested. You generally want to use the "SvUPGRADE" macro wrapper, which checks the type before calling "sv_upgrade", and hence does not croak. See also "svtype". 

        void    sv_upgrade(SV *const sv, svtype new_type)
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". It must be the start of a mallocked block of memory, and not a pointer to the middle of it. 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 *const sv, char* ptr,
                                const STRLEN len,
                                const U32 flags)
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 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 *const sv)
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 *const sv,
                                  const bool fail_ok)
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 *const sv)
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)
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 *const sv,
                                      const I32 flags)
Like sv_utf8_upgrade, but doesn't do magic on "sv". 

        STRLEN  sv_utf8_upgrade_nomg(SV *sv)
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 *const sv, const char *const pat,
                           va_list *const args)
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 *const sv, const char *const pat,
                            const STRLEN patlen,
                            va_list *const args,
                            SV **const svargs, const I32 svmax,
                            bool *const maybe_tainted)
Like "sv_vcatpvf", but also handles 'set' magic.

Usually used via its frontend "sv_catpvf_mg".

        void    sv_vcatpvf_mg(SV *const sv,
                              const char *const pat,
                              va_list *const args)
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 *const sv, const char *const pat,
                           va_list *const args)
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 *const sv, const char *const pat,
                            const STRLEN patlen,
                            va_list *const args,
                            SV **const svargs, const I32 svmax,
                            bool *const maybe_tainted)
Like "sv_vsetpvf", but also handles 'set' magic.

Usually used via its frontend "sv_setpvf_mg".

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

Unicode Support

Compares the sequence of characters (stored as octets) in "b", "blen" with the sequence of characters (stored as UTF-8) in "u", "ulen". Returns 0 if they are equal, -1 or -2 if the first string is less than the second string, +1 or +2 if the first string is greater than the second string.

-1 or +1 is returned if the shorter string was identical to the start of the longer string. -2 or +2 is returned if the was a difference between characters within the strings.

        int     bytes_cmp_utf8(const U8 *b, STRLEN blen,
                               const U8 *u, STRLEN ulen)
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)
Converts a string "s" of length "len" bytes from the native encoding into UTF-8. Returns a pointer to the newly-created string, and sets "len" to reflect the new length in bytes.

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)
Returns true if the leading portions of the strings "s1" and "s2" (either or both of which may be in UTF-8) are the same case-insensitively; false otherwise. How far into the strings to compare is determined by other input parameters.

If "u1" is true, the string "s1" is assumed to be in UTF-8-encoded Unicode; otherwise it is assumed to be in native 8-bit encoding. Correspondingly for "u2" with respect to "s2".

If the byte length "l1" is non-zero, it says how far into "s1" to check for fold equality. In other words, "s1"+"l1" will be used as a goal to reach. The scan will not be considered to be a match unless the goal is reached, and scanning won't continue past that goal. Correspondingly for "l2" with respect to "s2".

If "pe1" is non-NULL and the pointer it points to is not NULL, that pointer is considered an end pointer beyond which scanning of "s1" will not continue under any circumstances. This means that if both "l1" and "pe1" are specified, and "pe1" is less than "s1"+"l1", the match will never be successful because it can never get as far as its goal (and in fact is asserted against). Correspondingly for "pe2" with respect to "s2".

At least one of "s1" and "s2" must have a goal (at least one of "l1" and "l2" must be non-zero), and if both do, both have to be reached for a successful match. Also, if the fold of a character is multiple characters, all of them must be matched (see tr21 reference below for 'folding').

Upon a successful match, if "pe1" is non-NULL, it will be set to point to the beginning of the next character of "s1" beyond what was matched. Correspondingly for "pe2" and "s2".

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     foldEQ_utf8(const char *s1, char **pe1, UV l1,
                            bool u1, const char *s2, char **pe2,
                            UV l2, bool u2)
Returns true if the first "len" bytes of the string "s" are the same whether or not the string is encoded in UTF-8 (or UTF-EBCDIC on EBCDIC machines). That is, if they are invariant. On ASCII-ish machines, only ASCII characters fit this definition, hence the function's name.

If "len" is 0, it will be calculated using strlen(s).

See also "is_utf8_string"(), "is_utf8_string_loclen"(), and "is_utf8_string_loc"().

        bool    is_ascii_string(const U8 *s, STRLEN len)
DEPRECATED!

Tests if some arbitrary number of bytes begins in a valid UTF-8 character. Note that an INVARIANT (i.e. ASCII on non-EBCDIC machines) character is a valid UTF-8 character. The actual number of bytes in the UTF-8 character will be returned if it is valid, otherwise 0.

This function is deprecated due to the possibility that malformed input could cause reading beyond the end of the input buffer. Use "is_utf8_char_buf" instead.

        STRLEN  is_utf8_char(const U8 *s)
Returns the number of bytes that comprise the first UTF-8 encoded character in buffer "buf". "buf_end" should point to one position beyond the end of the buffer. 0 is returned if "buf" does not point to a complete, valid UTF-8 encoded character.

Note that an INVARIANT character (i.e. ASCII on non-EBCDIC machines) is a valid UTF-8 character.

        STRLEN  is_utf8_char_buf(const U8 *buf,
                                 const U8 *buf_end)
Returns true if the first "len" bytes of string "s" form a valid UTF-8 string, false otherwise. If "len" is 0, it will be calculated using strlen(s) (which means if you use this option, that "s" has to have a terminating NUL byte). Note that all characters being ASCII constitute 'a valid UTF-8 string'.

See also "is_ascii_string"(), "is_utf8_string_loclen"(), and "is_utf8_string_loc"().

        bool    is_utf8_string(const U8 *s, STRLEN len)
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)
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)
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)
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)
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)
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)
The "p" contains the pointer to the UTF-8 string encoding the character that is being converted. This routine assumes that the character at "p" is well-formed.

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 in 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)
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.)

The character at "p" is assumed by this routine to be well-formed.

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

The character at "p" is assumed by this routine to be well-formed.

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

The character at "p" is assumed by this routine to be well-formed.

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

The character at "p" is assumed by this routine to be well-formed.

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

"length" and "flags" are the same as "utf8n_to_uvuni"().

        UV      utf8n_to_uvchr(const U8 *s, STRLEN curlen,
                               STRLEN *retlen, U32 flags)
Bottom level UTF-8 decode routine. Returns the code point value of the first character in the string "s", which is assumed to be in UTF-8 (or UTF-EBCDIC) encoding, and no longer than "curlen" bytes; *retlen (if "retlen" isn't NULL) will be set to the length, in bytes, of that character.

The value of "flags" determines the behavior when "s" does not point to a well-formed UTF-8 character. If "flags" is 0, when a malformation is found, zero is returned and *retlen is set so that ("s" + *retlen) is the next possible position in "s" that could begin a non-malformed character. Also, if UTF-8 warnings haven't been lexically disabled, a warning is raised.

Various ALLOW flags can be set in "flags" to allow (and not warn on) individual types of malformations, such as the sequence being overlong (that is, when there is a shorter sequence that can express the same code point; overlong sequences are expressly forbidden in the UTF-8 standard due to potential security issues). Another malformation example is the first byte of a character not being a legal first byte. See utf8.h for the list of such flags. For allowed 0 length strings, this function returns 0; for allowed overlong sequences, the computed code point is returned; for all other allowed malformations, the Unicode REPLACEMENT CHARACTER is returned, as these have no determinable reasonable value.

The UTF8_CHECK_ONLY flag overrides the behavior when a non-allowed (by other flags) malformation is found. If this flag is set, the routine assumes that the caller will raise a warning, and this function will silently just set "retlen" to "-1" and return zero.

Certain code points are considered problematic. These are Unicode surrogates, Unicode non-characters, and code points above the Unicode maximum of 0x10FFFF. By default these are considered regular code points, but certain situations warrant special handling for them. If "flags" contains UTF8_DISALLOW_ILLEGAL_INTERCHANGE, all three classes are treated as malformations and handled as such. The flags UTF8_DISALLOW_SURROGATE, UTF8_DISALLOW_NONCHAR, and UTF8_DISALLOW_SUPER (meaning above the legal Unicode maximum) can be set to disallow these categories individually.

The flags UTF8_WARN_ILLEGAL_INTERCHANGE, UTF8_WARN_SURROGATE, UTF8_WARN_NONCHAR, and UTF8_WARN_SUPER will cause warning messages to be raised for their respective categories, but otherwise the code points are considered valid (not malformations). To get a category to both be treated as a malformation and raise a warning, specify both the WARN and DISALLOW flags. (But note that warnings are not raised if lexically disabled nor if UTF8_CHECK_ONLY is also specified.)

Very large code points (above 0x7FFF_FFFF) are considered more problematic than the others that are above the Unicode legal maximum. There are several reasons: they requre at least 32 bits to represent them on ASCII platforms, are not representable at all on EBCDIC platforms, and the original UTF-8 specification never went above this number (the current 0x10FFFF limit was imposed later). (The smaller ones, those that fit into 32 bits, are representable by a UV on ASCII platforms, but not by an IV, which means that the number of operations that can be performed on them is quite restricted.) The UTF-8 encoding on ASCII platforms for these large code points begins with a byte containing 0xFE or 0xFF. The UTF8_DISALLOW_FE_FF flag will cause them to be treated as malformations, while allowing smaller above-Unicode code points. (Of course UTF8_DISALLOW_SUPER will treat all above-Unicode code points, including these, as malformations.) Similarly, UTF8_WARN_FE_FF acts just like the other WARN flags, but applies just to these code points.

All other code points corresponding to Unicode characters, including private use and those yet to be assigned, are never considered malformed and never warn.

Most code should use "utf8_to_uvchr_buf"() rather than call this directly.

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

Returns the native 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.

Some, but not all, UTF-8 malformations are detected, and in fact, some malformed input could cause reading beyond the end of the input buffer, which is why this function is deprecated. Use "utf8_to_uvchr_buf" instead.

If "s" points to one of the detected malformations, and UTF8 warnings are enabled, zero is returned and *retlen is set (if "retlen" isn't NULL) to -1. If those warnings are off, the computed value if well-defined (or the Unicode REPLACEMENT CHARACTER, if not) is silently returned, and *retlen is set (if "retlen" isn't NULL) so that ("s" + *retlen) is the next possible position in "s" that could begin a non-malformed character. See "utf8n_to_uvuni" for details on when the REPLACEMENT CHARACTER is returned.

        UV      utf8_to_uvchr(const U8 *s, STRLEN *retlen)
Returns the native code point of the first character in the string "s" which is assumed to be in UTF-8 encoding; "send" points to 1 beyond the end of "s". *retlen will be set to the length, in bytes, of that character.

If "s" does not point to a well-formed UTF-8 character and UTF8 warnings are enabled, zero is returned and *retlen is set (if "retlen" isn't NULL) to -1. If those warnings are off, the computed value if well-defined (or the Unicode REPLACEMENT CHARACTER, if not) is silently returned, and *retlen is set (if "retlen" isn't NULL) so that ("s" + *retlen) is the next possible position in "s" that could begin a non-malformed character. See "utf8n_to_uvuni" for details on when the REPLACEMENT CHARACTER is returned.

        UV      utf8_to_uvchr_buf(const U8 *s, const U8 *send,
                                  STRLEN *retlen)
DEPRECATED!

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).

Some, but not all, UTF-8 malformations are detected, and in fact, some malformed input could cause reading beyond the end of the input buffer, which is why this function is deprecated. Use "utf8_to_uvuni_buf" instead.

If "s" points to one of the detected malformations, and UTF8 warnings are enabled, zero is returned and *retlen is set (if "retlen" doesn't point to NULL) to -1. If those warnings are off, the computed value if well-defined (or the Unicode REPLACEMENT CHARACTER, if not) is silently returned, and *retlen is set (if "retlen" isn't NULL) so that ("s" + *retlen) is the next possible position in "s" that could begin a non-malformed character. See "utf8n_to_uvuni" for details on when the REPLACEMENT CHARACTER is returned.

        UV      utf8_to_uvuni(const U8 *s, STRLEN *retlen)
Returns the Unicode code point of the first character in the string "s" which is assumed to be in UTF-8 encoding; "send" points to 1 beyond the end of "s". "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 and UTF8 warnings are enabled, zero is returned and *retlen is set (if "retlen" isn't NULL) to -1. If those warnings are off, the computed value if well-defined (or the Unicode REPLACEMENT CHARACTER, if not) is silently returned, and *retlen is set (if "retlen" isn't NULL) so that ("s" + *retlen) is the next possible position in "s" that could begin a non-malformed character. See "utf8n_to_uvuni" for details on when the REPLACEMENT CHARACTER is returned.

        UV      utf8_to_uvuni_buf(const U8 *s, const U8 *send,
                                  STRLEN *retlen)
Adds the UTF-8 representation of the Native code point "uv" to the end of the string "d"; "d" should 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)
Adds the UTF-8 representation of the code point "uv" to the end of the string "d"; "d" should 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);

This is the recommended Unicode-aware way of saying

    *(d++) = uv;

This function will convert to UTF-8 (and not warn) even code points that aren't legal Unicode or are problematic, unless "flags" contains one or more of the following flags:

If "uv" is a Unicode surrogate code point and UNICODE_WARN_SURROGATE is set, the function will raise a warning, provided UTF8 warnings are enabled. If instead UNICODE_DISALLOW_SURROGATE is set, the function will fail and return NULL. If both flags are set, the function will both warn and return NULL.

The UNICODE_WARN_NONCHAR and UNICODE_DISALLOW_NONCHAR flags correspondingly affect how the function handles a Unicode non-character. And, likewise for the UNICODE_WARN_SUPER and UNICODE_DISALLOW_SUPER flags, and code points that are above the Unicode maximum of 0x10FFFF. Code points above 0x7FFF_FFFF (which are even less portable) can be warned and/or disallowed even if other above-Unicode code points are accepted by the UNICODE_WARN_FE_FF and UNICODE_DISALLOW_FE_FF flags.

And finally, the flag UNICODE_WARN_ILLEGAL_INTERCHANGE selects all four of the above WARN flags; and UNICODE_DISALLOW_ILLEGAL_INTERCHANGE selects all four DISALLOW flags.

        U8*     uvuni_to_utf8_flags(U8 *d, UV uv, UV flags)

Variables created by "xsubpp" and "xsubpp" internal functions

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

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

                dAXMARK;
Sets up the "items" variable. This is usually handled automatically by "xsubpp" by calling "dXSARGS". 

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

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

                dXSI32;
Variable which is setup by "xsubpp" to indicate the number of items on the stack. See "Variable-length Parameter Lists" in perlxs. 

        I32     items
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
Used by "xsubpp" to hook up XSUBs as Perl subs. Adds Perl prototypes to the subs.
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
Used to access elements on the XSUB's stack. 

        SV*     ST(int ix)
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
The SV* corresponding to the $_ variable. Works even if there is a lexical $_ in scope.
Macro to declare an XSUB and its C parameter list. This is handled by "xsubpp". It is the same as using the more explicit XS_EXTERNAL macro.
Macro to verify that the perl api version an XS module has been compiled against matches the api version of the perl interpreter it's being loaded into. 

                XS_APIVERSION_BOOTCHECK;
Macro to declare an XSUB and its C parameter list explicitly exporting the symbols.
Macro to declare an XSUB and its C parameter list without exporting the symbols. This is handled by "xsubpp" and generally preferable over exporting the XSUB symbols unnecessarily.
The version identifier for an XS module. This is usually handled automatically by "ExtUtils::MakeMaker". See "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

This is an XS interface to Perl's "die" function.

Take a sprintf-style format pattern and argument list. These are used to generate a string message. If the message does not end with a newline, then it will be extended with some indication of the current location in the code, as described for "mess_sv".

The error message will be used as an exception, by default returning control to the nearest enclosing "eval", but subject to modification by a $SIG{__DIE__} handler. In any case, the "croak" function never returns normally.

For historical reasons, if "pat" is null then the contents of "ERRSV" ($@) will be used as an error message or object instead of building an error message from arguments. If you want to throw a non-string object, or build an error message in an SV yourself, it is preferable to use the "croak_sv" function, which does not involve clobbering "ERRSV".

        void    croak(const char *pat, ...)
Exactly equivalent to "Perl_croak(aTHX_ "%s", PL_no_modify)", but generates terser object code than using "Perl_croak". Less code used on exception code paths reduces CPU cache pressure. 

        void    croak_no_modify()
This is an XS interface to Perl's "die" function.

"baseex" is the error message or object. If it is a reference, it will be used as-is. Otherwise it is used as a string, and if it does not end with a newline then it will be extended with some indication of the current location in the code, as described for "mess_sv".

The error message or object will be used as an exception, by default returning control to the nearest enclosing "eval", but subject to modification by a $SIG{__DIE__} handler. In any case, the "croak_sv" function never returns normally.

To die with a simple string message, the "croak" function may be more convenient.

        void    croak_sv(SV *baseex)
Behaves the same as "croak", except for the return type. It should be used only where the "OP *" return type is required. The function never actually returns. 

        OP *    die(const char *pat, ...)
Behaves the same as "croak_sv", except for the return type. It should be used only where the "OP *" return type is required. The function never actually returns. 

        OP *    die_sv(SV *baseex)
This is an XS interface to Perl's "die" function.

"pat" and "args" are a sprintf-style format pattern and encapsulated argument list. These are used to generate a string message. If the message does not end with a newline, then it will be extended with some indication of the current location in the code, as described for "mess_sv".

The error message will be used as an exception, by default returning control to the nearest enclosing "eval", but subject to modification by a $SIG{__DIE__} handler. In any case, the "croak" function never returns normally.

For historical reasons, if "pat" is null then the contents of "ERRSV" ($@) will be used as an error message or object instead of building an error message from arguments. If you want to throw a non-string object, or build an error message in an SV yourself, it is preferable to use the "croak_sv" function, which does not involve clobbering "ERRSV".

        void    vcroak(const char *pat, va_list *args)
This is an XS interface to Perl's "warn" function.

"pat" and "args" are a sprintf-style format pattern and encapsulated argument list. These are used to generate a string message. If the message does not end with a newline, then it will be extended with some indication of the current location in the code, as described for "mess_sv".

The error message or object will by default be written to standard error, but this is subject to modification by a $SIG{__WARN__} handler.

Unlike with "vcroak", "pat" is not permitted to be null.

        void    vwarn(const char *pat, va_list *args)
This is an XS interface to Perl's "warn" function.

Take a sprintf-style format pattern and argument list. These are used to generate a string message. If the message does not end with a newline, then it will be extended with some indication of the current location in the code, as described for "mess_sv".

The error message or object will by default be written to standard error, but this is subject to modification by a $SIG{__WARN__} handler.

Unlike with "croak", "pat" is not permitted to be null.

        void    warn(const char *pat, ...)
This is an XS interface to Perl's "warn" function.

"baseex" is the error message or object. If it is a reference, it will be used as-is. Otherwise it is used as a string, and if it does not end with a newline then it will be extended with some indication of the current location in the code, as described for "mess_sv".

The error message or object will by default be written to standard error, but this is subject to modification by a $SIG{__WARN__} handler.

To warn with a simple string message, the "warn" function may be more convenient.

        void    warn_sv(SV *baseex)

Undocumented functions

The following functions have been flagged as part of the public API, but are currently undocumented. Use them at your own risk, as the interfaces are subject to change.

If you use one of them, you may wish to consider creating and submitting documentation for it. If your patch is accepted, this will indicate that the interface is stable (unless it is explicitly marked otherwise).

_is_utf8_quotemeta

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, perlxs, perlxstut, perlintern

2021-02-02 perl v5.16.3