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perlintern

NAME
DESCRIPTION
Compile-time scope hooks
Custom Operators
CV Manipulation Functions
CV reference counts and CvOUTSIDE
Embedding Functions
GV Functions
Hash Manipulation Functions
IO Functions
Lexer interface
Magical Functions
Miscellaneous Functions
MRO Functions
Optree Manipulation Functions
Pad Data Structures
Per-Interpreter Variables
Stack Manipulation Macros
SV-Body Allocation
SV Manipulation Functions
Unicode Support
Undocumented functions
AUTHORS
SEE ALSO

NAME

perlintern - autogenerated documentation of purely internal Perl functions

DESCRIPTION

This file is the autogenerated documentation of functions in the Perl interpreter that are documented using Perl's internal documentation format but are not marked as part of the Perl API. In other words, they are not for use in extensions!

Compile-time scope hooks

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

Return an entry from the BHK structure. which is a preprocessor token indicating which entry to return. If the appropriate flag is not set this will return NULL . The type of the return value depends on which entry you ask for.
```
	void *	BhkENTRY(BHK *hk, which)
```
BhkFLAGS
NOTE: this function is experimental and may change or be removed without notice.

Return the BHK's flags.
```
	U32	BhkFLAGS(BHK *hk)
```
CALL_BLOCK_HOOKS
NOTE: this function is experimental and may change or be removed without notice.

Call all the registered block hooks for type which . which is a preprocessing token; the type of arg depends on which .
```
	void	CALL_BLOCK_HOOKS(which, arg)
```

Custom Operators

core_prototype
This function assigns the prototype of the named core function to sv , or to a new mortal SV if sv is NULL . It returns the modified sv , or NULL if the core function has no prototype. code is a code as returned by keyword() . It must not be equal to 0.
```
	SV *	core_prototype(SV *sv, const char *name,
		               const int code,
		               int * const opnum)
```

CV Manipulation Functions

docatch
Check for the cases 0 or 3 of cur_env.je_ret, only used inside an eval context.

0 is used as continue inside eval,

3 is used for a die caught by an inner eval - continue inner loop

See cop.h: je_mustcatch, when set at any runlevel to TRUE, means eval ops must establish a local jmpenv to handle exception traps.
```
	OP*	docatch(Perl_ppaddr_t firstpp)
```

CV reference counts and CvOUTSIDE

CvWEAKOUTSIDE
Each CV has a pointer, CvOUTSIDE() , to its lexically enclosing CV (if any). Because pointers to anonymous sub prototypes are stored in & pad slots, it is a possible to get a circular reference, with the parent pointing to the child and vice-versa. To avoid the ensuing memory leak, we do not increment the reference count of the CV pointed to by CvOUTSIDE in the one specific instance that the parent has a & pad slot pointing back to us. In this case, we set the CvWEAKOUTSIDE flag in the child. This allows us to determine under what circumstances we should decrement the refcount of the parent when freeing the child.

There is a further complication with non-closure anonymous subs (i.e. those that do not refer to any lexicals outside that sub). In this case, the anonymous prototype is shared rather than being cloned. This has the consequence that the parent may be freed while there are still active children, e.g.,
```
    BEGIN { $a = sub { eval '$x' } }
```
In this case, the BEGIN is freed immediately after execution since there are no active references to it: the anon sub prototype has CvWEAKOUTSIDE set since it's not a closure, and $a points to the same CV, so it doesn't contribute to BEGIN's refcount either. When $a is executed, the eval '$x' causes the chain of CvOUTSIDE s to be followed, and the freed BEGIN is accessed.

To avoid this, whenever a CV and its associated pad is freed, any & entries in the pad are explicitly removed from the pad, and if the refcount of the pointed-to anon sub is still positive, then that child's CvOUTSIDE is set to point to its grandparent. This will only occur in the single specific case of a non-closure anon prototype having one or more active references (such as $a above).

One other thing to consider is that a CV may be merely undefined rather than freed, eg undef &foo . In this case, its refcount may not have reached zero, but we still delete its pad and its CvROOT etc. Since various children may still have their CvOUTSIDE pointing at this undefined CV, we keep its own CvOUTSIDE for the time being, so that the chain of lexical scopes is unbroken. For example, the following should print 123:
```
    my $x = 123;
    sub tmp { sub { eval '$x' } }
    my $a = tmp();
    undef &tmp;
    print  $a->();
	bool	CvWEAKOUTSIDE(CV *cv)
```

Embedding Functions

cv_dump

dump the contents of a CV

	void	cv_dump(CV *cv, const char *title)

cv_forget_slab
When a CV has a reference count on its slab (CvSLABBED ), it is responsible for making sure it is freed. (Hence, no two CVs should ever have a reference count on the same slab.) The CV only needs to reference the slab during compilation. Once it is compiled and CvROOT attached, it has finished its job, so it can forget the slab.
```
	void	cv_forget_slab(CV *cv)
```

do_dump_pad

Dump the contents of a padlist

	void	do_dump_pad(I32 level, PerlIO *file,
		            PADLIST *padlist, int full)

pad_alloc_name
Allocates a place in the currently-compiling pad (via pad_alloc in perlapi) and then stores a name for that entry. name is adopted and becomes the name entry; it must already contain the name string. typestash and ourstash and the padadd_STATE flag get added to name . None of the other processing of pad_add_name_pvn in perlapi is done. Returns the offset of the allocated pad slot.
```
	PADOFFSET pad_alloc_name(PADNAME *name, U32 flags,
	                         HV *typestash, HV *ourstash)
```
pad_block_start
Update the pad compilation state variables on entry to a new block.
```
	void	pad_block_start(int full)
```

pad_check_dup

Check for duplicate declarations: report any of:

     * a 'my' in the current scope with the same name;
     * an 'our' (anywhere in the pad) with the same name and the
       same stash as 'ourstash'

is_our indicates that the name to check is an "our" declaration.

	void	pad_check_dup(PADNAME *name, U32 flags,
		              const HV *ourstash)

pad_findlex
Find a named lexical anywhere in a chain of nested pads. Add fake entries in the inner pads if it's found in an outer one.

Returns the offset in the bottom pad of the lex or the fake lex. cv is the CV in which to start the search, and seq is the current cop_seq to match against. If warn is true, print appropriate warnings. The out_ * vars return values, and so are pointers to where the returned values should be stored. out_capture , if non-null, requests that the innermost instance of the lexical is captured; out_name is set to the innermost matched pad name or fake pad name; out_flags returns the flags normally associated with the PARENT_FAKELEX_FLAGS field of a fake pad name.

Note that pad_findlex() is recursive; it recurses up the chain of CVs, then comes back down, adding fake entries as it goes. It has to be this way because fake names in anon protoypes have to store in xpadn_low the index into the parent pad.
```
	PADOFFSET pad_findlex(const char *namepv,
	                      STRLEN namelen, U32 flags,
	                      const CV* cv, U32 seq, int warn,
	                      SV** out_capture,
	                      PADNAME** out_name,
	                      int *out_flags)
```
pad_fixup_inner_anons
For any anon CVs in the pad, change CvOUTSIDE of that CV from old_cv to new_cv if necessary. Needed when a newly-compiled CV has to be moved to a pre-existing CV struct.
```
	void	pad_fixup_inner_anons(PADLIST *padlist,
		                      CV *old_cv, CV *new_cv)
```
pad_free
Free the SV at offset po in the current pad.
```
	void	pad_free(PADOFFSET po)
```
pad_leavemy
Cleanup at end of scope during compilation: set the max seq number for lexicals in this scope and warn of any lexicals that never got introduced.
```
	void	pad_leavemy()
```

padlist_dup

Duplicates a pad.

	PADLIST * padlist_dup(PADLIST *srcpad,
	                      CLONE_PARAMS *param)

padname_dup

Duplicates a pad name.

	PADNAME * padname_dup(PADNAME *src, CLONE_PARAMS *param)

padnamelist_dup

Duplicates a pad name list.

	PADNAMELIST * padnamelist_dup(PADNAMELIST *srcpad,
	                              CLONE_PARAMS *param)

pad_push
Push a new pad frame onto the padlist, unless there's already a pad at this depth, in which case don't bother creating a new one. Then give the new pad an @_ in slot zero.
```
	void	pad_push(PADLIST *padlist, int depth)
```
pad_reset
Mark all the current temporaries for reuse
```
	void	pad_reset()
```
pad_swipe
Abandon the tmp in the current pad at offset po and replace with a new one.
```
	void	pad_swipe(PADOFFSET po, bool refadjust)
```

GV Functions

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

If the typeglob gv can be expressed more succinctly, by having something other than a real GV in its place in the stash, replace it with the optimised form. Basic requirements for this are that gv is a real typeglob, is sufficiently ordinary, and is only referenced from its package. This function is meant to be used when a GV has been looked up in part to see what was there, causing upgrading, but based on what was found it turns out that the real GV isn't required after all.

If gv is a completely empty typeglob, it is deleted from the stash.

If gv is a typeglob containing only a sufficiently-ordinary constant sub, the typeglob is replaced with a scalar-reference placeholder that more compactly represents the same thing.
```
	void	gv_try_downgrade(GV* gv)
```

Hash Manipulation Functions

hv_ename_add
Adds a name to a stash's internal list of effective names. See hv_ename_delete.

This is called when a stash is assigned to a new location in the symbol table.
```
	void	hv_ename_add(HV *hv, const char *name, U32 len,
		             U32 flags)
```
hv_ename_delete
Removes a name from a stash's internal list of effective names. If this is the name returned by HvENAME , then another name in the list will take its place (HvENAME will use it).

This is called when a stash is deleted from the symbol table.
```
	void	hv_ename_delete(HV *hv, const char *name,
		                U32 len, U32 flags)
```
refcounted_he_chain_2hv
Generates and returns a HV * representing the content of a refcounted_he chain. flags is currently unused and must be zero.
```
	HV *	refcounted_he_chain_2hv(
		    const struct refcounted_he *c, U32 flags
		)
```

refcounted_he_fetch_pv

Like refcounted_he_fetch_pvn, but takes a nul-terminated string instead of a string/length pair.

	SV *	refcounted_he_fetch_pv(
		    const struct refcounted_he *chain,
		    const char *key, U32 hash, U32 flags
		)

refcounted_he_fetch_pvn
Search along a refcounted_he chain for an entry with the key specified by keypv and keylen . If flags has the REFCOUNTED_HE_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 representing the value associated with the key, or &PL_sv_placeholder if there is no value associated with the key.
```
	SV *	refcounted_he_fetch_pvn(
		    const struct refcounted_he *chain,
		    const char *keypv, STRLEN keylen, U32 hash,
		    U32 flags
		)
```
refcounted_he_fetch_pvs
Like refcounted_he_fetch_pvn, but takes a literal string instead of a string/length pair, and no precomputed hash.
```
	SV *	refcounted_he_fetch_pvs(
		    const struct refcounted_he *chain,
		    "literal string" key, U32 flags
		)
```

refcounted_he_fetch_sv

Like refcounted_he_fetch_pvn, but takes a Perl scalar instead of a string/length pair.

	SV *	refcounted_he_fetch_sv(
		    const struct refcounted_he *chain, SV *key,
		    U32 hash, U32 flags
		)

refcounted_he_free
Decrements the reference count of a refcounted_he by one. If the reference count reaches zero the structure's memory is freed, which (recursively) causes a reduction of its parent refcounted_he 's reference count. It is safe to pass a null pointer to this function: no action occurs in this case.
```
	void	refcounted_he_free(struct refcounted_he *he)
```
refcounted_he_inc
Increment the reference count of a refcounted_he . The pointer to the refcounted_he is also returned. It is safe to pass a null pointer to this function: no action occurs and a null pointer is returned.
```
	struct refcounted_he * refcounted_he_inc(
	                           struct refcounted_he *he
	                       )
```

refcounted_he_new_pv

Like refcounted_he_new_pvn, but takes a nul-terminated string instead of a string/length pair.

	struct refcounted_he * refcounted_he_new_pv(
	                           struct refcounted_he *parent,
	                           const char *key, U32 hash,
	                           SV *value, U32 flags
	                       )

refcounted_he_new_pvn
Creates a new refcounted_he . This consists of a single key/value pair and a reference to an existing refcounted_he chain (which may be empty), and thus forms a longer chain. When using the longer chain, the new key/value pair takes precedence over any entry for the same key further along the chain.

The new key is specified by keypv and keylen . If flags has the REFCOUNTED_HE_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 refcounted_he . Complex types of scalar will not be stored with referential integrity, but will be coerced to strings. value may be either null or &PL_sv_placeholder to indicate that no value is to be associated with the key; this, as with any non-null value, takes precedence over the existence of a value for the key further along the chain.

parent points to the rest of the refcounted_he chain to be attached to the new refcounted_he . This function takes ownership of one reference to parent , and returns one reference to the new refcounted_he .
```
	struct refcounted_he * refcounted_he_new_pvn(
	                           struct refcounted_he *parent,
	                           const char *keypv,
	                           STRLEN keylen, U32 hash,
	                           SV *value, U32 flags
	                       )
```

refcounted_he_new_pvs

Like refcounted_he_new_pvn, but takes a literal string instead of a string/length pair, and no precomputed hash.

	struct refcounted_he * refcounted_he_new_pvs(
	                           struct refcounted_he *parent,
	                           "literal string" key,
	                           SV *value, U32 flags
	                       )

refcounted_he_new_sv

Like refcounted_he_new_pvn, but takes a Perl scalar instead of a string/length pair.

	struct refcounted_he * refcounted_he_new_sv(
	                           struct refcounted_he *parent,
	                           SV *key, U32 hash, SV *value,
	                           U32 flags
	                       )

IO Functions

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

Function called by do_readline to spawn a glob (or do the glob inside perl on VMS). This code used to be inline, but now perl uses File::Glob this glob starter is only used by miniperl during the build process, or when PERL_EXTERNAL_GLOB is defined. Moving it away shrinks pp_hot.c; shrinking pp_hot.c helps speed perl up.
```
	PerlIO*	start_glob(SV *tmpglob, IO *io)
```

Lexer interface

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

This function performs syntax checking on a prototype, proto . If warn is true, any illegal characters or mismatched brackets will trigger illegalproto warnings, declaring that they were detected in the prototype for name .

The return value is true if this is a valid prototype, and false if it is not, regardless of whether warn was true or false .

Note that NULL is a valid proto and will always return true .

NOTE: the perl_ form of this function is deprecated.
```
	bool	validate_proto(SV *name, SV *proto, bool warn,
		               bool curstash)
```

Magical Functions

magic_clearhint
Triggered by a delete from %^H , records the key to PL_compiling.cop_hints_hash .
```
	int	magic_clearhint(SV* sv, MAGIC* mg)
```
magic_clearhints
Triggered by clearing %^H , resets PL_compiling.cop_hints_hash .
```
	int	magic_clearhints(SV* sv, MAGIC* mg)
```

magic_methcall

Invoke a magic method (like FETCH).

sv and mg are the tied thingy and the tie magic.

meth is the name of the method to call.

argc is the number of args (in addition to $self) to pass to the method.

The flags can be:

    G_DISCARD     invoke method with G_DISCARD flag and don't
                  return a value
    G_UNDEF_FILL  fill the stack with argc pointers to
                  PL_sv_undef

The arguments themselves are any values following the flags argument.

Returns the SV (if any) returned by the method, or NULL on failure.

	SV*	magic_methcall(SV *sv, const MAGIC *mg,
		               SV *meth, U32 flags, U32 argc,
		               ...)

magic_sethint
Triggered by a store to %^H , records the key/value pair to PL_compiling.cop_hints_hash . It is assumed that hints aren't storing anything that would need a deep copy. Maybe we should warn if we find a reference.
```
	int	magic_sethint(SV* sv, MAGIC* mg)
```
mg_localize
Copy some of the magic from an existing SV to new localized version of that SV. Container magic (e.g., %ENV , $1 , tie) gets copied, value magic doesn't (e.g., taint , pos).

If setmagic is false then no set magic will be called on the new (empty) SV. This typically means that assignment will soon follow (e.g. 'local $x = $y' ), and that will handle the magic.
```
	void	mg_localize(SV* sv, SV* nsv, bool setmagic)
```

Miscellaneous Functions

free_c_backtrace
Deallocates a backtrace received from get_c_bracktrace.
```
	void	free_c_backtrace(Perl_c_backtrace* bt)
```
get_c_backtrace
Collects the backtrace (aka "stacktrace") into a single linear malloced buffer, which the caller must Perl_free_c_backtrace() .

Scans the frames back by depth + skip , then drops the skip innermost, returning at most depth frames.
```
	Perl_c_backtrace* get_c_backtrace(int max_depth,
	                                  int skip)
```

MRO Functions

mro_get_linear_isa_dfs
Returns the Depth-First Search linearization of @ISA the given stash. The return value is a read-only AV*. level should be 0 (it is used internally in this function's recursion).

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_dfs(HV* stash, U32 level)
```
mro_isa_changed_in
Takes the necessary steps (cache invalidations, mostly) when the @ISA of the given package has changed. Invoked by the setisa magic, should not need to invoke directly.
```
	void	mro_isa_changed_in(HV* stash)
```
mro_package_moved
Call this function to signal to a stash that it has been assigned to another spot in the stash hierarchy. stash is the stash that has been assigned. oldstash is the stash it replaces, if any. gv is the glob that is actually being assigned to.

This can also be called with a null first argument to indicate that oldstash has been deleted.

This function invalidates isa caches on the old stash, on all subpackages nested inside it, and on the subclasses of all those, including non-existent packages that have corresponding entries in stash .

It also sets the effective names (HvENAME ) on all the stashes as appropriate.

If the gv is present and is not in the symbol table, then this function simply returns. This checked will be skipped if flags & 1 .
```
	void	mro_package_moved(HV * const stash,
		                  HV * const oldstash,
		                  const GV * const gv,
		                  U32 flags)
```

Optree Manipulation Functions

finalize_optree
This function finalizes the optree. Should be called directly after the complete optree is built. It does some additional checking which can't be done in the normal ck_ xxx functions and makes the tree thread-safe.
```
	void	finalize_optree(OP* o)
```
newATTRSUB_x
Construct a Perl subroutine, also performing some surrounding jobs.

This function is expected to be called in a Perl compilation context, and some aspects of the subroutine are taken from global variables associated with compilation. In particular, PL_compcv represents the subroutine that is currently being compiled. It must be non-null when this function is called, and some aspects of the subroutine being constructed are taken from it. The constructed subroutine may actually be a reuse of the PL_compcv object, but will not necessarily be so.

If block is null then the subroutine will have no body, and for the time being it will be an error to call it. This represents a forward subroutine declaration such as sub foo ($$); . If block is non-null then it provides the Perl code of the subroutine body, which will be executed when the subroutine is called. This body includes any argument unwrapping code resulting from a subroutine signature or similar. The pad use of the code must correspond to the pad attached to PL_compcv . The code is not expected to include a leavesub or leavesublv op; this function will add such an op. block is consumed by this function and will become part of the constructed subroutine.

proto specifies the subroutine's prototype, unless one is supplied as an attribute (see below). If proto is null, then the subroutine will not have a prototype. If proto is non-null, it must point to a const op whose value is a string, and the subroutine will have that string as its prototype. If a prototype is supplied as an attribute, the attribute takes precedence over proto , but in that case proto should preferably be null. In any case, proto is consumed by this function.

attrs supplies attributes to be applied the subroutine. A handful of attributes take effect by built-in means, being applied to PL_compcv immediately when seen. Other attributes are collected up and attached to the subroutine by this route. attrs may be null to supply no attributes, or point to a const op for a single attribute, or point to a list op whose children apart from the pushmark are const ops for one or more attributes. Each const op must be a string, giving the attribute name optionally followed by parenthesised arguments, in the manner in which attributes appear in Perl source. The attributes will be applied to the sub by this function. attrs is consumed by this function.

If o_is_gv is false and o is null, then the subroutine will be anonymous. If o_is_gv is false and o is non-null, then o must point to a const op, which will be consumed by this function, and its string value supplies a name for the subroutine. The name may be qualified or unqualified, and if it is unqualified then a default stash will be selected in some manner. If o_is_gv is true, then o doesn't point to an OP at all, but is instead a cast pointer to a GV by which the subroutine will be named.

If there is already a subroutine of the specified name, then the new sub will either replace the existing one in the glob or be merged with the existing one. A warning may be generated about redefinition.

If the subroutine has one of a few special names, such as BEGIN or END, then it will be claimed by the appropriate queue for automatic running of phase-related subroutines. In this case the relevant glob will be left not containing any subroutine, even if it did contain one before. In the case of BEGIN, the subroutine will be executed and the reference to it disposed of before this function returns.

The function returns a pointer to the constructed subroutine. If the sub is anonymous then ownership of one counted reference to the subroutine is transferred to the caller. If the sub is named then the caller does not get ownership of a reference. In most such cases, where the sub has a non-phase name, the sub will be alive at the point it is returned by virtue of being contained in the glob that names it. A phase-named subroutine will usually be alive by virtue of the reference owned by the phase's automatic run queue. But a BEGIN subroutine, having already been executed, will quite likely have been destroyed already by the time this function returns, making it erroneous for the caller to make any use of the returned pointer. It is the caller's responsibility to ensure that it knows which of these situations applies.
```
	CV *	newATTRSUB_x(I32 floor, OP *o, OP *proto,
		             OP *attrs, OP *block, bool o_is_gv)
```
newXS_len_flags
Construct an XS subroutine, also performing some surrounding jobs.

The subroutine will have the entry point subaddr . It will have the prototype specified by the nul-terminated string proto , or no prototype if proto is null. The prototype string is copied; the caller can mutate the supplied string afterwards. If filename is non-null, it must be a nul-terminated filename, and the subroutine will have its CvFILE set accordingly. By default CvFILE is set to point directly to the supplied string, which must be static. If flags has the XS_DYNAMIC_FILENAME bit set, then a copy of the string will be taken instead.

Other aspects of the subroutine will be left in their default state. If anything else needs to be done to the subroutine for it to function correctly, it is the caller's responsibility to do that after this function has constructed it. However, beware of the subroutine potentially being destroyed before this function returns, as described below.

If name is null then the subroutine will be anonymous, with its CvGV referring to an __ANON__ glob. If name is non-null then the subroutine will be named accordingly, referenced by the appropriate glob. name is a string of length len bytes giving a sigilless symbol name, in UTF-8 if flags has the SVf_UTF8 bit set and in Latin-1 otherwise. The name may be either qualified or unqualified, with the stash defaulting in the same manner as for gv_fetchpvn_flags . flags may contain flag bits understood by gv_fetchpvn_flags with the same meaning as they have there, such as GV_ADDWARN . The symbol is always added to the stash if necessary, with GV_ADDMULTI semantics.

If there is already a subroutine of the specified name, then the new sub will replace the existing one in the glob. A warning may be generated about the redefinition. If the old subroutine was CvCONST then the decision about whether to warn is influenced by an expectation about whether the new subroutine will become a constant of similar value. That expectation is determined by const_svp . (Note that the call to this function doesn't make the new subroutine CvCONST in any case; that is left to the caller.) If const_svp is null then it indicates that the new subroutine will not become a constant. If const_svp is non-null then it indicates that the new subroutine will become a constant, and it points to an SV* that provides the constant value that the subroutine will have.

If the subroutine has one of a few special names, such as BEGIN or END, then it will be claimed by the appropriate queue for automatic running of phase-related subroutines. In this case the relevant glob will be left not containing any subroutine, even if it did contain one before. In the case of BEGIN, the subroutine will be executed and the reference to it disposed of before this function returns, and also before its prototype is set. If a BEGIN subroutine would not be sufficiently constructed by this function to be ready for execution then the caller must prevent this happening by giving the subroutine a different name.

The function returns a pointer to the constructed subroutine. If the sub is anonymous then ownership of one counted reference to the subroutine is transferred to the caller. If the sub is named then the caller does not get ownership of a reference. In most such cases, where the sub has a non-phase name, the sub will be alive at the point it is returned by virtue of being contained in the glob that names it. A phase-named subroutine will usually be alive by virtue of the reference owned by the phase's automatic run queue. But a BEGIN subroutine, having already been executed, will quite likely have been destroyed already by the time this function returns, making it erroneous for the caller to make any use of the returned pointer. It is the caller's responsibility to ensure that it knows which of these situations applies.
```
	CV *	newXS_len_flags(const char *name, STRLEN len,
		                XSUBADDR_t subaddr,
		                const char *const filename,
		                const char *const proto,
		                SV **const_svp, U32 flags)
```
optimize_optree
This function applies some optimisations to the optree in top-down order. It is called before the peephole optimizer, which processes ops in execution order. Note that finalize_optree() also does a top-down scan, but is called *after* the peephole optimizer.
```
	void	optimize_optree(OP* o)
```

Pad Data Structures

CX_CURPAD_SAVE
Save the current pad in the given context block structure.
```
	void	CX_CURPAD_SAVE(struct context)
```
CX_CURPAD_SV
Access the SV at offset po in the saved current pad in the given context block structure (can be used as an lvalue).
```
	SV *	CX_CURPAD_SV(struct context, PADOFFSET po)
```
PAD_BASE_SV
Get the value from slot po in the base (DEPTH=1) pad of a padlist
```
	SV *	PAD_BASE_SV(PADLIST padlist, PADOFFSET po)
```

PAD_CLONE_VARS

Clone the state variables associated with running and compiling pads.

	void	PAD_CLONE_VARS(PerlInterpreter *proto_perl,
		               CLONE_PARAMS* param)

PAD_COMPNAME_FLAGS
Return the flags for the current compiling pad name at offset po . Assumes a valid slot entry.
```
	U32	PAD_COMPNAME_FLAGS(PADOFFSET po)
```
PAD_COMPNAME_GEN
The generation number of the name at offset po in the current compiling pad (lvalue).
```
	STRLEN	PAD_COMPNAME_GEN(PADOFFSET po)
```
PAD_COMPNAME_GEN_set
Sets the generation number of the name at offset po in the current ling pad (lvalue) to gen . STRLEN PAD_COMPNAME_GEN_set(PADOFFSET po, int gen)
PAD_COMPNAME_OURSTASH
Return the stash associated with an our variable. Assumes the slot entry is a valid our lexical.
```
	HV *	PAD_COMPNAME_OURSTASH(PADOFFSET po)
```
PAD_COMPNAME_PV
Return the name of the current compiling pad name at offset po . Assumes a valid slot entry.
```
	char *	PAD_COMPNAME_PV(PADOFFSET po)
```
PAD_COMPNAME_TYPE
Return the type (stash) of the current compiling pad name at offset po . Must be a valid name. Returns null if not typed.
```
	HV *	PAD_COMPNAME_TYPE(PADOFFSET po)
```
PadnameIsOUR
Whether this is an "our" variable.
```
	bool	PadnameIsOUR(PADNAME pn)
```
PadnameIsSTATE
Whether this is a "state" variable.
```
	bool	PadnameIsSTATE(PADNAME pn)
```
PadnameOURSTASH
The stash in which this "our" variable was declared.
```
	HV *	PadnameOURSTASH()
```
PadnameOUTER
Whether this entry belongs to an outer pad. Entries for which this is true are often referred to as 'fake'.
```
	bool	PadnameOUTER(PADNAME pn)
```
PadnameTYPE
The stash associated with a typed lexical. This returns the %Foo:: hash for my Foo $bar .
```
	HV *	PadnameTYPE(PADNAME pn)
```
PAD_RESTORE_LOCAL
Restore the old pad saved into the local variable opad by PAD_SAVE_LOCAL()
```
	void	PAD_RESTORE_LOCAL(PAD *opad)
```
PAD_SAVE_LOCAL
Save the current pad to the local variable opad , then make the current pad equal to npad
```
	void	PAD_SAVE_LOCAL(PAD *opad, PAD *npad)
```
PAD_SAVE_SETNULLPAD
Save the current pad then set it to null.
```
	void	PAD_SAVE_SETNULLPAD()
```
PAD_SETSV
Set the slot at offset po in the current pad to sv
```
	SV *	PAD_SETSV(PADOFFSET po, SV* sv)
```
PAD_SET_CUR
Set the current pad to be pad n in the padlist, saving the previous current pad. NB currently this macro expands to a string too long for some compilers, so it's best to replace it with
```
    SAVECOMPPAD();
    PAD_SET_CUR_NOSAVE(padlist,n);
	void	PAD_SET_CUR(PADLIST padlist, I32 n)
```
PAD_SET_CUR_NOSAVE
like PAD_SET_CUR, but without the save
```
	void	PAD_SET_CUR_NOSAVE(PADLIST padlist, I32 n)
```
PAD_SV
Get the value at offset po in the current pad
```
	SV *	PAD_SV(PADOFFSET po)
```
PAD_SVl
Lightweight and lvalue version of PAD_SV . Get or set the value at offset po in the current pad. Unlike PAD_SV , does not print diagnostics with -DX. For internal use only.
```
	SV *	PAD_SVl(PADOFFSET po)
```
SAVECLEARSV
Clear the pointed to pad value on scope exit. (i.e. the runtime action of my)
```
	void	SAVECLEARSV(SV **svp)
```
SAVECOMPPAD
save PL_comppad and PL_curpad
```
	void	SAVECOMPPAD()
```
SAVEPADSV
Save a pad slot (used to restore after an iteration)

XXX DAPM it would make more sense to make the arg a PADOFFSET void SAVEPADSV(PADOFFSET po)

Per-Interpreter Variables

PL_DBsingle
When Perl is run in debugging mode, with the -d switch, this SV is a boolean which indicates whether subs are being single-stepped. Single-stepping is automatically turned on after every step. This is the C variable which corresponds to Perl's $DB::single variable. See PL_DBsub.
```
	SV *	PL_DBsingle
```
PL_DBsub
When Perl is run in debugging mode, with the -d switch, this GV contains the SV which holds the name of the sub being debugged. This is the C variable which corresponds to Perl's $DB::sub variable. See PL_DBsingle.
```
	GV *	PL_DBsub
```
PL_DBtrace
Trace variable used when Perl is run in debugging mode, with the -d switch. This is the C variable which corresponds to Perl's $DB::trace variable. See PL_DBsingle.
```
	SV *	PL_DBtrace
```
PL_dowarn
The C variable that roughly corresponds to Perl's $^W warning variable. However, $^W is treated as a boolean, whereas PL_dowarn is a collection of flag bits.
```
	U8	PL_dowarn
```
PL_last_in_gv
The GV which was last used for a filehandle input operation. (<FH> )
```
	GV*	PL_last_in_gv
```
PL_ofsgv
The glob containing the output field separator - *, in Perl space.
```
	GV*	PL_ofsgv
```
PL_rs
The input record separator - $/ in Perl space.
```
	SV*	PL_rs
```

Stack Manipulation Macros

djSP
Declare Just SP . This is actually identical to dSP , and declares a local copy of perl's stack pointer, available via the SP macro. See SP in perlapi. (Available for backward source code compatibility with the old (Perl 5.005) thread model.)
```
		djSP;
```
LVRET
True if this op will be the return value of an lvalue subroutine

SV-Body Allocation

sv_2num
NOTE: this function is experimental and may change or be removed without notice.

Return an SV with the numeric value of the source SV, doing any necessary reference or overload conversion. The caller is expected to have handled get-magic already.
```
	SV*	sv_2num(SV *const sv)
```

SV Manipulation Functions

An SV (or AV, HV, etc.) is allocated in two parts: the head (struct sv, av, hv...) contains type and reference count information, and for many types, a pointer to the body (struct xrv, xpv, xpviv...), which contains fields specific to each type. Some types store all they need in the head, so don't have a body.

In all but the most memory-paranoid configurations (ex: PURIFY), heads and bodies are allocated out of arenas, which by default are approximately 4K chunks of memory parcelled up into N heads or bodies. Sv-bodies are allocated by their sv-type, guaranteeing size consistency needed to allocate safely from arrays.

For SV-heads, the first slot in each arena is reserved, and holds a link to the next arena, some flags, and a note of the number of slots. Snaked through each arena chain is a linked list of free items; when this becomes empty, an extra arena is allocated and divided up into N items which are threaded into the free list.

SV-bodies are similar, but they use arena-sets by default, which separate the link and info from the arena itself, and reclaim the 1st slot in the arena. SV-bodies are further described later.

The following global variables are associated with arenas:

 PL_sv_arenaroot     pointer to list of SV arenas
 PL_sv_root          pointer to list of free SV structures
 PL_body_arenas      head of linked-list of body arenas
 PL_body_roots[]     array of pointers to list of free bodies of svtype
                     arrays are indexed by the svtype needed

A few special SV heads are not allocated from an arena, but are instead directly created in the interpreter structure, eg PL_sv_undef. The size of arenas can be changed from the default by setting PERL_ARENA_SIZE appropriately at compile time.

The SV arena serves the secondary purpose of allowing still-live SVs to be located and destroyed during final cleanup.

At the lowest level, the macros new_SV() and del_SV() grab and free an SV head. (If debugging with -DD, del_SV() calls the function S_del_sv() to return the SV to the free list with error checking.) new_SV() calls more_sv() / sv_add_arena() to add an extra arena if the free list is empty. SVs in the free list have their SvTYPE field set to all ones.

At the time of very final cleanup, sv_free_arenas() is called from perl_destruct() to physically free all the arenas allocated since the start of the interpreter.

The function visit() scans the SV arenas list, and calls a specified function for each SV it finds which is still live - ie which has an SvTYPE other than all 1's, and a non-zero SvREFCNT. visit() is used by the following functions (specified as [function that calls visit()] / [function called by visit() for each SV]):

    sv_report_used() / do_report_used()
			dump all remaining SVs (debugging aid)
    sv_clean_objs() / do_clean_objs(),do_clean_named_objs(),
		      do_clean_named_io_objs(),do_curse()
			Attempt to free all objects pointed to by RVs,
			try to do the same for all objects indir-
			ectly referenced by typeglobs too, and
			then do a final sweep, cursing any
			objects that remain.  Called once from
			perl_destruct(), prior to calling sv_clean_all()
			below.
    sv_clean_all() / do_clean_all()
			SvREFCNT_dec(sv) each remaining SV, possibly
			triggering an sv_free(). It also sets the
			SVf_BREAK flag on the SV to indicate that the
			refcnt has been artificially lowered, and thus
			stopping sv_free() from giving spurious warnings
			about SVs which unexpectedly have a refcnt
			of zero.  called repeatedly from perl_destruct()
			until there are no SVs left.

sv_add_arena
Given a chunk of memory, link it to the head of the list of arenas, and split it into a list of free SVs.
```
	void	sv_add_arena(char *const ptr, const U32 size,
		             const U32 flags)
```
sv_clean_all
Decrement the refcnt of each remaining SV, possibly triggering a cleanup. This function may have to be called multiple times to free SVs which are in complex self-referential hierarchies.
```
	I32	sv_clean_all()
```
sv_clean_objs
Attempt to destroy all objects not yet freed.
```
	void	sv_clean_objs()
```
sv_free_arenas
Deallocate the memory used by all arenas. Note that all the individual SV heads and bodies within the arenas must already have been freed.
```
	void	sv_free_arenas()
```
SvTHINKFIRST
A quick flag check to see whether an sv should be passed to sv_force_normal to be "downgraded" before SvIVX or SvPVX can be modified directly.

For example, if your scalar is a reference and you want to modify the SvIVX slot, you can't just do SvROK_off , as that will leak the referent.

This is used internally by various sv-modifying functions, such as sv_setsv , sv_setiv and sv_pvn_force .

One case that this does not handle is a gv without SvFAKE set. After
```
    if (SvTHINKFIRST(gv)) sv_force_normal(gv);
```
it will still be a gv.

SvTHINKFIRST sometimes produces false positives. In those cases sv_force_normal does nothing.
```
	U32	SvTHINKFIRST(SV *sv)
```

Unicode Support

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

Find the name of the undefined variable (if any) that caused the operator to issue a "Use of uninitialized value" warning. If match is true, only return a name if its value matches uninit_sv . So roughly speaking, if a unary operator (such as OP_COS ) generates a warning, then following the direct child of the op may yield an OP_PADSV or OP_GV that gives the name of the undefined variable. On the other hand, with OP_ADD there are two branches to follow, so we only print the variable name if we get an exact match. desc_p points to a string pointer holding the description of the op. This may be updated if needed.

The name is returned as a mortal SV.

Assumes that PL_op is the OP that originally triggered the error, and that PL_comppad /PL_curpad points to the currently executing pad.
```
	SV*	find_uninit_var(const OP *const obase,
		                const SV *const uninit_sv,
		                bool match, const char **desc_p)
```
isSCRIPT_RUN
Returns a bool as to whether or not the sequence of bytes from s up to but not including send form a "script run". utf8_target is TRUE iff the sequence starting at s is to be treated as UTF-8. To be precise, except for two degenerate cases given below, this function returns TRUE iff all code points in it come from any combination of three "scripts" given by the Unicode "Script Extensions" property: Common, Inherited, and possibly one other. Additionally all decimal digits must come from the same consecutive sequence of 10.

For example, if all the characters in the sequence are Greek, or Common, or Inherited, this function will return TRUE, provided any decimal digits in it are the ASCII digits "0".."9". For scripts (unlike Greek) that have their own digits defined this will accept either digits from that set or from 0..9, but not a combination of the two. Some scripts, such as Arabic, have more than one set of digits. All digits must come from the same set for this function to return TRUE.

*ret_script , if ret_script is not NULL, will on return of TRUE contain the script found, using the SCX_enum typedef. Its value will be SCX_INVALID if the function returns FALSE.

If the sequence is empty, TRUE is returned, but *ret_script (if asked for) will be SCX_INVALID .

If the sequence contains a single code point which is unassigned to a character in the version of Unicode being used, the function will return TRUE, and the script will be SCX_Unknown . Any other combination of unassigned code points in the input sequence will result in the function treating the input as not being a script run.

The returned script will be SCX_Inherited iff all the code points in it are from the Inherited script.

Otherwise, the returned script will be SCX_Common iff all the code points in it are from the Inherited or Common scripts.
```
	bool	isSCRIPT_RUN(const U8 *s, const U8 *send,
		             const bool utf8_target)
```
is_utf8_non_invariant_string
Returns TRUE if is_utf8_invariant_string in perlapi returns FALSE for the first len bytes of the string s, but they are, nonetheless, legal Perl-extended UTF-8; otherwise returns FALSE.

A TRUE return means that at least one code point represented by the sequence either is a wide character not representable as a single byte, or the representation differs depending on whether the sequence is encoded in UTF-8 or not.

See also is_utf8_invariant_string in perlapi, is_utf8_string in perlapi
```
	bool	is_utf8_non_invariant_string(const U8* const s,
		                             STRLEN len)
```
report_uninit
Print appropriate "Use of uninitialized variable" warning.
```
	void	report_uninit(const SV *uninit_sv)
```
variant_under_utf8_count
This function looks at the sequence of bytes between s and e , which are assumed to be encoded in ASCII/Latin1, and returns how many of them would change should the string be translated into UTF-8. Due to the nature of UTF-8, each of these would occupy two bytes instead of the single one in the input string. Thus, this function returns the precise number of bytes the string would expand by when translated to UTF-8.

Unlike most of the other functions that have utf8 in their name, the input to this function is NOT a UTF-8-encoded string. The function name is slightly odd to emphasize this.

This function is internal to Perl because khw thinks that any XS code that would want this is probably operating too close to the internals. Presenting a valid use case could change that.

See also is_utf8_invariant_string in perlapi and is_utf8_invariant_string_loc in perlapi,
```
	Size_t	variant_under_utf8_count(const U8* const s,
		                         const U8* const e)
```

Undocumented functions

The following functions are currently undocumented. If you use one of them, you may wish to consider creating and submitting documentation for it.

PerlIO_restore_errno
PerlIO_save_errno
PerlLIO_dup2_cloexec
PerlLIO_dup_cloexec
PerlLIO_open3_cloexec
PerlLIO_open_cloexec
PerlProc_pipe_cloexec
PerlSock_accept_cloexec
PerlSock_socket_cloexec
PerlSock_socketpair_cloexec
Slab_Alloc
Slab_Free
Slab_to_ro
Slab_to_rw
_add_range_to_invlist
_byte_dump_string
_core_swash_init
_get_regclass_nonbitmap_data
_get_swash_invlist
_inverse_folds
_invlistEQ
_invlist_array_init
_invlist_contains_cp
_invlist_dump
_invlist_intersection
_invlist_intersection_maybe_complement_2nd
_invlist_invert
_invlist_len
_invlist_populate_swatch
_invlist_search
_invlist_subtract
_invlist_union
_invlist_union_maybe_complement_2nd
_is_grapheme
_is_in_locale_category
_mem_collxfrm
_new_invlist
_new_invlist_C_array
_setup_canned_invlist
_swash_to_invlist
_to_fold_latin1
_to_upper_title_latin1
_warn_problematic_locale
abort_execution
add_cp_to_invlist
alloc_LOGOP
alloc_maybe_populate_EXACT
allocmy
amagic_is_enabled
append_utf8_from_native_byte
apply
av_extend_guts
av_nonelem
av_reify
bind_match
boot_core_ActivePerl
boot_core_PerlIO
boot_core_UNIVERSAL
boot_core_mro
cando
check_utf8_print
ck_anoncode
ck_backtick
ck_bitop
ck_cmp
ck_concat
ck_defined
ck_delete
ck_each
ck_entersub_args_core
ck_eof
ck_eval
ck_exec
ck_exists
ck_ftst
ck_fun
ck_glob
ck_grep
ck_index
ck_join
ck_length
ck_lfun
ck_listiob
ck_match
ck_method
ck_null
ck_open
ck_prototype
ck_readline
ck_refassign
ck_repeat
ck_require
ck_return
ck_rfun
ck_rvconst
ck_sassign
ck_select
ck_shift
ck_smartmatch
ck_sort
ck_spair
ck_split
ck_stringify
ck_subr
ck_substr
ck_svconst
ck_tell
ck_trunc
closest_cop
compute_EXACTish
coresub_op
create_eval_scope
croak_caller
croak_no_mem
croak_popstack
current_re_engine
custom_op_get_field
cv_ckproto_len_flags
cv_clone_into
cv_const_sv_or_av
cv_undef_flags
cvgv_from_hek
cvgv_set
cvstash_set
deb_stack_all
defelem_target
delete_eval_scope
delimcpy_no_escape
die_unwind
do_aexec
do_aexec5
do_eof
do_exec
do_exec3
do_ipcctl
do_ipcget
do_msgrcv
do_msgsnd
do_ncmp
do_open6
do_open_raw
do_print
do_readline
do_seek
do_semop
do_shmio
do_sysseek
do_tell
do_trans
do_vecget
do_vecset
do_vop
does_utf8_overflow
dofile
drand48_init_r
drand48_r
dtrace_probe_call
dtrace_probe_load
dtrace_probe_op
dtrace_probe_phase
dump_all_perl
dump_packsubs_perl
dump_sub_perl
dump_sv_child
emulate_cop_io
feature_is_enabled
find_lexical_cv
find_runcv_where
find_script
form_short_octal_warning
free_tied_hv_pool
get_db_sub
get_debug_opts
get_hash_seed
get_invlist_iter_addr
get_invlist_offset_addr
get_invlist_previous_index_addr
get_no_modify
get_opargs
get_re_arg
getenv_len
grok_atoUV
grok_bslash_c
grok_bslash_o
grok_bslash_x
gv_fetchmeth_internal
gv_override
gv_setref
gv_stashpvn_internal
gv_stashsvpvn_cached
handle_named_backref
hfree_next_entry
hv_backreferences_p
hv_kill_backrefs
hv_placeholders_p
hv_pushkv
hv_undef_flags
init_argv_symbols
init_constants
init_dbargs
init_debugger
init_named_cv
init_uniprops
invert
invlist_array
invlist_clear
invlist_clone
invlist_highest
invlist_is_iterating
invlist_iterfinish
invlist_iterinit
invlist_max
invlist_previous_index
invlist_set_len
invlist_set_previous_index
invlist_trim
io_close
isFF_OVERLONG
isFOO_lc
is_utf8_common
is_utf8_common_with_len
is_utf8_overlong_given_start_byte_ok
isinfnansv
jmaybe
keyword
keyword_plugin_standard
list
localize
magic_clear_all_env
magic_cleararylen_p
magic_clearenv
magic_clearisa
magic_clearpack
magic_clearsig
magic_copycallchecker
magic_existspack
magic_freearylen_p
magic_freeovrld
magic_get
magic_getarylen
magic_getdebugvar
magic_getdefelem
magic_getnkeys
magic_getpack
magic_getpos
magic_getsig
magic_getsubstr
magic_gettaint
magic_getuvar
magic_getvec
magic_killbackrefs
magic_nextpack
magic_regdata_cnt
magic_regdatum_get
magic_regdatum_set
magic_scalarpack
magic_set
magic_set_all_env
magic_setarylen
magic_setcollxfrm
magic_setdbline
magic_setdebugvar
magic_setdefelem
magic_setenv
magic_setisa
magic_setlvref
magic_setmglob
magic_setnkeys
magic_setnonelem
magic_setpack
magic_setpos
magic_setregexp
magic_setsig
magic_setsubstr
magic_settaint
magic_setutf8
magic_setuvar
magic_setvec
magic_sizepack
magic_wipepack
malloc_good_size
malloced_size
mem_collxfrm
mem_log_alloc
mem_log_free
mem_log_realloc
mg_find_mglob
mode_from_discipline
more_bodies
mro_meta_dup
mro_meta_init
multiconcat_stringify
multideref_stringify
my_attrs
my_clearenv
my_lstat_flags
my_memrchr
my_mkostemp
my_mkstemp
my_mkstemp_cloexec
my_stat_flags
my_strerror
my_unexec
newGP
newMETHOP_internal
newSTUB
newSVavdefelem
newXS_deffile
new_warnings_bitfield
nextargv
noperl_die
notify_parser_that_changed_to_utf8
oopsAV
oopsHV
op_clear
op_integerize
op_lvalue_flags
op_refcnt_dec
op_refcnt_inc
op_relocate_sv
op_std_init
op_unscope
opmethod_stash
opslab_force_free
opslab_free
opslab_free_nopad
package
package_version
pad_add_weakref
padlist_store
padname_free
padnamelist_free
parse_unicode_opts
parse_uniprop_string
parser_free
parser_free_nexttoke_ops
path_is_searchable
peep
pmruntime
populate_isa
ptr_hash
qerror
re_exec_indentf
re_indentf
re_op_compile
re_printf
reg_named_buff
reg_named_buff_iter
reg_numbered_buff_fetch
reg_numbered_buff_length
reg_numbered_buff_store
reg_qr_package
reg_skipcomment
reg_temp_copy
regcurly
regprop
report_evil_fh
report_redefined_cv
report_wrongway_fh
rpeep
rsignal_restore
rsignal_save
rxres_save
same_dirent
save_strlen
save_to_buffer
sawparens
scalar
scalarvoid
set_caret_X
set_numeric_standard
set_numeric_underlying
set_padlist
setfd_cloexec
setfd_cloexec_for_nonsysfd
setfd_cloexec_or_inhexec_by_sysfdness
setfd_inhexec
setfd_inhexec_for_sysfd
should_warn_nl
sighandler
softref2xv
ssc_add_range
ssc_clear_locale
ssc_cp_and
ssc_intersection
ssc_union
sub_crush_depth
sv_add_backref
sv_buf_to_ro
sv_del_backref
sv_free2
sv_kill_backrefs
sv_len_utf8_nomg
sv_magicext_mglob
sv_mortalcopy_flags
sv_only_taint_gmagic
sv_or_pv_pos_u2b
sv_resetpvn
sv_sethek
sv_setsv_cow
sv_unglob
swash_fetch
swash_init
tied_method
tmps_grow_p
translate_substr_offsets
try_amagic_bin
try_amagic_un
unshare_hek
utf16_to_utf8
utf16_to_utf8_reversed
utilize
varname
vivify_defelem
vivify_ref
wait4pid
was_lvalue_sub
watch
win32_croak_not_implemented
write_to_stderr
xs_boot_epilog
xs_handshake
yyerror
yyerror_pv
yyerror_pvn
yylex
yyparse
yyquit
yyunlex

AUTHORS

The autodocumentation system was originally added to the Perl core by Benjamin Stuhl. Documentation is by whoever was kind enough to document their functions.