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# perlintern

Perl 5 version 18.2 documentation
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# perlintern

- NAME
- DESCRIPTION
- Compile-time scope hooks
- CV reference counts and CvOUTSIDE
- Embedding Functions
- Functions in file op.c
- Functions in file pp_ctl.c
- GV Functions
- Hash Manipulation Functions
- IO Functions
- Magical Functions
- MRO Functions
- Optree Manipulation Functions
- Pad Data Structures
- Per-Interpreter Variables
- Stack Manipulation Macros
- SV Manipulation Functions
- SV-Body Allocation
- 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

  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.

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

      	void *	BhkENTRY(BHK *hk, which)

- BhkFLAGS

  Return the BHK's flags.

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

      	U32	BhkFLAGS(BHK *hk)

- CALL_BLOCK_HOOKS

  Call all the registered block hooks for type which. which is a preprocessing token; the type of arg depends on which.

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

      	void	CALL_BLOCK_HOOKS(which, arg)

# 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, eg

          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)

- intro_my

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

      	U32	intro_my()

- padlist_dup

  Duplicates a pad.

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

- pad_alloc_name

  Allocates a place in the currently-compiling pad (via pad_alloc in perlapi) and then stores a name for that entry. namesv is adopted and becomes the name entry; it must already contain the name string and be sufficiently upgraded. typestash and ourstash and the `padadd_STATE` flag get added to namesv. 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(SV *namesv, 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 C<ourstash>

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

      	void	pad_check_dup(SV *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_sv is set to the innermost matched namesv or fake namesv; out_flags returns the flags normally associated with the IVX field of a fake namesv.

  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 namesvs in anon protoypes have to store in xlow 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,	                      SV** out_name_sv, 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()

- 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)

# Functions in file op.c

- 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 or -KEY_CORE.

      	SV *	core_prototype(SV *sv, const char *name,		               const int code,		               int * const opnum)

# Functions in file pp_ctl.c

- 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(OP *o)

# GV Functions

- gv_try_downgrade

  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.

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

      	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,		    const char *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,	                           const char *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

  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. Moving it away shrinks pp_hot.c; shrinking pp_hot.c helps speed perl up.

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

      	PerlIO*	start_glob(SV *tmpglob, IO *io)

# 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,		               const char *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 (eg %ENV, $1, tie) gets copied, value magic doesn't (eg 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)

# 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)

# 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)

- 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.

      	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_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). Note that `SvUVX` is hijacked for this purpose.

      	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` . Note that `SvUV_set` is hijacked for this purpose.

      	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)

- pad_peg

  When PERL_MAD is enabled, this is a small no-op function that gets called at the start of each pad-related function. It can be breakpointed to track all pad operations. The parameter is a string indicating the type of pad operation being performed.

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

      	void	pad_peg(const char *s)

- 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

      	void	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 which corresponds to Perl's $^W warning variable.

      	bool	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` . (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 Manipulation Functions

- 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)

- 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()

# SV-Body Allocation

- sv_2num

  Return an SV with the numeric value of the source SV, doing any necessary reference or overload conversion. You must use the `SvNUM(sv)` macro to access this function.

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

      	SV*	sv_2num(SV *const sv)

- sv_copypv

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

      	void	sv_copypv(SV *const dsv, SV *const ssv)

- sv_ref

  Returns a SV describing what the SV passed in is a reference to.

      	SV*	sv_ref(SV *dst, const SV *const sv,		       const int ob)

# Unicode Support

- find_uninit_var

  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.

  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.

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

      	SV*	find_uninit_var(const OP *const obase,		                const SV *const uninit_sv,		                bool top)

- report_uninit

  Print appropriate "Use of uninitialized variable" warning.

      	void	report_uninit(const SV *uninit_sv)

# 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.

- Perl_croak_memory_wrap
- Slab_Alloc
- Slab_Free
- Slab_to_ro
- Slab_to_rw
- _add_range_to_invlist
- _core_swash_init
- _get_invlist_len_addr
- _get_swash_invlist
- _invlist_array_init
- _invlist_contains_cp
- _invlist_contents
- _invlist_intersection
- _invlist_intersection_maybe_complement_2nd
- _invlist_invert
- _invlist_invert_prop
- _invlist_len
- _invlist_populate_swatch
- _invlist_search
- _invlist_subtract
- _invlist_union
- _invlist_union_maybe_complement_2nd
- _new_invlist
- _swash_inversion_hash
- _swash_to_invlist
- _to_fold_latin1
- _to_upper_title_latin1
- aassign_common_vars
- add_cp_to_invlist
- addmad
- alloc_maybe_populate_EXACT
- allocmy
- amagic_is_enabled
- append_madprops
- apply
- av_extend_guts
- av_reify
- bind_match
- block_end
- block_start
- boot_core_PerlIO
- boot_core_UNIVERSAL
- boot_core_mro
- cando
- check_utf8_print
- ck_entersub_args_core
- compute_EXACTish
- convert
- coresub_op
- create_eval_scope
- croak_no_mem
- croak_popstack
- current_re_engine
- cv_ckproto_len_flags
- cv_clone_into
- cvgv_set
- cvstash_set
- deb_stack_all
- delete_eval_scope
- die_unwind
- do_aexec
- do_aexec5
- do_eof
- do_exec
- do_exec3
- do_execfree
- do_ipcctl
- do_ipcget
- do_msgrcv
- do_msgsnd
- do_ncmp
- do_op_xmldump
- do_pmop_xmldump
- do_print
- do_readline
- do_seek
- do_semop
- do_shmio
- do_sysseek
- do_tell
- do_trans
- do_vecget
- do_vecset
- do_vop
- dofile
- 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_rundefsv2
- find_script
- free_tied_hv_pool
- get_and_check_backslash_N_name
- get_db_sub
- get_debug_opts
- get_hash_seed
- get_invlist_iter_addr
- get_invlist_previous_index_addr
- get_invlist_version_id_addr
- get_invlist_zero_addr
- get_no_modify
- get_opargs
- get_re_arg
- getenv_len
- grok_bslash_x
- hfree_next_entry
- hv_backreferences_p
- hv_kill_backrefs
- hv_undef_flags
- init_argv_symbols
- init_constants
- init_dbargs
- init_debugger
- invert
- invlist_array
- 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
- isALNUM_lazy
- isIDFIRST_lazy
- is_utf8_char_slow
- is_utf8_common
- jmaybe
- keyword
- keyword_plugin_standard
- list
- localize
- mad_free
- madlex
- madparse
- 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_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_setdefelem
- magic_setenv
- magic_setisa
- magic_setmglob
- magic_setnkeys
- 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
- mode_from_discipline
- more_bodies
- mro_meta_dup
- mro_meta_init
- my_attrs
- my_betoh16
- my_betoh32
- my_betoh64
- my_betohi
- my_betohl
- my_betohs
- my_clearenv
- my_htobe16
- my_htobe32
- my_htobe64
- my_htobei
- my_htobel
- my_htobes
- my_htole16
- my_htole32
- my_htole64
- my_htolei
- my_htolel
- my_htoles
- my_letoh16
- my_letoh32
- my_letoh64
- my_letohi
- my_letohl
- my_letohs
- my_lstat_flags
- my_stat_flags
- my_swabn
- my_unexec
- newATTRSUB_flags
- newGP
- newMADPROP
- newMADsv
- newSTUB
- newTOKEN
- newXS_len_flags
- new_warnings_bitfield
- nextargv
- oopsAV
- oopsHV
- op_clear
- op_const_sv
- op_getmad
- op_getmad_weak
- op_integerize
- op_lvalue_flags
- op_refcnt_dec
- op_refcnt_inc
- op_std_init
- op_unscope
- op_xmldump
- opslab_force_free
- opslab_free
- opslab_free_nopad
- package
- package_version
- padlist_store
- parse_unicode_opts
- parser_free
- parser_free_nexttoke_ops
- peep
- pmop_xmldump
- pmruntime
- populate_isa
- prepend_madprops
- qerror
- re_op_compile
- reg_named_buff
- reg_named_buff_iter
- reg_numbered_buff_fetch
- reg_numbered_buff_length
- reg_numbered_buff_store
- reg_qr_package
- reg_temp_copy
- regcurly
- regpposixcc
- regprop
- report_evil_fh
- report_redefined_cv
- report_wrongway_fh
- rpeep
- rsignal_restore
- rsignal_save
- rxres_save
- same_dirent
- sawparens
- scalar
- scalarvoid
- sighandler
- softref2xv
- sub_crush_depth
- sv_add_backref
- sv_catxmlpv
- sv_catxmlpvn
- sv_catxmlsv
- sv_del_backref
- sv_free2
- sv_kill_backrefs
- sv_len_utf8_nomg
- sv_mortalcopy_flags
- sv_resetpvn
- sv_sethek
- sv_setsv_cow
- sv_unglob
- sv_xmlpeek
- tied_method
- token_free
- token_getmad
- translate_substr_offsets
- try_amagic_bin
- try_amagic_un
- unshare_hek
- utilize
- varname
- vivify_defelem
- vivify_ref
- wait4pid
- was_lvalue_sub
- watch
- win32_croak_not_implemented
- write_to_stderr
- xmldump_all
- xmldump_all_perl
- xmldump_eval
- xmldump_form
- xmldump_indent
- xmldump_packsubs
- xmldump_packsubs_perl
- xmldump_sub
- xmldump_sub_perl
- xmldump_vindent
- xs_apiversion_bootcheck
- xs_version_bootcheck
- yyerror
- yyerror_pv
- yyerror_pvn
- yylex
- yyparse
- 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.

# SEE ALSO

perlguts, perlapi

Page index

- NAME
- DESCRIPTION
- Compile-time scope hooks
- CV reference counts and CvOUTSIDE
- Embedding Functions
- Functions in file op.c
- Functions in file pp_ctl.c
- GV Functions
- Hash Manipulation Functions
- IO Functions
- Magical Functions
- MRO Functions
- Optree Manipulation Functions
- Pad Data Structures
- Per-Interpreter Variables
- Stack Manipulation Macros
- SV Manipulation Functions
- SV-Body Allocation
- Unicode Support
- Undocumented functions
- AUTHORS
- SEE ALSO