perlintern(1)


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(OP *o)

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 "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,
                                         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 "NUL"-terminated
           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 "NUL"-terminated
           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
           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)

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)

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 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" 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_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 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)

   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.

   PerlIO_restore_errno
   PerlIO_save_errno
   Slab_Alloc
   Slab_Free
   Slab_to_ro
   Slab_to_rw
   _add_range_to_invlist
   _core_swash_init
   _get_encoding
   _get_swash_invlist
   _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
   _load_PL_utf8_foldclosures
   _new_invlist
   _setup_canned_invlist
   _swash_inversion_hash
   _swash_to_invlist
   _to_fold_latin1
   _to_upper_title_latin1
   _warn_problematic_locale
   add_cp_to_invlist
   alloc_maybe_populate_EXACT
   allocmy
   amagic_is_enabled
   apply
   av_extend_guts
   av_reify
   bind_match
   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_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
   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_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
   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_and_check_backslash_N_name
   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_undef_flags
   init_argv_symbols
   init_constants
   init_dbargs
   init_debugger
   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
   isGCB
   is_utf8_common
   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_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
   multideref_stringify
   my_attrs
   my_clearenv
   my_lstat_flags
   my_stat_flags
   my_unexec
   newATTRSUB_x
   newGP
   newMETHOP_internal
   newSTUB
   newSVavdefelem
   newXS_deffile
   newXS_len_flags
   new_warnings_bitfield
   nextargv
   noperl_die
   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_subsignature
   parse_unicode_opts
   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
   sawparens
   scalar
   scalarvoid
   set_caret_X
   set_padlist
   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
   tied_method
   tmps_grow_p
   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
   xs_boot_epilog
   xs_handshake
   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


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