Provided by: perl-doc_5.26.2-7_all bug

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 "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 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)

       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
       _byte_dump_string
       _core_swash_init
       _get_regclass_nonbitmap_data
       _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
       _is_grapheme
       _load_PL_utf8_foldclosures
       _mem_collxfrm
       _new_invlist
       _new_invlist_C_array
       _setup_canned_invlist
       _swash_inversion_hash
       _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_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_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_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
       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_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
       isFF_OVERLONG
       isFOO_lc
       is_utf8_common
       is_utf8_common_with_len
       is_utf8_cp_above_31_bits
       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_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
       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
       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
       swash_fetch
       swash_init
       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
       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.

SEE ALSO

       perlguts, perlapi