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PERLINTERN(1)	       Perl Programmers Reference Guide 	 PERLINTERN(1)

       perlintern - autogenerated documentation of purely internal
       Perl functions

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

CV reference counts and CvOUTSIDE
	       Each CV has a pointer, "CvOUTSIDE()", to its lexically enclos
	       ing 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 incre
	       ment 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 cir
	       cumstances we should decrement the refcount of the parent when
	       freeing the child.

	       There is a further complication with non-closure anonymous subs
	       (i.e. those that do not refer to any lexicals outside that
	       sub). In this case, the anonymous prototype is shared rather
	       than being cloned. This has the consequence that the parent may
	       be freed while there are still active children, eg

		   BEGIN { $a = sub { eval $x } }

	       In this case, the BEGIN is freed immediately after execution
	       since there are no active references to it: the anon sub proto
	       type has "CvWEAKOUTSIDE" set since its not a closure, and $a
	       points to the same CV, so it doesnt contribute to BEGINs ref
	       count either.  When $a is executed, the "eval $x" causes the
	       chain of "CvOUTSIDE"s to be followed, and the freed BEGIN is

	       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 posi
	       tive, then that childs "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 ref
	       erences (such as $a above).

	       One other thing to consider is that a CV may be merely unde
	       fined 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 lexi
	       cal scopes is unbroken. For example, the following should print

		   my $x = 123;
		   sub tmp { sub { eval $x } }
		   my $a = tmp();
		   undef &tmp;
		   print  $a->();

		       bool    CvWEAKOUTSIDE(CV *cv)

Functions in file pad.h
	       Save the current pad in the given context block structure.

		       void    CX_CURPAD_SAVE(struct context)

	       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)

	       Get the value from slot "po" in the base (DEPTH=1) pad of a

		       SV *    PAD_BASE_SV(PADLIST padlist, PADOFFSET po)

	       |CLONE_PARAMS* param Clone the state variables associated with
	       running and compiling pads.

		       void    PAD_CLONE_VARS(PerlInterpreter *proto_perl \)

	       Return the flags for the current compiling pad name at offset
	       "po". Assumes a valid slot entry.


	       The generation number of the name at offset "po" in the current
	       compiling pad (lvalue). Note that "SvCUR" is hijacked for this


	       Sets the generation number of the name at offset "po" in the
	       current ling pad (lvalue) to "gen".  Note that "SvCUR_set" is
	       hijacked for this purpose.

		       STRLEN  PAD_COMPNAME_GEN_set(PADOFFSET po, int gen)

	       Return the stash associated with an "our" variable.  Assumes
	       the slot entry is a valid "our" lexical.


	       Return the name of the current compiling pad name at offset
	       "po". Assumes a valid slot entry.

		       char *  PAD_COMPNAME_PV(PADOFFSET po)

	       Return the type (stash) of the current compiling pad name at
	       offset "po". Must be a valid name. Returns null if not typed.


       PAD_DUP Clone a padlist.

		       void    PAD_DUP(PADLIST dstpad, PADLIST srcpad, CLONE_PARAMS* param)

	       Restore the old pad saved into the local variable opad by

		       void    PAD_RESTORE_LOCAL(PAD *opad)

	       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)

	       Save the current pad then set it to null.

		       void    PAD_SAVE_SETNULLPAD()

	       Set the slot at offset "po" in the current pad to "sv"

		       SV *    PAD_SETSV(PADOFFSET po, SV* sv)

	       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 its best to replace it


		       void    PAD_SET_CUR(PADLIST padlist, I32 n)

	       like PAD_SET_CUR, but without the save

		       void    PAD_SET_CUR_NOSAVE(PADLIST padlist, I32 n)

       PAD_SV  Get the value at offset "po" in the current pad

		       void    PAD_SV(PADOFFSET po)

       PAD_SVl Lightweight and lvalue version of "PAD_SV".  Get or set the
	       value at offset "po" in the current pad.  Unlike "PAD_SV", does
	       not print diagnostics with -DX.	For internal use only.

		       SV *    PAD_SVl(PADOFFSET po)

	       Clear the pointed to pad value on scope exit. (i.e. the runtime
	       action of my)

		       void    SAVECLEARSV(SV **svp)

	       save PL_comppad and PL_curpad

		       void    SAVECOMPPAD()

	       Save a pad slot (used to restore after an iteration)

	       XXX DAPM it would make more sense to make the arg a PADOFFSET

Functions in file pp_ctl.c
	       Locate the CV corresponding to the currently executing sub or
	       eval.  If db_seqp is non_null, skip CVs that are in the DB
	       package and populate *db_seqp with the cop sequence number at
	       the point that the DB:: code was entered. (allows debuggers to
	       eval in the scope of the breakpoint rather than in the scope of
	       the debugger itself).

		       CV*     find_runcv(U32 *db_seqp)

Global Variables
	       When Perl is run in debugging mode, with the -d switch, this SV
	       is a boolean which indicates whether subs are being sin
	       gle-stepped.  Single-stepping is automatically turned on after
	       every step.  This is the C variable which corresponds to Perls
	       $DB::single variable.  See "PL_DBsub".

		       SV *    PL_DBsingle

	       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 Perls $DB::sub
	       variable.  See "PL_DBsingle".

		       GV *    PL_DBsub

	       Trace variable used when Perl is run in debugging mode, with
	       the -d switch.  This is the C variable which corresponds to
	       Perls $DB::trace variable.  See "PL_DBsingle".

		       SV *    PL_DBtrace

	       The C variable which corresponds to Perls $^W warning vari

		       bool    PL_dowarn

	       The GV which was last used for a filehandle input operation.

		       GV*     PL_last_in_gv

	       The output field separator - $, in Perl space.

		       SV*     PL_ofs_sv

       PL_rs   The input record separator - $/ in Perl space.

		       SV*     PL_rs

GV Functions
	       Returns "TRUE" if given the name of a magical GV.

	       Currently only useful internally when determining if a GV
	       should be created even in rvalue contexts.

	       "flags" is not used at present but available for future exten
	       sion to allow selecting particular classes of magical variable.

	       Currently assumes that "name" is NUL terminated (as well as len
	       being valid).  This assumption is met by all callers within the
	       perl core, which all pass pointers returned by SvPV.

		       bool    is_gv_magical(char *name, STRLEN len, U32 flags)

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

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

Pad Data Structures
	       CVs can have CvPADLIST(cv) set to point to an AV.

	       For these purposes "forms" are a kind-of CV, eval""s are too
	       (except theyre not callable at will and are always thrown away
	       after the eval"" is done executing).

	       XSUBs dont have CvPADLIST set - dXSTARG fetches values from
	       PL_curpad, but that is really the callers pad (a slot of which
	       is allocated by every entersub).

	       The CvPADLIST AV has does not have AvREAL set, so REFCNT of
	       component items is managed "manual" (mostly in pad.c) rather
	       than normal av.c rules.	The items in the AV are not SVs as for
	       a normal AV, but other AVs:

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

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

	       During compilation: "PL_comppad_name" is set to the names AV.
	       "PL_comppad" is set to the frame AV for the frame CvDEPTH == 1.
	       "PL_curpad" is set to the body of the frame AV (i.e. AvAR

	       During execution, "PL_comppad" and "PL_curpad" refer to the
	       live frame of the currently executing sub.

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

	       Only my/our variable (SVs_PADMY/SVs_PADOUR) slots get valid
	       names.  The rest are op targets/GVs/constants which are stati
	       cally allocated or resolved at compile time.  These dont have
	       names by which they can be looked up from Perl code at run time
	       through eval"" like my/our variables can be.  Since they cant
	       be looked up by "name" but only by their index allocated at
	       compile time (which is usually in PL_op->op_targ), wasting a
	       name SV for them doesnt make sense.

	       The SVs in the names AV have their PV being the name of the
	       variable.  NV+1..IV inclusive is a range of cop_seq numbers for
	       which the name is valid.  For typed lexicals name SV is
	       SVt_PVMG and SvSTASH points at the type.  For "our" lexicals,
	       the type is SVt_PVGV, and GvSTASH points at the stash of the
	       associated global (so that duplicate "our" declarations in the
	       same package can be detected).  SvCUR is sometimes hijacked to
	       store the generation number during compilation.

	       If SvFAKE is set on the name SV then slot in the frame AVs are
	       a REFCNTed references to a lexical from "outside". In this
	       case, the name SV does not have a cop_seq range, since it is in
	       scope throughout.

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

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

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

		       AV *    CvPADLIST(CV *cv)

	       Clone a CV: make a new CV which points to the same code etc,
	       but which has a newly-created pad built by copying the proto
	       type pad and capturing any outer lexicals.

		       CV*     cv_clone(CV* proto)

       cv_dump dump the contents of a CV

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

	       Dump the contents of a padlist

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

	       "Introduce" my variables to visible status.

		       U32     intro_my()

	       Add an anon code entry to the current compiling pad

		       PADOFFSET       pad_add_anon(SV* sv, OPCODE op_type)

	       Create a new name in the current pad at the specified offset.
	       If "typestash" is valid, the name is for a typed lexical; set
	       the names stash to that value.  If "ourstash" is valid, its
	       an our lexical, set the names GvSTASH to that value

	       Also, if the name is @.. or %.., create a new array or hash for
	       that slot

	       If fake, it means were cloning an existing entry

		       PADOFFSET       pad_add_name(char *name, HV* typestash, HV* ourstash, bool clone)

	       Allocate a new my or tmp pad entry. For a my, simply push a
	       null SV onto the end of PL_comppad, but for a tmp, scan the pad
	       from PL_padix upwards for a slot which has no name and no
	       active value.

		       PADOFFSET       pad_alloc(I32 optype, U32 tmptype)

	       Update the pad compilation state variables on entry to a new

		       void    pad_block_start(int full)

	       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(char* name, bool is_our, HV* ourstash)

	       Find a named lexical anywhere in a chain of nested pads. Add
	       fake entries in the inner pads if its found in an outer one.
	       innercv is the CV *inside* the chain of outer CVs to be
	       searched. If newoff is non-null, this is a run-time cloning:
	       dont add fake entries, just find the lexical and add a ref to
	       it at newoff in the current pad.

		       PADOFFSET       pad_findlex(const char* name, PADOFFSET newoff, const CV* innercv)

	       Given a lexical name, try to find its offset, first in the cur
	       rent pad, or failing that, in the pads of any lexically enclos
	       ing subs (including the complications introduced by eval). If
	       the name is found in an outer pad, then a fake entry is added
	       to the current pad.  Returns the offset in the current pad, or
	       NOT_IN_PAD on failure.

		       PADOFFSET       pad_findmy(char* name)

	       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)

	       Free the SV at offset po in the current pad.

		       void    pad_free(PADOFFSET po)

	       Cleanup at end of scope during compilation: set the max seq
	       number for lexicals in this scope and warn of any lexicals that
	       never got introduced.

		       void    pad_leavemy()

       pad_new Create a new compiling padlist, saving and updating the various
	       global vars at the same time as creating the pad itself. The
	       following flags can be ORed together:

		   padnew_CLONE        this pad is for a cloned CV
		   padnew_SAVE	       save old globals
		   padnew_SAVESUB      also save extra stuff for start of sub

		       PADLIST*        pad_new(int flags)

	       Push a new pad frame onto the padlist, unless theres already a
	       pad at this depth, in which case dont bother creating a new
	       one.  If has_args is true, give the new pad an @_ in slot zero.

		       void    pad_push(PADLIST *padlist, int depth, int has_args)

	       Mark all the current temporaries for reuse

		       void    pad_reset()

	       Set the entry at offset po in the current pad to sv.  Use the
	       macro PAD_SETSV() rather than calling this function directly.

		       void    pad_setsv(PADOFFSET po, SV* sv)

	       Abandon the tmp in the current pad at offset po and replace
	       with a new one.

		       void    pad_swipe(PADOFFSET po, bool refadjust)

	       Tidy up a pad after weve finished compiling it:
		   * remove most stuff from the pads of anonsub prototypes;
		   * give it a @_;
		   * mark tmps as such.

		       void    pad_tidy(padtidy_type type)

	       Free the padlist associated with a CV.  If parts of it happen
	       to be current, we null the relevant PL_*pad* global vars so
	       that we dont have any dangling references left.	We also
	       repoint the CvOUTSIDE of any about-to-be-orphaned inner subs to
	       the outer of this cv.

	       (This function should really be called pad_free, but the name
	       was already taken)

		       void    pad_undef(CV* cv)

Stack Manipulation Macros
       djSP    Declare Just "SP". This is actually identical to "dSP", and
	       declares a local copy of perls stack pointer, available via
	       the "SP" macro.	See "SP".  (Available for backward source code
	       compatibility with the old (Perl 5.005) thread model.)


       LVRET   True if this op will be the return value of an lvalue subrou

SV Manipulation Functions
	       Print appropriate "Use of uninitialized variable" warning

		       void    report_uninit()

	       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* ptr, U32 size, U32 flags)

	       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()

	       Attempt to destroy all objects not yet freed

		       void    sv_clean_objs()

	       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()

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

       perlguts(1), perlapi(1)

perl v5.8.8			  2008-04-25			 PERLINTERN(1)

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