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perlintern




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!


CV reference counts and CvOUTSIDE

       CvWEAKOUTSIDE
               Each CV has a pointer, "CvOUTSIDE()", to its lexi­
               cally enclosing CV (if any). Because pointers to
               anonymous sub prototypes are stored in "&" pad
               slots, it is a possible to get a circular refer­
               ence, 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 point­
               ing back to us. In this case, we set the "CvWEAK­
               OUTSIDE" 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 (ie 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 chil­
               dren, eg

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

               In this case, the BEGIN is freed immediately after
               execution since there are no active references to
               it: the anon sub prototype has "CvWEAKOUTSIDE" set
               since it's not a closure, and $a points to the
               same CV, so it doesn't contribute to BEGIN's ref­
               count either.  When $a is executed, the "eval
               '$x'" causes the chain of "CvOUTSIDE"s to be fol­
               lowed, 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 ref­
               count of the pointed-to anon sub is still posi­
               tive, 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
                   sub tmp { sub { eval '$x' } }
                   my $a = tmp();
                   undef &tmp;
                   print  $a->();

                       bool    CvWEAKOUTSIDE(CV *cv)


Functions in file pad.h

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

                       void    PAD_CLONE_VARS(PerlInterpreter *proto_perl \)

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

                       U32     PAD_COMPNAME_FLAGS(PADOFFSET po)

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

                       STRLEN  PAD_COMPNAME_GEN(PADOFFSET po)

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

                       HV *    PAD_COMPNAME_OURSTASH(PADOFFSET po)

       PAD_DUP Clone a padlist.

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

       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.

                       void    PAD_SET_CUR     (PADLIST padlist, I32 n)

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

                       void    PAD_SV  (PADOFFSET po)

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

                       SV *    PAD_SVl (PADOFFSET po)

       SAVECLEARSV
               Clear the pointed to pad value on scope exit. (ie
               the runtime action of 'my')

                       void    SAVECLEARSV     (SV **svp)

       SAVECOMPPAD
               save PL_comppad and PL_curpad
               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 in the scope of the debuger itself).

                       CV*     find_runcv(U32 *db_seqp)


Global 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_ofs_sv
               The output field separator - $, in Perl space.

                       SV*     PL_ofs_sv

               classes of magical variable.

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


IO Functions

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

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


Pad Data Structures

       CvPADLIST
               CV's can have CvPADLIST(cv) set to point to an AV.

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

               XSUBs don't 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:

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

               The CvDEPTH'th entry of CvPADLIST AV is an AV
               which is the stack frame at that depth of recur­
               sion into the CV.  The 0'th 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. AvARRAY(PL_comp­
               pad)).

               During execution, "PL_comppad" and "PL_curpad"
               Since they can't 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 doesn't 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" delarations 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 REFCNT'ed 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 combi­
               nation currently but could become so if "my sub
               foo {}" is implemented.)

                       AV *    CvPADLIST(CV *cv)

       cv_clone
               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 prototype pad and capturing any
               outer lexicals.

                       CV*     cv_clone(CV* proto)

       cv_dump dump the contents of a CV

                       void    cv_dump(CV *cv, char *title)

       do_dump_pad
               Dump the contents of a padlist

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

       intro_my
               "Introduce" my variables to visible status.

                       U32     intro_my()

               array or hash for that slot

               If fake, it means we're cloning an existing entry

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

       pad_alloc
               Allocate a new my or tmp pad entry. For a my, sim­
               ply 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 and no active value.

                       PADOFFSET       pad_alloc(I32 optype, U32 tmptype)

       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(char* name, bool is_our, 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. innercv is the CV *inside*
               the chain of outer CVs to be searched. If newoff
               is non-null, this is a run-time cloning: don't add
               fake entries, just find the lexical and add a ref
               to it at newoff in the current pad.

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

       pad_findmy
               Given a lexical name, try to find its offset,
               first in the current pad, or failing that, in the
               pads of any lexically enclosing 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)

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

                       void    pad_leavemy()

       pad_new Create a new compiling padlist, saving and updat­
               ing the various global vars at the same time as
               creating the pad itself. The following flags can
               be OR'ed 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)

       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.  If has_args is
               true, give the new pad an @_ in slot zero.

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

       pad_reset
               Mark all the current temporaries for reuse

                       void    pad_reset()

       pad_setsv
               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)

       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)

       pad_tidy
               Tidy up a pad after we've 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)


Stack Manipulation Macros

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

                               djSP;

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


SV Manipulation Functions

       report_uninit
               Print appropriate "Use of uninitialized variable"
               warning

                       void    report_uninit()

       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* ptr, U32 size, U32 flags)

       sv_clean_all
               Decrement the refcnt of each remaining SV, possi­
               bly 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()


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


  

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