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
    Return an entry from the BHK structure. which is a preprocessor token indicating which entry to return. If the appropriate flag is not set this will return NULL. The type of the return value depends on which entry you ask for.

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

            void *  BhkENTRY(BHK *hk, which)

BhkFLAGS
    Return the BHK's flags.

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

            U32     BhkFLAGS(BHK *hk)

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

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

            void    CALL_BLOCK_HOOKS(which, arg)

CV reference counts and CvOUTSIDE

CvWEAKOUTSIDE
    Each CV has a pointer, "CvOUTSIDE()", to its lexically enclosing CV (if any). Because pointers to anonymous sub prototypes are stored in "&" pad slots, it is a possible to get a circular reference, with the parent pointing to the child and vice-versa. To avoid the ensuing memory leak, we do not increment the reference count of the CV pointed to by "CvOUTSIDE" in the one specific instance that the parent has a "&" pad slot pointing back to us. In this case, we set the "CvWEAKOUTSIDE" flag in the child. This allows us to determine under what circumstances we should decrement the refcount of the parent when freeing the child.

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

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

    In this case, the BEGIN is freed immediately after execution since there are no active references to it: the anon sub prototype has "CvWEAKOUTSIDE" set since it's not a closure, and $a points to the same CV, so it doesn't contribute to BEGIN's refcount either. When $a is executed, the "eval '$x'" causes the chain of "CvOUTSIDE"s to be followed, and the freed BEGIN is accessed.

    To avoid this, whenever a CV and its associated pad is freed, any "&" entries in the pad are explicitly removed from the pad, and if the refcount of the pointed-to anon sub is still positive, then that child's "CvOUTSIDE" is set to point to its grandparent. This will only occur in the single specific case of a non-closure anon prototype having one or more active references (such as $a above).

    One other thing to consider is that a CV may be merely undefined rather than freed, eg "undef &foo". In this case, its refcount may not have reached zero, but we still delete its pad and its "CvROOT" etc. Since various children may still have their "CvOUTSIDE" pointing at this undefined CV, we keep its own "CvOUTSIDE" for the time being, so that the chain of lexical scopes is unbroken. For example, the following should print 123:

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

            bool    CvWEAKOUTSIDE(CV *cv)

Embedding Functions

cv_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(const CV *cv, const 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()

pad_add_anon
    Add an anon code entry to the current compiling pad

            PADOFFSET       pad_add_anon(SV* sv, OPCODE op_type)

pad_add_name
    Create a new name and associated PADMY SV in the current pad; return the offset. If "typestash" is valid, the name is for a typed lexical; set the name's stash to that value. If "ourstash" is valid, it's an our lexical, set the name's SvOURSTASH to that value

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

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

            PADOFFSET       pad_add_name(const char *name, const STRLEN len, const U32 flags, HV *typestash, HV *ourstash)

pad_alloc
    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)

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(SV *name, const U32 flags, const HV *ourstash)

pad_findlex
    Find a named lexical anywhere in a chain of nested pads. Add fake entries in the inner pads if it's found in an outer one.

    Returns the offset in the bottom pad of the lex or the fake lex. cv is the CV in which to start the search, and seq is the current cop_seq to match against. If warn is true, print appropriate warnings. The out_* vars return values, and so are pointers to where the returned values should be stored. out_capture, if non-null, requests that the innermost instance of the lexical is captured; out_name_sv is set to the innermost matched namesv or fake namesv; out_flags returns the flags normally associated with the IVX field of a fake namesv.

    Note that pad_findlex() is recursive; it recurses up the chain of CVs, then comes back down, adding fake entries as it goes. It has to be this way because fake namesvs in anon protoypes have to store in xlow the index into the parent pad.

            PADOFFSET       pad_findlex(const char *name, const CV* cv, U32 seq, int warn, SV** out_capture, SV** out_name_sv, int *out_flags)

pad_fixup_inner_anons
    For any anon CVs in the pad, change CvOUTSIDE of that CV from old_cv to new_cv if necessary. Needed when a newly-compiled CV has to be moved to a pre-existing CV struct.

            void    pad_fixup_inner_anons(PADLIST *padlist, CV *old_cv, CV *new_cv)

pad_free
    Free the SV at offset po in the current pad.

            void    pad_free(PADOFFSET po)

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

            void    pad_leavemy()

pad_push
    Push a new pad frame onto the padlist, unless there's already a pad at this depth, in which case don't bother creating a new one. Then give the new pad an @_ in slot zero.

            void    pad_push(PADLIST *padlist, int depth)

pad_reset
    Mark all the current temporaries for reuse

            void    pad_reset()

pad_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)

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 the state variables associated with running and compiling pads.

            void    PAD_CLONE_VARS(PerlInterpreter *proto_perl, CLONE_PARAMS* param)

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

            U32     PAD_COMPNAME_FLAGS(PADOFFSET po)

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

            STRLEN  PAD_COMPNAME_GEN(PADOFFSET po)

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

            STRLEN  PAD_COMPNAME_GEN_set(PADOFFSET po, int gen)

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

            HV *    PAD_COMPNAME_OURSTASH(PADOFFSET po)

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

            char *  PAD_COMPNAME_PV(PADOFFSET po)

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

            HV *    PAD_COMPNAME_TYPE(PADOFFSET po)

PAD_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. NB currently this macro expands to a string too long for some compilers, so it's best to replace it with

        SAVECOMPPAD();
        PAD_SET_CUR_NOSAVE(padlist,n);

            void    PAD_SET_CUR(PADLIST padlist, I32 n)

PAD_SET_CUR_NOSAVE
    like PAD_SET_CUR, but without the save

            void    PAD_SET_CUR_NOSAVE(PADLIST padlist, I32 n)

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

            void    PAD_SV(PADOFFSET po)

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

            SV *    PAD_SVl(PADOFFSET po)

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

            void    SAVECLEARSV(SV **svp)

SAVECOMPPAD
    save PL_comppad and PL_curpad

            void    SAVECOMPPAD()

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

    XXX DAPM it would make more sense to make the arg a PADOFFSET
        void    SAVEPADSV(PADOFFSET po)

Functions in file pp_ctl.c

docatch
    Check for the cases 0 or 3 of cur_env.je_ret, only used inside an eval context.

    0 is used as continue inside eval,

    3 is used for a die caught by an inner eval - continue inner loop

    See cop.h: je_mustcatch, when set at any runlevel to TRUE, means eval ops must establish a local jmpenv to handle exception traps.

            OP*     docatch(OP *o)

GV Functions

gv_try_downgrade
    If the typeglob "gv" can be expressed more succinctly, by having something other than a real GV in its place in the stash, replace it with the optimised form. Basic requirements for this are that "gv" is a real typeglob, is sufficiently ordinary, and is only referenced from its package. This function is meant to be used when a GV has been looked up in part to see what was there, causing upgrading, but based on what was found it turns out that the real GV isn't required after all.

    If "gv" is a completely empty typeglob, it is deleted from the stash.

    If "gv" is a typeglob containing only a sufficiently-ordinary constant sub, the typeglob is replaced with a scalar-reference placeholder that more compactly represents the same thing.

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

            void    gv_try_downgrade(GV* gv)

is_gv_magical_sv
    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 extension 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_sv(SV *const name_sv, U32 flags)

Hash Manipulation Functions

hv_ename_add
    Adds a name to a stash's internal list of effective names. See "hv_ename_delete".

    This is called when a stash is assigned to a new location in the symbol table.

            void    hv_ename_add(HV *hv, const char *name, U32 len, U32 flags)

hv_ename_delete
    Removes a name from a stash's internal list of effective names. If this is the name returned by "HvENAME", then another name in the list will take its place ("HvENAME" will use it).

    This is called when a stash is deleted from the symbol table.

            void    hv_ename_delete(HV *hv, const char *name, U32 len, U32 flags)

refcounted_he_chain_2hv
    Generates and returns a "HV *" representing the content of a "refcounted_he" chain. flags is currently unused and must be zero.

            HV *    refcounted_he_chain_2hv(const struct refcounted_he *c, U32 flags)

refcounted_he_fetch_pv
    Like "refcounted_he_fetch_pvn", but takes a nul-terminated string instead of a string/length pair.

            SV *    refcounted_he_fetch_pv(const struct refcounted_he *chain, const char *key, U32 hash, U32 flags)

refcounted_he_fetch_pvn
    Search along a "refcounted_he" chain for an entry with the key specified by keypv and keylen. If flags has the "REFCOUNTED_HE_KEY_UTF8" bit set, the key octets are interpreted as UTF-8, otherwise they are interpreted as Latin-1. hash is a precomputed hash of the key string, or zero if it has not been precomputed. Returns a mortal scalar representing the value associated with the key, or &PL_sv_placeholder if there is no value associated with the key.

            SV *    refcounted_he_fetch_pvn(const struct refcounted_he *chain, const char *keypv, STRLEN keylen, U32 hash, U32 flags)

refcounted_he_fetch_pvs
    Like "refcounted_he_fetch_pvn", but takes a literal string instead of a string/length pair, and no precomputed hash.

            SV *    refcounted_he_fetch_pvs(const struct refcounted_he *chain, const char *key, U32 flags)

refcounted_he_fetch_sv
    Like "refcounted_he_fetch_pvn", but takes a Perl scalar instead of a string/length pair.

            SV *    refcounted_he_fetch_sv(const struct refcounted_he *chain, SV *key, U32 hash, U32 flags)

refcounted_he_free
    Decrements the reference count of a "refcounted_he" by one. If the reference count reaches zero the structure's memory is freed, which (recursively) causes a reduction of its parent "refcounted_he"'s reference count. It is safe to pass a null pointer to this function: no action occurs in this case.

            void    refcounted_he_free(struct refcounted_he *he)

refcounted_he_inc
    Increment the reference count of a "refcounted_he". The pointer to the "refcounted_he" is also returned. It is safe to pass a null pointer to this function: no action occurs and a null pointer is returned.

            struct refcounted_he *  refcounted_he_inc(struct refcounted_he *he)

refcounted_he_new_pv
    Like "refcounted_he_new_pvn", but takes a nul-terminated string instead of a string/length pair.

            struct refcounted_he *  refcounted_he_new_pv(struct refcounted_he *parent, const char *key, U32 hash, SV *value, U32 flags)

refcounted_he_new_pvn
    Creates a new "refcounted_he". This consists of a single key/value pair and a reference to an existing "refcounted_he" chain (which may be empty), and thus forms a longer chain. When using the longer chain, the new key/value pair takes precedence over any entry for the same key further along the chain.

    The new key is specified by keypv and keylen. If flags has the "REFCOUNTED_HE_KEY_UTF8" bit set, the key octets are interpreted as UTF-8, otherwise they are interpreted as Latin-1. hash is a precomputed hash of the key string, or zero if it has not been precomputed.

    value is the scalar value to store for this key. value is copied by this function, which thus does not take ownership of any reference to it, and later changes to the scalar will not be reflected in the value visible in the "refcounted_he". Complex types of scalar will not be stored with referential integrity, but will be coerced to strings. value may be either null or &PL_sv_placeholder to indicate that no value is to be associated with the key; this, as with any non-null value, takes precedence over the existence of a value for the key further along the chain.

    parent points to the rest of the "refcounted_he" chain to be attached to the new "refcounted_he". This function takes ownership of one reference to parent, and returns one reference to the new "refcounted_he".

            struct refcounted_he *  refcounted_he_new_pvn(struct refcounted_he *parent, const char *keypv, STRLEN keylen, U32 hash, SV *value, U32 flags)

refcounted_he_new_pvs
    Like "refcounted_he_new_pvn", but takes a literal string instead of a string/length pair, and no precomputed hash.

            struct refcounted_he *  refcounted_he_new_pvs(struct refcounted_he *parent, const char *key, SV *value, U32 flags)

refcounted_he_new_sv
    Like "refcounted_he_new_pvn", but takes a Perl scalar instead of a string/length pair.

            struct refcounted_he *  refcounted_he_new_sv(struct refcounted_he *parent, SV *key, U32 hash, SV *value, U32 flags)

IO Functions

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

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

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

Magical Functions

magic_clearhint
    Triggered by a delete from %^H, records the key to "PL_compiling.cop_hints_hash".

            int     magic_clearhint(SV* sv, MAGIC* mg)

magic_clearhints
    Triggered by clearing %^H, resets "PL_compiling.cop_hints_hash".

            int     magic_clearhints(SV* sv, MAGIC* mg)

magic_methcall
    Invoke a magic method (like FETCH).

    * sv and mg are the tied thingy and the tie magic; * meth is the name of the method to call; * argc is the number of args (in addition to $self) to pass to the method;
           the args themselves are any values following the argc argument. * flags:
        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.

    Returns the SV (if any) returned by the method, or NULL on failure.

            SV*     magic_methcall(SV *sv, const MAGIC *mg, const char *meth, U32 flags, U32 argc, ...)

magic_sethint
    Triggered by a store to %^H, records the key/value pair to "PL_compiling.cop_hints_hash". It is assumed that hints aren't storing anything that would need a deep copy. Maybe we should warn if we find a reference.

            int     magic_sethint(SV* sv, MAGIC* mg)

mg_localize
    Copy some of the magic from an existing SV to new localized version of that SV. Container magic (eg %ENV, $1, tie) gets copied, value magic doesn't (eg taint, pos).

    If setmagic is false then no set magic will be called on the new (empty) SV. This typically means that assignment will soon follow (e.g. 'local $x = $y'), and that will handle the magic.

            void    mg_localize(SV* sv, SV* nsv, bool setmagic)

MRO Functions

mro_get_linear_isa_dfs
    Returns the Depth-First Search linearization of @ISA the given stash. The return value is a read-only AV*. "level" should be 0 (it is used internally in this function's recursion).

    You are responsible for "SvREFCNT_inc()" on the return value if you plan to store it anywhere semi-permanently (otherwise it might be deleted out from under you the next time the cache is invalidated).

            AV*     mro_get_linear_isa_dfs(HV* stash, U32 level)

mro_isa_changed_in
    Takes the necessary steps (cache invalidations, mostly) when the @ISA of the given package has changed. Invoked by the "setisa" magic, should not need to invoke directly.

            void    mro_isa_changed_in(HV* stash)

mro_package_moved
    Call this function to signal to a stash that it has been assigned to another spot in the stash hierarchy. "stash" is the stash that has been assigned. "oldstash" is the stash it replaces, if any. "gv" is the glob that is actually being assigned to.

    This can also be called with a null first argument to indicate that "oldstash" has been deleted.

    This function invalidates isa caches on the old stash, on all subpackages nested inside it, and on the subclasses of all those, including non-existent packages that have corresponding entries in "stash".

    It also sets the effective names ("HvENAME") on all the stashes as appropriate.

    If the "gv" is present and is not in the symbol table, then this function simply returns. This checked will be skipped if "flags & 1".

            void    mro_package_moved(HV * const stash, HV * const oldstash, const GV * const gv, U32 flags)

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). Require'd files are simply evals without any outer lexical scope.

    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 represents 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 recursion 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_comppad)).

    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 statically allocated or resolved at compile time. These don't 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 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. xlow+1..xhigh inclusive in the NV union is a range of cop_seq numbers for which the name is valid (accessed through the macros COP_SEQ_RANGE_LOW and _HIGH). During compilation, these fields may hold the special value PERL_PADSEQ_INTRO to indicate various stages:

       COP_SEQ_RANGE_LOW        _HIGH
       -----------------        -----
       PERL_PADSEQ_INTRO            0   variable not yet introduced:   { my ($x
       valid-seq#   PERL_PADSEQ_INTRO   variable in scope:             { my ($x)
       valid-seq#          valid-seq#   compilation of scope complete: { my ($x) }

    For typed lexicals name SV is SVt_PVMG and SvSTASH points at the type. For "our" lexicals, the type is also SVt_PVMG, with the SvOURSTASH slot pointing at the stash of the associated global (so that duplicate "our" declarations in the same package can be detected). SvUVX is sometimes hijacked to store the generation number during compilation.

    If SvFAKE is set on the name SV, then that slot in the frame AV is a REFCNT'ed reference to a lexical from "outside". In this case, the name SV does not use xlow and xhigh to store a cop_seq range, since it is in scope throughout. Instead xhigh stores some flags containing info about the real lexical (is it declared in an anon, and is it capable of being instantiated multiple times?), and for fake ANONs, xlow contains the index within the parent's pad where the lexical's value is stored, to make cloning quicker.

    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.)

    Note that formats are treated as anon subs, and are cloned each time write is called (if necessary).

    The flag SVs_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();

    For state vars, SVs_PADSTALE is overloaded to mean 'not yet initialised'

            AV *    CvPADLIST(CV *cv)

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 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)

Per-Interpreter Variables

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

            SV *    PL_DBsingle

PL_DBsub
    When Perl is run in debugging mode, with the -d switch, this GV contains the SV which holds the name of the sub being debugged. This is the C variable which corresponds to Perl's $DB::sub variable. See "PL_DBsingle".

            GV *    PL_DBsub

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

            SV *    PL_DBtrace

PL_dowarn
    The C variable which corresponds to Perl's $^W warning variable.

            bool    PL_dowarn

PL_last_in_gv
    The GV which was last used for a filehandle input operation. ("<FH>")

            GV*     PL_last_in_gv

PL_ofsgv
    The glob containing the output field separator - "*," in Perl space.

            GV*     PL_ofsgv

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

            SV*     PL_rs

Stack Manipulation Macros

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

                    djSP;

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

SV Manipulation Functions

sv_add_arena
    Given a chunk of memory, link it to the head of the list of arenas, and split it into a list of free SVs.

            void    sv_add_arena(char *const ptr, const U32 size, const U32 flags)

sv_clean_all
    Decrement the refcnt of each remaining SV, possibly triggering a cleanup. This function may have to be called multiple times to free SVs which are in complex self-referential hierarchies.

            I32     sv_clean_all()

sv_clean_objs
    Attempt to destroy all objects not yet freed

            void    sv_clean_objs()

sv_free_arenas
    Deallocate the memory used by all arenas. Note that all the individual SV heads and bodies within the arenas must already have been freed.

            void    sv_free_arenas()

SV-Body Allocation

sv_2num
    Return an SV with the numeric value of the source SV, doing any necessary reference or overload conversion. You must use the "SvNUM(sv)" macro to access this function.

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

            SV*     sv_2num(SV *const sv)

Unicode Support

find_uninit_var
    Find the name of the undefined variable (if any) that caused the operator o to issue a "Use of uninitialized value" warning. If match is true, only return a name if it's value matches uninit_sv. So roughly speaking, if a unary operator (such as OP_COS) generates a warning, then following the direct child of the op may yield an OP_PADSV or OP_GV that gives the name of the undefined variable. On the other hand, with OP_ADD there are two branches to follow, so we only print the variable name if we get an exact match.

    The name is returned as a mortal SV.

    Assumes that PL_op is the op that originally triggered the error, and that PL_comppad/PL_curpad points to the currently executing pad.

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

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

report_uninit
    Print appropriate "Use of uninitialized variable" warning

            void    report_uninit(const SV *uninit_sv)

Undocumented functions
The following functions have been flagged as part of the public API, but are currently undocumented. Use them at your own risk, as the interfaces are subject to change.

If you use one of them, you may wish to consider creating and submitting documentation for it. If your patch is accepted, this will indicate that the interface is stable (unless it is explicitly marked otherwise).

F0convert
Slab_to_rw
_append_range_to_invlist
_new_invlist
_swash_inversion_hash
_swash_to_invlist
add_alternate
add_cp_to_invlist
add_data
add_range_to_invlist
add_utf16_textfilter
addmad
allocmy
amagic_cmp
amagic_cmp_locale
amagic_i_ncmp
amagic_ncmp
anonymise_cv_maybe
ao
append_madprops
apply
apply_attrs
apply_attrs_my
assert_uft8_cache_coherent
av_reify
bad_type
bind_match
block_end
block_start
boot_core_PerlIO
boot_core_UNIVERSAL
boot_core_mro
bytes_to_uni
cando
check_type_and_open
check_uni
check_utf8_print
checkcomma
checkposixcc
ckwarn_common
cl_and
cl_anything
cl_init
cl_is_anything
cl_or
clear_placeholders
closest_cop
convert
cop_free
cr_textfilter
create_eval_scope
curmad
curse
cv_ckproto_len
cvgv_set
cvstash_set
deb_curcv
deb_stack_all
deb_stack_n
debprof
debug_start_match
del_sv
delete_eval_scope
deprecate_commaless_var_list
destroy_matcher
die_unwind
div128
do_aexec
do_aexec5
do_chomp
do_delete_local
do_eof
do_exec
do_exec3
do_execfree
do_ipcctl
do_ipcget
do_msgrcv
do_msgsnd
do_oddball
do_op_xmldump
do_pmop_xmldump
do_print
do_readline
do_seek
do_semop
do_shmio
do_smartmatch
do_sysseek
do_tell
do_trans
do_trans_complex
do_trans_complex_utf8
do_trans_count
do_trans_count_utf8
do_trans_simple
do_trans_simple_utf8
do_vecget
do_vecset
do_vop
doeval
dofile
dofindlabel
doform
dooneliner
doopen_pm
doparseform
dopoptoeval
dopoptogiven
dopoptolabel
dopoptoloop
dopoptosub_at
dopoptowhen
dump_all_perl
dump_exec_pos
dump_packsubs_perl
dump_sub_perl
dump_sv_child
dump_trie
dump_trie_interim_list
dump_trie_interim_table
dumpuntil
dup_attrlist
emulate_cop_io
exec_failed
expect_number
feature_is_enabled
filter_gets
find_and_forget_pmops
find_array_subscript
find_beginning
find_byclass
find_hash_subscript
find_in_my_stash
find_script
first_symbol
fold_constants
forbid_setid
force_ident
force_list
force_next
force_strict_version
force_version
force_word
forget_pmop
free_tied_hv_pool
gen_constant_list
get_aux_mg
get_db_sub
get_debug_opts
get_hash_seed
get_no_modify
get_num
get_opargs
get_re_arg
getenv_len
glob_2number
glob_assign_glob
glob_assign_ref
grok_bslash_c
grok_bslash_o
group_end
gv_ename
gv_get_super_pkg
gv_init_sv
gv_magicalize_isa
gv_magicalize_overload
hfreeentries
hsplit
hv_auxinit
hv_backreferences_p
hv_delete_common
hv_kill_backrefs
hv_magic_check
hv_notallowed
hv_undef_flags
incline
incpush
incpush_if_exists
incpush_use_sep
ingroup
init_argv_symbols
init_dbargs
init_debugger
init_ids
init_interp
init_main_stash
init_perllib
init_postdump_symbols
init_predump_symbols
intuit_method
intuit_more
invert
invlist_array
invlist_destroy
invlist_extend
invlist_intersection
invlist_len
invlist_max
invlist_set_len
invlist_set_max
invlist_trim
invlist_union
invoke_exception_hook
io_close
is_an_int
is_handle_constructor
is_inplace_av
is_list_assignment
is_utf8_X_L
is_utf8_X_LV
is_utf8_X_LVT
is_utf8_X_LV_LVT_V
is_utf8_X_T
is_utf8_X_V
is_utf8_X_begin
is_utf8_X_extend
is_utf8_X_non_hangul
is_utf8_X_prepend
is_utf8_char_slow
is_utf8_common
isa_lookup
jmaybe
join_exact
keyword
keyword_plugin_standard
list
listkids
localize
looks_like_bool
lop
mad_free
madlex
madparse
magic_clear_all_env
magic_clearenv
magic_clearisa
magic_clearpack
magic_clearsig
magic_existspack
magic_freearylen_p
magic_freeovrld
magic_get
magic_getarylen
magic_getdefelem
magic_getnkeys
magic_getpack
magic_getpos
magic_getsig
magic_getsubstr
magic_gettaint
magic_getuvar
magic_getvec
magic_killbackrefs
magic_len
magic_methcall1
magic_methpack
magic_nextpack
magic_regdata_cnt
magic_regdatum_get
magic_regdatum_set
magic_scalarpack
magic_set
magic_set_all_env
magic_setamagic
magic_setarylen
magic_setcollxfrm
magic_setdbline
magic_setdefelem
magic_setenv
magic_setisa
magic_setmglob
magic_setnkeys
magic_setpack
magic_setpos
magic_setregexp
magic_setsig
magic_setsubstr
magic_settaint
magic_setutf8
magic_setuvar
magic_setvec
magic_sizepack
magic_wipepack
make_matcher
make_trie
make_trie_failtable
malloc_good_size
malloced_size
matcher_matches_sv
measure_struct
mem_collxfrm
mem_log_common
mess_alloc
method_common
missingterm
mod
mode_from_discipline
modkids
more_bodies
more_sv
mro_clean_isarev
mro_gather_and_rename
mro_meta_dup
mro_meta_init
mul128
mulexp10
munge_qwlist_to_paren_list
my_attrs
my_betoh16
my_betoh32
my_betoh64
my_betohi
my_betohl
my_betohs
my_clearenv
my_exit_jump
my_htobe16
my_htobe32
my_htobe64
my_htobei
my_htobel
my_htobes
my_htole16
my_htole32
my_htole64
my_htolei
my_htolel
my_htoles
my_kid
my_letoh16
my_letoh32
my_letoh64
my_letohi
my_letohl
my_letohs
my_lstat_flags
my_stat_flags
my_swabn
my_unexec
need_utf8
newDEFSVOP
newGIVWHENOP
newGP
newMADPROP
newMADsv
newTOKEN
new_constant
new_he
new_logop
new_warnings_bitfield
next_symbol
nextargv
nextchar
no_bareword_allowed
no_fh_allowed
no_op
not_a_number
nuke_stacks
num_overflow
oopsAV
oopsHV
op_clear
op_const_sv
op_getmad
op_getmad_weak
op_refcnt_dec
op_refcnt_inc
op_xmldump
open_script
opt_scalarhv
pack_rec
package
package_version
pad_add_name_sv
pad_compname_type
pad_peg
padlist_dup
parse_body
parse_unicode_opts
parser_free
path_is_absolute
peep
pending_Slabs_to_ro
pidgone
pm_description
pmop_xmldump
pmruntime
pmtrans
populate_isa
prepend_madprops
printbuf
process_special_blocks
ptr_table_find
put_byte
qerror
qsortsvu
re_croak2
readpipe_override
ref_array_or_hash
refcounted_he_value
refkids
refto
reg
reg_check_named_buff_matched
reg_named_buff
reg_named_buff_iter
reg_namedseq
reg_node
reg_numbered_buff_fetch
reg_numbered_buff_length
reg_numbered_buff_store
reg_qr_package
reg_recode
reg_scan_name
reg_skipcomment
reg_temp_copy
reganode
regatom
regbranch
regclass
regcppop
regcppush
regcurly
regdump_extflags
reghop3
reghop4
reghopmaybe3
reginclass
reginsert
regmatch
regpiece
regpposixcc
regprop
regrepeat
regtail
regtail_study
regtry
reguni
regwhite
report_evil_fh
report_wrongway_fh
require_tie_mod
restore_magic
rpeep
rsignal_restore
rsignal_save
run_body
run_user_filter
rxres_free
rxres_restore
rxres_save
same_dirent
save_hek_flags
save_lines
save_magic
save_pushptri32ptr
save_scalar_at
sawparens
scalar
scalar_mod_type
scalarboolean
scalarkids
scalarseq
scalarvoid
scan_commit
scan_const
scan_formline
scan_heredoc
scan_ident
scan_inputsymbol
scan_pat
scan_str
scan_subst
scan_trans
scan_word
search_const
sequence
sequence_num
sequence_tail
set_regclass_bit
set_regclass_bit_fold
share_hek_flags
sighandler
simplify_sort
skipspace
skipspace0
skipspace1
skipspace2
softref2xv
sortcv
sortcv_stacked
sortcv_xsub
space_join_names_mortal
start_force
stdize_locale
store_cop_label
strip_return
study_chunk
sub_crush_depth
sublex_done
sublex_push
sublex_start
sv_2iuv_common
sv_2iuv_non_preserve
sv_add_backref
sv_catxmlpv
sv_catxmlpvn
sv_catxmlsv
sv_compile_2op_is_broken
sv_del_backref
sv_dup_common
sv_dup_inc_multiple
sv_exp_grow
sv_free2
sv_i_ncmp
sv_kill_backrefs
sv_ncmp
sv_pos_b2u_midway
sv_pos_u2b_cached
sv_pos_u2b_forwards
sv_pos_u2b_midway
sv_release_COW
sv_setsv_cow
sv_unglob
sv_xmlpeek
swallow_bom
swash_get
tied_method
to_byte_substr
to_utf8_substr
token_free
token_getmad
tokenize_use
tokeq
tokereport
too_few_arguments
too_many_arguments
try_amagic_bin
try_amagic_un
uiv_2buf
unpack_rec
unreferenced_to_tmp_stack
unshare_hek
unshare_hek_or_pvn
unwind_handler_stack
update_debugger_info
usage
utf16_textfilter
utf8_mg_len_cache_update
utf8_mg_pos_cache_update
utilize
validate_suid
varname
visit
vivify_defelem
vivify_ref
wait4pid
watch
with_queued_errors
write_no_mem
write_to_stderr
xmldump_all
xmldump_all_perl
xmldump_attr
xmldump_eval
xmldump_form
xmldump_indent
xmldump_packsubs
xmldump_packsubs_perl
xmldump_sub
xmldump_sub_perl
xmldump_vindent
xs_apiversion_bootcheck
xs_version_bootcheck
yyerror
yylex
yyparse
yyunlex
yywarn

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