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!
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 byCvOUTSIDE
in the one specific instance that the parent has a&
pad slot pointing back to us. In this case, we set theCvWEAKOUTSIDE
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 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 $a is executed, theeval '$x'
causes the chain ofCvOUTSIDE
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'sCvOUTSIDE
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 itsCvROOT
etc. Since various children may still have theirCvOUTSIDE
pointing at this undefined CV, we keep its ownCvOUTSIDE
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)
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 padlistSV * 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 thatSvCUR
is hijacked for this purpose.STRLEN PAD_COMPNAME_GEN(PADOFFSET po)
- PAD_COMPNAME_OURSTASH
-
Return the stash associated with an
our
variable. Assumes the slot entry is a validour
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 tosv
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_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 padvoid PAD_SV (PADOFFSET po)
- PAD_SVl
-
Lightweight and lvalue version of
PAD_SV
. Get or set the value at offsetpo
in the current pad. UnlikePAD_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
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
- find_runcv
-
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 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
- PL_rs
-
The input record separator -
$/
in Perl space.SV* PL_rs
GV Functions
- is_gv_magical
-
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.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 usesFile::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). 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
andPL_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. 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 duplicateour
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 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 NVX and IVX to store a cop_seq range, since it is in scope throughout. Instead IVX 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, NVX 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).
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()
- 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. Ifourstash
is valid, it's an our lexical, set the name's GvSTASH to that valueIf 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, 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 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' declarationvoid 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.
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 NVX the index into the parent pad.
PADOFFSET pad_findlex(char *name, CV* cv, U32 seq, int warn, SV** out_capture, SV** out_name_sv, int *out_flags)
- 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_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 offet 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_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)
- 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)
- pad_undef
-
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 don't 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 todSP
, and declares a local copy of perl's stack pointer, available via theSP
macro. SeeSP
. (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, 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()
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(1), perlapi(1)