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PERLINTERN(1) Perl Programmers Reference Guide 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!
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)
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 "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)
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.
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(const char *name, STRLEN len, U32 flags)
is_gv_magical_sv
Returns "TRUE" if given the name of a magical GV. Calls is_gv_magical.
bool is_gv_magical_sv(SV *name, U32 flags)
Hash Manipulation Functions
refcounted_he_chain_2hv
Generates and returns a "HV *" by walking up the tree starting at the passed in
"struct refcounted_he *".
HV * refcounted_he_chain_2hv(const struct refcounted_he *c)
refcounted_he_free
Decrements the reference count of the passed in "struct refcounted_he *" by one.
If the reference count reaches zero the structure's memory is freed, and
"refcounted_he_free" iterates onto the parent node.
void refcounted_he_free(struct refcounted_he *he)
refcounted_he_new
Creates a new "struct refcounted_he". As key is copied, and value is stored in a
compact form, all references remain the property of the caller. The "struct
refcounted_he" is returned with a reference count of 1.
struct refcounted_he * refcounted_he_new(struct refcounted_he *const parent, SV *const key, SV *const value)
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)
Magical Functions
magic_sethint
Triggered by a delete from %^H, records the key to "PL_compiling.cop_hints_hash".
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).
void mg_localize(SV* sv, SV* nsv)
MRO Functions
mro_get_linear_isa_c3
Returns the C3 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_c3(HV* stash, I32 level)
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, I32 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)
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. 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 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)
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
PADOFFSET pad_add_name(const char *name, HV* typestash, HV* ourstash, bool clone, bool state)
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(const char* name, bool is_our, 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_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(const 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 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_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. 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)
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)
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_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
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* 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()
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.
SV* sv_2num(SV* 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.
SV* find_uninit_var(OP* obase, SV* uninit_sv, bool top)
report_uninit
Print appropriate "Use of uninitialized variable" warning
void report_uninit(SV* uninit_sv)
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)
perl v5.10.0 2011-06-30 PERLINTERN(1)
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On Apache
Under GNU General Public License
2012-05-26 01:36 @38.107.179.239 Crawled by CCBot/1.0 (+http://www.commoncrawl.org/bot.html)