perlintern - autogenerated documentation of purely internal Perl functions
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!
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
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:
Save the current pad in the given context block structure.
- void CX_CURPAD_SAVE(struct context)
Access the SV at offset po in the saved current pad in the given context block structure (can be used as an lvalue).
- SV * CX_CURPAD_SV(struct context, PADOFFSET po)
Get the value from slot po
in the base (DEPTH=1) pad of a padlist
- SV * PAD_BASE_SV(PADLIST padlist, PADOFFSET po)
Clone the state variables associated with running and compiling pads.
- void PAD_CLONE_VARS(PerlInterpreter *proto_perl, CLONE_PARAMS* param)
Return the flags for the current compiling pad name
at offset po
. Assumes a valid slot entry.
- U32 PAD_COMPNAME_FLAGS(PADOFFSET po)
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)
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)
Return the stash associated with an our variable.
Assumes the slot entry is a valid our lexical.
- HV * PAD_COMPNAME_OURSTASH(PADOFFSET po)
Return the name of the current compiling pad name
at offset po
. Assumes a valid slot entry.
- char * PAD_COMPNAME_PV(PADOFFSET po)
Return the type (stash) of the current compiling pad name at offset
po
. Must be a valid name. Returns null if not typed.
- HV * PAD_COMPNAME_TYPE(PADOFFSET po)
Clone a padlist.
- void PAD_DUP(PADLIST dstpad, PADLIST srcpad, CLONE_PARAMS* param)
Restore the old pad saved into the local variable opad by PAD_SAVE_LOCAL()
- void PAD_RESTORE_LOCAL(PAD *opad)
Save the current pad to the local variable opad, then make the current pad equal to npad
- void PAD_SAVE_LOCAL(PAD *opad, PAD *npad)
Save the current pad then set it to null.
- void PAD_SAVE_SETNULLPAD()
Set the slot at offset po
in the current pad to sv
- SV * PAD_SETSV(PADOFFSET po, SV* sv)
Set the current pad to be pad n
in the padlist, saving
the previous current pad. NB currently this macro expands to a string too
long for some compilers, so it's best to replace it with
- SAVECOMPPAD();
- PAD_SET_CUR_NOSAVE(padlist,n);
- void PAD_SET_CUR(PADLIST padlist, I32 n)
like PAD_SET_CUR, but without the save
- void PAD_SET_CUR_NOSAVE(PADLIST padlist, I32 n)
Get the value at offset po
in the current pad
- void PAD_SV(PADOFFSET po)
Lightweight and lvalue version of PAD_SV
.
Get or set the value at offset po
in the current pad.
Unlike PAD_SV
, does not print diagnostics with -DX.
For internal use only.
- SV * PAD_SVl(PADOFFSET po)
Clear the pointed to pad value on scope exit. (i.e. the runtime action of 'my')
- void SAVECLEARSV(SV **svp)
save PL_comppad and PL_curpad
- void SAVECOMPPAD()
Save a pad slot (used to restore after an iteration)
XXX DAPM it would make more sense to make the arg a PADOFFSET void SAVEPADSV(PADOFFSET po)
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)
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)
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)
Generates and returns a HV *
by walking up the tree starting at the passed
in struct refcounted_he *
.
NOTE: this function is experimental and may change or be removed without notice.
- HV * refcounted_he_chain_2hv(const struct refcounted_he *c)
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.
NOTE: this function is experimental and may change or be removed without notice.
- void refcounted_he_free(struct refcounted_he *he)
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.
NOTE: this function is experimental and may change or be removed without notice.
- struct refcounted_he * refcounted_he_new(struct refcounted_he *const parent, SV *const key, SV *const value)
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)
Triggered by a delete from %^H, records the key to
PL_compiling.cop_hints_hash
.
- int magic_clearhint(SV* sv, MAGIC* mg)
Triggered by clearing %^H, resets PL_compiling.cop_hints_hash
.
- int magic_clearhints(SV* sv, MAGIC* mg)
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)
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)
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)
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)
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 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
For state vars, SVs_PADSTALE is overloaded to mean 'not yet initialised'
- AV * CvPADLIST(CV *cv)
Clone a CV: make a new CV which points to the same code etc, but which has a newly-created pad built by copying the prototype pad and capturing any outer lexicals.
- CV* cv_clone(CV* proto)
dump the contents of a CV
- void cv_dump(const CV *cv, const char *title)
Dump the contents of a padlist
- void do_dump_pad(I32 level, PerlIO *file, PADLIST *padlist, int full)
"Introduce" my variables to visible status.
- U32 intro_my()
Add an anon code entry to the current compiling pad
- PADOFFSET pad_add_anon(SV* sv, OPCODE op_type)
Create a new name 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)
Allocate a new my or tmp pad entry. For a my, simply push a null SV onto the end of PL_comppad, but for a tmp, scan the pad from PL_padix upwards for a slot which has no name and no active value.
- PADOFFSET pad_alloc(I32 optype, U32 tmptype)
Update the pad compilation state variables on entry to a new block
- void pad_block_start(int full)
Check for duplicate declarations: report any of:
* a my in the current scope with the same name;
* an our (anywhere in the pad) with the same name and the same stash
as ourstash
is_our
indicates that the name to check is an 'our' declaration
- void pad_check_dup(SV *name, const U32 flags, const HV *ourstash)
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.
For any anon CVs in the pad, change CvOUTSIDE of that CV from old_cv to new_cv if necessary. Needed when a newly-compiled CV has to be moved to a pre-existing CV struct.
- void pad_fixup_inner_anons(PADLIST *padlist, CV *old_cv, CV *new_cv)
Free the SV at offset po in the current pad.
- void pad_free(PADOFFSET po)
Cleanup at end of scope during compilation: set the max seq number for lexicals in this scope and warn of any lexicals that never got introduced.
- void pad_leavemy()
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)
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)
Mark all the current temporaries for reuse
- void pad_reset()
Set the entry at offset po in the current pad to sv. Use the macro PAD_SETSV() rather than calling this function directly.
- void pad_setsv(PADOFFSET po, SV* sv)
Abandon the tmp in the current pad at offset po and replace with a new one.
- void pad_swipe(PADOFFSET po, bool refadjust)
Tidy up a pad after 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)
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)
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
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
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
The C variable which corresponds to Perl's $^W warning variable.
- bool PL_dowarn
The GV which was last used for a filehandle input operation. (<FH>
)
- GV* PL_last_in_gv
The glob containing the output field separator - *,
in Perl space.
- GV* PL_ofsgv
The input record separator - $/
in Perl space.
- SV* PL_rs
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;
True if this op will be the return value of an lvalue subroutine
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)
Decrement the refcnt of each remaining SV, possibly triggering a cleanup. This function may have to be called multiple times to free SVs which are in complex self-referential hierarchies.
- I32 sv_clean_all()
Attempt to destroy all objects not yet freed
- void sv_clean_objs()
Deallocate the memory used by all arenas. Note that all the individual SV heads and bodies within the arenas must already have been freed.
- void sv_free_arenas()
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)
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)
Print appropriate "Use of uninitialized variable" warning
- void report_uninit(const SV *uninit_sv)
These functions are currently undocumented:
The autodocumentation system was originally added to the Perl core by Benjamin Stuhl. Documentation is by whoever was kind enough to document their functions.