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✏️ Editing: perlintern.pod

-*- buffer-read-only: t -*-
!!!!!!!   DO NOT EDIT THIS FILE   !!!!!!!
This file is built by autodoc.pl extracting documentation from the C source
files.
Any changes made here will be lost!

=head1 NAME

perlintern - autogenerated documentation of purely B<internal>
		 Perl functions

=head1 DESCRIPTION
X<internal Perl functions> X<interpreter 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,
B<they are not for use in extensions>!

=head1 Compile-time scope hooks

=over 8

=item BhkENTRY
X<BhkENTRY>

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

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

void *	BhkENTRY(BHK *hk, which)

=for hackers
Found in file op.h

=item BhkFLAGS
X<BhkFLAGS>

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

Return the BHK's flags.

U32	BhkFLAGS(BHK *hk)

=for hackers
Found in file op.h

=item CALL_BLOCK_HOOKS
X<CALL_BLOCK_HOOKS>

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

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

void	CALL_BLOCK_HOOKS(which, arg)

=for hackers
Found in file op.h

=back

=head1 Custom Operators

=over 8

=item core_prototype
X<core_prototype>

This function assigns the prototype of the named core function to C<sv>, or
to a new mortal SV if C<sv> is C<NULL>.  It returns the modified C<sv>, or
C<NULL> if the core function has no prototype.  C<code> is a code as returned
by C<keyword()>.  It must not be equal to 0.

SV *	core_prototype(SV *sv, const char *name,
		               const int code,
		               int * const opnum)

=for hackers
Found in file op.c

=back

=head1 CV Manipulation Functions

=over 8

=item docatch
X<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 F<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(Perl_ppaddr_t firstpp)

=for hackers
Found in file pp_ctl.c

=back

=head1 CV reference counts and CvOUTSIDE

=over 8

=item CvWEAKOUTSIDE
X<CvWEAKOUTSIDE>

Each CV has a pointer, C<CvOUTSIDE()>, to its lexically enclosing
CV (if any).  Because pointers to anonymous sub prototypes are
stored in C<&> 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 C<CvOUTSIDE> in the I<one specific instance> that the parent
has a C<&> pad slot pointing back to us.  In this case, we set the
C<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, I<e.g.>,

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
C<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 $a is
executed, the C<eval '$x'> causes the chain of C<CvOUTSIDE>s to be followed,
and the freed BEGIN is accessed.

To avoid this, whenever a CV and its associated pad is freed, any
C<&> 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 C<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 C<$a> above).

One other thing to consider is that a CV may be merely undefined
rather than freed, eg C<undef &foo>.  In this case, its refcount may
not have reached zero, but we still delete its pad and its C<CvROOT> etc.
Since various children may still have their C<CvOUTSIDE> pointing at this
undefined CV, we keep its own C<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)

=for hackers
Found in file cv.h

=back

=head1 Embedding Functions

=over 8

=item cv_dump
X<cv_dump>

dump the contents of a CV

void	cv_dump(CV *cv, const char *title)

=for hackers
Found in file pad.c

=item cv_forget_slab
X<cv_forget_slab>

When a CV has a reference count on its slab (C<CvSLABBED>), it is responsible
for making sure it is freed.  (Hence, no two CVs should ever have a
reference count on the same slab.)  The CV only needs to reference the slab
during compilation.  Once it is compiled and C<CvROOT> attached, it has
finished its job, so it can forget the slab.

void	cv_forget_slab(CV *cv)

=for hackers
Found in file pad.c

=item do_dump_pad
X<do_dump_pad>

Dump the contents of a padlist

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

=for hackers
Found in file pad.c

=item pad_alloc_name
X<pad_alloc_name>

Allocates a place in the currently-compiling
pad (via L<perlapi/pad_alloc>) and
then stores a name for that entry.  C<name> is adopted and
becomes the name entry; it must already contain the name
string.  C<typestash> and C<ourstash> and the C<padadd_STATE>
flag get added to C<name>.  None of the other
processing of L<perlapi/pad_add_name_pvn>
is done.  Returns the offset of the allocated pad slot.

PADOFFSET pad_alloc_name(PADNAME *name, U32 flags,
	                         HV *typestash, HV *ourstash)

=for hackers
Found in file pad.c

=item pad_block_start
X<pad_block_start>

Update the pad compilation state variables on entry to a new block.

void	pad_block_start(int full)

=for hackers
Found in file pad.c

=item pad_check_dup
X<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'

C<is_our> indicates that the name to check is an C<"our"> declaration.

void	pad_check_dup(PADNAME *name, U32 flags,
		              const HV *ourstash)

=for hackers
Found in file pad.c

=item pad_findlex
X<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.
C<cv> is the CV in which to start the search, and seq is the current C<cop_seq>
to match against.  If C<warn> is true, print appropriate warnings.  The C<out_>*
vars return values, and so are pointers to where the returned values
should be stored.  C<out_capture>, if non-null, requests that the innermost
instance of the lexical is captured; C<out_name> is set to the innermost
matched pad name or fake pad name; C<out_flags> returns the flags normally
associated with the C<PARENT_FAKELEX_FLAGS> field of a fake pad name.

Note that C<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 names in anon protoypes have to store in C<xpadn_low> the
index into the parent pad.

PADOFFSET pad_findlex(const char *namepv,
	                      STRLEN namelen, U32 flags,
	                      const CV* cv, U32 seq, int warn,
	                      SV** out_capture,
	                      PADNAME** out_name,
	                      int *out_flags)

=for hackers
Found in file pad.c

=item pad_fixup_inner_anons
X<pad_fixup_inner_anons>

For any anon CVs in the pad, change C<CvOUTSIDE> of that CV from
C<old_cv> to C<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)

=for hackers
Found in file pad.c

=item pad_free
X<pad_free>

Free the SV at offset po in the current pad.

void	pad_free(PADOFFSET po)

=for hackers
Found in file pad.c

=item pad_leavemy
X<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()

=for hackers
Found in file pad.c

=item padlist_dup
X<padlist_dup>

Duplicates a pad.

PADLIST * padlist_dup(PADLIST *srcpad,
	                      CLONE_PARAMS *param)

=for hackers
Found in file pad.c

=item padname_dup
X<padname_dup>

Duplicates a pad name.

PADNAME * padname_dup(PADNAME *src, CLONE_PARAMS *param)

=for hackers
Found in file pad.c

=item padnamelist_dup
X<padnamelist_dup>

Duplicates a pad name list.

PADNAMELIST * padnamelist_dup(PADNAMELIST *srcpad,
	                              CLONE_PARAMS *param)

=for hackers
Found in file pad.c

=item pad_push
X<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 C<@_> in slot zero.

void	pad_push(PADLIST *padlist, int depth)

=for hackers
Found in file pad.c

=item pad_reset
X<pad_reset>

Mark all the current temporaries for reuse

void	pad_reset()

=for hackers
Found in file pad.c

=item pad_swipe
X<pad_swipe>

Abandon the tmp in the current pad at offset C<po> and replace with a
new one.

void	pad_swipe(PADOFFSET po, bool refadjust)

=for hackers
Found in file pad.c

=back

=head1 GV Functions

=over 8

=item gv_try_downgrade
X<gv_try_downgrade>

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

If the typeglob C<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 C<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 C<gv> is a completely empty typeglob, it is deleted from the stash.

If C<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.

void	gv_try_downgrade(GV* gv)

=for hackers
Found in file gv.c

=back

=head1 Hash Manipulation Functions

=over 8

=item hv_ename_add
X<hv_ename_add>

Adds a name to a stash's internal list of effective names.  See
C<L</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)

=for hackers
Found in file hv.c

=item hv_ename_delete
X<hv_ename_delete>

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

=for hackers
Found in file hv.c

=item refcounted_he_chain_2hv
X<refcounted_he_chain_2hv>

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

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

=for hackers
Found in file hv.c

=item refcounted_he_fetch_pv
X<refcounted_he_fetch_pv>

Like L</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
		)

=for hackers
Found in file hv.c

=item refcounted_he_fetch_pvn
X<refcounted_he_fetch_pvn>

Search along a C<refcounted_he> chain for an entry with the key specified
by C<keypv> and C<keylen>.  If C<flags> has the C<REFCOUNTED_HE_KEY_UTF8>
bit set, the key octets are interpreted as UTF-8, otherwise they
are interpreted as Latin-1.  C<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 C<&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
		)

=for hackers
Found in file hv.c

=item refcounted_he_fetch_pvs
X<refcounted_he_fetch_pvs>

Like L</refcounted_he_fetch_pvn>, but takes a C<NUL>-terminated 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
		)

=for hackers
Found in file hv.h

=item refcounted_he_fetch_sv
X<refcounted_he_fetch_sv>

Like L</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
		)

=for hackers
Found in file hv.c

=item refcounted_he_free
X<refcounted_he_free>

Decrements the reference count of a C<refcounted_he> by one.  If the
reference count reaches zero the structure's memory is freed, which
(recursively) causes a reduction of its parent C<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)

=for hackers
Found in file hv.c

=item refcounted_he_inc
X<refcounted_he_inc>

Increment the reference count of a C<refcounted_he>.  The pointer to the
C<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
	                       )

=for hackers
Found in file hv.c

=item refcounted_he_new_pv
X<refcounted_he_new_pv>

Like L</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
	                       )

=for hackers
Found in file hv.c

=item refcounted_he_new_pvn
X<refcounted_he_new_pvn>

Creates a new C<refcounted_he>.  This consists of a single key/value
pair and a reference to an existing C<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 C<keypv> and C<keylen>.  If C<flags> has
the C<REFCOUNTED_HE_KEY_UTF8> bit set, the key octets are interpreted
as UTF-8, otherwise they are interpreted as Latin-1.  C<hash> is
a precomputed hash of the key string, or zero if it has not been
precomputed.

C<value> is the scalar value to store for this key.  C<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 C<refcounted_he>.  Complex types of scalar will not
be stored with referential integrity, but will be coerced to strings.
C<value> may be either null or C<&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.

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

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

=for hackers
Found in file hv.c

=item refcounted_he_new_pvs
X<refcounted_he_new_pvs>

Like L</refcounted_he_new_pvn>, but takes a C<NUL>-terminated 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
	                       )

=for hackers
Found in file hv.h

=item refcounted_he_new_sv
X<refcounted_he_new_sv>

Like L</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
	                       )

=for hackers
Found in file hv.c

=back

=head1 IO Functions

=over 8

=item start_glob
X<start_glob>

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

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

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

=for hackers
Found in file doio.c

=back

=head1 Lexer interface

=over 8

=item validate_proto
X<validate_proto>

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

This function performs syntax checking on a prototype, C<proto>.
If C<warn> is true, any illegal characters or mismatched brackets
will trigger illegalproto warnings, declaring that they were
detected in the prototype for C<name>.

The return value is C<true> if this is a valid prototype, and
C<false> if it is not, regardless of whether C<warn> was C<true> or
C<false>.

Note that C<NULL> is a valid C<proto> and will always return C<true>.

NOTE: the perl_ form of this function is deprecated.

bool	validate_proto(SV *name, SV *proto, bool warn)

=for hackers
Found in file toke.c

=back

=head1 Magical Functions

=over 8

=item magic_clearhint
X<magic_clearhint>

Triggered by a delete from C<%^H>, records the key to
C<PL_compiling.cop_hints_hash>.

int	magic_clearhint(SV* sv, MAGIC* mg)

=for hackers
Found in file mg.c

=item magic_clearhints
X<magic_clearhints>

Triggered by clearing C<%^H>, resets C<PL_compiling.cop_hints_hash>.

int	magic_clearhints(SV* sv, MAGIC* mg)

=for hackers
Found in file mg.c

=item magic_methcall
X<magic_methcall>

Invoke a magic method (like FETCH).

C<sv> and C<mg> are the tied thingy and the tie magic.

C<meth> is the name of the method to call.

C<argc> is the number of args (in addition to $self) to pass to the method.

The C<flags> can be:

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

The arguments themselves are any values following the C<flags> argument.

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

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

=for hackers
Found in file mg.c

=item magic_sethint
X<magic_sethint>

Triggered by a store to C<%^H>, records the key/value pair to
C<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)

=for hackers
Found in file mg.c

=item mg_localize
X<mg_localize>

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

If C<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. S<C<'local $x = $y'>>),
and that will handle the magic.

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

=for hackers
Found in file mg.c

=back

=head1 Miscellaneous Functions

=over 8

=item free_c_backtrace
X<free_c_backtrace>

Deallocates a backtrace received from get_c_bracktrace.

void	free_c_backtrace(Perl_c_backtrace* bt)

=for hackers
Found in file util.c

=item get_c_backtrace
X<get_c_backtrace>

Collects the backtrace (aka "stacktrace") into a single linear
malloced buffer, which the caller B<must> C<Perl_free_c_backtrace()>.

Scans the frames back by S<C<depth + skip>>, then drops the C<skip> innermost,
returning at most C<depth> frames.

Perl_c_backtrace* get_c_backtrace(int max_depth,
	                                  int skip)

=for hackers
Found in file util.c

=back

=head1 MRO Functions

=over 8

=item mro_get_linear_isa_dfs
X<mro_get_linear_isa_dfs>

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

You are responsible for C<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)

=for hackers
Found in file mro_core.c

=item mro_isa_changed_in
X<mro_isa_changed_in>

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

void	mro_isa_changed_in(HV* stash)

=for hackers
Found in file mro_core.c

=item mro_package_moved
X<mro_package_moved>

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

This can also be called with a null first argument to
indicate that C<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 C<stash>.

It also sets the effective names (C<HvENAME>) on all the stashes as
appropriate.

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

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

=for hackers
Found in file mro_core.c

=back

=head1 Optree Manipulation Functions

=over 8

=item finalize_optree
X<finalize_optree>

This function finalizes the optree.  Should be called directly after
the complete optree is built.  It does some additional
checking which can't be done in the normal C<ck_>xxx functions and makes
the tree thread-safe.

void	finalize_optree(OP* o)

=for hackers
Found in file op.c

=back

=head1 Pad Data Structures

=over 8

=item CX_CURPAD_SAVE
X<CX_CURPAD_SAVE>

Save the current pad in the given context block structure.

void	CX_CURPAD_SAVE(struct context)