Doc patches: assorted minor nits

[perl5.git] / pod / perlintern.pod

=head1 NAME

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

=head1 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,
B<they are not for use in extensions>!


=head1 Global Variables

=over 8

=item PL_DBsingle

When Perl is run in debugging mode, with the B<-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
C<PL_DBsub>.

	SV *	PL_DBsingle

=for hackers
Found in file intrpvar.h

=item PL_DBsub

When Perl is run in debugging mode, with the B<-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
C<PL_DBsingle>.

	GV *	PL_DBsub

=for hackers
Found in file intrpvar.h

=item PL_DBtrace

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

	SV *	PL_DBtrace

=for hackers
Found in file intrpvar.h

=item PL_dowarn

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

	bool	PL_dowarn

=for hackers
Found in file intrpvar.h

=item PL_last_in_gv

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

	GV*	PL_last_in_gv

=for hackers
Found in file thrdvar.h

=item PL_ofs_sv

The output field separator - C<$,> in Perl space.

	SV*	PL_ofs_sv

=for hackers
Found in file thrdvar.h

=item PL_rs

The input record separator - C<$/> in Perl space.

	SV*	PL_rs

=for hackers
Found in file thrdvar.h


=back

=head1 GV Functions

=over 8

=item is_gv_magical

Returns C<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.

C<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)

=for hackers
Found in file gv.c


=back

=head1 IO Functions

=over 8

=item start_glob

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.
Moving it away shrinks pp_hot.c; shrinking pp_hot.c helps speed perl up.

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

=for hackers
Found in file doio.c


=back

=head1 Pad Data Structures

=over 8

=item 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).

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 op.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:
C<PL_comppad_name> is set the the the names AV.
C<PL_comppad> is set the the frame AV for the frame CvDEPTH == 1.
C<PL_curpad> is set the body of the frame AV (i.e. AvARRAY(PL_comppad)).

Itterating over the names AV itterates 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.

If SvFAKE is set on the name SV then slot in the frame AVs are
a REFCNT'ed references to a lexical from "outside".

If the 'name' is '&' the 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 C<my sub foo {}> is implemented.)

	AV *	CvPADLIST(CV *cv)

=for hackers
Found in file cv.h


=back

=head1 Stack Manipulation Macros

=over 8

=item djSP

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

		djSP;

=for hackers
Found in file pp.h

=item LVRET

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

=for hackers
Found in file pp.h


=back

=head1 SV Manipulation Functions

=over 8

=item report_uninit

Print appropriate "Use of uninitialized variable" warning

	void	report_uninit()

=for hackers
Found in file sv.c

=item 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)

=for hackers
Found in file sv.c

=item 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()

=for hackers
Found in file sv.c

=item sv_clean_objs

Attempt to destroy all objects not yet freed

	void	sv_clean_objs()

=for hackers
Found in file sv.c

=item 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()

=for hackers
Found in file sv.c


=back

=head1 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.

=head1 SEE ALSO

perlguts(1), perlapi(1)