important. Note that this function requires you to specify the length of
the format.
+STRLEN is an integer type (Size_t, usually defined as size_t in
+config.h) guaranteed to be large enough to represent the size of
+any string that perl can handle.
+
The C<sv_set*()> functions are not generic enough to operate on values
that have "magic". See L<Magic Virtual Tables> later in this document.
SV* newSVrv(SV* rv, const char* classname);
-Copies integer or double into an SV whose reference is C<rv>. SV is blessed
+Copies integer, unsigned integer or double into an SV whose reference is C<rv>. SV is blessed
if C<classname> is non-null.
SV* sv_setref_iv(SV* rv, const char* classname, IV iv);
+ SV* sv_setref_uv(SV* rv, const char* classname, UV uv);
SV* sv_setref_nv(SV* rv, const char* classname, NV iv);
Copies the pointer value (I<the address, not the string!>) into an SV whose
Inside such a I<pseudo-block> the following service is available:
-=over
+=over 4
=item C<SAVEINT(int i)>
or Perlish C<GV *>s). Where the above macros take C<int>, a similar
function takes C<int *>.
-=over
+=over 4
=item C<SV* save_scalar(GV *gv)>
These macros automatically adjust the stack for you, if needed. Thus, you
do not need to call C<EXTEND> to extend the stack.
+However, see L</Putting a C value on Perl stack>
For more information, consult L<perlxs> and L<perlxstut>.
instances of the size of the C<type> data structure (using the C<sizeof>
function).
-Here is a handy table of equivalents between ordinary C and Perl's
-memory abstraction layer:
-
- Instead Of: Use:
-
- malloc New
- calloc Newz
- realloc Renew
- memcopy Copy
- memmove Move
- free Safefree
- strdup savepv
- strndup savepvn (Hey, strndup doesn't exist!)
- memcpy/*(struct foo *) StructCopy
-
=head2 PerlIO
The most recent development releases of Perl has been experimenting with
directly used in some opcodes, as well as indirectly in zillions of
others, which use it via C<(X)PUSH[pni]>.
+Because the target is reused, you must be careful when pushing multiple
+values on the stack. The following code will not do what you think:
+
+ XPUSHi(10);
+ XPUSHi(20);
+
+This translates as "set C<TARG> to 10, push a pointer to C<TARG> onto
+the stack; set C<TARG> to 20, push a pointer to C<TARG> onto the stack".
+At the end of the operation, the stack does not contain the values 10
+and 20, but actually contains two pointers to C<TARG>, which we have set
+to 20. If you need to push multiple different values, use C<XPUSHs>,
+which bypasses C<TARG>.
+
+On a related note, if you do use C<(X)PUSH[npi]>, then you're going to
+need a C<dTARG> in your variable declarations so that the C<*PUSH*>
+macros can make use of the local variable C<TARG>.
+
=head2 Scratchpads
The question remains on when the SVs which are I<target>s for opcodes
4 5 6> (node C<6> is not included into above listing), i.e.,
C<gvsv gvsv add whatever>.
+Each of these nodes represents an op, a fundamental operation inside the
+Perl core. The code which implements each operation can be found in the
+F<pp*.c> files; the function which implements the op with type C<gvsv>
+is C<pp_gvsv>, and so on. As the tree above shows, different ops have
+different numbers of children: C<add> is a binary operator, as one would
+expect, and so has two children. To accommodate the various different
+numbers of children, there are various types of op data structure, and
+they link together in different ways.
+
+The simplest type of op structure is C<OP>: this has no children. Unary
+operators, C<UNOP>s, have one child, and this is pointed to by the
+C<op_first> field. Binary operators (C<BINOP>s) have not only an
+C<op_first> field but also an C<op_last> field. The most complex type of
+op is a C<LISTOP>, which has any number of children. In this case, the
+first child is pointed to by C<op_first> and the last child by
+C<op_last>. The children in between can be found by iteratively
+following the C<op_sibling> pointer from the first child to the last.
+
+There are also two other op types: a C<PMOP> holds a regular expression,
+and has no children, and a C<LOOP> may or may not have children. If the
+C<op_children> field is non-zero, it behaves like a C<LISTOP>. To
+complicate matters, if a C<UNOP> is actually a C<null> op after
+optimization (see L</Compile pass 2: context propagation>) it will still
+have children in accordance with its former type.
+
=head2 Compile pass 1: check routines
The tree is created by the compiler while I<yacc> code feeds it
done in the subroutine peep(). Optimizations performed at this stage
are subject to the same restrictions as in the pass 2.
+=head1 Examining internal data structures with the C<dump> functions
+
+To aid debugging, the source file F<dump.c> contains a number of
+functions which produce formatted output of internal data structures.
+
+The most commonly used of these functions is C<Perl_sv_dump>; it's used
+for dumping SVs, AVs, HVs, and CVs. The C<Devel::Peek> module calls
+C<sv_dump> to produce debugging output from Perl-space, so users of that
+module should already be familiar with its format.
+
+C<Perl_op_dump> can be used to dump an C<OP> structure or any of its
+derivatives, and produces output similiar to C<perl -Dx>; in fact,
+C<Perl_dump_eval> will dump the main root of the code being evaluated,
+exactly like C<-Dx>.
+
+Other useful functions are C<Perl_dump_sub>, which turns a C<GV> into an
+op tree, C<Perl_dump_packsubs> which calls C<Perl_dump_sub> on all the
+subroutines in a package like so: (Thankfully, these are all xsubs, so
+there is no op tree)
+
+ (gdb) print Perl_dump_packsubs(PL_defstash)
+
+ SUB attributes::bootstrap = (xsub 0x811fedc 0)
+
+ SUB UNIVERSAL::can = (xsub 0x811f50c 0)
+
+ SUB UNIVERSAL::isa = (xsub 0x811f304 0)
+
+ SUB UNIVERSAL::VERSION = (xsub 0x811f7ac 0)
+
+ SUB DynaLoader::boot_DynaLoader = (xsub 0x805b188 0)
+
+and C<Perl_dump_all>, which dumps all the subroutines in the stash and
+the op tree of the main root.
+
=head1 How multiple interpreters and concurrency are supported
=head2 Background and PERL_IMPLICIT_CONTEXT
something like this:
ifdef PERL_IMPLICIT_CONTEXT
- define sv_setsv(a,b) Perl_sv_setsv(aTHX_ a, b)
+ define sv_setsv(a,b) Perl_sv_setsv(aTHX_ a, b)
/* can't do this for vararg functions, see below */
else
- define sv_setsv Perl_sv_setsv
+ define sv_setsv Perl_sv_setsv
endif
This works well, and means that XS authors can gleefully write:
The second, more efficient way is to use the following template for
your Foo.xs:
- #define PERL_NO_GET_CONTEXT /* we want efficiency */
- #include "EXTERN.h"
- #include "perl.h"
- #include "XSUB.h"
+ #define PERL_NO_GET_CONTEXT /* we want efficiency */
+ #include "EXTERN.h"
+ #include "perl.h"
+ #include "XSUB.h"
static my_private_function(int arg1, int arg2);
- static SV *
- my_private_function(int arg1, int arg2)
- {
- dTHX; /* fetch context */
- ... call many Perl API functions ...
- }
+ static SV *
+ my_private_function(int arg1, int arg2)
+ {
+ dTHX; /* fetch context */
+ ... call many Perl API functions ...
+ }
[... etc ...]
- MODULE = Foo PACKAGE = Foo
+ MODULE = Foo PACKAGE = Foo
- /* typical XSUB */
+ /* typical XSUB */
- void
- my_xsub(arg)
- int arg
- CODE:
- my_private_function(arg, 10);
+ void
+ my_xsub(arg)
+ int arg
+ CODE:
+ my_private_function(arg, 10);
Note that the only two changes from the normal way of writing an
extension is the addition of a C<#define PERL_NO_GET_CONTEXT> before
the Perl guts:
- #define PERL_NO_GET_CONTEXT /* we want efficiency */
- #include "EXTERN.h"
- #include "perl.h"
- #include "XSUB.h"
+ #define PERL_NO_GET_CONTEXT /* we want efficiency */
+ #include "EXTERN.h"
+ #include "perl.h"
+ #include "XSUB.h"
/* pTHX_ only needed for functions that call Perl API */
static my_private_function(pTHX_ int arg1, int arg2);
- static SV *
- my_private_function(pTHX_ int arg1, int arg2)
- {
- /* dTHX; not needed here, because THX is an argument */
- ... call Perl API functions ...
- }
+ static SV *
+ my_private_function(pTHX_ int arg1, int arg2)
+ {
+ /* dTHX; not needed here, because THX is an argument */
+ ... call Perl API functions ...
+ }
[... etc ...]
- MODULE = Foo PACKAGE = Foo
+ MODULE = Foo PACKAGE = Foo
- /* typical XSUB */
+ /* typical XSUB */
- void
- my_xsub(arg)
- int arg
- CODE:
- my_private_function(aTHX_ arg, 10);
+ void
+ my_xsub(arg)
+ int arg
+ CODE:
+ my_private_function(aTHX_ arg, 10);
This implementation never has to fetch the context using a function
call, since it is always passed as an extra argument. Depending on
formatting codes like C<%d>, C<%ld>, C<%f>, you should use the
following macros for portability
- IVdf IV in decimal
- UVuf UV in decimal
- UVof UV in octal
- UVxf UV in hexadecimal
- NVef NV %e-like
- NVff NV %f-like
- NVgf NV %g-like
+ IVdf IV in decimal
+ UVuf UV in decimal
+ UVof UV in octal
+ UVxf UV in hexadecimal
+ NVef NV %e-like
+ NVff NV %f-like
+ NVgf NV %g-like
These will take care of 64-bit integers and long doubles.
For example:
- printf("IV is %"IVdf"\n", iv);
+ printf("IV is %"IVdf"\n", iv);
The IVdf will expand to whatever is the correct format for the IVs.
Because pointer size does not necessarily equal integer size,
use the follow macros to do it right.
- PTR2UV(pointer)
- PTR2IV(pointer)
- PTR2NV(pointer)
- INT2PTR(pointertotype, integer)
+ PTR2UV(pointer)
+ PTR2IV(pointer)
+ PTR2NV(pointer)
+ INT2PTR(pointertotype, integer)
For example:
- IV iv = ...;
- SV *sv = INT2PTR(SV*, iv);
+ IV iv = ...;
+ SV *sv = INT2PTR(SV*, iv);
and
- AV *av = ...;
- UV uv = PTR2UV(av);
+ AV *av = ...;
+ UV uv = PTR2UV(av);
=head2 Source Documentation
projects / p5sagit/p5-mst-13.2.git / blobdiff