Re^4: Dynaloader/XS: sharing C symbols across shared objects

[creamygoodness]

Pointers to functions in C ? ... then wrapped in an SV ?

C function pointers are directly analogous to perl subroutine references. The big differences are...

• They're typed, so function signatures must match.
• The syntax for declaring them is bloody awful. In fact, it's so awful that many people use typedefs whenever possible.
• You can't verify that a non-NULL function pointer actually points to anything valid, unlike in Perl where you can verify a sub ref with ref($sub).

Here's a demo for passing a function pointer around via SV.

use strict;
use warnings;
use Inline C => <<'END_C';

typedef void
(*hello_func_t)();

void
hola_mundo()
{
    printf("Hola, mundo!\n");
}

SV*
get_hola_mundo_func_ptr()
{
    return newSViv( PTR2IV(hola_mundo) );
}

void
do_hello(SV *sv_with_func_ptr)
{
    IV temp = SvIV(sv_with_func_ptr);
    hello_func_t hello = INT2PTR(hello_func_t, temp);
    hello();
}


END_C

my $func_ptr = get_hola_mundo_func_ptr();
do_hello($func_ptr);