A little guidance in the form of a few lines of code illustrating a C subroutine (ala Inline::C) calling a Perl sub and getting an int from its rv would be helpful to me.

The perlcall documentation is your friend for this. It contains good examples - some of which have been used in the Inline-0.48/C/t/10callback.t test script. Here's one of them: 
use warnings;
use strict;

use Inline C => Config =>
    BUILD_NOISY => 1;

use Inline C =><<'EOC';

void call_Adder(int a, int b) {
     dSP;
     int count;

     ENTER;
     SAVETMPS;

     PUSHMARK(SP);
     XPUSHs(sv_2mortal(newSViv(a)));
     XPUSHs(sv_2mortal(newSViv(b)));
     PUTBACK;

     count = call_pv("Adder", G_SCALAR);

     SPAGAIN;

     if (count != 1)
        croak("Big trouble\n");

     printf ("The sum of %d and %d is %d\n", a, b, POPi);

     PUTBACK;
     FREETMPS;
     LEAVE;
}

EOC

call_Adder(17, 16);

sub Adder {
    my($a, $b) = @_;
    $a + $b;
}

[download]
I gather you've already discovered that the Inline::C stack macros are, by themselves, usually incapable of dealing with callbacks.

Cheers,
Rob

In reply to Re: When to (and not to) use sv_2mortal() by syphilis
in thread When to (and not to) use sv_2mortal() by davido

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