Hi,
The perlcall documentation has a number of fine examples of an XSub retrieving a perl sub's return value. But my requirement is that the XSub then return the value that the perl sub returned (and I didn't see an example of that in the perlcall documentation).

Based on that documentation,I came up with this: 
use warnings;

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

use Inline C => <<'EOC';

SV * call_Adder(SV * a, SV * b) {
 dSP;
 I32 ax;
 int count;

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

 count = call_pv("Adder", G_SCALAR);

 SPAGAIN;
 SP -= count;
 ax = (SP - PL_stack_base) + 1;

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

 /* Avoid "Attempt to free unreferenced scalar" warning */
 SvREFCNT_inc(ST(0));

 return ST(0);
}

EOC

my $val = call_Adder(13,118);
print $val, "\n";

my $val2 = call_Adder(14,119);
print $val2, "\n";

my $val3 = call_Adder(14,8);
print $val3, "\n";

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

__END__
Outputs (as expected):
131
133
22

[download]
As can be seen, the "call_Adder" XSub passes its arguments on to the "Adder" perl sub, and then returns the same value as "Adder" itself has returned.

Have I committed any sins with that approach ?
It varies from the perlcall examples mainly in that there's no ENTER/LEAVE and SAVETMPS/FREETMPS calls.

It seems to be working fine for me, but corrections and/or suggestions for improvement are welcome. (It's planned that this approach will eventually make it into some of my modules, so it's probably better to sort out the shortcomings *before* that happens.)

Cheers,
Rob

In reply to [XS] Callbacks to perl by syphilis

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