Hi,
Hidden below my sig (by readmore tags) is a full Inline::C script that demos the problem. It uses overload, so that the subroutine 'overload_add_eq' is invoked whenever a '+=' is applied to the blessed object. At one stage, 'overload_add_eq' looked like this: 
SV * overload_add_eq(SV * obj, SV * addon, SV * third) {
     Card* c = (Card *)SvIV(SvRV(obj));
     SvREFCNT_inc(obj);
     c->value += SvIV(addon);
     return obj;
}

[download]
And that works fine - but it occurred to me that I should be able to rewrite the function as in 'in place' operation (ie one that did not return anything) so I rewrote it as: 
void overload_add_eq(SV * obj, SV * addon, SV * third) {
     Card* c = (Card *)SvIV(SvRV(obj));
     c->value += SvIV(addon);
}

[download]
Now, when I do $obj += $addon; windows intervenes to tell me that perl.exe has stopped working (but fails to come up with any other information). On linux I get a segfault. Interestingly, I find that this modified 'overload_add_eq' works fine (on both linux and windows) when invoked explicitly in perl code as overload_add_eq($obj, $addon, 0);. It's only when it's invoked by the overload mechanism that the problem arises. Anyone know why that is, and what to do about it ?

Cheers,
Rob 
use warnings;
package My_struct;

use Inline (C => Config =>
            BUILD_NOISY => 1,
            );

use Inline C => <<'EOC';

     typedef struct {
       char * suit;
       int value;
       } Card;

SV * create_struct(SV * s, SV * v) {
     Card * cptr;

     New(123, cptr, sizeof(Card), Card);
     if(cptr == NULL) croak("Failed to allocate memory in create_struc
+t function");
     
     cptr->suit = SvPV_nolen(s);
     cptr->value = SvIV(v);
     return sv_setref_pv(newSViv(0), "My_struct", cptr);
}

void deref_ref(SV * obj) {
     Inline_Stack_Vars;

     Inline_Stack_Reset;
     Inline_Stack_Push(newSVpv(((Card *)SvIV(SvRV(obj)))->suit, 0));
     Inline_Stack_Push(newSViv(((Card *)SvIV(SvRV(obj)))->value));
     Inline_Stack_Done;
     Inline_Stack_Return(2);

}

void DESTROY(SV * obj) {
      printf("Destroying ...");
      Card* c = (Card *)SvIV(SvRV(obj));
      Safefree(c);
      printf("...destroyed\n");
}

void overload_add_eq(SV * obj, SV * addon, SV * third) {
     Card* c = (Card *)SvIV(SvRV(obj));
//     SvREFCNT_inc(obj);
     c->value += SvIV(addon);
//     return obj;
}


EOC

use overload '+='   => \&overload_add_eq;

$suit = ('Hearts', 'Spades', 'Clubs', 'Diamonds')[rand(4)];
$value = int(rand(13)) + 1;

$obj = create_struct($suit, $value);
$addon = 5;

@members = deref_ref($obj);
print "@members\n";

#$obj += $addon; # Crashes
overload_add_eq($obj, $addon, 0);

@members = deref_ref($obj);
print "@members\n";

[download]

In reply to Overload '+=' with XSub by syphilis

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