And it appears that the overloading is not causing your _copy() function to be called

Damn!! ... that's the oversight I was ... ummmm ... overlooking. I should've thought to stick a printf() in there as a check. Thanks for picking that up.

Another approach is to simply comment out the 'use overload ...' code - which has no effect on the output of the script at all. Oh, well .... live and learn ....

why doesn't use overload '=' => \&_copy; throw an error?

Good question. Thanks BrowserUK.

Cheers,
Rob
Update: I think, at last, I start to see the light. The overloading of the assignment operator takes its effect only when the value of either $num1 or $num2 is subsequently altered using an overloaded operator. Consider the following:

use warnings;
use Devel::Peek;

package Grief;
use overload
    '++'   => \&_inc,
    '='    => \&_copy,
;


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

use Inline C => <<'EOC';

typedef struct {
    long num;
} Number;

SV * new(SV * x) {
     Number * num_obj;
     SV * obj_ref, * obj;

     New(1, num_obj, 1, Number);
     if(num_obj == NULL)
      croak("Failed to allocate memory in new() function");
     obj_ref = newSViv(0);
     obj = newSVrv(obj_ref, "Grief");
     num_obj->num = SvUV(x);

     sv_setiv(obj, (IV)num_obj);
     SvREADONLY_on(obj);
     return obj_ref;
}

SV * _get_val(SV * obj) {
     return newSVuv(((Number*)SvIV(SvRV(obj)))->num);
}

void _inc(SV * obj, SV * second, SV * third) {
     (((Number*)SvIV(SvRV(obj)))->num)++;
}

SV * _copy(SV * arg_obj, SV * second, SV * third) {
     Number * num_obj;
     SV * obj_ref, * obj;
     printf( "_copy:%p %p %p\n", arg_obj, second, third  );
     New(1, num_obj, 1, Number);
     if(num_obj == NULL)
      croak("Failed to allocate memory in _copy() function");
     obj_ref = newSViv(0);
     obj = newSVrv(obj_ref, "Grief");
     num_obj->num = ((Number*)SvIV(SvRV(arg_obj)))->num;

     sv_setiv(obj, (IV)num_obj);
     SvREADONLY_on(obj);
     return obj_ref;
}

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


EOC

$num1 = Grief::new(113);
$num2 = $num1;
$num3 = _copy($num1, '', '');

#Run any one of the following 4 lines
$num1++; # _copy() gets called, 3 objects DESTROYed
#$num2++; # _copy() gets called, 3 objects DESTROYed
#_inc($num1, '', ''); # no _copy(), 2 objects DESTROYed
#_inc($num2, '', ''); # no _copy(), 2 objects DESTROYed

print _get_val($num2)," | ", _get_val($num3), "\n";
[download]

---

---

Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!

Titles consisting of a single word are discouraged, and in most cases are disallowed outright.

Read Where should I post X? if you're not absolutely sure you're posting in the right place.

Please read these before you post! —

• How do I compose an effective node title?
• How do I post a question effectively?
• Markup in the Monastery

Posts may use any of the Perl Monks Approved HTML tags:

a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr

You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)

	For:		Use:
	&		&
	<		&lt;
	>		&gt;
	[		&#91;
	]		&#93;

Link using PerlMonks shortcuts! What shortcuts can I use for linking?

See Writeup Formatting Tips and other pages linked from there for more info.