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Re: The number of references to a variable

by lima1 (Curate)
on Nov 26, 2007 at 12:29 UTC ( [id://652972]=note: print w/replies, xml ) Need Help??


in reply to The number of references to a variable

The SvREFCNT macro (perlguts) returns this number. I am sure this is already somewhere on cpan, but a simple XS routine could look like this: 
/* generated by h2xs -c Scalar::RefCount */
#include "EXTERN.h"
#include "perl.h"
#include "XSUB.h"

#include "ppport.h"



MODULE = Scalar::RefCount       PACKAGE = Scalar::RefCount

int
refcount(s)
    SV* s
PROTOTYPE: $
CODE:
    RETVAL = SvREFCNT(s);
OUTPUT:
    RETVAL

[download]
use Test::More tests => 6;
BEGIN { use_ok('Scalar::RefCount') };

#########################

my $a;

is(Scalar::RefCount::refcount($a),1, 'return 1');

my $b = \$a;
is(Scalar::RefCount::refcount($a),2, 'return 2');

my $c = \$a;
is(Scalar::RefCount::refcount($a),3, 'return 3');

{
my $d = \$a;
is(Scalar::RefCount::refcount($a),4, 'return 4');
}
is(Scalar::RefCount::refcount($a),3, 'return 3');

[download]
Update: Ah, thanks cdarke.

Replies are listed 'Best First'.
Re^2: The number of references to a variable
by cdarke (Prior) on Nov 26, 2007 at 13:12 UTC
    SvREFCNT is exposed in Devel::Peek (no need to go to CPAN), which is a bit easier to use than embedding XS. For example:
    use Devel::Peek qw(SvREFCNT);

$x = 42;
$y = \$x;

$refs_for_x = SvREFCNT($x);
print "$refs_for_x\n";

    [download]
    Prints 2.
[reply]
[d/l]

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