Peeter Joot's (OLD) Blog.

Math, physics, perl, and programming obscurity.

“fun” bug in 64-bit perl 5.10.0 bigint sprintf

Posted by peeterjoot on November 19, 2013

Here’s a rather unexpected bug with perl sprintf

#! /usr/bin/perl

use strict;
use warnings;
use bigint ;

my $a = hex( "0x0A0000001D05A820" ) ;
printf( "0x%016X\n", $a ) ;
printf( "%d\n", $a ) ;
printf( "$a\n" ) ;

The %X printf produces a value where the least significant 0x20 is lost:

$ ./bigint

Observe that the loss occurs in the printf and not the hex() call, since 720575940866189344 == 0x0A0000001D05A820.

This bug appears to be fixed in some version of perl <= 5.16.2. Oh, the joys of using ancient operating system versions so that we can support customers on many of the ancient deployments that they seem to like to run on.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: