Hi monks,

I'm running perl 5.8.8 on a SuSE 10.3 Xen guest and I am observing a rather strange array behaviour with the following program:

#!/usr/bin/perl
use strict;
use warnings;

my $i = 0;
BIGLOOP: while (1) {
        my @e;
        for  my $j (0..@e / 2 - 1) {
                print "died where I shouldn't have: $i\n";
                last BIGLOOP;
        }
        $i++;
}

[download]

Since @e is empty when the 'for' statement is evaluated, the "print" should never be called. Instead, it is called sooner or later, or the program dies. Some examples:

main:~ # perl for.pl 
died where I shouldn't have: 19756054
main:~ # perl for.pl 
Range iterator outside integer range at for.pl line 11.
main:~ # perl for.pl 
died where I shouldn't have: 5531064
main:~ # perl for.pl 
Illegal division by zero at for.pl line 11.
main:~ # perl for.pl 
Illegal division by zero at for.pl line 11.
main:~ # perl for.pl 
died where I shouldn't have: 24090
main:~ # perl for.pl 
died where I shouldn't have: 10987109
main:~ # perl for.pl 
died where I shouldn't have: 582219

... which means that at some point suddenly @e is not undef anymore.

I have a second VM installation on a different machine, there is no such effect. 'perl -V' is identical on those two systems. Also it's unlikely to be a memory problem: A memtest ran for hours without errors, and the very same Xen image on a different hardware shows the same problem. An strace shows also virtually no difference.

Do you have an idea how I could debug this further? Any help is appreciated.

Thank you!

Regards,
Thomas

In reply to Non-deterministic behaviour with simple array initialization by thkarcher

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