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Postings from December 2008
http://rt.perl.org/rt3/Ticket/Display.html?id=7112
It still crashes on 5.8.8 but does not on 5.10.
Modified version with "local $% = 0;" crashes even 5.10.
Error:
Attempt to free unreferenced scalar: SV 0x9bb964, Perl interpreter: 0x9a7584
Dec 03 02:20:46 2004, asavige wrote:
> Steve Peters wrote:
> >> $|= 1;
> >> for $var (1..3)
> >> {
> >> for (1..2)
> >> {
> >> if ( $pid=fork() )
> >> {
> >> print "Parent $$ created child $pid\n" ;
> >> sleep 1;
> >> waitpid($pid,0);
> >> exit 0;
> >> }
> >> elsif ( ! defined $pid )
> >> {
> >> die "Can not go to multi thread mode\n"
> >> }
> >> else
> >> {
> >> print "Child $$ running\n";
> >> }
> >> }
> >> print "\nThread team $var finished\n\n";
> >> }
> >> print "Program $$ finished\n";
> >
> > I was able to replicate the failure with ActiveState Perl 5.8.4 Build
> > 810 on Windows XP. Although I didn't get the nice failure above, it
> > did complain loudly in a popup about writing to a null pointer.
>
> This test program given also crashes the latest Perl 5.8.6.
>
> I was able to get rid of the crashes by replacing:
> for (1..2)
> above with:
> for my $z (1..2)
> For more variety, if you add:
> local $% = 0;
> as the first statement inside each loop, it not only crashes but
> generates some:
> Atttempt to free unreferenced scalar
> warnings for good measure.
>
> I'm guessing that a localized built-in variable inside the inner loop
> will be freed twice at end of scope: once by the original interpreter
> and once by the cloned one.
>
> I can't think of a way to simulate the above crash on Linux with plain
> old ithreads; if you think of a way, please let me know. Maybe the
> scenario above is impossible with plain ithreads?
--
Alexandr Ciornii, http://chorny.net