Event.pm memory leek ?

asdfgroup has asked for the wisdom of the Perl Monks concerning the following question:

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Re: Event.pm memory leek ? by cazz (Pilgrim) on Apr 22, 2005 at 13:17 UTC
No, this is a memory leak in your code. Don't put memory allocation in a signal handler. The underpinnings of printf are mallocing. Before printf can free, you are calling the signal handler again.	[reply]
Re^2: Event.pm memory leek ? by asdfgroup (Beadle) on Apr 22, 2005 at 19:02 UTC
This does not look correct, because : - signal is masked in own callback (normal Unix behaviour, tested this is ok in Event.pm as well) - if you change printf on print or even syswrite, memory leak will still exist - similar code works fine in test without Event.pm (using %SIG) Update: code like `use Event; Event->signal(signal=>'HUP', cb=>sub {kill 1, $$}); kill 1, $$; Event::loop;` [download] produce memory leak as well :)	[reply] [d/l]
Re^3: Event.pm memory leek ? by cazz (Pilgrim) on Apr 22, 2005 at 19:49 UTC
Ok, so not only does your code malloc inside a signal handler, so does Event. Well, Event.xs shows that when signal is called, it does copying. `_signal_signal(THIS, items == 2? sv_mortalcopy(ST(1)) : 0);` [download] sv_mortalcopy mallocs. Since you are calling the signal handler from inside the signal handler, it never frees that memory. Simple solution: Don't call the signal handler from inside the signal handler.	[reply] [d/l]
Re: Event.pm memory leek ? by salva (Canon) on Apr 22, 2005 at 14:52 UTC
Maybe... Programs using signals are tricky in perl (well, actually in any language), and I have been looking at Event.pm source code, and it is anything but simple, so I would not discard some bug there. Also because you are (ab)using the module in some unusual way, sending a HUP signal from the HUP signal handler all the time without letting it rest for a while... Yes I know, that sounds a bit silly, programs don't need to rest, but I have a reason to say that: the way perl vars are freed, marking them as mortals (see perlxs, perlguts and perlapi man pages for what's a mortal explanations). Maybe Event.pm only closes the callback calling scope when the event queue is empty, and not after every callback invocation... So, summarizing: send a bug report to the module author!!!	[reply]
Re^2: Event.pm memory leek ? by asdfgroup (Beadle) on Apr 22, 2005 at 19:07 UTC
Looks like this is really some memory leak in Event.pm, becuase code like this : `use Event; pipe(R,W); Event->io(fd=>\*R, poll=>"r", cb=>sub {sysread R, $r, 1 or warn "read: + $!"; syswrite W, $r, 1 or warn "write: $!"; i++}); Event->signal(signal=>'ALRM', cb=>sub {printf "%d\t%d\n", ++$t, $i-$ol +d_i; $old_i=$i; alarm 1}); alarm 1; syswrite W, "!" or die $!; Event::loop;` [download] produce memory leak as well :(	[reply] [d/l]