Signal Handling throws Core Dump

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

I'm trying to catch SIG_INTs in the usual way:

$SIG{INT} = \&handler;

sub handler {
    $sig++;
}
[download]

Trouble is, it seems that everytime a signal is sent/caught, the process core dumps. I've read the bit in perlipc that talks about safe and unsafe signals and although I was initially running slightly more complicated code in the handler() routine, it is now as simple as is demonstrated here but still core dumping.

I have no more ideas and could use some help.

Update:
Thanks Paul. I'm on Solaris 10, using Perl 5.8.8.

Thanks

dsb
This @ISA my( $cool ) %SIG

Comment on Signal Handling throws Core Dump Download Code

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Re: Signal Handling throws Core Dump by almut (Canon) on Apr 25, 2007 at 16:20 UTC
Not sure if this is of any help (because on the Solaris 10 box I have within reach, there's only an older Perl installed), but just in case: the following works fine here `#!/usr/bin/perl our $sig; # same for my $sig $SIG{INT} = \&handler; sub handler { print "got SIGINT\n"; $sig++; } until ($sig) { print "running...\n"; sleep 1; } print "terminated.\n";` [download] outputs as expected (until/when I send it SIGINT) `running... running... running... got SIGINT terminated.` [download] Can you produce a backtrace, loading your core file in a debugger (`gdb perl core`, then, at the prompt, typing "bt" — in case you have gdb available, that is...)? This might give a first hint at where things are going wrong. (A perl binary built with debugging info would be better, of course...) ___ `$ uname -a SunOS solaris10 5.10 Generic sun4u sparc SUNW,Sun-Blade-2500 $ perl -v This is perl, v5.8.4 built for sun4-solaris-64int (with 27 registered patches, see perl -V for more detail) (...)` [download]	[reply] [d/l] [select]
Re^2: Signal Handling throws Core Dump by dsb (Chaplain) on Apr 25, 2007 at 16:43 UTC
When I give `$SIG{INT}` an anonymous subroutine, I can at least get it it to increment `$sig` and exit cleanly. But when I try to run an object method designed to remove a stored PID from a DB, it cores. `# doesn't work $SIG{INT} = sub { $sig++; $control->removeMonitorPID($monitor->{PID}); };` [download] dsb This `@ISA my( $cool ) %SIG`	[reply] [d/l]
Re^3: Signal Handling throws Core Dump by jettero (Monsignor) on Apr 25, 2007 at 16:57 UTC
Well, that shouldn't be too surprising. You're not really supposed to do stuff like that from a signal handler. That's not even a perl specific issue. -Paul	[reply]
Re^3: Signal Handling throws Core Dump by former33t (Scribe) on Apr 26, 2007 at 03:05 UTC
I first want to clarify that there are WAY better ways to do this, but if you want to increment a global variable to detect a signal being caught this will do the trick. As Paul noted earlier you shouldn't be trying to do anything complicated in the signal handler itself. `our $sig; $sig = 1; $SIG{INT} = sub { $sig++; }; my $oldsig; while (1) { if ($sig != $oldsig) { $control->removeMonitorPID($monitor->{PID}); #Execute the code ori +ginally in the signal handler. $oldsig = $sig; } .... Run main loop, but make sure to poll the status of the global v +ariable .... }` [download]	[reply] [d/l]
Re^4: Signal Handling throws Core Dump by jrw (Monk) on Apr 26, 2007 at 16:52 UTC
Re^4: Signal Handling throws Core Dump by dsb (Chaplain) on Apr 28, 2007 at 03:13 UTC
Re: Signal Handling throws Core Dump by cengineer (Pilgrim) on Apr 25, 2007 at 15:29 UTC
Not sure if it's a Solaris specific thing, but I used this on Linux with perl 5.8.8 and it works fine: `use sigtrap qw(handler sig_handler INT TERM QUIT PIPE); use Switch; sub sig_handler { my($sig) = shift; print "Caught signal $sig\n"; switch($sig) { case ["INT","TERM","QUIT"] { print "Exiting"; exit(0); } case "PIPE" { print "Continuing\n"; } } }` [download]	[reply] [d/l]
Re^2: Signal Handling throws Core Dump by dsb (Chaplain) on Apr 25, 2007 at 15:50 UTC
Used this method but get the same result. It seems like as soon as I try to do anything that I get the core dump. dsb This `@ISA my( $cool ) %SIG`	[reply]
Re: Signal Handling throws Core Dump by jettero (Monsignor) on Apr 25, 2007 at 14:06 UTC
It would be helpful to know what unstable platform you're on or what unstable build of perl you're using. Update: wow, then that shouldn't be happening imo; but, I have no further information on why. Is it the sun build of perl 5.8.8? What is `$sig`? Signals are kinda strange monsters (or can be depending on the implementation) and I can't help but wonder if `$sig` is getting deallocated lexically and then cleaned up again during global destruction or something vile like that. -Paul	[reply] [d/l] [select]
Re^2: Signal Handling throws Core Dump by dsb (Chaplain) on Apr 25, 2007 at 15:13 UTC
`$sig` is just a scalar I use to determine when the loop should stop. `until ($sig) { # do some stuff }` [download] I declare `$sig` earlier with `our` in attempt to disqualify any scoping issues as the source of problems. I'm going to try it on another box with the same set up and see if I have the same issue. Update: I tried it on a different server running the same OS and version Perl, with the same result. dsb This `@ISA my( $cool ) %SIG`	[reply] [d/l]
Re^2: Signal Handling throws Core Dump by maard (Pilgrim) on Apr 25, 2007 at 15:21 UTC
in case of lexical $sig that code would create closure, so no deallocation could take place.	[reply]
Re: Signal Handling throws Core Dump by Steve_p (Priest) on Apr 26, 2007 at 17:19 UTC
I've tried a couple of the scripts above with Solaris Express and the supplied Perl 5.8.4 and bleadperl. I've not seen any core dumps with either. I do have some more questions, but they would best be answered by you pasting in the output from `perl -V` into a reply. Test your modules with bleadperl! rsync -avz rsync://public.activestate.com/perl-current/ . ./Configure -des -Dusedevel -Dprefix=/path/to/test/perl make test make install Now, please test you modules! If you have test failures that don't happen with Perl 5.8.8, send a simplified test case to perlbug at perl.org	[reply] [d/l]

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