Infinite loop in perl Carp module

Question

We have some code which catches an exception, logs the message and then calls Carp::longmess to get the stacktrace.

So a simplified view of what we are doing is:

eval { <some SOAP::Lite stuff> };
if( my $err = $@ )
{
    logwrite( "Caught Error: $err" );
}

The logwrite function is essentially:

sub logwrite($)
{
    my $msg = $_[0];
    my($pkg,$fil,$lin)=caller;
    my $timestamp = POSIX::strftime(...);
    print STDERR "$timestamp $fil/$lin $msg\n";
    print STDERR "$timestamp $fil/$lin Stack trace:\n" . Carp::longmess . "\n";
}

But in the log I am seeing:

20111030 Module.pm/42 Caught Error: at  line
Use of uninitialized value in caller at /usr/lib/perl5/5.8.8/Carp/Heavy.pm line 22.
Use of uninitialized value in string eq at /usr/lib/perl5/5.8.8/Carp/Heavy.pm line 91.
Use of uninitialized value in numeric lt (<) at /usr/lib/perl5/5.8.8/Carp/Heavy.pm line 200.
Use of uninitialized value in pattern match (m//) at /usr/lib/perl5/5.8.8/Carp/Heavy.pm line 55.
Use of uninitialized value in concatenation (.) or string at /usr/lib/perl5/5.8.8/Carp/Heavy.pm line 55.
Use of uninitialized value in concatenation (.) or string at /usr/lib/perl5/5.8.8/Carp/Heavy.pm line 142.
Use of uninitialized value in concatenation (.) or string at /usr/lib/perl5/5.8.8/Carp/Heavy.pm line 142.
Use of uninitialized value in concatenation (.) or string at /usr/lib/perl5/5.8.8/Carp/Heavy.pm line 142.
Use of uninitialized value in concatenation (.) or string at /usr/lib/perl5/5.8.8/Carp/Heavy.pm line 142.
...

And that sequence of warnings from the Carp/Heavy.pm module repeats over and over again indefiniately, blowing out the logifle. So we eventually kill it off. These warnings look like they're being triggered by the call to Carp::longmess. The other intersting thing here is the $@ variable appears to just be at. It as the at added by die, but no actual error message or line number.

Has anyone seen this before or have any idea what's coing on with the Carp package? This is rare, but has happenned a handful of times over the past month or so, and we have hundreds of these jobs running every day.

Answer 1

I realize this doesn't answer your actual question, but . . . since apparently $msg eq 'at line ' in this case, maybe you should just bypass the issue by tacking unless $msg eq 'at line ' onto the end of the print ... Carp::longmess ... statement? (I mean, unless someone proposes a real solution.)

Answer 2

Your code works for me on perl v5.10.1, with Carp.pm version 1.11.

However, note that what it does is perhaps not what you expect: the backtrace produced by longmess will show where the logwrite function was called from, not where the actual error occurred inside the eval.