If you get a core dump (segmentation fault), send a backtrace if possible. Before you try to produce it, rebuild mod_perl with:

panic% perl Makefile.PL PERL_DEBUG=1

which will:

  • Add -g to EXTRA_CFLAGS

  • Turn on PERL_TRACE

  • Set PERL_DESTRUCT_LEVEL=2 (additional checks during Perl cleanup)

  • Link against libperld, if it exists

You can read a full explanation in Chapter 21, but here is a summary of how to get a backtrace:

panic% cd mod_perl-1.xx
panic% gdb ../apache_1.3.xx/src/httpd
(gdb) run -X -f `pwd`/t/conf/httpd.conf -d `pwd`/t
[now make request that causes core dump]
(gdb) bt

In English: cd to the mod_perl source directory and start gdb with a path to the httpd binary, which is located in the Apache source tree. (Of course, replace x with real version numbers.) Next, start the httpd process from within gdb and issue a request that causes a core dump. When the code has died with the SIGSEGVsignal, run bt to get the backtrace.

Alternatively, you can also attach to an already running process like so:

panic% gdb httpd <process id number>

If the dump is happening in libperl, you have to rebuild Perl with -DDEBUGGING enabled during the ./Configure stage. A quick way to this is to go to your Perl source tree and run these commands:

panic% rm *.[oa]
panic% make LIBPERL=libperld.a
panic% cp libperld.a $Config{archlibexp}/CORE

where $Config{archlibexp} is:

% perl -V:archlibexp