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
 
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