Debugging PHP core files - No symbol "executor_globals" in current context

I'm trying to get a backtrace from a core file generated by PHP.

I'm following this guide and when I try to print the name of a function using:

print (char *)(executor_globals.function_state_ptr->function)->common.function_name

I get the error:

No symbol "executor_globals" in current context.

I'm running GDB with:

gdb /usr/sbin/apache2 /mnt/cores/core.apache2.8315

Interestingly, I don't have this problem when using the libapache2-mod-php5 package on Ubuntu. I had to compile my own PHP module to fix a different problem and it's this compiled module that's giving me the trouble.

A google search for "no symbol executor_globals" actually returns 0 results, which I find pretty strange. Am I seriously the only person to ever have this problem?

I ended up solving this by compiling PHP against a non-threaded Apache, effectively disabling thread safety in the PHP module which is what I wanted anyway.

More specifically, the apxs2 binary I was specifying in the configure args was from the Ubuntu apache2-threaded-dev package, while the Apache running on the server was prefork, not threaded. So I just had to install the apache2-prefork-dev package instead and recompile and I was good to go.