At the point it crashes, which may be earlier if an assertion fails, wait for the (gdb) prompt to reappear, and then do bt full. We should do this in a debug build so that we can see if any earlier trouble spots appear before the crash.
I'm sorry, even installing the debugger is currently beyond my abilities. HowToBuildFPR says "Decompress and copy the binary to /usr/local/bin/gdb7". What's "the binary"? When I download gdb768-104fx-4.tar and decompress it, I get a folder of stuff, not a single binary.
I have XCode 3.1.4 and built the debugger from the gdb-768 archive, then installed it to /usr/local/bin/gdb7. The binary is 3.7MB. Is this correct? I have close to zero experience with building in the terminal, and the instructions in the README files are a bit misleading.
Maybe we can continue this elsewhere, but when I cd to TenFourFoxDebug.app/Contents/MacOS/, run 'gdb7 firefox' and hit 'run' at the 'gdb' prompt, I get 'Unable to find Mach task port for process-id 91361: (os/kern) failure (0x5)'. Running the gdb version that came with XCode works, however.