Second, as promised, patchlevel 4 of the TenFourFox debugger (our hacked version of gdb) is available from SourceForge. This is a minor bugfix update that wallpapers a crash when doing certain backtraces or other operations requiring complex symbol resolution. However, the minimum patchlevel to debug TenFourFox is still 2, so this upgrade is merely recommended, not required.
http://tenfourfox.blogspot.com/2016/09/gdb7-patchlevel-4-available.html