[macos] gdb fails with "Unable to find Mach task port for process-id" error

The problem is that you are not logged in as a root user (which you don't want). You need to create a certificate for gdb to be allowed access. Follow this tutorial and you should be good to go...

http://sourceware.org/gdb/wiki/BuildingOnDarwin

If all else fails, just use: sudo gdb executableFileName