GDB provides the following commands specific to the Darwin target:
set debug darwin num
When set to a non zero value, enables debugging messages specific to the Darwin support. Higher values produce more verbose output.
show debug darwin
Show the current state of Darwin messages.
set debug mach-o num
When set to a non zero value, enables debugging messages while GDB is reading Darwin object files. (Mach-O is the file format used on Darwin for object and executable files.) Higher values produce more verbose output. This is a command to diagnose problems internal to GDB and should not be needed in normal usage.
show debug mach-o
Show the current state of Mach-O file messages.
set mach-exceptions on
set mach-exceptions off
On Darwin, faults are first reported as a Mach exception and are then mapped to a Posix signal. Use this command to turn on trapping of Mach exceptions in the inferior. This might be sometimes useful to better understand the cause of a fault. The default is off.
Show the current state of exceptions trapping.