Thanks to Matthew: gdb --args program/to/debug --whatever break Foo.c:532 # to put a breakpoint at line 532 of Foo.c run # to run it, until it hits that line bt # to display the stacktrace (backtrace) frame 2 # to change the stack frame you're looking at list # to list the sourcecode for that stack frame step # to step into the next command for that frame next # to run the code to the next command continue # to continue onwards print bar # to print the contents of variable bar printf "%08x", bar # standard printf for bar delete 2 # to remove the 2nd breakpoint Obviously, you need to compile things with -g as an argument to GCC.