I’ve come to like the GNU Debugger (GDB) and the
perf tool recently. This post will be a short summary of the various interesting commands you can use.
To attach gbd to an existing process do the following
gdb -p pid_of_process
Otherwise you can start a new application
Once it loads it will bring you into it’s own
REPL environment. Usually once this comes up I find it useful to add breakpoints to the program. You can either do it by function name or by line number.
(gdb) break FunctionName
(gdb) break code.cpp:81
If you just started a new application you can begin running the program with whatever arguments you wish
(gdb) run -arg1 -arg2
If you have attached to a process then you can continue its execution.
If you have set a breakpoint, it will stop the processes’ execution when it lands on the breakpoint. From here, we can take a look at what’s on the stack, print variables, and do whatever other debugging we wish.
Print variables on stack:
(gdb) info locals
Print a specific variable:
(gdb) print variable_name
Continue on with program execution:
I haven’t played with
perf as much but one thing I found that was cool was the
perf top command. This command gives you samples of which function calls keeps the program the most busy.
To attach to a process and show samples:
perf top -p pid -K