why does ltrace produce no output

Question

For several days I have left this command running in a terminal emulator

ltrace -p `pgrep xfwm4`

while using the system normally, and I'm yet to see any output from ltrace. Note: xfwm4 is Xfce's window manager.

Is this expected? A busy window manager does not make any library calls?

I am experiencing an unpredictable bug in xfwm4 that occurs at random, and I was hoping ltrace would provide some clue as to what was causing it.

Answer 1

because the parent process is not making any library calls...

like strace, there is a flag to follow child process.

check the man page;

   -f     Trace child processes as they are created by currently traced processes as a result of the fork(2) or clone(2) system calls. The new process is attached immediately.