在不修改源的情况下查找在多进程程序中调用哪些函数？

I'm working on a project where I need to find which functions get called in various Linux programs (written in C) given particular inputs. My current approach has been to compile a program with -pg (profiling option), run it, and find which functions get called by processing gprof's output. Only functions that are called at least once appear in the output file.I'm working on a project where I need to find w