Bill Mahoney wrote: > This much I knew. However! Let me rephrase my question. Suppose I > compile something with -finstrument-functions and don't supply my own > function. The linker must resolve it to something, so I assumed that > there is an empty function (e.g. a "ret" with a global label on it) > somewhere in the runtime library source; otherwise "ld" would barf. Is > this not the case, and the linker is just supplying that silently, or what? It depends on the target. glibc has an implementation which writes the profiling data to a FIFO named in the environment variable PCPROFILE_OUTPUT (otherwise a no-op if not set.) Other targets don't provide anything: $ gcc -finstrument-functions tc.c /tmp/cc92y1eZ.o:tc.c:(.text+0x15): undefined reference to `___cyg_profile_func_enter' /tmp/cc92y1eZ.o:tc.c:(.text+0x28): undefined reference to `___cyg_profile_func_exit' /tmp/cc92y1eZ.o:tc.c:(.text+0x63): undefined reference to `___cyg_profile_func_enter' /tmp/cc92y1eZ.o:tc.c:(.text+0x85): undefined reference to `___cyg_profile_func_exit' collect2: ld returned 1 exit status Brian
