#include <stdio.h>
int square(int x) { return x*x; }
int main(void) {
    square(2);
}

$ gcc -O0 --coverage square.c
$ ./a.out
$ gcov -i square.c
$ awk -F '[,:]' '$1 == "function" && $3 > 0 {print $3, $4}' square.c.gcov
1 square
1 main

$ gcc -O0 -pg square.c
$ ./a.out
$ gprof -b -P
            Call graph


granularity: each sample hit covers 2 byte(s) no time propagated

index % time    self  children    called     name
        0.00    0.00       1/1           main [7]
[1]      0.0    0.00    0.00       1         square [1]
-----------------------------------------------

Index by function name

   [1] square

#define _GNU_SOURCE
#include <dlfcn.h>

#include <stdlib.h>
#include <stdio.h>

#define TRACE_FD 3

void __cyg_profile_func_enter (void *, void *)
   __attribute__((no_instrument_function));

void __cyg_profile_func_enter (void *func,  void *caller)
{
  static FILE* trace = NULL;
  Dl_info info;

  if (trace == NULL) {
    trace = fdopen(TRACE_FD, "w");
    if (trace == NULL) abort();
    setbuf(trace, NULL);
  }
  if (dladdr(func, &info))
    fprintf (trace, "%p [%s] %sn",
             func,
             info.dli_fname ? info.dli_fname : "?",
             info.dli_sname ? info.dli_sname : "?");
}

$ gcc -O0 -rdynamic -finstrument-functions square.c instrument.c -ldl
$ ./a.out 3>&1
0x400a8f [./a.out] main
0x400a4f [./a.out] square