How can I get better profiling?

Question

I need to profile a program to see whether any changes need to be made regarding performance. I suspect there is a need, but measuring first is the way to go. This is not that program, but it illustrates the problem I'm having:

#include <stdio.h>
int main (int argc, char** argv)
{
  FILE* fp = fopen ("trivial.c", "r");
  if (fp)
  {
    char line[80];
    while (fgets (line, 80, fp))
      printf (line);

    fclose (fp);
  }
  return 0;
}

Here's what I did with it:

% gcc trivial.c -pg -o trivial
% ./trivial
...
% gprof trivial gmon.out

Granted, this is a trivial program, but I would have thought it would make some kind of blip on the profiling radar. It didn't:

                                  called/total       parents 
index  %time    self descendents  called+self    name       index
                                  called/total       children

                0.00        0.00       1/1           __start [1704]
[105]    0.0    0.00        0.00       1         _main [105]

-----------------------------------------------

  %   cumulative   self              self     total           
 time   seconds   seconds    calls  ms/call  ms/call  name    
  0.0       0.00     0.00        1     0.00     0.00  _main [105]

Index by function name

 [105] _main              

Can anyone guide me here? I would like the output to reflect that it called fgets and printf at least 14 times, and it did hit the disk after all - there should be some measured time, surely.

When I run the same command on the real program, I get more functions listed, but even then it is not a complete list - just a sample.

Perhaps gprof is not the right tool to use. What is?

This is on OS X Leopard.

Edit: I ran the real program and got this:

% time real_program
real      4m24.107s
user      2m34.630s
sys       0m38.716s

Answer 1

I think that you could try various Valgrind tools, especially callgrind (used to get call counts and inclusive cost for each call happening in your program).

There are various nice visualisation tools for the valgrind output. I don't know about particular tools for OS X though.