Re: help-using gnu's gprof for getting profiling information

[Stepan Kasal]

Hello,

On Tue, Mar 30, 2004 at 08:11:00PM -0600, Rakesh M. Patel wrote:
>   I am using gnu's gprof ...

OK, I tried it with a source file similar to your one:

$ cat test_prog.c
int increment(int x)
{
        int y = 0;
        int i = 0;
        for(i = 0; i < 100; i++)
                x=x+1;
        return x;
}
main() {
        int d;
        increment(d);
}

Then I run these commands:

$ gcc-2.95 -o test_prog test_prog.c -g -pg -a
$ rm bb.out; ./test_prog
$ perl /usr/share/doc/binutils/gprof/bbconv.pl <bb.out >BB-DATA
$ gprof -A -l test_prog gmon.out BB-DATA

And the output was as expected:

*** File /home/kasal/test_prog.c:
                int increment(int x)
         1,1 -> {
                        int y = 0;
                        int i = 0;
       101,1 ->         for(i = 0; i < 100; i++)
         100 ->                 x=x+1;
           1 ->         return x;
           1 -> }

There are several pitfalls though:
1) It seems that new versions of gcc (3.2.3, 3.3, at least) don't
   support -a.
2) OTOH, when the gcc is too old, like mine gcc-2.95.4, it outputs
   the basic-block details into separate file bb.out; you have to transform
   it by bbconv.pl, as described in the gprof manual.
3) You have to remove the old copy of bb.out before running the test program;
   the results cumulate otherwise.
4) It might be better to use gprof without `-x', the output shows mor clearly
   which lines are ``merged together''. 

You might avoid the bb.out hassle by using a suitable version of compiler,
perhaps gcc 3.0.x.  I haven't tried this.

Hope this helps,
        Stepan Kasal