Bug#589755: Segfaults/FPEs using -lc_p

[Ed]

Package: libc6-prof
Version: 2.7-18lenny4

Take the example program (example1) at

http://www.ibm.com/developerworks/library/l-gnuprof.html

(source appended at end for ease of reference).

e...@sagittarius:~/tmp$ gcc example.c -pg -o example -static-libgcc -lc_p
example.c: In function ‘main’:
example.c:27: warning: incompatible implicit declaration of built-in
function ‘exit’
e...@sagittarius:~/tmp$ ./example
Usage ./example <No of Iterations>
e...@sagittarius:~/tmp$ ./example 100
No of iterations = 100
e...@sagittarius:~/tmp$

Now try linking any other library, e.g. zlib (4 places in link order shown):

e...@sagittarius:~/tmp$ gcc example.c -pg -o example -static-libgcc -lc_p -lz
example.c: In function ‘main’:
example.c:27: warning: incompatible implicit declaration of built-in
function ‘exit’
e...@sagittarius:~/tmp$ ./example 100
Floating point exception
e...@sagittarius:~/tmp$

e...@sagittarius:~/tmp$ gcc example.c -pg -o example -lz -static-libgcc -lc_p
example.c: In function ‘main’:
example.c:27: warning: incompatible implicit declaration of built-in
function ‘exit’
e...@sagittarius:~/tmp$ ./example 100
Floating point exception
e...@sagittarius:~/tmp$

e...@sagittarius:~/tmp$ gcc example.c -pg -o example  -static-libgcc -lz -lc_p
example.c: In function ‘main’:
example.c:27: warning: incompatible implicit declaration of built-in
function ‘exit’
e...@sagittarius:~/tmp$ ./example 100
Floating point exception
e...@sagittarius:~/tmp$

e...@sagittarius:~/tmp$ gcc example.c -lz -pg -o example  -static-libgcc -lc_p
example.c: In function ‘main’:
example.c:27: warning: incompatible implicit declaration of built-in
function ‘exit’
e...@sagittarius:~/tmp$ ./example 100
Floating point exception

Now try specifying -static (e.g. there are many libraries in your program)

e...@sagittarius:~/tmp$ gcc example.c -pg -o example -static -static-libgcc 
-lc_p
example.c: In function ‘main’:
example.c:27: warning: incompatible implicit declaration of built-in
function ‘exit’
e...@sagittarius:~/tmp$ ./example 100
Segmentation fault

e...@sagittarius:~/tmp$ gcc example.c -pg -o example -static-libgcc -lc_p 
-static
example.c: In function ‘main’:
example.c:27: warning: incompatible implicit declaration of built-in
function ‘exit’
e...@sagittarius:~/tmp$ ./example 100
Segmentation fault

Thus it appears with this version you can only use -lc_p to debug
programs with no external dependencies, because you can't link other
libraries, and if you could, you still couldn't link them statically
to get proper gprof output.

I can't find any other reference to this behaviour; if it's just a
documentation problem, I'm happy to write the documentation if someone
tells me what the actual correct behaviour is (or necessary
limitations are).

Example program:

#include <stdio.h>

int a(void) {
  int i=0,g=0;
  while(i++<100000)
  {
     g+=i;
  }
  return g;
}
int b(void) {
  int i=0,g=0;
  while(i++<400000)
  {
    g+=i;
  }
  return g;
}

int main(int argc, char** argv)
{
   int iterations;

   if(argc != 2)
   {
      printf("Usage %s <No of Iterations>\n", argv[0]);
      exit(-1);
   }
   else
      iterations = atoi(argv[1]);

   printf("No of iterations = %d\n", iterations);

   while(iterations--)
   {
      a();
      b();
   }
}



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