Bug#524472: gcc-4.3: gcc 4.3.2 miscompiles GMP 4.3.0

[Vincent Lefevre <vincent@vinc17.org>]

retitle 524472 gcc-4.3: gcc 4.3.2 strict-aliasing bug / miscompiles GMP 4.3.0
thanks

I've tracked down the bug and managed to write a simple testcase:

/* With GCC 4.3.2 and -O2 option: output value is 1 instead of 0.
 * If -fno-strict-aliasing is added, this bug disappears.
 */

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

int test (int n)
{
  unsigned long *p, *q;
  int i;

  q = p = malloc (n * sizeof (unsigned long));
  if (p == NULL)
    return 2;
  for (i = 0; i < n - 1; i++)
    p[i] = 0;
  p[n - 1] = 1;
  while ((*(q++))-- == 0) ;
  return p[n - 1] == 1;
}

int main (void)
{
  int r;

  r = test (17);
  printf ("%d\n", r);
  return r;
}

-- 
Vincent Lefèvre <vincent@vinc17.org> - Web: <http://www.vinc17.org/>
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Work: CR INRIA - computer arithmetic / Arenaire project (LIP, ENS-Lyon)