[Bug c/11577] New: Gcc doesn't handle pointer subtraction right

["hjl at lucon dot org" <gcc-bugzilla at gcc dot gnu dot org>]

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11577

           Summary: Gcc doesn't handle pointer subtraction right
           Product: gcc
           Version: 3.3.1
            Status: UNCONFIRMED
          Severity: critical
          Priority: P2
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: hjl at lucon dot org
                CC: gcc-bugs at gcc dot gnu dot org

Gcc will produce the wrong result of pointer subtraction:

[hjl@gnu pointer]$ cat y.c
#include <stdlib.h>
#include <stdio.h>
 
struct a
{
  unsigned int x[11];
};
 
int
main()
{
  unsigned long i, delta;
  struct a *c, *b;
 
  c = (struct a *) malloc (sizeof (struct a) * 3);
  b = (struct a *) malloc (sizeof (struct a) * 2);
  if (b > c)
    {
      i = ((char *) b - (char *) c)/sizeof (struct a);
      delta = b - c;
    }
  else
    {
      i = ((char *) c - (char *) b)/sizeof (struct a);
      delta = c - b;
    }
  printf ("0x%lx, 0x%lx\n", c, b);
  printf ("0x%lx, 0x%lx \n", i, delta);
  if (i != delta)
    abort ();
  return 0;
}
[hjl@gnu pointer]$ gcc y.c
[hjl@gnu pointer]$ ./a.out
0x80496b0, 0x8049738
0x3, 0xba2e8ba6
Aborted