bugs/dggccbug.c

   1 /* NOCW */
   2 /* dggccbug.c */
   3 /* bug found by Eric Young (eay@cryptsoft.com) - May 1995 */
   4
   5 #include <stdio.h>
   6
   7 /* There is a bug in
   8  * gcc version 2.5.8 (88open OCS/BCS, DG-2.5.8.3, Oct 14 1994)
   9  * as shipped with DGUX 5.4R3.10 that can be bypassed by defining
  10  * DG_GCC_BUG in my code.
  11  * The bug manifests itself by the vaule of a pointer that is
  12  * used only by reference, not having it's value change when it is used
  13  * to check for exiting the loop.  Probably caused by there being 2
  14  * copies of the valiable, one in a register and one being an address
  15  * that is passed. */
  16
  17 /* compare the out put from
  18  * gcc dggccbug.c; ./a.out
  19  * and
  20  * gcc -O dggccbug.c; ./a.out
  21  * compile with -DFIXBUG to remove the bug when optimising.
  22  */
  23
  24 void inc(a)
  25 int *a;
  26         {
  27         (*a)++;
  28         }
  29
  30 main()
  31         {
  32         int p=0;
  33 #ifdef FIXBUG
  34         int dummy;
  35 #endif
  36
  37         while (p<3)
  38                 {
  39                 fprintf(stderr,"%08X\n",p);
  40                 inc(&p);
  41 #ifdef FIXBUG
  42                 dummy+=p;
  43 #endif
  44                 }
  45         }