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