dggccbug.c revision 296465 
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
25void inc(a)
26int *a;
27{
28    (*a)++;
29}
30
31main()
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}
46