dggccbug.c revision 55715 
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
24void inc(a)
25int *a;
26	{
27	(*a)++;
28	}
29
30main()
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	}
46