bugs/ultrixcc.c

   1 #include <stdio.h>
   2
   3 /* This is a cc optimiser bug for ultrix 4.3, mips CPU.
   4  * What happens is that the compiler, due to the (a)&7,
   5  * does
   6  * i=a&7;
   7  * i--;
   8  * i*=4;
   9  * Then uses i as the offset into a jump table.
  10  * The problem is that a value of 0 generates an offset of
  11  * 0xfffffffc.
  12  */
  13
  14 main()
  15         {
  16         f(5);
  17         f(0);
  18         }
  19
  20 int f(a)
  21 int a;
  22         {
  23         switch(a&7)
  24                 {
  25         case 7:
  26                 printf("7\n");
  27         case 6:
  28                 printf("6\n");
  29         case 5:
  30                 printf("5\n");
  31         case 4:
  32                 printf("4\n");
  33         case 3:
  34                 printf("3\n");
  35         case 2:
  36                 printf("2\n");
  37         case 1:
  38                 printf("1\n");
  39 #ifdef FIX_BUG
  40         case 0:
  41                 ;
  42 #endif
  43                 }
  44         }
  45