libgc/setjmp_t.c

   1 /*
   2  * Copyright (c) 1991-1994 by Xerox Corporation.  All rights reserved.
   3  *
   4  * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
   5  * OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
   6  *
   7  * Permission is hereby granted to use or copy this program
   8  * for any purpose,  provided the above notices are retained on all copies.
   9  * Permission to modify the code and to distribute modified code is granted,
  10  * provided the above notices are retained, and a notice that the code was
  11  * modified is included with the above copyright notice.
  12  */
  13
  14 /* Check whether setjmp actually saves registers in jmp_buf. */
  15 /* If it doesn't, the generic mark_regs code won't work.     */
  16 /* Compilers vary as to whether they will put x in a         */
  17 /* (callee-save) register without -O.  The code is           */
  18 /* contrived such that any decent compiler should put x in   */
  19 /* a callee-save register with -O.  Thus it is is            */
  20 /* recommended that this be run optimized.  (If the machine  */
  21 /* has no callee-save registers, then the generic code is    */
  22 /* safe, but this will not be noticed by this piece of       */
  23 /* code.)  This test appears to be far from perfect.         */
  24 #include <stdio.h>
  25 #include <setjmp.h>
  26 #include <string.h>
  27 #include "private/gcconfig.h"
  28
  29 #ifdef OS2
  30 /* GETPAGESIZE() is set to getpagesize() by default, but that   */
  31 /* doesn't really exist, and the collector doesn't need it.     */
  32 #define INCL_DOSFILEMGR
  33 #define INCL_DOSMISC
  34 #define INCL_DOSERRORS
  35 #include <os2.h>
  36
  37 int
  38 getpagesize()
  39 {
  40     ULONG result[1];
  41
  42     if (DosQuerySysInfo(QSV_PAGE_SIZE, QSV_PAGE_SIZE,
  43                         (void *)result, sizeof(ULONG)) != NO_ERROR) {
  44         fprintf(stderr, "DosQuerySysInfo failed\n");
  45         result[0] = 4096;
  46     }
  47     return((int)(result[0]));
  48 }
  49 #endif
  50
  51 struct {char a_a; char * a_b;} a;
  52
  53 int * nested_sp()
  54 {
  55     int dummy;
  56
  57     return(&dummy);
  58 }
  59
  60 main()
  61 {
  62         int dummy;
  63         long ps = GETPAGESIZE();
  64         jmp_buf b;
  65         register int x = (int)strlen("a");  /* 1, slightly disguised */
  66         static int y = 0;
  67
  68         printf("This appears to be a %s running %s\n", MACH_TYPE, OS_TYPE);
  69         if (nested_sp() < &dummy) {
  70           printf("Stack appears to grow down, which is the default.\n");
  71           printf("A good guess for STACKBOTTOM on this machine is 0x%lx.\n",
  72                  ((unsigned long)(&dummy) + ps) & ~(ps-1));
  73         } else {
  74           printf("Stack appears to grow up.\n");
  75           printf("Define STACK_GROWS_UP in gc_private.h\n");
  76           printf("A good guess for STACKBOTTOM on this machine is 0x%lx.\n",
  77                  ((unsigned long)(&dummy) + ps) & ~(ps-1));
  78         }
  79         printf("Note that this may vary between machines of ostensibly\n");
  80         printf("the same architecture (e.g. Sun 3/50s and 3/80s).\n");
  81         printf("On many machines the value is not fixed.\n");
  82         printf("A good guess for ALIGNMENT on this machine is %ld.\n",
  83                (unsigned long)(&(a.a_b))-(unsigned long)(&a));
  84
  85         /* Encourage the compiler to keep x in a callee-save register */
  86         x = 2*x-1;
  87         printf("");
  88         x = 2*x-1;
  89         setjmp(b);
  90         if (y == 1) {
  91             if (x == 2) {
  92                 printf("Generic mark_regs code probably wont work\n");
  93 #               if defined(SPARC) || defined(RS6000) || defined(VAX) || defined(MIPS) || defined(M68K) || defined(I386) || defined(NS32K) || defined(RT)
  94                     printf("Assembly code supplied\n");
  95 #               else
  96                     printf("Need assembly code\n");
  97 #               endif
  98             } else if (x == 1) {
  99                 printf("Generic mark_regs code may work\n");
 100             } else {
 101                 printf("Very strange setjmp implementation\n");
 102             }
 103         }
 104         y++;
 105         x = 2;
 106         if (y == 1) longjmp(b,1);
 107         return(0);
 108 }
 109
 110 int g(x)
 111 int x;
 112 {
 113         return(x);
 114 }