boehm-gc/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 /* Boehm, September 21, 1995 5:39 pm PDT */
  14
  15 /* Check whether setjmp actually saves registers in jmp_buf. */
  16 /* If it doesn't, the generic mark_regs code won't work.     */
  17 /* Compilers vary as to whether they will put x in a         */
  18 /* (callee-save) register without -O.  The code is           */
  19 /* contrived such that any decent compiler should put x in   */
  20 /* a callee-save register with -O.  Thus it is is            */
  21 /* recommended that this be run optimized.  (If the machine  */
  22 /* has no callee-save registers, then the generic code is    */
  23 /* safe, but this will not be noticed by this piece of       */
  24 /* code.)                                                    */
  25 #include <stdio.h>
  26 #include <setjmp.h>
  27 #include <string.h>
  28 #include "gcconfig.h"
  29
  30 #ifdef OS2
  31 /* GETPAGESIZE() is set to getpagesize() by default, but that   */
  32 /* doesn't really exist, and the collector doesn't need it.     */
  33 #define INCL_DOSFILEMGR
  34 #define INCL_DOSMISC
  35 #define INCL_DOSERRORS
  36 #include <os2.h>
  37
  38 int
  39 getpagesize()
  40 {
  41     ULONG result[1];
  42
  43     if (DosQuerySysInfo(QSV_PAGE_SIZE, QSV_PAGE_SIZE,
  44                         (void *)result, sizeof(ULONG)) != NO_ERROR) {
  45         fprintf(stderr, "DosQuerySysInfo failed\n");
  46         result[0] = 4096;
  47     }
  48     return((int)(result[0]));
  49 }
  50 #endif
  51
  52 struct {char a_a; char * a_b;} a;
  53
  54 int * nested_sp()
  55 {
  56     int dummy;
  57
  58     return(&dummy);
  59 }
  60
  61 main()
  62 {
  63         int dummy;
  64         long ps = GETPAGESIZE();
  65         jmp_buf b;
  66         register int x = (int)strlen("a");  /* 1, slightly disguised */
  67         static int y = 0;
  68
  69         printf("This appears to be a %s running %s\n", MACH_TYPE, OS_TYPE);
  70         if (nested_sp() < &dummy) {
  71           printf("Stack appears to grow down, which is the default.\n");
  72           printf("A good guess for STACKBOTTOM on this machine is 0x%lx.\n",
  73                  ((unsigned long)(&dummy) + ps) & ~(ps-1));
  74         } else {
  75           printf("Stack appears to grow up.\n");
  76           printf("Define STACK_GROWS_UP in gc_private.h\n");
  77           printf("A good guess for STACKBOTTOM on this machine is 0x%lx.\n",
  78                  ((unsigned long)(&dummy) + ps) & ~(ps-1));
  79         }
  80         printf("Note that this may vary between machines of ostensibly\n");
  81         printf("the same architecture (e.g. Sun 3/50s and 3/80s).\n");
  82         printf("On many machines the value is not fixed.\n");
  83         printf("A good guess for ALIGNMENT on this machine is %ld.\n",
  84                (unsigned long)(&(a.a_b))-(unsigned long)(&a));
  85
  86         /* Encourage the compiler to keep x in a callee-save register */
  87         x = 2*x-1;
  88         printf("");
  89         x = 2*x-1;
  90         setjmp(b);
  91         if (y == 1) {
  92             if (x == 2) {
  93                 printf("Generic mark_regs code probably wont work\n");
  94 #               if defined(SPARC) || defined(RS6000) || defined(VAX) || defined(MIPS) || defined(M68K) || defined(I386) || defined(NS32K) || defined(RT)
  95                     printf("Assembly code supplied\n");
  96 #               else
  97                     printf("Need assembly code\n");
  98 #               endif
  99             } else if (x == 1) {
 100                 printf("Generic mark_regs code may work\n");
 101             } else {
 102                 printf("Very strange setjmp implementation\n");
 103             }
 104         }
 105         y++;
 106         x = 2;
 107         if (y == 1) longjmp(b,1);
 108         return(0);
 109 }
 110
 111 int g(x)
 112 int x;
 113 {
 114         return(x);
 115 }