os_dep.c

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  void GC_init_linux_data_start()
  {
    extern ptr_t GC_find_limit(ptr_t, GC_bool);

#   if defined(LINUX) || defined(HURD)
      /* Try the easy approaches first:	*/
      if ((ptr_t)__data_start != 0) {
	  GC_data_start = (ptr_t)(__data_start);
	  return;
      }
      if ((ptr_t)data_start != 0) {
	  GC_data_start = (ptr_t)(data_start);
	  return;
      }
#   endif /* LINUX */
    GC_data_start = GC_find_limit((ptr_t)(_end), FALSE);
  }
#endif

# ifdef ECOS

# ifndef ECOS_GC_MEMORY_SIZE
# define ECOS_GC_MEMORY_SIZE (448 * 1024)
# endif /* ECOS_GC_MEMORY_SIZE */

// FIXME: This is a simple way of allocating memory which is
// compatible with ECOS early releases.  Later releases use a more
// sophisticated means of allocating memory than this simple static
// allocator, but this method is at least bound to work.
static char memory[ECOS_GC_MEMORY_SIZE];
static char *brk = memory;

static void *tiny_sbrk(ptrdiff_t increment)
{
  void *p = brk;

  brk += increment;

  if (brk >  memory + sizeof memory)
    {
      brk -= increment;
      return NULL;
    }

  return p;
}
#define sbrk tiny_sbrk
# endif /* ECOS */

#if (defined(NETBSD) || defined(OPENBSD)) && defined(__ELF__)
  ptr_t GC_data_start;

  void GC_init_netbsd_elf(void)
  {
    extern ptr_t GC_find_limit(ptr_t, GC_bool);
    extern char **environ;
	/* This may need to be environ, without the underscore, for	*/
	/* some versions.						*/
    GC_data_start = GC_find_limit((ptr_t)&environ, FALSE);
  }
#endif

# ifdef OS2

# include <stddef.h>

# if !defined(__IBMC__) && !defined(__WATCOMC__) /* e.g. EMX */

struct exe_hdr {
    unsigned short      magic_number;
    unsigned short      padding[29];
    long                new_exe_offset;
};

#define E_MAGIC(x)      (x).magic_number
#define EMAGIC          0x5A4D  
#define E_LFANEW(x)     (x).new_exe_offset

struct e32_exe {
    unsigned char       magic_number[2]; 
    unsigned char       byte_order; 
    unsigned char       word_order; 
    unsigned long       exe_format_level;
    unsigned short      cpu;       
    unsigned short      os;
    unsigned long       padding1[13];
    unsigned long       object_table_offset;
    unsigned long       object_count;    
    unsigned long       padding2[31];
};

#define E32_MAGIC1(x)   (x).magic_number[0]
#define E32MAGIC1       'L'
#define E32_MAGIC2(x)   (x).magic_number[1]
#define E32MAGIC2       'X'
#define E32_BORDER(x)   (x).byte_order
#define E32LEBO         0
#define E32_WORDER(x)   (x).word_order
#define E32LEWO         0
#define E32_CPU(x)      (x).cpu
#define E32CPU286       1
#define E32_OBJTAB(x)   (x).object_table_offset
#define E32_OBJCNT(x)   (x).object_count

struct o32_obj {
    unsigned long       size;  
    unsigned long       base;
    unsigned long       flags;  
    unsigned long       pagemap;
    unsigned long       mapsize; 
    unsigned long       reserved;
};

#define O32_FLAGS(x)    (x).flags
#define OBJREAD         0x0001L
#define OBJWRITE        0x0002L
#define OBJINVALID      0x0080L
#define O32_SIZE(x)     (x).size
#define O32_BASE(x)     (x).base

# else  /* IBM's compiler */

/* A kludge to get around what appears to be a header file bug */
# ifndef WORD
#   define WORD unsigned short
# endif
# ifndef DWORD
#   define DWORD unsigned long
# endif

# define EXE386 1
# include <newexe.h>
# include <exe386.h>

# endif  /* __IBMC__ */

# define INCL_DOSEXCEPTIONS
# define INCL_DOSPROCESS
# define INCL_DOSERRORS
# define INCL_DOSMODULEMGR
# define INCL_DOSMEMMGR
# include <os2.h>


/* Disable and enable signals during nontrivial allocations	*/

void GC_disable_signals(void)
{
    ULONG nest;
    
    DosEnterMustComplete(&nest);
    if (nest != 1) ABORT("nested GC_disable_signals");
}

void GC_enable_signals(void)
{
    ULONG nest;
    
    DosExitMustComplete(&nest);
    if (nest != 0) ABORT("GC_enable_signals");
}


# else

#  if !defined(PCR) && !defined(AMIGA) && !defined(MSWIN32) \
      && !defined(MSWINCE) \
      && !defined(MACOS) && !defined(DJGPP) && !defined(DOS4GW) \
      && !defined(NOSYS) && !defined(ECOS)

#   if 0
	/* Use the traditional BSD interface */
#	define SIGSET_T int
#	define SIG_DEL(set, signal) (set) &= ~(sigmask(signal))
#	define SIG_FILL(set)  (set) = 0x7fffffff
    	  /* Setting the leading bit appears to provoke a bug in some	*/
    	  /* longjmp implementations.  Most systems appear not to have	*/
    	  /* a signal 32.						*/
#	define SIGSETMASK(old, new) (old) = sigsetmask(new)
#   endif

    /* Use POSIX/SYSV interface	*/
#   define SIGSET_T sigset_t
#   define SIG_DEL(set, signal) sigdelset(&(set), (signal))
#   define SIG_FILL(set) sigfillset(&set)
#   define SIGSETMASK(old, new) sigprocmask(SIG_SETMASK, &(new), &(old))


static GC_bool mask_initialized = FALSE;

static SIGSET_T new_mask;

static SIGSET_T old_mask;

static SIGSET_T dummy;

#if defined(GC_ASSERTIONS) && !defined(THREADS)
# define CHECK_SIGNALS
  int GC_sig_disabled = 0;
#endif

void GC_disable_signals(void)
{
    if (!mask_initialized) {
    	SIG_FILL(new_mask);

	SIG_DEL(new_mask, SIGSEGV);
	SIG_DEL(new_mask, SIGILL);
	SIG_DEL(new_mask, SIGQUIT);
#	ifdef SIGBUS
	    SIG_DEL(new_mask, SIGBUS);
#	endif
#	ifdef SIGIOT
	    SIG_DEL(new_mask, SIGIOT);
#	endif
#	ifdef SIGEMT
	    SIG_DEL(new_mask, SIGEMT);
#	endif
#	ifdef SIGTRAP
	    SIG_DEL(new_mask, SIGTRAP);
#	endif 
	mask_initialized = TRUE;
    }
#   ifdef CHECK_SIGNALS
	if (GC_sig_disabled != 0) ABORT("Nested disables");
	GC_sig_disabled++;
#   endif
    SIGSETMASK(old_mask,new_mask);
}

void GC_enable_signals(void)
{
#   ifdef CHECK_SIGNALS
	if (GC_sig_disabled != 1) ABORT("Unmatched enable");
	GC_sig_disabled--;
#   endif
    SIGSETMASK(dummy,old_mask);
}

#  endif  /* !PCR */

# endif /*!OS/2 */

/* Ivan Demakov: simplest way (to me) */
#if defined (DOS4GW)
  void GC_disable_signals() { }
  void GC_enable_signals() { }
#endif

/* Find the page size */
word GC_page_size;

# if defined(MSWIN32) || defined(MSWINCE)
  void GC_setpagesize(void)
  {
    GetSystemInfo(&GC_sysinfo);
    GC_page_size = GC_sysinfo.dwPageSize;
  }

# else
#   if defined(MPROTECT_VDB) || defined(PROC_VDB) || defined(USE_MMAP)
	void GC_setpagesize(void)
	{
	    GC_page_size = GETPAGESIZE();
	}
#   else
	/* It's acceptable to fake it. */
	void GC_setpagesize(void)
	{
	    GC_page_size = HBLKSIZE;
	}
#   endif
# endif

/* 
 * Find the base of the stack. 
 * Used only in single-threaded environment.
 * With threads, GC_mark_roots needs to know how to do this.
 * Called with allocator lock held.
 */
# if defined(MSWIN32) || defined(MSWINCE) || defined(CYGWIN32)
# define is_writable(prot) ((prot) == PAGE_READWRITE \
			    || (prot) == PAGE_WRITECOPY \
			    || (prot) == PAGE_EXECUTE_READWRITE \
			    || (prot) == PAGE_EXECUTE_WRITECOPY)
/* Return the number of bytes that are writable starting at p.	*/
/* The pointer p is assumed to be page aligned.			*/
/* If base is not 0, *base becomes the beginning of the 	*/
/* allocation region containing p.				*/
word GC_get_writable_length(ptr_t p, ptr_t *base)
{
    MEMORY_BASIC_INFORMATION buf;
    word result;
    word protect;
    
    result = VirtualQuery(p, &buf, sizeof(buf));
    if (result != sizeof(buf)) ABORT("Weird VirtualQuery result");
    if (base != 0) *base = (ptr_t)(buf.AllocationBase);
    protect = (buf.Protect & ~(PAGE_GUARD | PAGE_NOCACHE));
    if (!is_writable(protect)) {
        return(0);
    }
    if (buf.State != MEM_COMMIT) return(0);
    return(buf.RegionSize);
}

int GC_get_stack_base(struct GC_stack_base *sb)
{
    int dummy;
    ptr_t sp = (ptr_t)(&dummy);
    ptr_t trunc_sp = (ptr_t)((word)sp & ~(GC_page_size - 1));
    word size = GC_get_writable_length(trunc_sp, 0);
   
    sb -> mem_base = trunc_sp + size;
    return GC_SUCCESS;
}

#define HAVE_GET_STACK_BASE

/* This is always called from the main thread.	*/
ptr_t GC_get_main_stack_base(void)
{
    struct GC_stack_base sb;

    GC_get_stack_base(&sb);
    return (ptr_t)sb.mem_base;
}

# endif /* MS Windows */

# ifdef BEOS
# include <kernel/OS.h>
ptr_t GC_get_main_stack_base(void){
	thread_info th;
	get_thread_info(find_thread(NULL),&th);
	return th.stack_end;
}
# endif /* BEOS */


# ifdef OS2

ptr_t GC_get_main_stack_base(void)
{
    PTIB ptib;
    PPIB ppib;
    
    if (DosGetInfoBlocks(&ptib, &ppib) != NO_ERROR) {
    	GC_err_printf("DosGetInfoBlocks failed\n");
    	ABORT("DosGetInfoBlocks failed\n");
    }
    return((ptr_t)(ptib -> tib_pstacklimit));
}

# endif /* OS2 */

# ifdef AMIGA
#   define GC_AMIGA_SB
#   include "AmigaOS.c"
#   undef GC_AMIGA_SB
# endif /* AMIGA */

# if defined(NEED_FIND_LIMIT) || defined(UNIX_LIKE)

    typedef void (*handler)(int);

#   if defined(SUNOS5SIGS) || defined(IRIX5) || defined(OSF1) \
    || defined(HURD) || defined(NETBSD)
	static struct sigaction old_segv_act;
#	if defined(_sigargs) /* !Irix6.x */ || defined(HPUX) \
	|| defined(HURD) || defined(NETBSD)
	    static struct sigaction old_bus_act;
#	endif
#   else
        static handler old_segv_handler, old_bus_handler;
#   endif
    
    void GC_set_and_save_fault_handler(handler h)
    {
#	if defined(SUNOS5SIGS) || defined(IRIX5)  \
        || defined(OSF1) || defined(HURD) || defined(NETBSD)
	  struct sigaction	act;

	  act.sa_handler	= h;
#	  if 0 /* Was necessary for Solaris 2.3 and very temporary 	*/
	       /* NetBSD bugs.						*/
            act.sa_flags          = SA_RESTART | SA_NODEFER;
#         else
            act.sa_flags          = SA_RESTART;
#	  endif

	  (void) sigemptyset(&act.sa_mask);
#	  ifdef GC_IRIX_THREADS
		/* Older versions have a bug related to retrieving and	*/
		/* and setting a handler at the same time.		*/
	        (void) sigaction(SIGSEGV, 0, &old_segv_act);
	        (void) sigaction(SIGSEGV, &act, 0);
#	  else
	        (void) sigaction(SIGSEGV, &act, &old_segv_act);
#		if defined(IRIX5) && defined(_sigargs) /* Irix 5.x, not 6.x */ \
		   || defined(HPUX) || defined(HURD) || defined(NETBSD)
		    /* Under Irix 5.x or HP/UX, we may get SIGBUS.	*/
		    /* Pthreads doesn't exist under Irix 5.x, so we	*/
		    /* don't have to worry in the threads case.		*/
		    (void) sigaction(SIGBUS, &act, &old_bus_act);
#		endif
#	  endif	/* GC_IRIX_THREADS */
#	else
    	  old_segv_handler = signal(SIGSEGV, h);
#	  ifdef SIGBUS
	    old_bus_handler = signal(SIGBUS, h);
#	  endif
#	endif
    }
# endif /* NEED_FIND_LIMIT || UNIX_LIKE */

# if defined(NEED_FIND_LIMIT) || \
     defined(USE_PROC_FOR_LIBRARIES) && defined(THREADS)
  /* Some tools to implement HEURISTIC2	*/
#   define MIN_PAGE_SIZE 256	/* Smallest conceivable page size, bytes */
    
    /*ARGSUSED*/
    void GC_fault_handler(int sig)
    {
        LONGJMP(GC_jmp_buf, 1);
    }

    void GC_setup_temporary_fault_handler(void)
    {
	/* Handler is process-wide, so this should only happen in */
	/* one thread at a time.				  */
	GC_ASSERT(I_HOLD_LOCK());
	GC_set_and_save_fault_handler(GC_fault_handler);
    }
    
    void GC_reset_fault_handler(void)
    {