text: /* 
   * Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers
   * Copyright (c) 1991-1994 by Xerox Corporation.  All rights reserved.
   * Copyright (c) 1996 by Silicon Graphics.  All rights reserved.
   * Copyright (c) 2000-2004 Hewlett-Packard Development Company, L.P.
   *
   * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
   * OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
   *
   * Permission is hereby granted to use or copy this program
   * for any purpose,  provided the above notices are retained on all copies.
   * Permission to modify the code and to distribute modified code is granted,
   * provided the above notices are retained, and a notice that the code was
   * modified is included with the above copyright notice.
   */
  
  /*
   * This header is private to the gc.  It is almost always included from
   * gc_priv.h.  However it is possible to include it by itself if just the
   * configuration macros are needed.  In that
   * case, a few declarations relying on types declared in gc_priv.h will be
   * omitted.
   */
   
  #ifndef GCCONFIG_H
  
  # define GCCONFIG_H
  
  # ifndef GC_PRIVATE_H
      /* Fake ptr_t declaration, just to avoid compilation errors.	*/
      /* This avoids many instances if "ifndef GC_PRIVATE_H" below.	*/
      typedef struct GC_undefined_struct * ptr_t;
  #   include <stddef.h>	/* For size_t etc. */
  # endif
  
  /* Machine dependent parameters.  Some tuning parameters can be found	*/
  /* near the top of gc_private.h.					*/
  
  /* Machine specific parts contributed by various people.  See README file. */
  
  /* First a unified test for Linux: */
  # if defined(linux) || defined(__linux__)
  #  ifndef LINUX
  #    define LINUX
  #  endif
  # endif
  
  /* And one for NetBSD: */
  # if defined(__NetBSD__)
  #    define NETBSD
  # endif
  
  /* And one for OpenBSD: */
  # if defined(__OpenBSD__)
  #    define OPENBSD
  # endif
  
  /* And one for FreeBSD: */
  # if (defined(__FreeBSD__) || defined(__DragonFly__) || \
        defined(__FreeBSD_kernel__)) && !defined(FREEBSD)
  #    define FREEBSD
  # endif
  
  /* Determine the machine type: */
  # if defined(__arm__) || defined(__thumb__)
  #    define ARM32
  #    if !defined(LINUX) && !defined(NETBSD)
  #      define NOSYS
  #      define mach_type_known
  #    endif
  # endif
  # if defined(sun) && defined(mc68000)
  #    error SUNOS4 no longer supported
  # endif
  # if defined(hp9000s300)
  #    error M68K based HP machines no longer supported.
  # endif
  # if defined(OPENBSD) && defined(m68k)
  #    define M68K
  #    define mach_type_known
  # endif
  # if defined(OPENBSD) && defined(__sparc__)
  #    define SPARC
  #    define mach_type_known
  # endif
  # if defined(NETBSD) && (defined(m68k) || defined(__m68k__))
  #    define M68K
  #    define mach_type_known
  # endif
  # if defined(NETBSD) && defined(__powerpc__)
  #    define POWERPC
  #    define mach_type_known
  # endif
  # if defined(NETBSD) && (defined(__arm32__) || defined(__arm__))
  #    define ARM32
  #    define mach_type_known
  # endif
  # if defined(NETBSD) && defined(__sh__)
  #    define SH
  #    define mach_type_known
  # endif
  # if defined(vax)
  #    define VAX
  #    ifdef ultrix
  #	define ULTRIX
  #    else
  #	define BSD
  #    endif
  #    define mach_type_known
  # endif
  # if defined(__NetBSD__) && defined(__vax__)
  #    define VAX
  #    define mach_type_known
  # endif
  # if defined(mips) || defined(__mips) || defined(_mips)
  #    define MIPS
  #    if defined(nec_ews) || defined(_nec_ews)
  #      define EWS4800
  #    endif
  #    if !defined(LINUX) && !defined(EWS4800) && !defined(NETBSD)
  #      if defined(ultrix) || defined(__ultrix)
  #	 define ULTRIX
  #      else
  #	 define IRIX5   /* or IRIX 6.X */
  #      endif
  #    endif /* !LINUX */
  #    if defined(__NetBSD__) && defined(__MIPSEL__)
  #      undef ULTRIX
  #    endif
  #    define mach_type_known
  # endif
  # if defined(DGUX) && (defined(i386) || defined(__i386__))
  #    define I386
  #    ifndef _USING_DGUX
  #    define _USING_DGUX
  #    endif
  #    define mach_type_known
  # endif
  # if defined(sequent) && (defined(i386) || defined(__i386__))
  #    define I386
  #    define SEQUENT
  #    define mach_type_known
  # endif
  # if defined(sun) && (defined(i386) || defined(__i386__))
  #    define I386
  #    define SOLARIS
  #    define mach_type_known
  # endif
  # if defined(sun) && defined(__amd64)
  #    define X86_64
  #    define SOLARIS
  #    define mach_type_known
  # endif
  # if (defined(__OS2__) || defined(__EMX__)) && defined(__32BIT__)
  #    define I386
  #    define OS2
  #    define mach_type_known
  # endif
  # if defined(ibm032)
  #   error IBM PC/RT no longer supported.
  # endif
  # if defined(sun) && (defined(sparc) || defined(__sparc))
  #   define SPARC
      /* Test for SunOS 5.x */
  #     include <errno.h>
  #     define SOLARIS
  #   define mach_type_known
  # endif
  # if defined(sparc) && defined(unix) && !defined(sun) && !defined(linux) \
       && !defined(__OpenBSD__) && !defined(__NetBSD__) && !defined(__FreeBSD__) \
       && !defined(__DragonFly__)
  #   define SPARC
  #   define DRSNX
  #   define mach_type_known
  # endif
  # if defined(_IBMR2)
  #   define POWERPC
  #   define AIX
  #   define mach_type_known
  # endif
  # if defined(__NetBSD__) && defined(__sparc__)
  #   define SPARC
  #   define mach_type_known
  # endif
  # if defined(_M_XENIX) && defined(_M_SYSV) && defined(_M_I386)
  	/* The above test may need refinement	*/
  #   define I386
  #   if defined(_SCO_ELF)
  #     define SCO_ELF
  #   else
  #     define SCO
  #   endif
  #   define mach_type_known
  # endif
  # if defined(_AUX_SOURCE)
  #   error A/UX no longer supported
  # endif
  # if defined(_PA_RISC1_0) || defined(_PA_RISC1_1) || defined(_PA_RISC2_0) \
       || defined(hppa) || defined(__hppa__)
  #   define HP_PA
  #   if !defined(LINUX) && !defined(HPUX)
  #     define HPUX
  #   endif
  #   define mach_type_known
  # endif
  # if defined(__ia64) && defined(_HPUX_SOURCE)
  #   define IA64
  #   ifndef HPUX
  #     define HPUX
  #   endif
  #   define mach_type_known
  # endif
  # if defined(__BEOS__) && defined(_X86_)
  #    define I386
  #    define BEOS
  #    define mach_type_known
  # endif
  # if defined(__HAIKU__) && defined(_X86_)
  #    define I386
  #    define HAIKU
  #    define mach_type_known
  # if defined(LINUX) && (defined(i386) || defined(__i386__))
  #    define I386
  #    define mach_type_known
  # endif
  # if defined(LINUX) && defined(__x86_64__)
  #    define X86_64
  #    define mach_type_known
  # endif
  # if defined(LINUX) && (defined(__ia64__) || defined(__ia64))
  #    define IA64
  #    define mach_type_known
  # endif
  # if defined(LINUX) && defined(__arm__)
  #    define ARM32
  #    define mach_type_known
  # endif
  # if defined(LINUX) && defined(__cris__)
  #    ifndef CRIS
  #	define CRIS
  #    endif
  #    define mach_type_known
  # endif
  # if defined(LINUX) && (defined(powerpc) || defined(__powerpc__) || \
  		        defined(powerpc64) || defined(__powerpc64__))
  #    define POWERPC
  #    define mach_type_known
  # endif
  # if defined(FREEBSD) && (defined(powerpc) || defined(__powerpc__))
  #    define POWERPC
  #    define mach_type_known
  # endif
  # if defined(LINUX) && defined(__mc68000__)
  #    define M68K
  #    define mach_type_known
  # endif
  # if defined(LINUX) && (defined(sparc) || defined(__sparc__))
  #    define SPARC
  #    define mach_type_known
  # endif
  # if defined(LINUX) && defined(__arm__)
  #    define ARM32
  #    define mach_type_known
  # endif
  # if defined(LINUX) && defined(__sh__)
  #    define SH
  #    define mach_type_known
  # endif
  # if defined(LINUX) && defined(__m32r__)
  #    define M32R
  #    define mach_type_known
  # endif
  # if defined(__alpha) || defined(__alpha__)
  #   define ALPHA
  #   if !defined(LINUX) && !defined(NETBSD) && !defined(OPENBSD) && !defined(FREEBSD)
  #     define OSF1	/* a.k.a Digital Unix */
  #   endif
  #   define mach_type_known
  # endif
  # if defined(_AMIGA) && !defined(AMIGA)
  #   define AMIGA
  # endif
  # ifdef AMIGA 
  #   define M68K
  #   define mach_type_known
  # endif
  # if defined(THINK_C) || defined(__MWERKS__) && !defined(__powerc)
  #   define M68K
  #   define MACOS
  #   define mach_type_known
  # endif
  # if defined(__MWERKS__) && defined(__powerc) && !defined(__MACH__)
  #   define POWERPC
  #   define MACOS
  #   define mach_type_known
  # endif
  # if defined(macosx) || (defined(__APPLE__) && defined(__MACH__))
  #   define DARWIN
  #   if defined(__ppc__)  || defined(__ppc64__)
  #    define POWERPC
  #    define mach_type_known
  #   elif defined(__x86_64__)
  #    define X86_64
  #    define mach_type_known
  #   elif defined(__i386__)
  #    define I386
  #    define mach_type_known
  #   endif
  # endif
  # if defined(NeXT) && defined(mc68000)
  #   define M68K
  #   define NEXT
  #   define mach_type_known
  # endif
  # if defined(NeXT) && (defined(i386) || defined(__i386__))
  #   define I386
  #   define NEXT
  #   define mach_type_known
  # endif
  # if defined(__OpenBSD__) && (defined(i386) || defined(__i386__))
  #   define I386
  #   define OPENBSD
  #   define mach_type_known
  # endif
  # if defined(FREEBSD) && (defined(i386) || defined(__i386__))
  #   define I386
  #   define mach_type_known
  # endif
  # if defined(FREEBSD) && defined(__x86_64__)
  #   define X86_64
  #   define mach_type_known
  # endif
  # if defined(__NetBSD__) && (defined(i386) || defined(__i386__))
  #   define I386
  #   define mach_type_known
  # endif
  # if defined(__NetBSD__) && defined(__x86_64__)
  #    define X86_64
  #    define mach_type_known
  # endif
  # if defined(FREEBSD) && defined(__sparc__)
  #    define SPARC
  #    define mach_type_known
  # endif
  # if defined(bsdi) && (defined(i386) || defined(__i386__))
  #    define I386
  #    define BSDI
  #    define mach_type_known
  # endif
  # if !defined(mach_type_known) && defined(__386BSD__)
  #   define I386
  #   define THREE86BSD
  #   define mach_type_known
  # endif
  # if defined(_CX_UX) && defined(_M88K)
  #   define M88K
  #   define CX_UX
  #   define mach_type_known
  # endif
  # if defined(DGUX) && defined(m88k)
  #   define M88K
      /* DGUX defined */
  #   define mach_type_known
  # endif
  # if defined(_WIN32_WCE)
      /* SH3, SH4, MIPS already defined for corresponding architectures */
  #   if defined(SH3) || defined(SH4)
  #     define SH
  #   endif
  #   if defined(x86)
  #     define I386
  #   endif
  #   if defined(ARM)
  #     define ARM32
  #   endif
  #   define MSWINCE
  #   define mach_type_known
  # else
  #   if (defined(_MSDOS) || defined(_MSC_VER)) && (_M_IX86 >= 300) \
          || defined(_WIN32) && !defined(__CYGWIN32__) && !defined(__CYGWIN__)
  #     if defined(__LP64__) || defined(_WIN64)
  #	define X86_64
  #     else
  #       define I386
  #     endif
  #     define MSWIN32	/* or Win64 */
  #     define mach_type_known
  #   endif
  #   if defined(_MSC_VER) && defined(_M_IA64)
  #     define IA64
  #     define MSWIN32	/* Really win64, but we don't treat 64-bit 	*/
  			/* variants as a differnt platform.		*/
  #   endif
  # endif
  # if defined(__DJGPP__)
  #   define I386
  #   ifndef DJGPP
  #     define DJGPP  /* MSDOS running the DJGPP port of GCC */
  #   endif
  #   define mach_type_known
  # endif
  # if defined(__CYGWIN32__) || defined(__CYGWIN__)
  #   define I386
  #   define CYGWIN32
  #   define mach_type_known
  # endif
  # if defined(__MINGW32__)
  #   define I386
  #   define MSWIN32
  #   define mach_type_known
  # endif
  # if defined(__BORLANDC__)
  #   define I386
  #   define MSWIN32
  #   define mach_type_known
  # endif
  # if defined(_UTS) && !defined(mach_type_known)
  #   define S370
  #   define UTS4
  #   define mach_type_known
  # endif
  # if defined(__pj__)
  #   error PicoJava no longer supported
      /* The implementation had problems, and I haven't heard of users	*/
      /* in ages.  If you want it resurrected, let me know.		*/
  # endif
  # if defined(__embedded__) && defined(PPC)
  #   define POWERPC
  #   define NOSYS
  #   define mach_type_known
  # endif
  /* Ivan Demakov */
  # if defined(__WATCOMC__) && defined(__386__)
  #   define I386
  #   if !defined(OS2) && !defined(MSWIN32) && !defined(DOS4GW)
  #     if defined(__OS2__)
  #       define OS2
  #     else
  #       if defined(__WINDOWS_386__) || defined(__NT__)
  #         define MSWIN32
  #       else
  #         define DOS4GW
  #       endif
  #     endif
  #   endif
  #   define mach_type_known
  # endif
  # if defined(__s390__) && defined(LINUX)
  #    define S390
  #    define mach_type_known
  # endif
  # if defined(__GNU__)
  #   if defined(__i386__)
  /* The Debian Hurd running on generic PC */  
  #     define  HURD
  #     define  I386
  #     define  mach_type_known
  #    endif 
  # endif
  # if defined(__TANDEM)
      /* Nonstop S-series */
      /* FIXME: Should recognize Integrity series? */
  #   define MIPS
  #   define NONSTOP
  #   define mach_type_known
  # endif
  
  /* Feel free to add more clauses here */
  
  /* Or manually define the machine type here.  A machine type is 	*/
  /* characterized by the architecture.  Some				*/
  /* machine types are further subdivided by OS.				*/
  /* Macros such as LINUX, FREEBSD, etc. distinguish them.		*/
  /* SYSV on an M68K actually means A/UX.					*/
  /* The distinction in these cases is usually the stack starting address */
  # ifndef mach_type_known
  #   error "The collector has not been ported to this machine/OS combination."
  # endif
  		    /* Mapping is: M68K       ==> Motorola 680X0	*/
  		    /*		   (NEXT, and SYSV (A/UX),		*/
  		    /*		   MACOS and AMIGA variants)		*/
  		    /*             I386       ==> Intel 386	 	*/
  		    /*		    (SEQUENT, OS2, SCO, LINUX, NETBSD,	*/
  		    /*		     FREEBSD, THREE86BSD, MSWIN32,	*/
  		    /* 		     BSDI,SOLARIS, NEXT, other variants)	*/
                      /*             NS32K      ==> Encore Multimax 	*/
                      /*             MIPS       ==> R2000 through R14K	*/
                      /*			(many variants)			*/
                      /*		   VAX	      ==> DEC VAX		*/
                      /*			(BSD, ULTRIX variants)		*/
                      /*		   HP_PA      ==> HP9000/700 & /800	*/
                      /*				  HP/UX, LINUX		*/
  		    /*		   SPARC      ==> SPARC	v7/v8/v9	*/
  		    /*			(SOLARIS, LINUX, DRSNX variants)	*/
  		    /* 		   ALPHA      ==> DEC Alpha 		*/
  		    /*			(OSF1 and LINUX variants)	*/
  		    /* 		   M88K       ==> Motorola 88XX0        */
  		    /* 		        (CX_UX and DGUX)		*/
  		    /* 		   S370	      ==> 370-like machine	*/
  		    /* 			running Amdahl UTS4		*/
                      /*             S390       ==> 390-like machine      */
  		    /*                  running LINUX                   */
  		    /* 		   ARM32      ==> Intel StrongARM	*/
  		    /* 		   IA64	      ==> Intel IPF		*/
  		    /*				  (e.g. Itanium)	*/
  		    /*			(LINUX and HPUX)	        */
  		    /*		   SH	      ==> Hitachi SuperH	*/
  		    /* 			(LINUX & MSWINCE)		*/
  		    /* 		   X86_64     ==> AMD x86-64		*/
  		    /*		   POWERPC    ==> IBM/Apple PowerPC	*/
  		    /*			(MACOS(<=9),DARWIN(incl.MACOSX),*/
  		    /*			 LINUX, NETBSD, AIX, NOSYS	*/
  		    /*			 variants)			*/
  		    /*			Handles 32 and 64-bit variants.	*/
  		    /*		   CRIS       ==> Axis Etrax		*/
  		    /*		   M32R	      ==> Renesas M32R		*/
  
  
  /*
   * For each architecture and OS, the following need to be defined:
   *
   * CPP_WORDSZ is a simple integer constant representing the word size.
   * in bits.  We assume byte addressibility, where a byte has 8 bits.
   * We also assume CPP_WORDSZ is either 32 or 64.
   * (We care about the length of pointers, not hardware
   * bus widths.  Thus a 64 bit processor with a C compiler that uses
   * 32 bit pointers should use CPP_WORDSZ of 32, not 64. Default is 32.)
   *
   * MACH_TYPE is a string representation of the machine type.
   * OS_TYPE is analogous for the OS.
   *
   * ALIGNMENT is the largest N, such that
   * all pointer are guaranteed to be aligned on N byte boundaries.
   * defining it to be 1 will always work, but perform poorly.
   *
   * DATASTART is the beginning of the data segment.
   * On some platforms SEARCH_FOR_DATA_START is defined.
   * SEARCH_FOR_DATASTART will cause GC_data_start to
   * be set to an address determined by accessing data backwards from _end
   * until an unmapped page is found.  DATASTART will be defined to be
   * GC_data_start.
   * On UNIX-like systems, the collector will scan the area between DATASTART
   * and DATAEND for root pointers.
   *
   * DATAEND, if not `end' where `end' is defined as ``extern int end[];''.
   * RTH suggests gaining access to linker script synth'd values with
   * this idiom instead of `&end' where `end' is defined as ``extern int end;'' .
   * Otherwise, ``GCC will assume these are in .sdata/.sbss'' and it will, e.g.,
   * cause failures on alpha*-*-* with ``-msmall-data or -fpic'' or mips-*-*
   * without any special options.
   *
   * STACKBOTTOM is the cool end of the stack, which is usually the
   * highest address in the stack.
   * Under PCR or OS/2, we have other ways of finding thread stacks.
   * For each machine, the following should:
   * 1) define STACK_GROWS_UP if the stack grows toward higher addresses, and
   * 2) define exactly one of
   *	STACKBOTTOM (should be defined to be an expression)
   *	LINUX_STACKBOTTOM
   *	HEURISTIC1
   *	HEURISTIC2
   * If STACKBOTTOM is defined, then it's value will be used directly as the
   * stack base.  If LINUX_STACKBOTTOM is defined, then it will be determined
   * with a method appropriate for most Linux systems.  Currently we look
   * first for __libc_stack_end, and if that fails read it from /proc.
   * If either of the last two macros are defined, then STACKBOTTOM is computed
   * during collector startup using one of the following two heuristics:
   * HEURISTIC1:  Take an address inside GC_init's frame, and round it up to
   *		the next multiple of STACK_GRAN.
   * HEURISTIC2:  Take an address inside GC_init's frame, increment it repeatedly
   *		in small steps (decrement if STACK_GROWS_UP), and read the value
   *		at each location.  Remember the value when the first
   *		Segmentation violation or Bus error is signalled.  Round that
   *		to the nearest plausible page boundary, and use that instead
   *		of STACKBOTTOM.
   *
   * Gustavo Rodriguez-Rivera points out that on most (all?) Unix machines,
   * the value of environ is a pointer that can serve as STACKBOTTOM.
   * I expect that HEURISTIC2 can be replaced by this approach, which
   * interferes far less with debugging.  However it has the disadvantage
   * that it's confused by a putenv call before the collector is initialized.
   * This could be dealt with by intercepting putenv ...
   *
   * If no expression for STACKBOTTOM can be found, and neither of the above
   * heuristics are usable, the collector can still be used with all of the above
   * undefined, provided one of the following is done:
   * 1) GC_mark_roots can be changed to somehow mark from the correct stack(s)
   *    without reference to STACKBOTTOM.  This is appropriate for use in
   *    conjunction with thread packages, since there will be multiple stacks.
   *    (Allocating thread stacks in the heap, and treating them as ordinary
   *    heap data objects is also possible as a last resort.  However, this is
   *    likely to introduce significant amounts of excess storage retention
   *    unless the dead parts of the thread stacks are periodically cleared.)
   * 2) Client code may set GC_stackbottom before calling any GC_ routines.
   *    If the author of the client code controls the main program, this is
   *    easily accomplished by introducing a new main program, setting
   *    GC_stackbottom to the address of a local variable, and then calling
   *    the original main program.  The new main program would read something
   *    like:
   *
   *		# include "gc_private.h"
   *
   *		main(argc, argv, envp)
   *		int argc;
   *		char **argv, **envp;
   *		{
   *		    int dummy;
   *
   *		    GC_stackbottom = (ptr_t)(&dummy);
   *		    return(real_main(argc, argv, envp));
   *		}
   *
   *
   * Each architecture may also define the style of virtual dirty bit
   * implementation to be used:
   *   MPROTECT_VDB: Write protect the heap and catch faults.
   *   GWW_VDB: Use win32 GetWriteWatch primitive.
   *   PROC_VDB: Use the SVR4 /proc primitives to read dirty bits.
   *
   * The first and second one may be combined, in which case a runtime
   * selection will be made, based on GetWriteWatch availability.
   *
   * An architecture may define DYNAMIC_LOADING if dynamic_load.c
   * defined GC_register_dynamic_libraries() for the architecture.
   *
   * An architecture may define PREFETCH(x) to preload the cache with *x.
   * This defaults to a no-op.
   *
   * PREFETCH_FOR_WRITE(x) is used if *x is about to be written.
   *
   * An architecture may also define CLEAR_DOUBLE(x) to be a fast way to
   * clear the two words at GC_malloc-aligned address x.  By default,
   * word stores of 0 are used instead.
   *
   * HEAP_START may be defined as the initial address hint for mmap-based
   * allocation.
   */
  
  /* If we are using a recent version of gcc, we can use __builtin_unwind_init()
   * to push the relevant registers onto the stack.
   */
  # if defined(__GNUC__) && ((__GNUC__ >= 3) || \
  			   (__GNUC__ == 2 && __GNUC_MINOR__ >= 8)) \
  		       && !defined(__INTEL_COMPILER) && !defined(__PATHCC__)
  #   define HAVE_BUILTIN_UNWIND_INIT
  # endif
  
  # define STACK_GRAN 0x1000000
  # ifdef M68K
  #   define MACH_TYPE "M68K"
  #   define ALIGNMENT 2
  #   ifdef OPENBSD
  #	define OS_TYPE "OPENBSD"
  #	define HEURISTIC2
  #	ifdef __ELF__
  #	  define DATASTART GC_data_start
  #	  define DYNAMIC_LOADING
  #	else
  	  extern char etext[];
  #	  define DATASTART ((ptr_t)(etext))
  #       endif
  #   endif
  #   ifdef NETBSD
  #	define OS_TYPE "NETBSD"
  #	define HEURISTIC2
  #	ifdef __ELF__
  #	  define DATASTART GC_data_start
  #	  define DYNAMIC_LOADING
  #	else
  	  extern char etext[];
  #	  define DATASTART ((ptr_t)(etext))
  #       endif
  #   endif
  #   ifdef LINUX
  #       define OS_TYPE "LINUX"
  #       define LINUX_STACKBOTTOM
  #       define MPROTECT_VDB
  #       ifdef __ELF__
  #            define DYNAMIC_LOADING
  #	     include <features.h>
  #	     if defined(__GLIBC__)&& __GLIBC__>=2
  #              define SEARCH_FOR_DATA_START
  #	     else /* !GLIBC2 */
                 extern char **__environ;
  #              define DATASTART ((ptr_t)(&__environ))
                               /* hideous kludge: __environ is the first */
                               /* word in crt0.o, and delimits the start */
                               /* of the data segment, no matter which   */
                               /* ld options were passed through.        */
                               /* We could use _etext instead, but that  */
                               /* would include .rodata, which may       */
                               /* contain large read-only data tables    */
                               /* that we'd rather not scan.             */
  #	     endif /* !GLIBC2 */
               extern int _end[];
  #            define DATAEND (_end)
  #       else
               extern int etext[];
  #            define DATASTART ((ptr_t)((((word) (etext)) + 0xfff) & ~0xfff))
  #       endif
  #   endif
  #   ifdef AMIGA
  #	define OS_TYPE "AMIGA"
   	    	/* STACKBOTTOM and DATASTART handled specially	*/
   	    	/* in os_dep.c					*/
  # 	define DATAEND	/* not needed */
  #	define GETPAGESIZE() 4096
  #   endif
  #   ifdef MACOS
  #     ifndef __LOWMEM__
  #     include <LowMem.h>
  #     endif
  #     define OS_TYPE "MACOS"
  			/* see os_dep.c for details of global data segments. */
  #     define STACKBOTTOM ((ptr_t) LMGetCurStackBase())
  #     define DATAEND	/* not needed */
  #     define GETPAGESIZE() 4096
  #   endif
  #   ifdef NEXT
  #	define OS_TYPE "NEXT"
  #	define DATASTART ((ptr_t) get_etext())
  #	define STACKBOTTOM ((ptr_t) 0x4000000)
  #	define DATAEND	/* not needed */
  #   endif
  # endif
  
  # if defined(POWERPC)
  #   define MACH_TYPE "POWERPC"
  #   ifdef MACOS
  #     define ALIGNMENT 2  /* Still necessary?  Could it be 4?	*/
  #     ifndef __LOWMEM__
  #     include <LowMem.h>
  #     endif
  #     define OS_TYPE "MACOS"
  			/* see os_dep.c for details of global data segments. */
  #     define STACKBOTTOM ((ptr_t) LMGetCurStackBase())
  #     define DATAEND  /* not needed */
  #   endif
  #   ifdef LINUX
  #     if defined(__powerpc64__)
  #       define ALIGNMENT 8
  #       define CPP_WORDSZ 64
  #       ifndef HBLKSIZE
  #         define HBLKSIZE 4096
  #       endif
  #     else
  #       define ALIGNMENT 4
  #     endif
  #     define OS_TYPE "LINUX"
        /* HEURISTIC1 has been reliably reported to fail for a 32-bit	*/
        /* executable on a 64 bit kernel.					*/
  #     define LINUX_STACKBOTTOM
  #     define DYNAMIC_LOADING
  #     define SEARCH_FOR_DATA_START
        extern int _end[];
  #     define DATAEND (_end)
  #   endif
  #   ifdef DARWIN
  #     define OS_TYPE "DARWIN"
  #     define DYNAMIC_LOADING
  #     if defined(__ppc64__)
  #       define ALIGNMENT 8
  #       define CPP_WORDSZ 64
  #       define STACKBOTTOM ((ptr_t) 0x7fff5fc00000)
  #       define CACHE_LINE_SIZE 64
  #       ifndef HBLKSIZE
  #         define HBLKSIZE 4096
  #       endif
  #     else
  #       define ALIGNMENT 4
  #       define STACKBOTTOM ((ptr_t) 0xc0000000)
  #     endif
        /* XXX: see get_end(3), get_etext() and get_end() should not be used.
  	 These aren't used when dyld support is enabled (it is by default) */
  #     define DATASTART ((ptr_t) get_etext())
  #     define DATAEND	((ptr_t) get_end())
  #     define USE_MMAP
  #     define USE_MMAP_ANON
  #     ifdef GC_DARWIN_THREADS
  #       define MPROTECT_VDB
  #     endif
  #     include <unistd.h>
  #     define GETPAGESIZE() getpagesize()
  #     if defined(USE_PPC_PREFETCH) && defined(__GNUC__)
  	/* The performance impact of prefetches is untested */
  #	define PREFETCH(x) \
  	  __asm__ __volatile__ ("dcbt 0,%0" : : "r" ((const void *) (x)))
  #	define PREFETCH_FOR_WRITE(x) \
  	  __asm__ __volatile__ ("dcbtst 0,%0" : : "r" ((const void *) (x)))
  #     endif
        /* There seems to be some issues with trylock hanging on darwin. This
  	 should be looked into some more */
  #     define NO_PTHREAD_TRYLOCK
  #   endif
  #   ifdef FREEBSD
  #       define ALIGNMENT 4
  #       define OS_TYPE "FREEBSD"
  #       ifndef GC_FREEBSD_THREADS
  #           define MPROTECT_VDB
  #       endif
  #       define SIG_SUSPEND SIGUSR1
  #       define SIG_THR_RESTART SIGUSR2
  #       define FREEBSD_STACKBOTTOM
  #       ifdef __ELF__
  #           define DYNAMIC_LOADING
  #       endif
          extern char etext[];
          extern char * GC_FreeBSDGetDataStart();
  #       define DATASTART GC_FreeBSDGetDataStart(0x1000, &etext)
  #   endif
  #   ifdef NETBSD
  #     define ALIGNMENT 4
  #     define OS_TYPE "NETBSD"
  #     define HEURISTIC2
        extern char etext[];
  #     define DATASTART GC_data_start
  #     define DYNAMIC_LOADING
  #   endif
  #   ifdef AIX
  #     define OS_TYPE "AIX"
  #     undef ALIGNMENT /* in case it's defined	*/
  #     ifdef IA64
  #       undef IA64
            /* DOB: some AIX installs stupidly define IA64 in */
            /* /usr/include/sys/systemcfg.h   		    */
  #     endif
  #     ifdef __64BIT__
  #       define ALIGNMENT 8
  #       define CPP_WORDSZ 64
  #       define STACKBOTTOM ((ptr_t)0x1000000000000000)
  #     else
  #       define ALIGNMENT 4
  #       define CPP_WORDSZ 32
  #       define STACKBOTTOM ((ptr_t)((ulong)&errno))
  #     endif
  #     define USE_MMAP
  #     define USE_MMAP_ANON
  	/* From AIX linker man page:
  	_text Specifies the first location of the program.
  	_etext Specifies the first location after the program.
  	_data Specifies the first location of the data.
  	_edata Specifies the first location after the initialized data
  	_end or end Specifies the first location after all data.
  	*/
        extern int _data[], _end[];
  #     define DATASTART ((ptr_t)((ulong)_data))
  #     define DATAEND ((ptr_t)((ulong)_end))
        extern int errno;
  #     define DYNAMIC_LOADING
  	/* For really old versions of AIX, this may have to be removed. */
  #   endif
  
  #   ifdef NOSYS
  #     define ALIGNMENT 4
  #     define OS_TYPE "NOSYS"
        extern void __end[], __dso_handle[];
  #     define DATASTART (__dso_handle)  /* OK, that's ugly.  */
  #     define DATAEND (__end)
  	/* Stack starts at 0xE0000000 for the simulator.  */
  #     undef STACK_GRAN
  #     define STACK_GRAN 0x10000000
  #     define HEURISTIC1
  #   endif
  # endif
  
  # ifdef VAX
  #   define MACH_TYPE "VAX"
  #   define ALIGNMENT 4	/* Pointers are longword aligned by 4.2 C compiler */
      extern char etext[];
  #   define DATASTART ((ptr_t)(etext))
  #   ifdef BSD
  #	define OS_TYPE "BSD"
  #	define HEURISTIC1
  			/* HEURISTIC2 may be OK, but it's hard to test. */
  #   endif
  #   ifdef ULTRIX
  #	define OS_TYPE "ULTRIX"
  #	define STACKBOTTOM ((ptr_t) 0x7fffc800)
  #   endif
  # endif
  
  # ifdef SPARC
  #   define MACH_TYPE "SPARC"
  #   if defined(__arch64__) || defined(__sparcv9)
  #     define ALIGNMENT 8
  #     define CPP_WORDSZ 64
  #     define ELF_CLASS ELFCLASS64
  #   else
  #     define ALIGNMENT 4	/* Required by hardware	*/
  #     define CPP_WORDSZ 32
  #   endif
      /* Don't define USE_ASM_PUSH_REGS.  We do use an asm helper, but	*/
      /* not to push the registers on the mark stack.			*/
  #   ifdef SOLARIS
  #	define OS_TYPE "SOLARIS"
  	extern int _etext[];
  	extern int _end[];
  	extern ptr_t GC_SysVGetDataStart(size_t, ptr_t);
  #       define DATASTART GC_SysVGetDataStart(0x10000, (ptr_t)_etext)
  #	define DATAEND (_end)
  #	if !defined(USE_MMAP) && defined(REDIRECT_MALLOC)
  #	    define USE_MMAP
  	    /* Otherwise we now use calloc.  Mmap may result in the	*/
  	    /* heap interleaved with thread stacks, which can result in	*/
  	    /* excessive blacklisting.  Sbrk is unusable since it	*/
  	    /* doesn't interact correctly with the system malloc.	*/
  #	endif
  #       ifdef USE_MMAP
  #         define HEAP_START (ptr_t)0x40000000
  #       else
  #	  define HEAP_START DATAEND
  #       endif
  #	define PROC_VDB
  /*	HEURISTIC1 reportedly no longer works under 2.7.  		*/
  /*  	HEURISTIC2 probably works, but this appears to be preferable.	*/
  /*	Apparently USRSTACK is defined to be USERLIMIT, but in some	*/
  /* 	installations that's undefined.  We work around this with a	*/
  /*	gross hack:							*/
  #       include <sys/vmparam.h>
  #	ifdef USERLIMIT
  	  /* This should work everywhere, but doesn't.	*/
  #	  define STACKBOTTOM USRSTACK
  #       else
  #	  define HEURISTIC2
  #       endif
  #	include <unistd.h>
  #       define GETPAGESIZE()  sysconf(_SC_PAGESIZE)
  		/* getpagesize() appeared to be missing from at least one */
  		/* Solaris 5.4 installation.  Weird.			  */
  #	define DYNAMIC_LOADING
  #   endif
  #   ifdef DRSNX
  #	define OS_TYPE "DRSNX"
  	extern ptr_t GC_SysVGetDataStart(size_t, ptr_t);
  	extern int etext[];
  #       define DATASTART GC_SysVGetDataStart(0x10000, (ptr_t)etext)
  #	define MPROTECT_VDB
  #       define STACKBOTTOM ((ptr_t) 0xdfff0000)
  #	define DYNAMIC_LOADING
  #   endif
  #   ifdef LINUX
  #     define OS_TYPE "LINUX"
  #     ifdef __ELF__
  #       define DYNAMIC_LOADING
  #     else
            Linux Sparc/a.out not supported
  #     endif
        extern int _end[];
        extern int _etext[];
  #     define DATAEND (_end)
  #     define SVR4
        extern ptr_t GC_SysVGetDataStart(size_t, ptr_t);
  #     ifdef __arch64__
  #	define DATASTART GC_SysVGetDataStart(0x100000, (ptr_t)_etext)
  #     else
  #       define DATASTART GC_SysVGetDataStart(0x10000, (ptr_t)_etext)
  #     endif
  #     define LINUX_STACKBOTTOM
  #   endif
  #   ifdef OPENBSD
  #     define OS_TYPE "OPENBSD"
  #     define STACKBOTTOM ((ptr_t) 0xf8000000)
        extern int etext[];
  #     define DATASTART ((ptr_t)(etext))
  #   endif
  #   ifdef NETBSD
  #     define OS_TYPE "NETBSD"
  #     define HEURISTIC2
  #     ifdef __ELF__
  #	define DATASTART GC_data_start
  #	define DYNAMIC_LOADING
  #     else
  	extern char etext[];
  #	define DATASTART ((ptr_t)(etext))
  #     endif
  #   endif
  #   ifdef FREEBSD
  #	define OS_TYPE "FREEBSD"
  #	define SIG_SUSPEND SIGUSR1
  #	define SIG_THR_RESTART SIGUSR2
  #	define FREEBSD_STACKBOTTOM
  #	ifdef __ELF__
  #	    define DYNAMIC_LOADING
  #	endif
  	extern char etext[];
  	extern char edata[];
  	extern char end[];
  #	define NEED_FIND_LIMIT
  #	define DATASTART ((ptr_t)(&etext))
  #	define DATAEND (GC_find_limit (DATASTART, TRUE))
  #	define DATASTART2 ((ptr_t)(&edata))
  #	define DATAEND2 ((ptr_t)(&end))
  #   endif
  # endif
  
  # ifdef I386
  #   define MACH_TYPE "I386"
  #   if defined(__LP64__) || defined(_WIN64)
  #     error This should be handled as X86_64
  #   else
  #     define CPP_WORDSZ 32
  #     define ALIGNMENT 4
  			/* Appears to hold for all "32 bit" compilers	*/
  			/* except Borland.  The -a4 option fixes 	*/
  			/* Borland.					*/
                          /* Ivan Demakov: For Watcom the option is -zp4. */
  #   endif
  #   ifdef SEQUENT
  #	define OS_TYPE "SEQUENT"
  	extern int etext[];
  #       define DATASTART ((ptr_t)((((word) (etext)) + 0xfff) & ~0xfff))
  #       define STACKBOTTOM ((ptr_t) 0x3ffff000) 
  #   endif
  #   ifdef BEOS
  #     define OS_TYPE "BEOS"
  #     include <OS.h>
  #     define GETPAGESIZE() B_PAGE_SIZE
        extern int etext[];
  #     define DATASTART ((ptr_t)((((word) (etext)) + 0xfff) & ~0xfff))
  #   endif
  #   ifdef HAIKU
  #     define OS_TYPE "HAIKU"
  #     include <OS.h>
  #     define GETPAGESIZE() B_PAGE_SIZE
  #     extern int etext[];
  #     define DATASTART ((ptr_t)((((word) (etext)) + 0xfff) & ~0xfff))
  #   endif
  #   ifdef SOLARIS
  #	define OS_TYPE "SOLARIS"
          extern int _etext[], _end[];
    	extern ptr_t GC_SysVGetDataStart(size_t, ptr_t);
  #       define DATASTART GC_SysVGetDataStart(0x1000, (ptr_t)_etext)
  #	define DATAEND (_end)
  /*	# define STACKBOTTOM ((ptr_t)(_start)) worked through 2.7,  	*/
  /*      but reportedly breaks under 2.8.  It appears that the stack	*/
  /* 	base is a property of the executable, so this should not break	*/
  /* 	old executables.						*/
  /*  	HEURISTIC2 probably works, but this appears to be preferable.	*/
  #       include <sys/vm.h>
  #	define STACKBOTTOM USRSTACK
  /* At least in Solaris 2.5, PROC_VDB gives wrong values for dirty bits. */
  /* It appears to be fixed in 2.8 and 2.9.				*/
  #	ifdef SOLARIS25_PROC_VDB_BUG_FIXED
  #	  define PROC_VDB
  #	endif
  #	define DYNAMIC_LOADING
  #	if !defined(USE_MMAP) && defined(REDIRECT_MALLOC)
  #	    define USE_MMAP
  	    /* Otherwise we now use calloc.  Mmap may result in the	*/
  	    /* heap interleaved with thread stacks, which can result in	*/
  	    /* excessive blacklisting.  Sbrk is unusable since it	*/
  	    /* doesn't interact correctly with the system malloc.	*/
  #	endif
  #       ifdef USE_MMAP
  #         define HEAP_START (ptr_t)0x40000000
  #       else
  #	  define HEAP_START DATAEND
  #       endif
  #   endif
  #   ifdef SCO
  #	define OS_TYPE "SCO"
  	extern int etext[];
  #   	define DATASTART ((ptr_t)((((word) (etext)) + 0x3fffff) \
  				  & ~0x3fffff) \
  				 +((word)etext & 0xfff))
  #	define STACKBOTTOM ((ptr_t) 0x7ffffffc)
  #   endif
  #   ifdef SCO_ELF
  #       define OS_TYPE "SCO_ELF"
          extern int etext[];
  #       define DATASTART ((ptr_t)(etext))
  #       define STACKBOTTOM ((ptr_t) 0x08048000)
  #       define DYNAMIC_LOADING
  #	define ELF_CLASS ELFCLASS32
  #   endif
  #   ifdef DGUX
  #	define OS_TYPE "DGUX"
  	extern int _etext, _end;
  	extern ptr_t GC_SysVGetDataStart(size_t, ptr_t);
  #	define DATASTART GC_SysVGetDataStart(0x1000, (ptr_t)(&_etext))
  #	define DATAEND (&_end)
  #	define STACK_GROWS_DOWN
  #	define HEURISTIC2
  #	include <unistd.h>
  #	define GETPAGESIZE()  sysconf(_SC_PAGESIZE)
  #	define DYNAMIC_LOADING
  #	ifndef USE_MMAP
  #	  define USE_MMAP
  #	endif /* USE_MMAP */
  #	define MAP_FAILED (void *) -1
  #	ifdef USE_MMAP
  #	  define HEAP_START (ptr_t)0x40000000
  #	else /* USE_MMAP */
  #	  define HEAP_START DATAEND
  #	endif /* USE_MMAP */
  #   endif /* DGUX */
  
  #   ifdef LINUX
  #	define OS_TYPE "LINUX"
  #       define LINUX_STACKBOTTOM
  #	if 0
  #	  define HEURISTIC1
  #         undef STACK_GRAN
  #         define STACK_GRAN 0x10000000
  	  /* STACKBOTTOM is usually 0xc0000000, but this changes with	*/
  	  /* different kernel configurations.  In particular, systems	*/
  	  /* with 2GB physical memory will usually move the user	*/
  	  /* address space limit, and hence initial SP to 0x80000000.	*/
  #       endif
  #       if !defined(GC_LINUX_THREADS) || !defined(REDIRECT_MALLOC)
  #	    define MPROTECT_VDB
  #	else
  	    /* We seem to get random errors in incremental mode,	*/
  	    /* possibly because Linux threads is itself a malloc client */
  	    /* and can't deal with the signals.				*/
  #	endif
  #	define HEAP_START (ptr_t)0x1000
  		/* This encourages mmap to give us low addresses,	*/
  		/* thus allowing the heap to grow to ~3GB		*/
  #       ifdef __ELF__
  #            define DYNAMIC_LOADING
  #	     ifdef UNDEFINED	/* includes ro data */
  	       extern int _etext[];
  #              define DATASTART ((ptr_t)((((word) (_etext)) + 0xfff) & ~0xfff))
  #	     endif
  #	     include <features.h>
  #	     if defined(__GLIBC__) && __GLIBC__ >= 2
  #		 define SEARCH_FOR_DATA_START
  #	     else
       	         extern char **__environ;
  #                define DATASTART ((ptr_t)(&__environ))
  			      /* hideous kludge: __environ is the first */
  			      /* word in crt0.o, and delimits the start */
  			      /* of the data segment, no matter which   */
  			      /* ld options were passed through.        */
  			      /* We could use _etext instead, but that  */
  			      /* would include .rodata, which may       */
  			      /* contain large read-only data tables    */
  			      /* that we'd rather not scan.		*/
  #	     endif
  	     extern int _end[];
  #	     define DATAEND (_end)
  #	else
  	     extern int etext[];
  #            define DATASTART ((ptr_t)((((word) (etext)) + 0xfff) & ~0xfff))
  #       endif
  #	ifdef USE_I686_PREFETCH
  	  /* FIXME: Thus should use __builtin_prefetch, but we'll leave that	*/
  	  /* for the next rtelease.						*/
  #	  define PREFETCH(x) \
  	    __asm__ __volatile__ ("	prefetchnta	%0": : "m"(*(char *)(x)))
  	    /* Empirically prefetcht0 is much more effective at reducing	*/
  	    /* cache miss stalls for the targetted load instructions.  But it	*/
  	    /* seems to interfere enough with other cache traffic that the net	*/
  	    /* result is worse than prefetchnta.				*/
  #         if 0 
  	    /* Using prefetches for write seems to have a slight negative	*/
  	    /* impact on performance, at least for a PIII/500.			*/
  #	    define PREFETCH_FOR_WRITE(x) \
  	      __asm__ __volatile__ ("	prefetcht0	%0": : "m"(*(char *)(x)))
  #	  endif
  #	endif
  #	ifdef USE_3DNOW_PREFETCH
  #	  define PREFETCH(x) \
  	    __asm__ __volatile__ ("	prefetch	%0": : "m"(*(char *)(x)))
  #	  define PREFETCH_FOR_WRITE(x) \
  	    __asm__ __volatile__ ("	prefetchw	%0": : "m"(*(char *)(x)))
  #	endif
  #   endif
  #   ifdef CYGWIN32
  #       define OS_TYPE "CYGWIN32"
  #       define DATASTART ((ptr_t)GC_DATASTART)  /* From gc.h */
  #       define DATAEND	 ((ptr_t)GC_DATAEND)
  #	undef STACK_GRAN
  #       define STACK_GRAN 0x10000
  #       define HEURISTIC1
  #   endif
  #   ifdef OS2
  #	define OS_TYPE "OS2"
   	    	/* STACKBOTTOM and DATASTART are handled specially in 	*/
  		/* os_dep.c. OS2 actually has the right			*/
  		/* system call!						*/
  #	define DATAEND	/* not needed */
  #   endif
  #   ifdef MSWIN32
  #	define OS_TYPE "MSWIN32"
  		/* STACKBOTTOM and DATASTART are handled specially in 	*/
  		/* os_dep.c.						*/
  #       if !defined(__WATCOMC__)
  #	  define MPROTECT_VDB
  	  /* We also avoided doing this in the past with GC_WIN32_THREADS */
  	  /* Hopefully that's fixed.					  */
  #	endif
  #	if _MSC_VER >= 1300  /* .NET, i.e. > VisualStudio 6	*/
  #         define GWW_VDB
  #	endif
  #       define DATAEND  /* not needed */
  #   endif
  #   ifdef MSWINCE
  #	define OS_TYPE "MSWINCE"
  #       define DATAEND  /* not needed */
  #   endif
  #   ifdef DJGPP
  #       define OS_TYPE "DJGPP"
  #       include "stubinfo.h"
          extern int etext[];
          extern int _stklen;
          extern int __djgpp_stack_limit;
  #       define DATASTART ((ptr_t)((((word) (etext)) + 0x1ff) & ~0x1ff))
  /* #       define STACKBOTTOM ((ptr_t)((word) _stubinfo + _stubinfo->size \
                                                       + _stklen)) */
  #       define STACKBOTTOM ((ptr_t)((word) __djgpp_stack_limit + _stklen))
  		/* This may not be right.  */
  #   endif
  #   ifdef OPENBSD
  #	define OS_TYPE "OPENBSD"
  #   endif
  #   ifdef FREEBSD
  #	define OS_TYPE "FREEBSD"
  #	ifndef GC_FREEBSD_THREADS
  #	    define MPROTECT_VDB
  #	endif
  #	ifdef __GLIBC__
  #	    define SIG_SUSPEND		(32+6)
  #	    define SIG_THR_RESTART	(32+5)
  	    extern int _end[];
  #	    define DATAEND (_end)
  #	else
  #	    define SIG_SUSPEND SIGUSR1
  #	    define SIG_THR_RESTART SIGUSR2
  #	endif
  #	define FREEBSD_STACKBOTTOM
  #	ifdef __ELF__
  #	    define DYNAMIC_LOADING
  #	endif
  	extern char etext[];
  	extern char * GC_FreeBSDGetDataStart(size_t, ptr_t);
  #	define DATASTART GC_FreeBSDGetDataStart(0x1000, (ptr_t)etext)
  #   endif
  #   ifdef NETBSD
  #	define OS_TYPE "NETBSD"
  #	ifdef __ELF__
  #	    define DYNAMIC_LOADING
  #	endif
  #   endif
  #   ifdef THREE86BSD
  #	define OS_TYPE "THREE86BSD"
  #   endif
  #   ifdef BSDI
  #	define OS_TYPE "BSDI"
  #   endif
  #   if defined(OPENBSD) || defined(NETBSD) \
          || defined(THREE86BSD) || defined(BSDI)
  #	define HEURISTIC2
  	extern char etext[];
  #	define DATASTART ((ptr_t)(etext))
  #   endif
  #   ifdef NEXT
  #	define OS_TYPE "NEXT"
  #	define DATASTART ((ptr_t) get_etext())
  #	define STACKBOTTOM ((ptr_t)0xc0000000)
  #	define DATAEND	/* not needed */
  #   endif
  #   ifdef DOS4GW
  #     define OS_TYPE "DOS4GW"
        extern long __nullarea;
        extern char _end;
        extern char *_STACKTOP;
        /* Depending on calling conventions Watcom C either precedes
           or does not precedes with undescore names of C-variables.
           Make sure startup code variables always have the same names.  */
        #pragma aux __nullarea "*";
        #pragma aux _end "*";
  #     define STACKBOTTOM ((ptr_t) _STACKTOP)
                           /* confused? me too. */
  #     define DATASTART ((ptr_t) &__nullarea)
  #     define DATAEND ((ptr_t) &_end)
  #   endif
  #   ifdef HURD
  #     define OS_TYPE "HURD"
  #     define STACK_GROWS_DOWN
  #     define HEURISTIC2
  #     define SIG_SUSPEND SIGUSR1
  #     define SIG_THR_RESTART SIGUSR2
  #     define SEARCH_FOR_DATA_START
        extern int _end[];
  #     define DATAEND ((ptr_t) (_end))
  /* #     define MPROTECT_VDB  Not quite working yet? */
  #     define DYNAMIC_LOADING
  #   endif
  #   ifdef DARWIN
  #     define OS_TYPE "DARWIN"
  #     define DARWIN_DONT_PARSE_STACK
  #     define DYNAMIC_LOADING
        /* XXX: see get_end(3), get_etext() and get_end() should not be used.
  	 These aren't used when dyld support is enabled (it is by default) */
  #     define DATASTART ((ptr_t) get_etext())
  #     define DATAEND	((ptr_t) get_end())
  #     define STACKBOTTOM ((ptr_t) 0xc0000000)
  #     define USE_MMAP
  #     define USE_MMAP_ANON
  #     ifdef GC_DARWIN_THREADS
  #       define MPROTECT_VDB
  #     endif
  #     include <unistd.h>
  #     define GETPAGESIZE() getpagesize()
        /* There seems to be some issues with trylock hanging on darwin. This
  	 should be looked into some more */
  #      define NO_PTHREAD_TRYLOCK
  #   endif /* DARWIN */
  # endif
  
  # ifdef NS32K
  #   define MACH_TYPE "NS32K"
  #   define ALIGNMENT 4
      extern char **environ;
  #   define DATASTART ((ptr_t)(&environ))
  			      /* hideous kludge: environ is the first   */
  			      /* word in crt0.o, and delimits the start */
  			      /* of the data segment, no matter which   */
  			      /* ld options were passed through.        */
  #   define STACKBOTTOM ((ptr_t) 0xfffff000) /* for Encore */
  # endif
  
  # ifdef MIPS
  #   define MACH_TYPE "MIPS"
  #   ifdef LINUX
        /* This was developed for a linuxce style platform.  Probably	*/
        /* needs to be tweaked for workstation class machines.		*/
  #     define OS_TYPE "LINUX"
  #     define DYNAMIC_LOADING
        extern int _end[];
  #     define DATAEND (_end)
        extern int __data_start[];
  #     define DATASTART ((ptr_t)(__data_start))
  #     define ALIGNMENT 4
  #     if __GLIBC__ == 2 && __GLIBC_MINOR__ >= 2 || __GLIBC__ > 2
  #        define LINUX_STACKBOTTOM
  #     else
  #        define STACKBOTTOM 0x80000000
  #     endif
  #   endif /* Linux */
  #   ifdef EWS4800
  #      define HEURISTIC2
  #      if defined(_MIPS_SZPTR) && (_MIPS_SZPTR == 64)
           extern int _fdata[], _end[];
  #        define DATASTART ((ptr_t)_fdata)
  #        define DATAEND ((ptr_t)_end)
  #        define CPP_WORDSZ _MIPS_SZPTR
  #        define ALIGNMENT (_MIPS_SZPTR/8)
  #      else
           extern int etext[], edata[], end[];
           extern int _DYNAMIC_LINKING[], _gp[];
  #        define DATASTART ((ptr_t)((((word)etext + 0x3ffff) & ~0x3ffff) \
                 + ((word)etext & 0xffff)))
  #        define DATAEND (edata)
  #        define DATASTART2 (_DYNAMIC_LINKING \
                 ? (ptr_t)(((word)_gp + 0x8000 + 0x3ffff) & ~0x3ffff) \
                 : (ptr_t)edata)
  #        define DATAEND2 (end)
  #        define ALIGNMENT 4
  #      endif
  #      define OS_TYPE "EWS4800"
  #   endif
  #   ifdef ULTRIX
  #	define HEURISTIC2
  #       define DATASTART (ptr_t)0x10000000
  			      /* Could probably be slightly higher since */
  			      /* startup code allocates lots of stuff.   */
  #	define OS_TYPE "ULTRIX"
  #       define ALIGNMENT 4
  #   endif
  #   ifdef IRIX5
  #	define HEURISTIC2
          extern int _fdata[];
  #       define DATASTART ((ptr_t)(_fdata))
  #       ifdef USE_MMAP
  #         define HEAP_START (ptr_t)0x30000000
  #       else
  #	  define HEAP_START DATASTART
  #       endif
  			      /* Lowest plausible heap address.		*/
  			      /* In the MMAP case, we map there.	*/
  			      /* In either case it is used to identify	*/
  			      /* heap sections so they're not 		*/
  			      /* considered as roots.			*/
  #	define OS_TYPE "IRIX5"
  /*#       define MPROTECT_VDB DOB: this should work, but there is evidence */
  /* 	  	of recent breakage.					   */
  #       ifdef _MIPS_SZPTR
  #	  define CPP_WORDSZ _MIPS_SZPTR
  #	  define ALIGNMENT (_MIPS_SZPTR/8)
  #	else
  #         define ALIGNMENT 4
  #	endif
  #	define DYNAMIC_LOADING
  #   endif
  #   ifdef MSWINCE
  #       define OS_TYPE "MSWINCE"
  #       define ALIGNMENT 4
  #       define DATAEND /* not needed */
  #   endif
  #   if defined(NETBSD)
  #     define OS_TYPE "NETBSD"
  #     define ALIGNMENT 4
  #     define HEURISTIC2
  #     ifdef __ELF__
          extern int etext[];
  #       define DATASTART GC_data_start
  #       define NEED_FIND_LIMIT
  #       define DYNAMIC_LOADING
  #     else
  #       define DATASTART ((ptr_t) 0x10000000)
  #       define STACKBOTTOM ((ptr_t) 0x7ffff000)
  #     endif /* _ELF_ */
  #  endif
  #  if defined(NONSTOP)
  #    define CPP_WORDSZ 32
  #    define OS_TYPE "NONSTOP"
  #    define ALIGNMENT 4
  #    define DATASTART ((ptr_t) 0x08000000)
       extern char **environ;
  #    define DATAEND ((ptr_t)(environ - 0x10))
  #    define STACKBOTTOM ((ptr_t) 0x4fffffff)
  #   endif
  # endif
  
  # ifdef HP_PA
  #   define MACH_TYPE "HP_PA"
  #   ifdef __LP64__
  #     define CPP_WORDSZ 64
  #     define ALIGNMENT 8
  #   else
  #     define CPP_WORDSZ 32
  #     define ALIGNMENT 4
  #   endif
  #   if !defined(GC_HPUX_THREADS) && !defined(GC_LINUX_THREADS)
  #     ifndef LINUX /* For now. */
  #       define MPROTECT_VDB
  #     endif
  #   else
  #     ifdef PARALLEL_MARK
  #	define USE_MARK_BYTES
  		/* Minimize compare-and-swap usage.		*/
  #     endif
  #   endif
  #   define STACK_GROWS_UP
  #   ifdef HPUX
  #     define OS_TYPE "HPUX"
        extern int __data_start[];
  #     define DATASTART ((ptr_t)(__data_start))
  #     if 0
  	/* The following appears to work for 7xx systems running HP/UX	*/
  	/* 9.xx Furthermore, it might result in much faster		*/
  	/* collections than HEURISTIC2, which may involve scanning	*/
  	/* segments that directly precede the stack.  It is not the	*/
  	/* default, since it may not work on older machine/OS		*/
  	/* combinations. (Thanks to Raymond X.T. Nijssen for uncovering	*/
  	/* this.)							*/
  #       define STACKBOTTOM ((ptr_t) 0x7b033000)  /* from /etc/conf/h/param.h */
  #     else
  	/* Gustavo Rodriguez-Rivera suggested changing HEURISTIC2	*/
  	/* to this.  Note that the GC must be initialized before the	*/
      	/* first putenv call.						*/
  	extern char ** environ;
  #       define STACKBOTTOM ((ptr_t)environ)
  #     endif
  #     define DYNAMIC_LOADING
  #     include <unistd.h>
  #     define GETPAGESIZE() sysconf(_SC_PAGE_SIZE)
  #     ifndef __GNUC__
  #       define PREFETCH(x)  { \
                                register long addr = (long)(x); \
                                (void) _asm ("LDW", 0, 0, addr, 0); \
                              }
  #     endif
  #   endif /* HPUX */
  #   ifdef LINUX
  #     define OS_TYPE "LINUX"
  #     define LINUX_STACKBOTTOM
  #     define DYNAMIC_LOADING
  #     define SEARCH_FOR_DATA_START
        extern int _end[];
  #     define DATAEND (&_end)
  #   endif /* LINUX */
  # endif /* HP_PA */
  
  # ifdef ALPHA
  #   define MACH_TYPE "ALPHA"
  #   define ALIGNMENT 8
  #   define CPP_WORDSZ 64
  #   ifdef NETBSD
  #	define OS_TYPE "NETBSD"
  #	define HEURISTIC2
  #	define DATASTART GC_data_start
  #	define ELFCLASS32 32
  #	define ELFCLASS64 64
  #	define ELF_CLASS ELFCLASS64
  #       define DYNAMIC_LOADING
  #   endif
  #   ifdef OPENBSD
  #	define OS_TYPE "OPENBSD"
  #	define HEURISTIC2
  #   	ifdef __ELF__	/* since OpenBSD/Alpha 2.9 */
  #	   define DATASTART GC_data_start
  #   	   define ELFCLASS32 32
  #   	   define ELFCLASS64 64
  #   	   define ELF_CLASS ELFCLASS64
  #       else		/* ECOFF, until OpenBSD/Alpha 2.7 */
  #   	   define DATASTART ((ptr_t) 0x140000000)
  #   	endif
  #   endif
  #   ifdef FREEBSD
  #	define OS_TYPE "FREEBSD"
  /* MPROTECT_VDB is not yet supported at all on FreeBSD/alpha. */
  #	define SIG_SUSPEND SIGUSR1
  #	define SIG_THR_RESTART SIGUSR2
  #	define FREEBSD_STACKBOTTOM
  #	ifdef __ELF__
  #	    define DYNAMIC_LOADING
  #	endif
  /* Handle unmapped hole alpha*-*-freebsd[45]* puts between etext and edata. */
  	extern char etext[];
  	extern char edata[];
  	extern char end[];
  #	define NEED_FIND_LIMIT
  #	define DATASTART ((ptr_t)(&etext))
  #	define DATAEND (GC_find_limit (DATASTART, TRUE))
  #	define DATASTART2 ((ptr_t)(&edata))
  #	define DATAEND2 ((ptr_t)(&end))
  #   endif
  #   ifdef OSF1
  #	define OS_TYPE "OSF1"
  #   	define DATASTART ((ptr_t) 0x140000000)
  	extern int _end[];
  #   	define DATAEND ((ptr_t) &_end)
   	extern char ** environ;
  	/* round up from the value of environ to the nearest page boundary */
  	/* Probably breaks if putenv is called before collector 	   */
  	/* initialization.						   */
  #	define STACKBOTTOM ((ptr_t)(((word)(environ) | (getpagesize()-1))+1))
  /* #   	define HEURISTIC2 */
  	/* Normally HEURISTIC2 is too conervative, since		*/
  	/* the text segment immediately follows the stack.		*/
  	/* Hence we give an upper pound.				*/
  	/* This is currently unused, since we disabled HEURISTIC2	*/
      	extern int __start[];
  #   	define HEURISTIC2_LIMIT ((ptr_t)((word)(__start) & ~(getpagesize()-1)))
  #	ifndef GC_OSF1_THREADS
  	  /* Unresolved signal issues with threads.	*/
  #   	  define MPROTECT_VDB
  #       endif
  #   	define DYNAMIC_LOADING
  #   endif
  #   ifdef LINUX
  #       define OS_TYPE "LINUX"
  #       define LINUX_STACKBOTTOM
  #       ifdef __ELF__
  #	  define SEARCH_FOR_DATA_START
  #         define DYNAMIC_LOADING
  #       else
  #           define DATASTART ((ptr_t) 0x140000000)
  #       endif
  	extern int _end[];
  #	define DATAEND (_end)
  #	define MPROTECT_VDB
  		/* Has only been superficially tested.  May not	*/
  		/* work on all versions.			*/
  #   endif
  # endif
  
  # ifdef IA64
  #   define MACH_TYPE "IA64"
  #   ifdef HPUX
  #	ifdef _ILP32
  #	  define CPP_WORDSZ 32
  	    /* Requires 8 byte alignment for malloc */
  #   	  define ALIGNMENT 4
  #       else
  #	  ifndef _LP64
  		---> unknown ABI
  #         endif
  #	  define CPP_WORDSZ 64
  	    /* Requires 16 byte alignment for malloc */
  #         define ALIGNMENT 8
  #       endif
  #       define OS_TYPE "HPUX"	
          extern int __data_start[];
  #       define DATASTART ((ptr_t)(__data_start))
          /* Gustavo Rodriguez-Rivera suggested changing HEURISTIC2	*/
          /* to this.  Note that the GC must be initialized before the	*/
      	/* first putenv call.						*/
  	extern char ** environ;
  #       define STACKBOTTOM ((ptr_t)environ)
  #       define HPUX_STACKBOTTOM
  #       define DYNAMIC_LOADING
  #       include <unistd.h>
  #       define GETPAGESIZE() sysconf(_SC_PAGE_SIZE)
   	/* The following was empirically determined, and is probably	*/
  	/* not very robust.						*/
  	/* Note that the backing store base seems to be at a nice 	*/
  	/* address minus one page.					*/
  #	define BACKING_STORE_DISPLACEMENT 0x1000000
  #	define BACKING_STORE_ALIGNMENT 0x1000
  	extern ptr_t GC_register_stackbottom;
  #	define BACKING_STORE_BASE GC_register_stackbottom
  	/* Known to be wrong for recent HP/UX versions!!!	*/
  #   endif
  #   ifdef LINUX
  #   	define CPP_WORDSZ 64
  #   	define ALIGNMENT 8
  #       define OS_TYPE "LINUX"
  	/* The following works on NUE and older kernels:	*/
  /* #       define STACKBOTTOM ((ptr_t) 0xa000000000000000l)	*/
  	/* This does not work on NUE:				*/
  #       define LINUX_STACKBOTTOM
  	/* We also need the base address of the register stack	*/
  	/* backing store.  This is computed in 			*/
  	/* GC_linux_register_stack_base based on the following	*/
  	/* constants:						*/
  #       define BACKING_STORE_ALIGNMENT 0x100000
  #       define BACKING_STORE_DISPLACEMENT 0x80000000
  	extern ptr_t GC_register_stackbottom;
  #	define BACKING_STORE_BASE GC_register_stackbottom
  #	define SEARCH_FOR_DATA_START
  #	ifdef __GNUC__
  #         define DYNAMIC_LOADING
  #	else
  	  /* In the Intel compiler environment, we seem to end up with  */
  	  /* statically linked executables and an undefined reference	*/
  	  /* to _DYNAMIC						*/
  #  	endif
  #	define MPROTECT_VDB
  		/* Requires Linux 2.3.47 or later.	*/
  	extern int _end[];
  #	define DATAEND (_end)
  #       ifdef __GNUC__
  #	  ifndef __INTEL_COMPILER
  #	    define PREFETCH(x) \
  	      __asm__ ("	lfetch	[%0]": : "r"(x))
  #	    define PREFETCH_FOR_WRITE(x) \
  	      __asm__ ("	lfetch.excl	[%0]": : "r"(x))
  #	    define CLEAR_DOUBLE(x) \
  	      __asm__ ("	stf.spill	[%0]=f0": : "r"((void *)(x)))
  #	  else
  #           include <ia64intrin.h>
  #	    define PREFETCH(x) \
  	      __lfetch(__lfhint_none, (x))
  #	    define PREFETCH_FOR_WRITE(x) \
  	      __lfetch(__lfhint_nta,  (x))
  #	    define CLEAR_DOUBLE(x) \
  	      __stf_spill((void *)(x), 0)
  #	  endif // __INTEL_COMPILER
  #       endif
  #   endif
  #   ifdef MSWIN32
        /* FIXME: This is a very partial guess.  There is no port, yet.	*/
  #     define OS_TYPE "MSWIN32"
  		/* STACKBOTTOM and DATASTART are handled specially in 	*/
  		/* os_dep.c.						*/
  #     define DATAEND  /* not needed */
  #     if defined(_WIN64)
  #       define CPP_WORDSZ 64
  #     else
  #       define CPP_WORDSZ 32   /* Is this possible?	*/
  #     endif
  #     define ALIGNMENT 8
  #     define STRTOULL _strtoui64
  #   endif
  # endif
  
  # ifdef M88K
  #   define MACH_TYPE "M88K"
  #   define ALIGNMENT 4
      extern int etext[];
  #   ifdef CX_UX
  #	define OS_TYPE "CX_UX"
  #       define DATASTART ((((word)etext + 0x3fffff) & ~0x3fffff) + 0x10000)
  #   endif
  #   ifdef  DGUX
  #	define OS_TYPE "DGUX"
  	extern ptr_t GC_SysVGetDataStart(size_t, ptr_t);
  #       define DATASTART GC_SysVGetDataStart(0x10000, (ptr_t)etext)
  #   endif
  #   define STACKBOTTOM ((char*)0xf0000000) /* determined empirically */
  # endif
  
  # ifdef S370
      /* If this still works, and if anyone cares, this should probably	*/
      /* be moved to the S390 category.					*/
  #   define MACH_TYPE "S370"
  #   define ALIGNMENT 4	/* Required by hardware	*/
  #   ifdef UTS4
  #       define OS_TYPE "UTS4"
  	extern int etext[];
  	extern int _etext[];
  	extern int _end[];
  	extern ptr_t GC_SysVGetDataStart(size_t, ptr_t);
  #       define DATASTART GC_SysVGetDataStart(0x10000, (ptr_t)_etext)
  #	define DATAEND (_end)
  #	define HEURISTIC2
  #   endif
  # endif
  
  # ifdef S390
  #   define MACH_TYPE "S390"
  #   ifndef __s390x__
  #   define ALIGNMENT 4
  #   define CPP_WORDSZ 32
  #   else
  #   define ALIGNMENT 8
  #   define CPP_WORDSZ 64
  #   ifndef HBLKSIZE
  #     define HBLKSIZE 4096
  #   endif
  #   endif
  #   ifdef LINUX
  #       define OS_TYPE "LINUX"
  #       define LINUX_STACKBOTTOM
  #       define DYNAMIC_LOADING
  	extern int __data_start[];
  #       define DATASTART ((ptr_t)(__data_start))
      extern int _end[];
  #   define DATAEND (_end)
  #   define CACHE_LINE_SIZE 256
  #   define GETPAGESIZE() 4096
  #   endif
  # endif
  
  # ifdef ARM32
  #   define CPP_WORDSZ 32
  #   define MACH_TYPE "ARM32"
  #   define ALIGNMENT 4
  #   ifdef NETBSD
  #       define OS_TYPE "NETBSD"
  #       define HEURISTIC2
  #	ifdef __ELF__
  #          define DATASTART GC_data_start
  #	   define DYNAMIC_LOADING
  #	else
             extern char etext[];
  #          define DATASTART ((ptr_t)(etext))
  #	endif
  #   endif
  #   ifdef LINUX
  #       define OS_TYPE "LINUX"
  #       define LINUX_STACKBOTTOM
  #       undef STACK_GRAN
  #       define STACK_GRAN 0x10000000
  #       ifdef __ELF__
  #            define DYNAMIC_LOADING
  #	     include <features.h>
  #	     if defined(__GLIBC__) && __GLIBC__ >= 2
  #		 define SEARCH_FOR_DATA_START
  #	     else
       	         extern char **__environ;
  #                define DATASTART ((ptr_t)(&__environ))
  			      /* hideous kludge: __environ is the first */
  			      /* word in crt0.o, and delimits the start */
  			      /* of the data segment, no matter which   */
  			      /* ld options were passed through.        */
  			      /* We could use _etext instead, but that  */
  			      /* would include .rodata, which may       */
  			      /* contain large read-only data tables    */
  			      /* that we'd rather not scan.		*/
  #	     endif
  	     extern int _end[];
  #	     define DATAEND (_end)
  #	else
  	     extern int etext[];
  #            define DATASTART ((ptr_t)((((word) (etext)) + 0xfff) & ~0xfff))
  #       endif
  #   endif
  #   ifdef MSWINCE
  #     define OS_TYPE "MSWINCE"
  #     define DATAEND /* not needed */
  #   endif
  #   ifdef NOSYS
        /* __data_start is usually defined in the target linker script.  */
        extern int __data_start[];
  #     define DATASTART (ptr_t)(__data_start)
        /* __stack_base__ is set in newlib/libc/sys/arm/crt0.S  */
        extern void *__stack_base__;
  #     define STACKBOTTOM ((ptr_t) (__stack_base__))
  #   endif
  #endif
  
  # ifdef CRIS
  #   define MACH_TYPE "CRIS"
  #   define CPP_WORDSZ 32
  #   define ALIGNMENT 1
  #   define OS_TYPE "LINUX"
  #   define DYNAMIC_LOADING
  #   define LINUX_STACKBOTTOM
  #   define SEARCH_FOR_DATA_START
        extern int _end[];
  #   define DATAEND (_end)
  # endif
  
  # ifdef SH
  #   define MACH_TYPE "SH"
  #   define ALIGNMENT 4
  #   ifdef MSWINCE
  #     define OS_TYPE "MSWINCE"
  #     define DATAEND /* not needed */
  #   endif
  #   ifdef LINUX
  #     define OS_TYPE "LINUX"
  #     define LINUX_STACKBOTTOM
  #     define DYNAMIC_LOADING
  #     define SEARCH_FOR_DATA_START
        extern int _end[];
  #     define DATAEND (_end)
  #   endif
  #   ifdef NETBSD
  #      define OS_TYPE "NETBSD"
  #      define HEURISTIC2
  #      define DATASTART GC_data_start
  #      define DYNAMIC_LOADING
  #   endif
  # endif
   
  # ifdef SH4
  #   define MACH_TYPE "SH4"
  #   define OS_TYPE "MSWINCE"
  #   define ALIGNMENT 4
  #   define DATAEND /* not needed */
  # endif
  
  # ifdef M32R
  #   define CPP_WORDSZ 32
  #   define MACH_TYPE "M32R"
  #   define ALIGNMENT 4
  #   ifdef LINUX
  #     define OS_TYPE "LINUX"
  #     define LINUX_STACKBOTTOM
  #     undef STACK_GRAN
  #     define STACK_GRAN 0x10000000
  #     define DYNAMIC_LOADING
  #     define SEARCH_FOR_DATA_START
        extern int _end[];
  #     define DATAEND (_end)
  #   endif
  # endif
  
  # ifdef X86_64
  #   define MACH_TYPE "X86_64"
  #   define ALIGNMENT 8
  #   define CPP_WORDSZ 64
  #   ifndef HBLKSIZE
  #     define HBLKSIZE 4096
  #   endif
  #   define CACHE_LINE_SIZE 64
  #   ifdef LINUX
  #	define OS_TYPE "LINUX"
  #       define LINUX_STACKBOTTOM
  #       if !defined(GC_LINUX_THREADS) || !defined(REDIRECT_MALLOC)
  #	    define MPROTECT_VDB
  #	else
  	    /* We seem to get random errors in incremental mode,	*/
  	    /* possibly because Linux threads is itself a malloc client */
  	    /* and can't deal with the signals.				*/
  #	endif
  #       ifdef __ELF__
  #            define DYNAMIC_LOADING
  #	     ifdef UNDEFINED	/* includes ro data */
  	       extern int _etext[];
  #              define DATASTART ((ptr_t)((((word) (_etext)) + 0xfff) & ~0xfff))
  #	     endif
  #	     include <features.h>
  #	     define SEARCH_FOR_DATA_START
  	     extern int _end[];
  #	     define DATAEND (_end)
  #	else
  	     extern int etext[];
  #            define DATASTART ((ptr_t)((((word) (etext)) + 0xfff) & ~0xfff))
  #       endif
  #       if defined(__GNUC__) && __GNUC__ >= 3
  #	    define PREFETCH(x) __builtin_prefetch((x), 0, 0)
  #	    define PREFETCH_FOR_WRITE(x) __builtin_prefetch((x), 1)
  #	endif
  #   endif
  #   ifdef DARWIN
  #     define OS_TYPE "DARWIN"
  #     define DARWIN_DONT_PARSE_STACK
  #     define DYNAMIC_LOADING
        /* XXX: see get_end(3), get_etext() and get_end() should not be used.
  	 These aren't used when dyld support is enabled (it is by default) */
  #     define DATASTART ((ptr_t) get_etext())
  #     define DATAEND	((ptr_t) get_end())
  #     define STACKBOTTOM ((ptr_t) 0x7fff5fc00000)
  #     define USE_MMAP
  #     define USE_MMAP_ANON
  #     ifdef GC_DARWIN_THREADS
  #       define MPROTECT_VDB
  #     endif
  #     include <unistd.h>
  #     define GETPAGESIZE() getpagesize()
        /* There seems to be some issues with trylock hanging on darwin. This
  	 should be looked into some more */
  #     define NO_PTHREAD_TRYLOCK
  #   endif
  #   ifdef FREEBSD
  #	define OS_TYPE "FREEBSD"
  #	ifndef GC_FREEBSD_THREADS
  #	    define MPROTECT_VDB
  #	endif
  #	ifdef __GLIBC__
  #	    define SIG_SUSPEND		(32+6)
  #	    define SIG_THR_RESTART	(32+5)
  	    extern int _end[];
  #	    define DATAEND (_end)
  #	else
  #	    define SIG_SUSPEND SIGUSR1
  #	    define SIG_THR_RESTART SIGUSR2
  #	endif
  #	define FREEBSD_STACKBOTTOM
  #	ifdef __ELF__
  #	    define DYNAMIC_LOADING
  #	endif
  	extern char etext[];
  	extern char * GC_FreeBSDGetDataStart();
  #	define DATASTART GC_FreeBSDGetDataStart(0x1000, &etext)
  #   endif
  #   ifdef NETBSD
  #	define OS_TYPE "NETBSD"
  #	ifdef __ELF__
  #	    define DYNAMIC_LOADING
  #	endif
  #	define HEURISTIC2
  	extern char etext[];
  #	define SEARCH_FOR_DATA_START
  #   endif
  #   ifdef SOLARIS
  #	define OS_TYPE "SOLARIS"
  #	define ELF_CLASS ELFCLASS64
          extern int _etext[], _end[];
    	extern ptr_t GC_SysVGetDataStart(size_t, ptr_t);
  #       define DATASTART GC_SysVGetDataStart(0x1000, (ptr_t)_etext)
  #	define DATAEND (_end)
  /*	# define STACKBOTTOM ((ptr_t)(_start)) worked through 2.7,  	*/
  /*      but reportedly breaks under 2.8.  It appears that the stack	*/
  /* 	base is a property of the executable, so this should not break	*/
  /* 	old executables.						*/
  /*  	HEURISTIC2 probably works, but this appears to be preferable.	*/
  /*	Apparently USRSTACK is defined to be USERLIMIT, but in some	*/
  /* 	installations that's undefined.  We work around this with a	*/
  /*	gross hack:							*/
  #       include <sys/vmparam.h>
  #	ifdef USERLIMIT
  	  /* This should work everywhere, but doesn't.	*/
  #	  define STACKBOTTOM USRSTACK
  #       else
  #	  define HEURISTIC2
  #       endif
  /* At least in Solaris 2.5, PROC_VDB gives wrong values for dirty bits. */
  /* It appears to be fixed in 2.8 and 2.9.				*/
  #	ifdef SOLARIS25_PROC_VDB_BUG_FIXED
  #	  define PROC_VDB
  #	endif
  #	define DYNAMIC_LOADING
  #	if !defined(USE_MMAP) && defined(REDIRECT_MALLOC)
  #	    define USE_MMAP
  	    /* Otherwise we now use calloc.  Mmap may result in the	*/
  	    /* heap interleaved with thread stacks, which can result in	*/
  	    /* excessive blacklisting.  Sbrk is unusable since it	*/
  	    /* doesn't interact correctly with the system malloc.	*/
  #	endif
  #       ifdef USE_MMAP
  #         define HEAP_START (ptr_t)0x40000000
  #       else
  #	  define HEAP_START DATAEND
  #       endif
  #   endif
  #   ifdef MSWIN32
  #	define OS_TYPE "MSWIN32"
  		/* STACKBOTTOM and DATASTART are handled specially in 	*/
  		/* os_dep.c.						*/
  #       if !defined(__WATCOMC__)
  #	  define MPROTECT_VDB
  	  /* We also avoided doing this in the past with GC_WIN32_THREADS */
  	  /* Hopefully that's fixed.					  */
  #	endif
  #	if _MSC_VER >= 1300  /* .NET, i.e. > VisualStudio 6	*/
  #         define GWW_VDB
  #	endif
  #       define DATAEND  /* not needed */
  #   endif
  # endif
  
  #if defined(LINUX) && defined(USE_MMAP)
      /* The kernel may do a somewhat better job merging mappings etc.	*/
      /* with anonymous mappings.						*/
  #   define USE_MMAP_ANON
  #endif
  
  #if defined(GC_LINUX_THREADS) && defined(REDIRECT_MALLOC)
      /* Nptl allocates thread stacks with mmap, which is fine.  But it	*/
      /* keeps a cache of thread stacks.  Thread stacks contain the	*/
      /* thread control blocks.  These in turn contain a pointer to	*/
      /* (sizeof (void *) from the beginning of) the dtv for thread-local	*/
      /* storage, which is calloc allocated.  If we don't scan the cached	*/
      /* thread stacks, we appear to lose the dtv.  This tends to		*/
      /* result in something that looks like a bogus dtv count, which	*/
      /* tends to result in a memset call on a block that is way too	*/
      /* large.  Sometimes we're lucky and the process just dies ...	*/
      /* There seems to be a similar issue with some other memory 	*/
      /* allocated by the dynamic loader.					*/
      /* This can be avoided by either:					*/
      /* - Defining USE_PROC_FOR_LIBRARIES here.				*/
      /*   That performs very poorly, precisely because we end up 	*/
      /*   scanning cached stacks.					*/
      /* - Have calloc look at its callers.  That is currently what we do.*/
      /*   In spite of the fact that it is gross and disgusting.		*/
  /* #   define USE_PROC_FOR_LIBRARIES */
  #endif
  
  # ifndef STACK_GROWS_UP
  #   define STACK_GROWS_DOWN
  # endif
  
  # ifndef CPP_WORDSZ
  #   define CPP_WORDSZ 32
  # endif
  
  # ifndef OS_TYPE
  #   define OS_TYPE ""
  # endif
  
  # ifndef DATAEND
      extern int end[];
  #   define DATAEND (end)
  # endif
  
  # if defined(SVR4) && !defined(GETPAGESIZE)
  #    include <unistd.h>
  #    define GETPAGESIZE()  sysconf(_SC_PAGESIZE)
  # endif
  
  # ifndef GETPAGESIZE
  #   if defined(SOLARIS) || defined(IRIX5) || defined(LINUX) \
         || defined(NETBSD) || defined(FREEBSD) || defined(HPUX)
  #	include <unistd.h>
  #   endif
  #   define GETPAGESIZE() getpagesize()
  # endif
  
  # if defined(SOLARIS) || defined(DRSNX) || defined(UTS4)
  	    /* OS has SVR4 generic features.		*/
      	    /* Probably others also qualify.		*/
  #   define SVR4
  # endif
  
  # if defined(SOLARIS) || defined(DRSNX)
  	    /* OS has SOLARIS style semi-undocumented interface */
      	    /* to dynamic loader.				*/
  #   define SOLARISDL
  	    /* OS has SOLARIS style signal handlers.		*/
  #   define SUNOS5SIGS
  # endif
  
  # if defined(HPUX)
  #   define SUNOS5SIGS
  # endif
  
  # if defined(FREEBSD) && \
       (defined(__DragonFly__) || __FreeBSD__ >= 4 || (__FreeBSD_kernel__ >= 4))
  #   define SUNOS5SIGS
  # endif
  
  # ifdef GC_NETBSD_THREADS
  #   define SIGRTMIN 33
  #   define SIGRTMAX 63
  # endif
  
  # if defined(SVR4) || defined(LINUX) || defined(IRIX5) || defined(HPUX) \
  	    || defined(OPENBSD) || defined(NETBSD) || defined(FREEBSD) \
  	    || defined(DGUX) || defined(BSD) \
  	    || defined(AIX) || defined(DARWIN) || defined(OSF1) \
  	    || defined(HURD)
  #   define UNIX_LIKE   /* Basic Unix-like system calls work.	*/
  # endif
  
  # if CPP_WORDSZ != 32 && CPP_WORDSZ != 64
  	   -> bad word size
  # endif
  
  # ifdef PCR
  #   undef DYNAMIC_LOADING
  #   undef STACKBOTTOM
  #   undef HEURISTIC1
  #   undef HEURISTIC2
  #   undef PROC_VDB
  #   undef MPROTECT_VDB
  #   define PCR_VDB
  # endif
  
  # ifdef SMALL_CONFIG
  	/* Presumably not worth the space it takes. */
  #   undef PROC_VDB
  #   undef MPROTECT_VDB
  # endif
  
  # ifdef USE_MUNMAP
  #   undef MPROTECT_VDB  /* Can't deal with address space holes. */
  # endif
  
  # ifdef PARALLEL_MARK
  #   undef MPROTECT_VDB  /* For now.	*/
  # endif
  
  # if !defined(PCR_VDB) && !defined(PROC_VDB) && !defined(MPROTECT_VDB) \
      && !defined(GWW_VDB)
  #   define DEFAULT_VDB
  # endif
  
  # ifndef PREFETCH
  #   define PREFETCH(x)
  #   define NO_PREFETCH
  # endif
  
  # ifndef PREFETCH_FOR_WRITE
  #   define PREFETCH_FOR_WRITE(x)
  #   define NO_PREFETCH_FOR_WRITE
  # endif
  
  # ifndef CACHE_LINE_SIZE
  #   define CACHE_LINE_SIZE 32	/* Wild guess	*/
  # endif
  
  # if defined(LINUX) || defined(HURD) || defined(__GLIBC__)
  #   define REGISTER_LIBRARIES_EARLY
      /* We sometimes use dl_iterate_phdr, which may acquire an internal	*/
      /* lock.  This isn't safe after the world has stopped.  So we must	*/
      /* call GC_register_dynamic_libraries before stopping the world.	*/
      /* For performance reasons, this may be beneficial on other		*/
      /* platforms as well, though it should be avoided in win32.		*/
  # endif /* LINUX */
  
  # if defined(SEARCH_FOR_DATA_START)
      extern ptr_t GC_data_start;
  #   define DATASTART GC_data_start
  # endif
  
  # ifndef CLEAR_DOUBLE
  #   define CLEAR_DOUBLE(x) \
  		((word*)x)[0] = 0; \
  		((word*)x)[1] = 0;
  # endif /* CLEAR_DOUBLE */
  
  # if defined(GC_LINUX_THREADS) && defined(REDIRECT_MALLOC) \
       && !defined(INCLUDE_LINUX_THREAD_DESCR)
      /* Will not work, since libc and the dynamic loader use thread 	*/
      /* locals, sometimes as the only reference.				*/
  #   define INCLUDE_LINUX_THREAD_DESCR
  # endif
  
  # if defined(GC_IRIX_THREADS) && !defined(IRIX5)
  	--> inconsistent configuration
  # endif
  # if defined(GC_LINUX_THREADS) && !defined(LINUX)
  	--> inconsistent configuration
  # endif
  # if defined(GC_NETBSD_THREADS) && !defined(NETBSD)
  	--> inconsistent configuration
  # endif
  # if defined(GC_SOLARIS_THREADS) && !defined(SOLARIS)
  	--> inconsistent configuration
  # endif
  # if defined(GC_HPUX_THREADS) && !defined(HPUX)
  	--> inconsistent configuration
  # endif
  # if defined(GC_AIX_THREADS) && !defined(_AIX)
  	--> inconsistent configuration
  # endif
  # if defined(GC_GNU_THREADS) && !defined(HURD)
  	--> inconsistent configuration
  # endif
  # if defined(GC_WIN32_THREADS) && !defined(MSWIN32) && !defined(CYGWIN32)
  	--> inconsistent configuration
  # endif
  
  # if defined(PCR) || defined(GC_WIN32_THREADS) || defined(GC_PTHREADS)
  #   define THREADS
  # endif
  
  # if !defined(USE_MARK_BITS) && !defined(USE_MARK_BYTES)
  #   if defined(THREADS) && defined(PARALLEL_MARK)
  #     define USE_MARK_BYTES
  #   else
  #     define USE_MARK_BITS
  #   endif
  # endif
  
  # if defined(MSWINCE)
  #   define NO_GETENV
  # endif
  
  # if defined(SPARC)
  #   define ASM_CLEAR_CODE	/* Stack clearing is crucial, and we 	*/
  				/* include assembly code to do it well.	*/
  # endif
  
    /* Can we save call chain in objects for debugging?   	        */
    /* SET NFRAMES (# of saved frames) and NARGS (#of args for each 	*/
    /* frame) to reasonable values for the platform.			*/
    /* Set SAVE_CALL_CHAIN if we can.  SAVE_CALL_COUNT can be specified 	*/
    /* at build time, though we feel free to adjust it slightly.		*/
    /* Define NEED_CALLINFO if we either save the call stack or 		*/
    /* GC_ADD_CALLER is defined.						*/
    /* GC_CAN_SAVE_CALL_STACKS is set in gc.h.				*/
  
  #if defined(SPARC)
  # define CAN_SAVE_CALL_ARGS
  #endif
  #if (defined(I386) || defined(X86_64)) && (defined(LINUX) || defined(__GLIBC__))
  	    /* SAVE_CALL_CHAIN is supported if the code is compiled to save	*/
  	    /* frame pointers by default, i.e. no -fomit-frame-pointer flag.	*/
  # define CAN_SAVE_CALL_ARGS
  #endif
  
  # if defined(SAVE_CALL_COUNT) && !defined(GC_ADD_CALLER) \
  	     && defined(GC_CAN_SAVE_CALL_STACKS)
  #   define SAVE_CALL_CHAIN 
  # endif
  # ifdef SAVE_CALL_CHAIN
  #   if defined(SAVE_CALL_NARGS) && defined(CAN_SAVE_CALL_ARGS)
  #     define NARGS SAVE_CALL_NARGS
  #   else
  #     define NARGS 0	/* Number of arguments to save for each call.	*/
  #   endif
  # endif
  # ifdef SAVE_CALL_CHAIN
  #   ifndef SAVE_CALL_COUNT
  #     define NFRAMES 6	/* Number of frames to save. Even for		*/
  			/* alignment reasons.				*/
  #   else
  #     define NFRAMES ((SAVE_CALL_COUNT + 1) & ~1)
  #   endif
  #   define NEED_CALLINFO
  # endif /* SAVE_CALL_CHAIN */
  # ifdef GC_ADD_CALLER
  #   define NFRAMES 1
  #   define NARGS 0
  #   define NEED_CALLINFO
  # endif
  
  # if defined(MAKE_BACK_GRAPH) && !defined(DBG_HDRS_ALL)
  #   define DBG_HDRS_ALL
  # endif
  
  # if defined(POINTER_MASK) && !defined(POINTER_SHIFT)
  #   define POINTER_SHIFT 0
  # endif
  
  # if defined(POINTER_SHIFT) && !defined(POINTER_MASK)
  #   define POINTER_MASK ((GC_word)(-1))
  # endif
  
  # if !defined(FIXUP_POINTER) && defined(POINTER_MASK)
  #   define FIXUP_POINTER(p) (p) = ((p) & (POINTER_MASK) << POINTER_SHIFT)
  # endif
  
  # if defined(FIXUP_POINTER)
  #   define NEED_FIXUP_POINTER 1
  # else
  #   define NEED_FIXUP_POINTER 0
  #   define FIXUP_POINTER(p)
  # endif
  
  # if !defined(MARK_BIT_PER_GRANULE) && !defined(MARK_BIT_PER_OBJ)
  #   define MARK_BIT_PER_GRANULE	/* Usually faster */
  # endif
  
  /* Some static sanity tests.	*/
  # if defined(MARK_BIT_PER_GRANULE) && defined(MARK_BIT_PER_OBJ)
  #   error Define only one of MARK_BIT_PER_GRANULE and MARK_BIT_PER_OBJ.
  # endif
  
  # if defined(STACK_GROWS_UP) && defined(STACK_GROWS_DOWN)
  #   error "Only one of STACK_GROWS_UP and STACK_GROWS_DOWN should be defd."
  # endif
  # if !defined(STACK_GROWS_UP) && !defined(STACK_GROWS_DOWN)
  #   error "One of STACK_GROWS_UP and STACK_GROWS_DOWN should be defd."
  # endif
  
  # if defined(REDIRECT_MALLOC) && defined(THREADS) && !defined(LINUX)
  #   error "REDIRECT_MALLOC with THREADS works at most on Linux."
  # endif
  
  #ifdef GC_PRIVATE_H
  	/* This relies on some type definitions from gc_priv.h, from	*/
          /* where it's normally included.				*/
  	/*								*/
  	/* How to get heap memory from the OS:				*/
  	/* Note that sbrk()-like allocation is preferred, since it 	*/
  	/* usually makes it possible to merge consecutively allocated	*/
  	/* chunks.  It also avoids unintented recursion with		*/
  	/* -DREDIRECT_MALLOC.						*/
  	/* GET_MEM() returns a HLKSIZE aligned chunk.			*/
  	/* 0 is taken to mean failure. 					*/
  	/* In the case os USE_MMAP, the argument must also be a 	*/
  	/* physical page size.						*/
  	/* GET_MEM is currently not assumed to retrieve 0 filled space, */
  	/* though we should perhaps take advantage of the case in which */
  	/* does.							*/
  	struct hblk;	/* See gc_priv.h.	*/
  # if defined(PCR)
      char * real_malloc();
  #   define GET_MEM(bytes) HBLKPTR(real_malloc((size_t)bytes + GC_page_size) \
  					  + GC_page_size-1)
  # elif defined(OS2)
      void * os2_alloc(size_t bytes);
  #   define GET_MEM(bytes) HBLKPTR((ptr_t)os2_alloc((size_t)bytes \
  					    + GC_page_size) \
  					    + GC_page_size-1)
  # elif defined(NEXT) || defined(DOS4GW) || defined(NONSTOP) || \
  		 (defined(AMIGA) && !defined(GC_AMIGA_FASTALLOC)) || \
  		 (defined(SOLARIS) && !defined(USE_MMAP))
  #   define GET_MEM(bytes) HBLKPTR((size_t) calloc(1, (size_t)bytes + GC_page_size) \
  					             + GC_page_size-1)
  # elif defined(MSWIN32)
      extern ptr_t GC_win32_get_mem();
  #   define GET_MEM(bytes) (struct hblk *)GC_win32_get_mem(bytes)
  # elif defined(MACOS)
  #   if defined(USE_TEMPORARY_MEMORY)
        extern Ptr GC_MacTemporaryNewPtr(size_t size, Boolean clearMemory);
  #     define GET_MEM(bytes) HBLKPTR( \
  			    GC_MacTemporaryNewPtr(bytes + GC_page_size, true) \
  			    + GC_page_size-1)
  #   else
  #     define GET_MEM(bytes) HBLKPTR( \
  				NewPtrClear(bytes + GC_page_size) + GC_page_size-1)
  #   endif
  # elif defined(MSWINCE)
      extern ptr_t GC_wince_get_mem();
  #   define GET_MEM(bytes) (struct hblk *)GC_wince_get_mem(bytes)
  # elif defined(AMIGA) && defined(GC_AMIGA_FASTALLOC)
      extern void *GC_amiga_get_mem(size_t size);
  #   define GET_MEM(bytes) HBLKPTR((size_t) \
  			  GC_amiga_get_mem((size_t)bytes + GC_page_size) \
  			  + GC_page_size-1)
  # else
      extern ptr_t GC_unix_get_mem();
  #   define GET_MEM(bytes) (struct hblk *)GC_unix_get_mem(bytes)
  # endif
  
  #endif /* GC_PRIVATE_H */
  
  # endif /* GCCONFIG_H */
  