/* Copyright (C) 1990, Digital Equipment Corporation.         */
/* All rights reserved.                                       */
/* See the file COPYRIGHT for a full description.             */

/* Last modified on Wed Jul 18 01:34:29 1990 by muller        */

/* for DS3100 */

/* This depends on the direction in which the stack grows */

extern char* _ThreadSup__stackLimit;
#define CHECKSTACKOVERFLOW  \
  { char foo; if (&foo <= _ThreadSup__stackLimit) \
            _M3Runtime__StackOverflow (); }


/* This is actually the default value used by the linker */

IMPORT etext;
#define IS_CLOSURE(p)    (((char*)p) > ((char*)&etext))


/* How to check for NIL pointers:
   NICHECKA and NILCHECKB must evaluate their argument e (a char*) and
   generate a trap if it is NIL (0).
   The compiler generates NILCHECKA when there is a future reference to
   e[0..1023]; otherwise NICHECKB. 
   Thus, if referencing one of the first 1024 bytes of virtual memory
   causes a trap, NILCHECKA can just evaluate e; the future reference
   will generate the trap. */

volatile char nil_check_char;

#define NILCHECKA(e)    e;
#define NILCHECKB(e)    nil_check_char = ((char*)(e))[-1];


/* The garbage collector needs to know two things:
   - what is the alignment of pointers in the stacks ?
   - what is the alignment of objects ? */

/* The following definition expresses in bytes the amount by which the
pointer sweeping the stacks to discover pointers to roots have to be
advanced.  */
#define STACK_INC  4		/* pointers in stacks are word-aligned */

/* The allocator aligns all the structures it allocates to satisify any
   possble alignment constraint, in the style of malloc. The quantity is
   expressed in words. */ 
#define ALIGNMENT 2		/* objects are word aligned */


/* The type 'signed_char' is 'signed char' in ANSI-C,
   but CC may not like that */
typedef signed char  signed_char;