mark.c

	my_top = GC_mark_stack_top;
	n_on_stack = my_top - my_first_nonempty + 1;
        if (0 == n_on_stack) {
	    GC_acquire_mark_lock();
            my_top = GC_mark_stack_top;
            n_on_stack = my_top - my_first_nonempty + 1;
	    if (0 == n_on_stack) {
		GC_active_count--;
		GC_ASSERT(GC_active_count <= GC_helper_count);
		/* Other markers may redeposit objects	*/
		/* on the stack.				*/
		if (0 == GC_active_count) GC_notify_all_marker();
		while (GC_active_count > 0
		       && GC_first_nonempty > GC_mark_stack_top) {
		    /* We will be notified if either GC_active_count	*/
		    /* reaches zero, or if more objects are pushed on	*/
		    /* the global mark stack.				*/
		    GC_wait_marker();
		}
		if (GC_active_count == 0 &&
		    GC_first_nonempty > GC_mark_stack_top) { 
		    GC_bool need_to_notify = FALSE;
		    /* The above conditions can't be falsified while we	*/
		    /* hold the mark lock, since neither 		*/
		    /* GC_active_count nor GC_mark_stack_top can	*/
		    /* change.  GC_first_nonempty can only be		*/
		    /* incremented asynchronously.  Thus we know that	*/
		    /* both conditions actually held simultaneously.	*/
		    GC_helper_count--;
		    if (0 == GC_helper_count) need_to_notify = TRUE;
#		    ifdef PRINTSTATS
		      GC_printf1(
		        "Finished mark helper %lu\n", (unsigned long)id);
#   		    endif
		    GC_release_mark_lock();
		    if (need_to_notify) GC_notify_all_marker();
		    return;
		}
		/* else there's something on the stack again, or	*/
		/* another helper may push something.			*/
		GC_active_count++;
	        GC_ASSERT(GC_active_count > 0);
		GC_release_mark_lock();
		continue;
	    } else {
		GC_release_mark_lock();
	    }
	}
	n_to_get = ENTRIES_TO_GET;
	if (n_on_stack < 2 * ENTRIES_TO_GET) n_to_get = 1;
	local_top = GC_steal_mark_stack(my_first_nonempty, my_top,
					local_mark_stack, n_to_get,
				        &my_first_nonempty);
        GC_ASSERT(my_first_nonempty >= GC_mark_stack && 
	          my_first_nonempty <= GC_mark_stack_top + 1);
	GC_do_local_mark(local_mark_stack, local_top);
    }
}

/* Perform Parallel mark.			*/
/* We hold the GC lock, not the mark lock.	*/
/* Currently runs until the mark stack is	*/
/* empty.					*/
void GC_do_parallel_mark()
{
    mse local_mark_stack[LOCAL_MARK_STACK_SIZE];
    mse * local_top;
    mse * my_top;

    GC_acquire_mark_lock();
    GC_ASSERT(I_HOLD_LOCK());
    /* This could be a GC_ASSERT, but it seems safer to keep it on	*/
    /* all the time, especially since it's cheap.			*/
    if (GC_help_wanted || GC_active_count != 0 || GC_helper_count != 0)
	ABORT("Tried to start parallel mark in bad state");
#   ifdef PRINTSTATS
	GC_printf1("Starting marking for mark phase number %lu\n",
		   (unsigned long)GC_mark_no);
#   endif
    GC_first_nonempty = GC_mark_stack;
    GC_active_count = 0;
    GC_helper_count = 1;
    GC_help_wanted = TRUE;
    GC_release_mark_lock();
    GC_notify_all_marker();
	/* Wake up potential helpers.	*/
    GC_mark_local(local_mark_stack, 0);
    GC_acquire_mark_lock();
    GC_help_wanted = FALSE;
    /* Done; clean up.	*/
    while (GC_helper_count > 0) GC_wait_marker();
    /* GC_helper_count cannot be incremented while GC_help_wanted == FALSE */
#   ifdef PRINTSTATS
	GC_printf1(
	    "Finished marking for mark phase number %lu\n",
	    (unsigned long)GC_mark_no);
#   endif
    GC_mark_no++;
    GC_release_mark_lock();
    GC_notify_all_marker();
}


/* Try to help out the marker, if it's running.	        */
/* We do not hold the GC lock, but the requestor does.	*/
void GC_help_marker(word my_mark_no)
{
    mse local_mark_stack[LOCAL_MARK_STACK_SIZE];
    unsigned my_id;
    mse * my_first_nonempty;

    if (!GC_parallel) return;
    GC_acquire_mark_lock();
    while (GC_mark_no < my_mark_no
           || !GC_help_wanted && GC_mark_no == my_mark_no) {
      GC_wait_marker();
    }
    my_id = GC_helper_count;
    if (GC_mark_no != my_mark_no || my_id >= GC_markers) {
      /* Second test is useful only if original threads can also	*/
      /* act as helpers.  Under Linux they can't.			*/
      GC_release_mark_lock();
      return;
    }
    GC_helper_count = my_id + 1;
    GC_release_mark_lock();
    GC_mark_local(local_mark_stack, my_id);
    /* GC_mark_local decrements GC_helper_count. */
}

#endif /* PARALLEL_MARK */

/* Allocate or reallocate space for mark stack of size s words  */
/* May silently fail.						*/
static void alloc_mark_stack(n)
word n;
{
    mse * new_stack = (mse *)GC_scratch_alloc(n * sizeof(struct GC_ms_entry));
    
    GC_mark_stack_too_small = FALSE;
    if (GC_mark_stack_size != 0) {
        if (new_stack != 0) {
          word displ = (word)GC_mark_stack & (GC_page_size - 1);
          signed_word size = GC_mark_stack_size * sizeof(struct GC_ms_entry);
          
          /* Recycle old space */
	      if (0 != displ) displ = GC_page_size - displ;
	      size = (size - displ) & ~(GC_page_size - 1);
	      if (size > 0) {
	        GC_add_to_heap((struct hblk *)
	      			((word)GC_mark_stack + displ), (word)size);
	      }
          GC_mark_stack = new_stack;
          GC_mark_stack_size = n;
	  GC_mark_stack_limit = new_stack + n;
#	  ifdef CONDPRINT
	    if (GC_print_stats) {
	      GC_printf1("Grew mark stack to %lu frames\n",
		    	 (unsigned long) GC_mark_stack_size);
	    }
#	  endif
        } else {
#	  ifdef CONDPRINT
	    if (GC_print_stats) {
	      GC_printf1("Failed to grow mark stack to %lu frames\n",
		    	 (unsigned long) n);
	    }
#	  endif
        }
    } else {
        if (new_stack == 0) {
            GC_err_printf0("No space for mark stack\n");
            EXIT();
        }
        GC_mark_stack = new_stack;
        GC_mark_stack_size = n;
	GC_mark_stack_limit = new_stack + n;
    }
    GC_mark_stack_top = GC_mark_stack-1;
}

void GC_mark_init()
{
    alloc_mark_stack(INITIAL_MARK_STACK_SIZE);
}

/*
 * Push all locations between b and t onto the mark stack.
 * b is the first location to be checked. t is one past the last
 * location to be checked.
 * Should only be used if there is no possibility of mark stack
 * overflow.
 */
void GC_push_all(bottom, top)
ptr_t bottom;
ptr_t top;
{
    register word length;
    
    bottom = (ptr_t)(((word) bottom + ALIGNMENT-1) & ~(ALIGNMENT-1));
    top = (ptr_t)(((word) top) & ~(ALIGNMENT-1));
    if (top == 0 || bottom == top) return;
    GC_mark_stack_top++;
    if (GC_mark_stack_top >= GC_mark_stack_limit) {
	ABORT("unexpected mark stack overflow");
    }
    length = top - bottom;
#   if GC_DS_TAGS > ALIGNMENT - 1
	length += GC_DS_TAGS;
	length &= ~GC_DS_TAGS;
#   endif
    GC_mark_stack_top -> mse_start = (word *)bottom;
    GC_mark_stack_top -> mse_descr = length;
}

/*
 * Analogous to the above, but push only those pages h with dirty_fn(h) != 0.
 * We use push_fn to actually push the block.
 * Used both to selectively push dirty pages, or to push a block
 * in piecemeal fashion, to allow for more marking concurrency.
 * Will not overflow mark stack if push_fn pushes a small fixed number
 * of entries.  (This is invoked only if push_fn pushes a single entry,
 * or if it marks each object before pushing it, thus ensuring progress
 * in the event of a stack overflow.)
 */
void GC_push_selected(bottom, top, dirty_fn, push_fn)
ptr_t bottom;
ptr_t top;
int (*dirty_fn) GC_PROTO((struct hblk * h));
void (*push_fn) GC_PROTO((ptr_t bottom, ptr_t top));
{
    register struct hblk * h;

    bottom = (ptr_t)(((long) bottom + ALIGNMENT-1) & ~(ALIGNMENT-1));
    top = (ptr_t)(((long) top) & ~(ALIGNMENT-1));

    if (top == 0 || bottom == top) return;
    h = HBLKPTR(bottom + HBLKSIZE);
    if (top <= (ptr_t) h) {
  	if ((*dirty_fn)(h-1)) {
	    (*push_fn)(bottom, top);
	}
	return;
    }
    if ((*dirty_fn)(h-1)) {
        (*push_fn)(bottom, (ptr_t)h);
    }
    while ((ptr_t)(h+1) <= top) {
	if ((*dirty_fn)(h)) {
	    if ((word)(GC_mark_stack_top - GC_mark_stack)
		> 3 * GC_mark_stack_size / 4) {
	 	/* Danger of mark stack overflow */
		(*push_fn)((ptr_t)h, top);
		return;
	    } else {
		(*push_fn)((ptr_t)h, (ptr_t)(h+1));
	    }
	}
	h++;
    }
    if ((ptr_t)h != top) {
	if ((*dirty_fn)(h)) {
            (*push_fn)((ptr_t)h, top);
        }
    }
    if (GC_mark_stack_top >= GC_mark_stack_limit) {
        ABORT("unexpected mark stack overflow");
    }
}

# ifndef SMALL_CONFIG

#ifdef PARALLEL_MARK
    /* Break up root sections into page size chunks to better spread 	*/
    /* out work.							*/
    GC_bool GC_true_func(struct hblk *h) { return TRUE; }
#   define GC_PUSH_ALL(b,t) GC_push_selected(b,t,GC_true_func,GC_push_all);
#else
#   define GC_PUSH_ALL(b,t) GC_push_all(b,t);
#endif


void GC_push_conditional(bottom, top, all)
ptr_t bottom;
ptr_t top;
int all;
{
    if (all) {
      if (GC_dirty_maintained) {
#	ifdef PROC_VDB
	    /* Pages that were never dirtied cannot contain pointers	*/
	    GC_push_selected(bottom, top, GC_page_was_ever_dirty, GC_push_all);
#	else
	    GC_push_all(bottom, top);
#	endif
      } else {
      	GC_push_all(bottom, top);
      }
    } else {
	GC_push_selected(bottom, top, GC_page_was_dirty, GC_push_all);
    }
}
#endif

# if defined(MSWIN32) || defined(MSWINCE)
  void __cdecl GC_push_one(p)
# else
  void GC_push_one(p)
# endif
word p;
{
    GC_PUSH_ONE_STACK(p, MARKED_FROM_REGISTER);
}

struct GC_ms_entry *GC_mark_and_push(obj, mark_stack_ptr, mark_stack_limit, src)
GC_PTR obj;
struct GC_ms_entry * mark_stack_ptr;
struct GC_ms_entry * mark_stack_limit;
GC_PTR *src;
{
   PREFETCH(obj);
   PUSH_CONTENTS(obj, mark_stack_ptr /* modified */, mark_stack_limit, src,
		 was_marked /* internally generated exit label */);
   return mark_stack_ptr;
}

# ifdef __STDC__
#   define BASE(p) (word)GC_base((void *)(p))
# else
#   define BASE(p) (word)GC_base((char *)(p))
# endif

/* Mark and push (i.e. gray) a single object p onto the main	*/
/* mark stack.  Consider p to be valid if it is an interior	*/
/* pointer.							*/
/* The object p has passed a preliminary pointer validity	*/
/* test, but we do not definitely know whether it is valid.	*/
/* Mark bits are NOT atomically updated.  Thus this must be the	*/
/* only thread setting them.					*/
# if defined(PRINT_BLACK_LIST) || defined(KEEP_BACK_PTRS)
    void GC_mark_and_push_stack(p, source)
    ptr_t source;
# else
    void GC_mark_and_push_stack(p)
#   define source 0
# endif
register word p;
{
    register word r;
    register hdr * hhdr; 
    register int displ;
  
    GET_HDR(p, hhdr);
    if (IS_FORWARDING_ADDR_OR_NIL(hhdr)) {
        if (hhdr != 0) {
          r = BASE(p);
	  hhdr = HDR(r);
	  displ = BYTES_TO_WORDS(HBLKDISPL(r));
	}
    } else {
        register map_entry_type map_entry;
        
        displ = HBLKDISPL(p);
        map_entry = MAP_ENTRY((hhdr -> hb_map), displ);
        if (map_entry >= MAX_OFFSET) {
          if (map_entry == OFFSET_TOO_BIG || !GC_all_interior_pointers) {
              r = BASE(p);
	      displ = BYTES_TO_WORDS(HBLKDISPL(r));
	      if (r == 0) hhdr = 0;
          } else {
	      /* Offset invalid, but map reflects interior pointers 	*/
              hhdr = 0;
          }
        } else {
          displ = BYTES_TO_WORDS(displ);
          displ -= map_entry;
          r = (word)((word *)(HBLKPTR(p)) + displ);
        }
    }
    /* If hhdr != 0 then r == GC_base(p), only we did it faster. */
    /* displ is the word index within the block.		 */
    if (hhdr == 0) {
#	ifdef PRINT_BLACK_LIST
	  GC_add_to_black_list_stack(p, source);
#	else
	  GC_add_to_black_list_stack(p);
#	endif
#	undef source  /* In case we had to define it. */
    } else {
	if (!mark_bit_from_hdr(hhdr, displ)) {
	    set_mark_bit_from_hdr(hhdr, displ);
 	    GC_STORE_BACK_PTR(source, (ptr_t)r);
	    PUSH_OBJ((word *)r, hhdr, GC_mark_stack_top,
	             GC_mark_stack_limit);
	}
    }
}

# ifdef TRACE_BUF

# define TRACE_ENTRIES 1000

struct trace_entry {
    char * kind;
    word gc_no;
    word words_allocd;
    word arg1;
    word arg2;
} GC_trace_buf[TRACE_ENTRIES];

int GC_trace_buf_ptr = 0;

void GC_add_trace_entry(char *kind, word arg1, word arg2)
{
    GC_trace_buf[GC_trace_buf_ptr].kind = kind;
    GC_trace_buf[GC_trace_buf_ptr].gc_no = GC_gc_no;
    GC_trace_buf[GC_trace_buf_ptr].words_allocd = GC_words_allocd;
    GC_trace_buf[GC_trace_buf_ptr].arg1 = arg1 ^ 0x80000000;
    GC_trace_buf[GC_trace_buf_ptr].arg2 = arg2 ^ 0x80000000;
    GC_trace_buf_ptr++;
    if (GC_trace_buf_ptr >= TRACE_ENTRIES) GC_trace_buf_ptr = 0;
}

void GC_print_trace(word gc_no, GC_bool lock)
{
    int i;
    struct trace_entry *p;
    
    if (lock) LOCK();
    for (i = GC_trace_buf_ptr-1; i != GC_trace_buf_ptr; i--) {
    	if (i < 0) i = TRACE_ENTRIES-1;
    	p = GC_trace_buf + i;
    	if (p -> gc_no < gc_no || p -> kind == 0) return;
    	printf("Trace:%s (gc:%d,words:%d) 0x%X, 0x%X\n",
    		p -> kind, p -> gc_no, p -> words_allocd,
    		(p -> arg1) ^ 0x80000000, (p -> arg2) ^ 0x80000000);
    }
    printf("Trace incomplete\n");
    if (lock) UNLOCK();
}

# endif /* TRACE_BUF */

/*
 * A version of GC_push_all that treats all interior pointers as valid
 * and scans the entire region immediately, in case the contents
 * change.
 */
void GC_push_all_eager(bottom, top)
ptr_t bottom;
ptr_t top;
{
    word * b = (word *)(((word) bottom + ALIGNMENT-1) & ~(ALIGNMENT-1));
    word * t = (word *)(((word) top) & ~(ALIGNMENT-1));
    register word *p;
    register word q;
    register word *lim;
    register ptr_t greatest_ha = GC_greatest_plausible_heap_addr;
    register ptr_t least_ha = GC_least_plausible_heap_addr;
#   define GC_greatest_plausible_heap_addr greatest_ha
#   define GC_least_plausible_heap_addr least_ha

    if (top == 0) return;
    /* check all pointers in range and push if they appear	*/
    /* to be valid.						*/
      lim = t - 1 /* longword */;
      for (p = b; p <= lim; p = (word *)(((char *)p) + ALIGNMENT)) {
	q = *p;
	GC_PUSH_ONE_STACK(q, p);
      }
#   undef GC_greatest_plausible_heap_addr
#   undef GC_least_plausible_heap_addr
}

#ifndef THREADS
/*
 * A version of GC_push_all that treats all interior pointers as valid
 * and scans part of the area immediately, to make sure that saved
 * register values are not lost.
 * Cold_gc_frame delimits the stack section that must be scanned
 * eagerly.  A zero value indicates that no eager scanning is needed.
 */
void GC_push_all_stack_partially_eager(bottom, top, cold_gc_frame)
ptr_t bottom;
ptr_t top;
ptr_t cold_gc_frame;
{
  if (!NEED_FIXUP_POINTER && GC_all_interior_pointers) {
#   define EAGER_BYTES 1024
    /* Push the hot end of the stack eagerly, so that register values   */
    /* saved inside GC frames are marked before they disappear.		*/
    /* The rest of the marking can be deferred until later.		*/
    if (0 == cold_gc_frame) {
	GC_push_all_stack(bottom, top);
	return;
    }
    GC_ASSERT(bottom <= cold_gc_frame && cold_gc_frame <= top);
#   ifdef STACK_GROWS_DOWN
	GC_push_all(cold_gc_frame - sizeof(ptr_t), top);
	GC_push_all_eager(bottom, cold_gc_frame);
#   else /* STACK_GROWS_UP */
	GC_push_all(bottom, cold_gc_frame + sizeof(ptr_t));
	GC_push_all_eager(cold_gc_frame, top);
#   endif /* STACK_GROWS_UP */
  } else {
    GC_push_all_eager(bottom, top);
  }
# ifdef TRACE_BUF
      GC_add_trace_entry("GC_push_all_stack", bottom, top);
# endif
}
#endif /* !THREADS */

void GC_push_all_stack(bottom, top)
ptr_t bottom;
ptr_t top;
{
  if (!NEED_FIXUP_POINTER && GC_all_interior_pointers) {
    GC_push_all(bottom, top);
  } else {
    GC_push_all_eager(bottom, top);
  }
}

#if !defined(SMALL_CONFIG) && !defined(USE_MARK_BYTES)
/* Push all objects reachable from marked objects in the given block */
/* of size 1 objects.						     */
void GC_push_marked1(h, hhdr)
struct hblk *h;
register hdr * hhdr;
{
    word * mark_word_addr = &(hhdr->hb_marks[0]);
    register word *p;
    word *plim;
    register int i;
    register word q;
    register word mark_word;
    register ptr_t greatest_ha = GC_greatest_plausible_heap_addr;
    register ptr_t least_ha = GC_least_plausible_heap_addr;
    register mse * mark_stack_top = GC_mark_stack_top;
    register mse * mark_stack_limit = GC_mark_stack_limit;
#   define GC_mark_stack_top mark_stack_top
#   define GC_mark_stack_limit mark_stack_limit
#   define GC_greatest_plausible_heap_addr greatest_ha
#   define GC_least_plausible_heap_addr least_ha
    
    p = (word *)(h->hb_body);
    plim = (word *)(((word)h) + HBLKSIZE);

    /* go through all words in block */
	while( p < plim )  {
	    mark_word = *mark_word_addr++;
	    i = 0;
	    while(mark_word != 0) {
	      if (mark_word & 1) {
	          q = p[i];
	          GC_PUSH_ONE_HEAP(q, p + i);
	      }
	      i++;
	      mark_word >>= 1;
	    }
	    p += WORDSZ;
	}
#   undef GC_greatest_plausible_heap_addr
#   undef GC_least_plausible_heap_addr        
#   undef GC_mark_stack_top
#   undef GC_mark_stack_limit
    GC_mark_stack_top = mark_stack_top;
}


#ifndef UNALIGNED

/* Push all objects reachable from marked objects in the given block */
/* of size 2 objects.						     */
void GC_push_marked2(h, hhdr)
struct hblk *h;
register hdr * hhdr;
{
    word * mark_word_addr = &(hhdr->hb_marks[0]);
    register word *p;
    word *plim;
    register int i;
    register word q;
    register word mark_word;
    register ptr_t greatest_ha = GC_greatest_plausible_heap_addr;
    register ptr_t least_ha = GC_least_plausible_heap_addr;
    register mse * mark_stack_top = GC_mark_stack_top;
    register mse * mark_stack_limit = GC_mark_stack_limit;
#   define GC_mark_stack_top mark_stack_top
#   define GC_mark_stack_limit mark_stack_limit
#   define GC_greatest_plausible_heap_addr greatest_ha
#   define GC_least_plausible_heap_addr least_ha
    
    p = (word *)(h->hb_body);
    plim = (word *)(((word)h) + HBLKSIZE);

    /* go through all words in block */
	while( p < plim )  {
	    mark_word = *mark_word_addr++;
	    i = 0;
	    while(mark_word != 0) {
	      if (mark_word & 1) {
	          q = p[i];
	          GC_PUSH_ONE_HEAP(q, p + i);
	          q = p[i+1];
	          GC_PUSH_ONE_HEAP(q, p + i);
	      }
	      i += 2;
	      mark_word >>= 2;
	    }
	    p += WORDSZ;
	}
#   undef GC_greatest_plausible_heap_addr
#   undef GC_least_plausible_heap_addr        
#   undef GC_mark_stack_top
#   undef GC_mark_stack_limit
    GC_mark_stack_top = mark_stack_top;
}

/* Push all objects reachable from marked objects in the given block */
/* of size 4 objects.						     */
/* There is a risk of mark stack overflow here.  But we handle that. */
/* And only unmarked objects get pushed, so it's not very likely.    */
void GC_push_marked4(h, hhdr)
struct hblk *h;
register hdr * hhdr;
{
    word * mark_word_addr = &(hhdr->hb_marks[0]);
    register word *p;
    word *plim;
    register int i;
    register word q;
    register word mark_word;
    register ptr_t greatest_ha = GC_greatest_plausible_heap_addr;
    register ptr_t least_ha = GC_least_plausible_heap_addr;
    register mse * mark_stack_top = GC_mark_stack_top;
    register mse * mark_stack_limit = GC_mark_stack_limit;
#   define GC_mark_stack_top mark_stack_top
#   define GC_mark_stack_limit mark_stack_limit
#   define GC_greatest_plausible_heap_addr greatest_ha
#   define GC_least_plausible_heap_addr least_ha
    
    p = (word *)(h->hb_body);
    plim = (word *)(((word)h) + HBLKSIZE);

    /* go through all words in block */
	while( p < plim )  {
	    mark_word = *mark_word_addr++;
	    i = 0;
	    while(mark_word != 0) {
	      if (mark_word & 1) {
	          q = p[i];
	          GC_PUSH_ONE_HEAP(q, p + i);
	          q = p[i+1];
	          GC_PUSH_ONE_HEAP(q, p + i + 1);
	          q = p[i+2];
	          GC_PUSH_ONE_HEAP(q, p + i + 2);
	          q = p[i+3];
	          GC_PUSH_ONE_HEAP(q, p + i + 3);
	      }
	      i += 4;
	      mark_word >>= 4;
	    }
	    p += WORDSZ;
	}
#   undef GC_greatest_plausible_heap_addr
#   undef GC_least_plausible_heap_addr        
#   undef GC_mark_stack_top
#   undef GC_mark_stack_limit
    GC_mark_stack_top = mark_stack_top;
}

#endif /* UNALIGNED */

#endif /* SMALL_CONFIG */

/* Push all objects reachable from marked objects in the given block */
void GC_push_marked(h, hhdr)
struct hblk *h;
register hdr * hhdr;
{
    register int sz = hhdr -> hb_sz;
    register int descr = hhdr -> hb_descr;
    register word * p;
    register int word_no;
    register word * lim;
    register mse * GC_mark_stack_top_reg;
    register mse * mark_stack_limit = GC_mark_stack_limit;
    
    /* Some quick shortcuts: */
	if ((0 | GC_DS_LENGTH) == descr) return;
        if (GC_block_empty(hhdr)/* nothing marked */) return;
    GC_n_rescuing_pages++;
    GC_objects_are_marked = TRUE;
    if (sz > MAXOBJSZ) {
        lim = (word *)h;
    } else {
        lim = (word *)(h + 1) - sz;
    }
    
    switch(sz) {
#   if !defined(SMALL_CONFIG) && !defined(USE_MARK_BYTES)   
     case 1:
       GC_push_marked1(h, hhdr);
       break;
#   endif
#   if !defined(SMALL_CONFIG) && !defined(UNALIGNED) && \
       !defined(USE_MARK_BYTES)
     case 2:
       GC_push_marked2(h, hhdr);
       break;
     case 4:
       GC_push_marked4(h, hhdr);
       break;
#   endif       
     default:
      GC_mark_stack_top_reg = GC_mark_stack_top;
      for (p = (word *)h, word_no = 0; p <= lim; p += sz, word_no += sz) {
         if (mark_bit_from_hdr(hhdr, word_no)) {
           /* Mark from fields inside the object */
             PUSH_OBJ((word *)p, hhdr, GC_mark_stack_top_reg, mark_stack_limit);
#	     ifdef GATHERSTATS
		/* Subtract this object from total, since it was	*/
		/* added in twice.					*/
		GC_composite_in_use -= sz;
#	     endif
         }
      }
      GC_mark_stack_top = GC_mark_stack_top_reg;
    }
}

#ifndef SMALL_CONFIG
/* Test whether any page in the given block is dirty	*/
GC_bool GC_block_was_dirty(h, hhdr)
struct hblk *h;
register hdr * hhdr;
{
    register int sz = hhdr -> hb_sz;
    
    if (sz <= MAXOBJSZ) {
         return(GC_page_was_dirty(h));
    } else {
    	 register ptr_t p = (ptr_t)h;
         sz = WORDS_TO_BYTES(sz);
         while (p < (ptr_t)h + sz) {
             if (GC_page_was_dirty((struct hblk *)p)) return(TRUE);
             p += HBLKSIZE;
         }
         return(FALSE);
    }
}
#endif /* SMALL_CONFIG */

/* Similar to GC_push_next_marked, but return address of next block	*/
struct hblk * GC_push_next_marked(h)
struct hblk *h;
{
    register hdr * hhdr;
    
    h = GC_next_used_block(h);
    if (h == 0) return(0);
    hhdr = HDR(h);
    GC_push_marked(h, hhdr);
    return(h + OBJ_SZ_TO_BLOCKS(hhdr -> hb_sz));
}

#ifndef SMALL_CONFIG
/* Identical to above, but mark only from dirty pages	*/
struct hblk * GC_push_next_marked_dirty(h)
struct hblk *h;
{
    register hdr * hhdr;
    
    if (!GC_dirty_maintained) { ABORT("dirty bits not set up"); }
    for (;;) {
        h = GC_next_used_block(h);
        if (h == 0) return(0);
        hhdr = HDR(h);
#	ifdef STUBBORN_ALLOC
          if (hhdr -> hb_obj_kind == STUBBORN) {
            if (GC_page_was_changed(h) && GC_block_was_dirty(h, hhdr)) {
                break;
            }
          } else {
            if (GC_block_was_dirty(h, hhdr)) break;
          }
#	else
	  if (GC_block_was_dirty(h, hhdr)) break;
#	endif
        h += OBJ_SZ_TO_BLOCKS(hhdr -> hb_sz);
    }
    GC_push_marked(h, hhdr);
    return(h + OBJ_SZ_TO_BLOCKS(hhdr -> hb_sz));
}
#endif

/* Similar to above, but for uncollectable pages.  Needed since we	*/
/* do not clear marks for such pages, even for full collections.	*/
struct hblk * GC_push_next_marked_uncollectable(h)
struct hblk *h;
{
    register hdr * hhdr = HDR(h);
    
    for (;;) {
        h = GC_next_used_block(h);
        if (h == 0) return(0);
        hhdr = HDR(h);
	if (hhdr -> hb_obj_kind == UNCOLLECTABLE) break;
        h += OBJ_SZ_TO_BLOCKS(hhdr -> hb_sz);
    }
    GC_push_marked(h, hhdr);
    return(h + OBJ_SZ_TO_BLOCKS(hhdr -> hb_sz));
}