Initial revision

1 files changed, 1161 insertions, 0 deletions

diff --git a/gc/mark.c b/gc/mark.c
new file mode 100644
index 0000000..34db472
--- /dev/null
+++ b/gc/mark.c
@@ -0,0 +1,1161 @@
+
+/*
+ * Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers
+ * Copyright (c) 1991-1995 by Xerox Corporation.  All rights reserved.
+ *
+ * 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.
+ *
+ */
+
+
+# include <stdio.h>
+# include "gc_priv.h"
+# include "gc_mark.h"
+
+/* We put this here to minimize the risk of inlining. */
+/*VARARGS*/
+#ifdef __WATCOMC__
+  void GC_noop(void *p, ...) {}
+#else
+  void GC_noop() {}
+#endif
+
+/* Single argument version, robust against whole program analysis. */
+void GC_noop1(x)
+word x;
+{
+    static VOLATILE word sink;
+
+    sink = x;
+}
+
+/* mark_proc GC_mark_procs[MAX_MARK_PROCS] = {0} -- declared in gc_priv.h */
+
+word GC_n_mark_procs = 0;
+
+/* Initialize GC_obj_kinds properly and standard free lists properly.  	*/
+/* This must be done statically since they may be accessed before 	*/
+/* GC_init is called.							*/
+/* It's done here, since we need to deal with mark descriptors.		*/
+struct obj_kind GC_obj_kinds[MAXOBJKINDS] = {
+/* PTRFREE */ { &GC_aobjfreelist[0], 0 /* filled in dynamically */,
+		0 | DS_LENGTH, FALSE, FALSE },
+/* NORMAL  */ { &GC_objfreelist[0], 0,
+#		if defined(ADD_BYTE_AT_END) && ALIGNMENT > DS_TAGS
+		(word)(-ALIGNMENT) | DS_LENGTH,
+#		else
+		0 | DS_LENGTH,
+#		endif
+		TRUE /* add length to descr */, TRUE },
+/* UNCOLLECTABLE */
+	      { &GC_uobjfreelist[0], 0,
+		0 | DS_LENGTH, TRUE /* add length to descr */, TRUE },
+# ifdef ATOMIC_UNCOLLECTABLE
+   /* AUNCOLLECTABLE */
+	      { &GC_auobjfreelist[0], 0,
+		0 | DS_LENGTH, FALSE /* add length to descr */, FALSE },
+# endif
+# ifdef STUBBORN_ALLOC
+/*STUBBORN*/ { &GC_sobjfreelist[0], 0,
+		0 | DS_LENGTH, TRUE /* add length to descr */, TRUE },
+# endif
+};
+
+# ifdef ATOMIC_UNCOLLECTABLE
+#   ifdef STUBBORN_ALLOC
+      int GC_n_kinds = 5;
+#   else
+      int GC_n_kinds = 4;
+#   endif
+# else
+#   ifdef STUBBORN_ALLOC
+      int GC_n_kinds = 4;
+#   else
+      int GC_n_kinds = 3;
+#   endif
+# endif
+
+
+# ifndef INITIAL_MARK_STACK_SIZE
+#   define INITIAL_MARK_STACK_SIZE (1*HBLKSIZE)
+		/* INITIAL_MARK_STACK_SIZE * sizeof(mse) should be a 	*/
+		/* multiple of HBLKSIZE.				*/
+# endif
+
+/*
+ * Limits of stack for GC_mark routine.
+ * All ranges between GC_mark_stack(incl.) and GC_mark_stack_top(incl.) still
+ * need to be marked from.
+ */
+
+word GC_n_rescuing_pages;	/* Number of dirty pages we marked from */
+				/* excludes ptrfree pages, etc.		*/
+
+mse * GC_mark_stack;
+
+word GC_mark_stack_size = 0;
+ 
+mse * GC_mark_stack_top;
+
+static struct hblk * scan_ptr;
+
+mark_state_t GC_mark_state = MS_NONE;
+
+GC_bool GC_mark_stack_too_small = FALSE;
+
+GC_bool GC_objects_are_marked = FALSE;	/* Are there collectable marked	*/
+					/* objects in the heap?		*/
+
+/* Is a collection in progress?  Note that this can return true in the	*/
+/* nonincremental case, if a collection has been abandoned and the	*/
+/* mark state is now MS_INVALID.					*/
+GC_bool GC_collection_in_progress()
+{
+    return(GC_mark_state != MS_NONE);
+}
+
+/* clear all mark bits in the header */
+void GC_clear_hdr_marks(hhdr)
+register hdr * hhdr;
+{
+    BZERO(hhdr -> hb_marks, MARK_BITS_SZ*sizeof(word));
+}
+
+/* Set all mark bits in the header.  Used for uncollectable blocks. */
+void GC_set_hdr_marks(hhdr)
+register hdr * hhdr;
+{
+    register int i;
+
+    for (i = 0; i < MARK_BITS_SZ; ++i) {
+    	hhdr -> hb_marks[i] = ONES;
+    }
+}
+
+/*
+ * Clear all mark bits associated with block h.
+ */
+/*ARGSUSED*/
+static void clear_marks_for_block(h, dummy)
+struct hblk *h;
+word dummy;
+{
+    register hdr * hhdr = HDR(h);
+    
+    if (IS_UNCOLLECTABLE(hhdr -> hb_obj_kind)) return;
+        /* Mark bit for these is cleared only once the object is 	*/
+        /* explicitly deallocated.  This either frees the block, or	*/
+        /* the bit is cleared once the object is on the free list.	*/
+    GC_clear_hdr_marks(hhdr);
+}
+
+/* Slow but general routines for setting/clearing/asking about mark bits */
+void GC_set_mark_bit(p)
+ptr_t p;
+{
+    register struct hblk *h = HBLKPTR(p);
+    register hdr * hhdr = HDR(h);
+    register int word_no = (word *)p - (word *)h;
+    
+    set_mark_bit_from_hdr(hhdr, word_no);
+}
+
+void GC_clear_mark_bit(p)
+ptr_t p;
+{
+    register struct hblk *h = HBLKPTR(p);
+    register hdr * hhdr = HDR(h);
+    register int word_no = (word *)p - (word *)h;
+    
+    clear_mark_bit_from_hdr(hhdr, word_no);
+}
+
+GC_bool GC_is_marked(p)
+ptr_t p;
+{
+    register struct hblk *h = HBLKPTR(p);
+    register hdr * hhdr = HDR(h);
+    register int word_no = (word *)p - (word *)h;
+    
+    return(mark_bit_from_hdr(hhdr, word_no));
+}
+
+
+/*
+ * Clear mark bits in all allocated heap blocks.  This invalidates
+ * the marker invariant, and sets GC_mark_state to reflect this.
+ * (This implicitly starts marking to reestablish the invariant.)
+ */
+void GC_clear_marks()
+{
+    GC_apply_to_all_blocks(clear_marks_for_block, (word)0);
+    GC_objects_are_marked = FALSE;
+    GC_mark_state = MS_INVALID;
+    scan_ptr = 0;
+#   ifdef GATHERSTATS
+	/* Counters reflect currently marked objects: reset here */
+        GC_composite_in_use = 0;
+        GC_atomic_in_use = 0;
+#   endif
+
+}
+
+/* Initiate a garbage collection.  Initiates a full collection if the	*/
+/* mark	state is invalid.						*/
+/*ARGSUSED*/
+void GC_initiate_gc()
+{
+    if (GC_dirty_maintained) GC_read_dirty();
+#   ifdef STUBBORN_ALLOC
+    	GC_read_changed();
+#   endif
+#   ifdef CHECKSUMS
+	{
+	    extern void GC_check_dirty();
+	    
+	    if (GC_dirty_maintained) GC_check_dirty();
+	}
+#   endif
+#   ifdef GATHERSTATS
+	GC_n_rescuing_pages = 0;
+#   endif
+    if (GC_mark_state == MS_NONE) {
+        GC_mark_state = MS_PUSH_RESCUERS;
+    } else if (GC_mark_state != MS_INVALID) {
+    	ABORT("unexpected state");
+    } /* else this is really a full collection, and mark	*/
+      /* bits are invalid.					*/
+    scan_ptr = 0;
+}
+
+
+static void alloc_mark_stack();
+
+/* Perform a small amount of marking.			*/
+/* We try to touch roughly a page of memory.		*/
+/* Return TRUE if we just finished a mark phase.	*/
+/* Cold_gc_frame is an address inside a GC frame that	*/
+/* remains valid until all marking is complete.		*/
+/* A zero value indicates that it's OK to miss some	*/
+/* register values.					*/
+GC_bool GC_mark_some(cold_gc_frame)
+ptr_t cold_gc_frame;
+{
+    switch(GC_mark_state) {
+    	case MS_NONE:
+    	    return(FALSE);
+    	    
+    	case MS_PUSH_RESCUERS:
+    	    if (GC_mark_stack_top
+    	        >= GC_mark_stack + INITIAL_MARK_STACK_SIZE/4) {
+    	        GC_mark_from_mark_stack();
+    	        return(FALSE);
+    	    } else {
+    	        scan_ptr = GC_push_next_marked_dirty(scan_ptr);
+    	        if (scan_ptr == 0) {
+#		    ifdef PRINTSTATS
+			GC_printf1("Marked from %lu dirty pages\n",
+				   (unsigned long)GC_n_rescuing_pages);
+#		    endif
+    	    	    GC_push_roots(FALSE, cold_gc_frame);
+    	    	    GC_objects_are_marked = TRUE;
+    	    	    if (GC_mark_state != MS_INVALID) {
+    	    	        GC_mark_state = MS_ROOTS_PUSHED;
+    	    	    }
+    	    	}
+    	    }
+    	    return(FALSE);
+    	
+    	case MS_PUSH_UNCOLLECTABLE:
+    	    if (GC_mark_stack_top
+    	        >= GC_mark_stack + INITIAL_MARK_STACK_SIZE/4) {
+    	        GC_mark_from_mark_stack();
+    	        return(FALSE);
+    	    } else {
+    	        scan_ptr = GC_push_next_marked_uncollectable(scan_ptr);
+    	        if (scan_ptr == 0) {
+    	    	    GC_push_roots(TRUE, cold_gc_frame);
+    	    	    GC_objects_are_marked = TRUE;
+    	    	    if (GC_mark_state != MS_INVALID) {
+    	    	        GC_mark_state = MS_ROOTS_PUSHED;
+    	    	    }
+    	    	}
+    	    }
+    	    return(FALSE);
+    	
+    	case MS_ROOTS_PUSHED:
+    	    if (GC_mark_stack_top >= GC_mark_stack) {
+    	        GC_mark_from_mark_stack();
+    	        return(FALSE);
+    	    } else {
+    	        GC_mark_state = MS_NONE;
+    	        if (GC_mark_stack_too_small) {
+    	            alloc_mark_stack(2*GC_mark_stack_size);
+    	        }
+    	        return(TRUE);
+    	    }
+    	    
+    	case MS_INVALID:
+    	case MS_PARTIALLY_INVALID:
+	    if (!GC_objects_are_marked) {
+		GC_mark_state = MS_PUSH_UNCOLLECTABLE;
+		return(FALSE);
+	    }
+    	    if (GC_mark_stack_top >= GC_mark_stack) {
+    	        GC_mark_from_mark_stack();
+    	        return(FALSE);
+    	    }
+    	    if (scan_ptr == 0 && GC_mark_state == MS_INVALID) {
+		/* About to start a heap scan for marked objects. */
+		/* Mark stack is empty.  OK to reallocate.	  */
+		if (GC_mark_stack_too_small) {
+    	            alloc_mark_stack(2*GC_mark_stack_size);
+		}
+		GC_mark_state = MS_PARTIALLY_INVALID;
+    	    }
+    	    scan_ptr = GC_push_next_marked(scan_ptr);
+    	    if (scan_ptr == 0 && GC_mark_state == MS_PARTIALLY_INVALID) {
+    	    	GC_push_roots(TRUE, cold_gc_frame);
+    	    	GC_objects_are_marked = TRUE;
+    	    	if (GC_mark_state != MS_INVALID) {
+    	    	    GC_mark_state = MS_ROOTS_PUSHED;
+    	    	}
+    	    }
+    	    return(FALSE);
+    	default:
+    	    ABORT("GC_mark_some: bad state");
+    	    return(FALSE);
+    }
+}
+
+
+GC_bool GC_mark_stack_empty()
+{
+    return(GC_mark_stack_top < GC_mark_stack);
+}	
+
+#ifdef PROF_MARKER
+    word GC_prof_array[10];
+#   define PROF(n) GC_prof_array[n]++
+#else
+#   define PROF(n)
+#endif
+
+/* Given a pointer to someplace other than a small object page or the	*/
+/* first page of a large object, return a pointer either to the		*/
+/* start of the large object or NIL.					*/
+/* In the latter case black list the address current.			*/
+/* Returns NIL without black listing if current points to a block	*/
+/* with IGNORE_OFF_PAGE set.						*/
+/*ARGSUSED*/
+# ifdef PRINT_BLACK_LIST
+  word GC_find_start(current, hhdr, source)
+  word source;
+# else
+  word GC_find_start(current, hhdr)
+# define source 0
+# endif
+register word current;
+register hdr * hhdr;
+{
+#   ifdef ALL_INTERIOR_POINTERS
+	if (hhdr != 0) {
+	    register word orig = current;
+	    
+	    current = (word)HBLKPTR(current) + HDR_BYTES;
+	    do {
+	      current = current - HBLKSIZE*(word)hhdr;
+	      hhdr = HDR(current);
+	    } while(IS_FORWARDING_ADDR_OR_NIL(hhdr));
+	    /* current points to the start of the large object */
+	    if (hhdr -> hb_flags & IGNORE_OFF_PAGE) return(0);
+	    if ((word *)orig - (word *)current
+	         >= (ptrdiff_t)(hhdr->hb_sz)) {
+	        /* Pointer past the end of the block */
+	        GC_ADD_TO_BLACK_LIST_NORMAL(orig, source);
+	        return(0);
+	    }
+	    return(current);
+	} else {
+	    GC_ADD_TO_BLACK_LIST_NORMAL(current, source);
+	    return(0);
+        }
+#   else
+        GC_ADD_TO_BLACK_LIST_NORMAL(current, source);
+        return(0);
+#   endif
+#   undef source
+}
+
+void GC_invalidate_mark_state()
+{
+    GC_mark_state = MS_INVALID;
+    GC_mark_stack_top = GC_mark_stack-1;
+}
+
+mse * GC_signal_mark_stack_overflow(msp)
+mse * msp;
+{
+    GC_mark_state = MS_INVALID;
+    GC_mark_stack_too_small = TRUE;
+#   ifdef PRINTSTATS
+	GC_printf1("Mark stack overflow; current size = %lu entries\n",
+	    	    GC_mark_stack_size);
+#    endif
+     return(msp-INITIAL_MARK_STACK_SIZE/8);
+}
+
+
+/*
+ * Mark objects pointed to by the regions described by
+ * mark stack entries between GC_mark_stack and GC_mark_stack_top,
+ * inclusive.  Assumes the upper limit of a mark stack entry
+ * is never 0.  A mark stack entry never has size 0.
+ * We try to traverse on the order of a hblk of memory before we return.
+ * Caller is responsible for calling this until the mark stack is empty.
+ */
+void GC_mark_from_mark_stack()
+{
+  mse * GC_mark_stack_reg = GC_mark_stack;
+  mse * GC_mark_stack_top_reg = GC_mark_stack_top;
+  mse * mark_stack_limit = &(GC_mark_stack[GC_mark_stack_size]);
+  int credit = HBLKSIZE;	/* Remaining credit for marking work	*/
+  register word * current_p;	/* Pointer to current candidate ptr.	*/
+  register word current;	/* Candidate pointer.			*/
+  register word * limit;	/* (Incl) limit of current candidate 	*/
+  				/* range				*/
+  register word descr;
+  register ptr_t greatest_ha = GC_greatest_plausible_heap_addr;
+  register ptr_t least_ha = GC_least_plausible_heap_addr;
+# define SPLIT_RANGE_WORDS 128  /* Must be power of 2.		*/
+
+  GC_objects_are_marked = TRUE;
+# ifdef OS2 /* Use untweaked version to circumvent compiler problem */
+  while (GC_mark_stack_top_reg >= GC_mark_stack_reg && credit >= 0) {
+# else
+  while ((((ptr_t)GC_mark_stack_top_reg - (ptr_t)GC_mark_stack_reg) | credit)
+  	>= 0) {
+# endif
+    current_p = GC_mark_stack_top_reg -> mse_start;
+  retry:
+    descr = GC_mark_stack_top_reg -> mse_descr;
+    if (descr & ((~(WORDS_TO_BYTES(SPLIT_RANGE_WORDS) - 1)) | DS_TAGS)) {
+      word tag = descr & DS_TAGS;
+      
+      switch(tag) {
+        case DS_LENGTH:
+          /* Large length.					        */
+          /* Process part of the range to avoid pushing too much on the	*/
+          /* stack.							*/
+          GC_mark_stack_top_reg -> mse_start =
+         	limit = current_p + SPLIT_RANGE_WORDS-1;
+          GC_mark_stack_top_reg -> mse_descr -=
+          		WORDS_TO_BYTES(SPLIT_RANGE_WORDS-1);
+          /* Make sure that pointers overlapping the two ranges are	*/
+          /* considered. 						*/
+          limit = (word *)((char *)limit + sizeof(word) - ALIGNMENT);
+          break;
+        case DS_BITMAP:
+          GC_mark_stack_top_reg--;
+          descr &= ~DS_TAGS;
+          credit -= WORDS_TO_BYTES(WORDSZ/2); /* guess */
+          while (descr != 0) {
+            if ((signed_word)descr < 0) {
+              current = *current_p;
+	      if ((ptr_t)current >= least_ha && (ptr_t)current < greatest_ha) {
+                PUSH_CONTENTS(current, GC_mark_stack_top_reg, mark_stack_limit,
+			      current_p, exit1);
+	      }
+            }
+	    descr <<= 1;
+	    ++ current_p;
+          }
+          continue;
+        case DS_PROC:
+          GC_mark_stack_top_reg--;
+          credit -= PROC_BYTES;
+          GC_mark_stack_top_reg =
+              (*PROC(descr))
+              	    (current_p, GC_mark_stack_top_reg,
+              	    mark_stack_limit, ENV(descr));
+          continue;
+        case DS_PER_OBJECT:
+          GC_mark_stack_top_reg -> mse_descr =
+			*(word *)((ptr_t)current_p + descr - tag);
+          goto retry;
+      }
+    } else {
+      GC_mark_stack_top_reg--;
+      limit = (word *)(((ptr_t)current_p) + (word)descr);
+    }
+    /* The simple case in which we're scanning a range.	*/
+    credit -= (ptr_t)limit - (ptr_t)current_p;
+    limit -= 1;
+    while (current_p <= limit) {
+      current = *current_p;
+      if ((ptr_t)current >= least_ha && (ptr_t)current <  greatest_ha) {
+        PUSH_CONTENTS(current, GC_mark_stack_top_reg,
+		      mark_stack_limit, current_p, exit2);
+      }
+      current_p = (word *)((char *)current_p + ALIGNMENT);
+    }
+  }
+  GC_mark_stack_top = GC_mark_stack_top_reg;
+}
+
+/* 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 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 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;
+#	  ifdef PRINTSTATS
+	      GC_printf1("Grew mark stack to %lu frames\n",
+		    	 (unsigned long) GC_mark_stack_size);
+#	  endif
+        } else {
+#	  ifdef PRINTSTATS
+	      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_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 + GC_mark_stack_size) {
+	ABORT("unexpected mark stack overflow");
+    }
+    length = top - bottom;
+#   if DS_TAGS > ALIGNMENT - 1
+	length += DS_TAGS;
+	length &= ~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 that may have been
+ * dirtied.  A block h is assumed dirty if dirty_fn(h) != 0.
+ * We use push_fn to actually push the block.
+ * 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_dirty(bottom, top, dirty_fn, push_fn)
+ptr_t bottom;
+ptr_t top;
+int (*dirty_fn)(/* struct hblk * h */);
+void (*push_fn)(/* 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 + GC_mark_stack_size) {
+        ABORT("unexpected mark stack overflow");
+    }
+}
+
+# ifndef SMALL_CONFIG
+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_dirty(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_dirty(bottom, top, GC_page_was_dirty, GC_push_all);
+    }
+}
+#endif
+
+# ifdef MSWIN32
+  void __cdecl GC_push_one(p)
+# else
+  void GC_push_one(p)
+# endif
+word p;
+{
+    GC_PUSH_ONE_STACK(p, 0);
+}
+
+# ifdef __STDC__
+#   define BASE(p) (word)GC_base((void *)(p))
+# else
+#   define BASE(p) (word)GC_base((char *)(p))
+# endif
+
+/* As above, but argument passed preliminary test. */
+# if defined(PRINT_BLACK_LIST) || defined(KEEP_BACK_PTRS)
+    void GC_push_one_checked(p, interior_ptrs, source)
+    ptr_t source;
+# else
+    void GC_push_one_checked(p, interior_ptrs)
+#   define source 0
+# endif
+register word p;
+register GC_bool interior_ptrs;
+{
+    register word r;
+    register hdr * hhdr; 
+    register int displ;
+  
+    GET_HDR(p, hhdr);
+    if (IS_FORWARDING_ADDR_OR_NIL(hhdr)) {
+        if (hhdr != 0 && interior_ptrs) {
+          r = BASE(p);
+	  hhdr = HDR(r);
+	  displ = BYTES_TO_WORDS(HBLKDISPL(r));
+	} else {
+	  hhdr = 0;
+	}
+    } else {
+        register map_entry_type map_entry;
+        
+        displ = HBLKDISPL(p);
+        map_entry = MAP_ENTRY((hhdr -> hb_map), displ);
+        if (map_entry == OBJ_INVALID) {
+#	  ifndef ALL_INTERIOR_POINTERS
+            if (interior_ptrs) {
+              r = BASE(p);
+	      displ = BYTES_TO_WORDS(HBLKDISPL(r));
+	      if (r == 0) hhdr = 0;
+            } else {
+              hhdr = 0;
+            }
+#	  else
+	    /* map already reflects interior pointers */
+	    hhdr = 0;
+#	  endif
+        } 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) {
+    	if (interior_ptrs) {
+#	    ifdef PRINT_BLACK_LIST
+	      GC_add_to_black_list_stack(p, source);
+#	    else
+	      GC_add_to_black_list_stack(p);
+#	    endif
+	} else {
+	    GC_ADD_TO_BLACK_LIST_NORMAL(p, source);
+#	    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[GC_mark_stack_size]));
+	}
+    }
+}
+
+# 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 *)(((long) bottom + ALIGNMENT-1) & ~(ALIGNMENT-1));
+    word * t = (word *)(((long) 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 put in 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;
+{
+# ifdef 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;
+    }
+#   ifdef STACK_GROWS_DOWN
+	GC_push_all_eager(bottom, cold_gc_frame);
+	GC_push_all(cold_gc_frame - sizeof(ptr_t), top);
+#   else /* STACK_GROWS_UP */
+	GC_push_all_eager(cold_gc_frame, top);
+	GC_push_all(bottom, cold_gc_frame + sizeof(ptr_t));
+#   endif /* STACK_GROWS_UP */
+# else
+    GC_push_all_eager(bottom, top);
+# endif
+# 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;
+{
+# ifdef ALL_INTERIOR_POINTERS
+    GC_push_all(bottom, top);
+# else
+    GC_push_all_eager(bottom, top);
+# endif
+}
+
+#ifndef SMALL_CONFIG
+/* 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[divWORDSZ(HDR_WORDS)]);
+    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;
+#   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        
+}
+
+
+#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[divWORDSZ(HDR_WORDS)]);
+    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;
+#   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        
+}
+
+/* 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[divWORDSZ(HDR_WORDS)]);
+    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;
+#   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        
+}
+
+#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 word * p;
+    register int word_no;
+    register word * lim;
+    register mse * GC_mark_stack_top_reg;
+    register mse * mark_stack_limit = &(GC_mark_stack[GC_mark_stack_size]);
+    
+    /* Some quick shortcuts: */
+	{ 
+	    struct obj_kind *ok = &(GC_obj_kinds[hhdr -> hb_obj_kind]);
+	    if ((0 | DS_LENGTH) == ok -> ok_descriptor
+		&& FALSE == ok -> ok_relocate_descr)
+		return;
+	}
+        if (GC_block_empty(hhdr)/* nothing marked */) return;
+#   ifdef GATHERSTATS
+        GC_n_rescuing_pages++;
+#   endif
+    GC_objects_are_marked = TRUE;
+    if (sz > MAXOBJSZ) {
+        lim = (word *)(h + 1);
+    } else {
+        lim = (word *)(h + 1) - sz;
+    }
+    
+    switch(sz) {
+#   if !defined(SMALL_CONFIG)    
+     case 1:
+       GC_push_marked1(h, hhdr);
+       break;
+#   endif
+#   if !defined(SMALL_CONFIG) && !defined(UNALIGNED)
+     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 + HDR_WORDS, word_no = HDR_WORDS; p <= lim;
+         p += sz, word_no += sz) {
+         /* This ignores user specified mark procs.  This currently	*/
+         /* doesn't matter, since marking from the whole object		*/
+         /* is always sufficient, and we will eventually use the user	*/
+         /* mark proc to avoid any bogus pointers.			*/
+         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 += HDR_WORDS;
+         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 = HDR(h);
+    
+    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));
+}
+
+