--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/ralloc.c	Mon Aug 13 11:28:15 2007 +0200
@@ -0,0 +1,2080 @@
+/* Block-relocating memory allocator.
+   Copyright (C) 1992, 1993, 1994, 1995 Free Software Foundation, Inc.
+
+This file is part of XEmacs.
+
+XEmacs is free software; you can redistribute it and/or modify it
+under the terms of the GNU General Public License as published by the
+Free Software Foundation; either version 2, or (at your option) any
+later version.
+
+XEmacs is distributed in the hope that it will be useful, but WITHOUT
+ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with GNU Emacs; see the file COPYING.  If not, write to
+the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+Boston, MA 02111-1307, USA.
+
+Synched Up with:  FSF 20.2 (non-mmap portion only)
+*/
+
+/* NOTES:
+
+   Only relocate the blocs necessary for SIZE in r_alloc_sbrk,
+   rather than all of them.  This means allowing for a possible
+   hole between the first bloc and the end of malloc storage. */
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#ifdef HAVE_UNISTD_H
+#include <unistd.h>  /* for getpagesize() */
+#endif
+
+#ifdef emacs
+
+#include "lisp.h"
+
+/* The important properties of this type are that 1) it's a pointer, and
+   2) arithmetic on it should work as if the size of the object pointed
+   to has a size of 1.  */
+#if 0 /* Arithmetic on void* is a GCC extension.  */
+#ifdef __STDC__
+typedef void *POINTER;
+#else
+typedef unsigned char *POINTER;
+#endif
+#endif /* 0 */
+
+/* Unconditionally use unsigned char * for this.  */
+typedef unsigned char *POINTER;
+
+typedef unsigned long SIZE;
+
+#ifdef DOUG_LEA_MALLOC
+#define M_TOP_PAD -2
+#include <malloc.h>
+#endif
+
+#include "getpagesize.h"
+
+#include <string.h>
+void refill_memory_reserve (void);
+
+#else	/* Not emacs.  */
+
+#include <stddef.h>
+
+typedef size_t SIZE;
+typedef void *POINTER;
+
+#include <unistd.h>
+#include <malloc.h>
+#include <string.h>
+
+#endif	/* emacs.  */
+
+void init_ralloc (void);
+#define safe_bcopy(x, y, z) memmove (y, x, z)
+
+#define NIL ((POINTER) 0)
+
+
+#if !defined(HAVE_MMAP) || defined(DOUG_LEA_MALLOC)
+
+/* A flag to indicate whether we have initialized ralloc yet.  For
+   Emacs's sake, please do not make this local to malloc_init; on some
+   machines, the dumping procedure makes all static variables
+   read-only.  On these machines, the word static is #defined to be
+   the empty string, meaning that r_alloc_initialized becomes an
+   automatic variable, and loses its value each time Emacs is started up.  */
+static int r_alloc_initialized = 0;
+
+
+/* Declarations for working with the malloc, ralloc, and system breaks.  */
+
+/* Function to set the real break value. */
+static POINTER (*real_morecore) (ptrdiff_t size);
+
+/* The break value, as seen by malloc (). */
+static POINTER virtual_break_value;
+
+/* The break value, viewed by the relocatable blocs. */
+static POINTER break_value;
+
+/* This is the size of a page.  We round memory requests to this boundary.  */
+static int page_size;
+
+/* Whenever we get memory from the system, get this many extra bytes.  This
+   must be a multiple of page_size.  */
+static int extra_bytes;
+
+/* Macros for rounding.  Note that rounding to any value is possible
+   by changing the definition of PAGE. */
+#define PAGE (getpagesize ())
+#define ALIGNED(addr) (((unsigned long int) (addr) & (page_size - 1)) == 0)
+#define ROUNDUP(size) (((unsigned long int) (size) + page_size - 1) \
+                       & ~(page_size - 1))
+#define ROUND_TO_PAGE(addr) (addr & (~(page_size - 1)))
+
+#define MEM_ALIGN sizeof(double)
+#define MEM_ROUNDUP(addr) (((unsigned long int)(addr) + MEM_ALIGN - 1) \
+				   & ~(MEM_ALIGN - 1))
+
+/* Data structures of heaps and blocs.  */
+
+/* The relocatable objects, or blocs, and the malloc data
+   both reside within one or more heaps.
+   Each heap contains malloc data, running from `start' to `bloc_start',
+   and relocatable objects, running from `bloc_start' to `free'.
+
+   Relocatable objects may relocate within the same heap
+   or may move into another heap; the heaps themselves may grow
+   but they never move.
+
+   We try to make just one heap and make it larger as necessary.
+   But sometimes we can't do that, because we can't get contiguous
+   space to add onto the heap.  When that happens, we start a new heap.  */
+
+typedef struct heap
+{
+  struct heap *next;
+  struct heap *prev;
+  /* Start of memory range of this heap.  */
+  POINTER start;
+  /* End of memory range of this heap.  */
+  POINTER end;
+  /* Start of relocatable data in this heap.  */
+  POINTER bloc_start;
+  /* Start of unused space in this heap.  */
+  POINTER free;
+  /* First bloc in this heap.  */
+  struct bp *first_bloc;
+  /* Last bloc in this heap.  */
+  struct bp *last_bloc;
+} *heap_ptr;
+
+#define NIL_HEAP ((heap_ptr) 0)
+#define HEAP_PTR_SIZE (sizeof (struct heap))
+
+/* This is the first heap object.
+   If we need additional heap objects, each one resides at the beginning of
+   the space it covers.   */
+static struct heap heap_base;
+
+/* Head and tail of the list of heaps.  */
+static heap_ptr first_heap, last_heap;
+
+/* These structures are allocated in the malloc arena.
+   The linked list is kept in order of increasing '.data' members.
+   The data blocks abut each other; if b->next is non-nil, then
+   b->data + b->size == b->next->data.
+
+   An element with variable==NIL denotes a freed block, which has not yet
+   been collected.  They may only appear while r_alloc_freeze > 0, and will be
+   freed when the arena is thawed.  Currently, these blocs are not reusable,
+   while the arena is frozen.  Very inefficient.  */
+
+typedef struct bp
+{
+  struct bp *next;
+  struct bp *prev;
+  POINTER *variable;
+  POINTER data;
+  SIZE size;
+  POINTER new_data;		/* temporarily used for relocation */
+  struct heap *heap; 		/* Heap this bloc is in.  */
+} *bloc_ptr;
+
+#define NIL_BLOC ((bloc_ptr) 0)
+#define BLOC_PTR_SIZE (sizeof (struct bp))
+
+/* Head and tail of the list of relocatable blocs. */
+static bloc_ptr first_bloc, last_bloc;
+
+static int use_relocatable_buffers;
+
+/* If >0, no relocation whatsoever takes place.  */
+static int r_alloc_freeze_level;
+
+/* Obtain SIZE bytes of space.  If enough space is not presently available
+   in our process reserve, (i.e., (page_break_value - break_value)),
+   this means getting more page-aligned space from the system.
+
+   Return non-zero if all went well, or zero if we couldn't allocate
+   the memory.  */
+
+/* Functions to get and return memory from the system.  */
+
+/* Find the heap that ADDRESS falls within.  */
+
+static heap_ptr
+find_heap (POINTER address)
+{
+  heap_ptr heap;
+
+  for (heap = last_heap; heap; heap = heap->prev)
+    {
+      if (heap->start <= address && address <= heap->end)
+	return heap;
+    }
+
+  return NIL_HEAP;
+}
+
+/* Find SIZE bytes of space in a heap.
+   Try to get them at ADDRESS (which must fall within some heap's range)
+   if we can get that many within one heap.
+
+   If enough space is not presently available in our reserve, this means
+   getting more page-aligned space from the system.  If the returned space
+   is not contiguous to the last heap, allocate a new heap, and append it
+
+   obtain does not try to keep track of whether space is in use
+   or not in use.  It just returns the address of SIZE bytes that
+   fall within a single heap.  If you call obtain twice in a row
+   with the same arguments, you typically get the same value.
+   to the heap list.  It's the caller's responsibility to keep
+   track of what space is in use.
+
+   Return the address of the space if all went well, or zero if we couldn't
+   allocate the memory.  */
+
+static POINTER
+obtain (POINTER address, SIZE size)
+{
+  heap_ptr heap;
+  SIZE already_available;
+
+  /* Find the heap that ADDRESS falls within.  */
+  for (heap = last_heap; heap; heap = heap->prev)
+    {
+      if (heap->start <= address && address <= heap->end)
+	break;
+    }
+
+  if (! heap)
+    abort ();
+
+  /* If we can't fit SIZE bytes in that heap,
+     try successive later heaps.  */
+  while (heap && address + size > heap->end)
+    {
+      heap = heap->next;
+      if (heap == NIL_HEAP)
+	break;
+      address = heap->bloc_start;
+    }
+
+  /* If we can't fit them within any existing heap,
+     get more space.  */
+  if (heap == NIL_HEAP)
+    {
+      POINTER new = (*real_morecore)(0);
+      SIZE get;
+
+      already_available = (char *)last_heap->end - (char *)address;
+
+      if (new != last_heap->end)
+	{
+	  /* Someone else called sbrk.  Make a new heap.  */
+
+	  heap_ptr new_heap = (heap_ptr) MEM_ROUNDUP (new);
+	  POINTER bloc_start = (POINTER) MEM_ROUNDUP ((POINTER)(new_heap + 1));
+
+	  if ((*real_morecore) (bloc_start - new) != new)
+	    return 0;
+
+	  new_heap->start = new;
+	  new_heap->end = bloc_start;
+	  new_heap->bloc_start = bloc_start;
+	  new_heap->free = bloc_start;
+	  new_heap->next = NIL_HEAP;
+	  new_heap->prev = last_heap;
+	  new_heap->first_bloc = NIL_BLOC;
+	  new_heap->last_bloc = NIL_BLOC;
+	  last_heap->next = new_heap;
+	  last_heap = new_heap;
+
+	  address = bloc_start;
+	  already_available = 0;
+	}
+
+      /* Add space to the last heap (which we may have just created).
+	 Get some extra, so we can come here less often.  */
+
+      get = size + extra_bytes - already_available;
+      get = (char *) ROUNDUP ((char *)last_heap->end + get)
+	- (char *) last_heap->end;
+
+      if ((*real_morecore) (get) != last_heap->end)
+	return 0;
+
+      last_heap->end += get;
+    }
+
+  return address;
+}
+
+#if 0
+/* Obtain SIZE bytes of space and return a pointer to the new area.
+   If we could not allocate the space, return zero.  */
+
+static POINTER
+get_more_space (SIZE size)
+{
+  POINTER ptr = break_value;
+  if (obtain (size))
+    return ptr;
+  else
+    return 0;
+}
+#endif
+
+/* Note that SIZE bytes of space have been relinquished by the process.
+   If SIZE is more than a page, return the space to the system. */
+
+static void
+relinquish (void)
+{
+  register heap_ptr h;
+  int excess = 0;
+
+  /* Add the amount of space beyond break_value
+     in all heaps which have extend beyond break_value at all.  */
+
+  for (h = last_heap; h && break_value < h->end; h = h->prev)
+    {
+      excess += (char *) h->end - (char *) ((break_value < h->bloc_start)
+					    ? h->bloc_start : break_value);
+    }
+
+  if (excess > extra_bytes * 2 && (*real_morecore) (0) == last_heap->end)
+    {
+      /* Keep extra_bytes worth of empty space.
+	 And don't free anything unless we can free at least extra_bytes.  */
+      excess -= extra_bytes;
+
+      if ((char *)last_heap->end - (char *)last_heap->bloc_start <= excess)
+	{
+	  /* This heap should have no blocs in it.  */
+	  if (last_heap->first_bloc != NIL_BLOC
+	      || last_heap->last_bloc != NIL_BLOC)
+	    abort ();
+
+	  /* Return the last heap, with its header, to the system.  */
+	  excess = (char *)last_heap->end - (char *)last_heap->start;
+	  last_heap = last_heap->prev;
+	  last_heap->next = NIL_HEAP;
+	}
+      else
+	{
+	  excess = (char *) last_heap->end
+			- (char *) ROUNDUP ((char *)last_heap->end - excess);
+	  last_heap->end -= excess;
+	}
+
+      if ((*real_morecore) (- excess) == 0)
+	abort ();
+    }
+}
+
+/* Return the total size in use by relocating allocator,
+   above where malloc gets space.  */
+
+long r_alloc_size_in_use (void);
+long
+r_alloc_size_in_use ()
+{
+  return break_value - virtual_break_value;
+}
+
+/* The meat - allocating, freeing, and relocating blocs.  */
+
+
+/* Find the bloc referenced by the address in PTR.  Returns a pointer
+   to that block. */
+
+static bloc_ptr
+find_bloc (POINTER *ptr)
+{
+  register bloc_ptr p = first_bloc;
+
+  while (p != NIL_BLOC)
+    {
+      if (p->variable == ptr && p->data == *ptr)
+	return p;
+
+      p = p->next;
+    }
+
+  return p;
+}
+
+/* Allocate a bloc of SIZE bytes and append it to the chain of blocs.
+   Returns a pointer to the new bloc, or zero if we couldn't allocate
+   memory for the new block.  */
+
+static bloc_ptr
+get_bloc (SIZE size)
+{
+  register bloc_ptr new_bloc;
+  register heap_ptr heap;
+
+  if (! (new_bloc = (bloc_ptr) malloc (BLOC_PTR_SIZE))
+      || ! (new_bloc->data = obtain (break_value, size)))
+    {
+      if (new_bloc)
+	free (new_bloc);
+
+      return 0;
+    }
+
+  break_value = new_bloc->data + size;
+
+  new_bloc->size = size;
+  new_bloc->next = NIL_BLOC;
+  new_bloc->variable = (POINTER *) NIL;
+  new_bloc->new_data = 0;
+
+  /* Record in the heap that this space is in use.  */
+  heap = find_heap (new_bloc->data);
+  heap->free = break_value;
+
+  /* Maintain the correspondence between heaps and blocs.  */
+  new_bloc->heap = heap;
+  heap->last_bloc = new_bloc;
+  if (heap->first_bloc == NIL_BLOC)
+    heap->first_bloc = new_bloc;
+
+  /* Put this bloc on the doubly-linked list of blocs.  */
+  if (first_bloc)
+    {
+      new_bloc->prev = last_bloc;
+      last_bloc->next = new_bloc;
+      last_bloc = new_bloc;
+    }
+  else
+    {
+      first_bloc = last_bloc = new_bloc;
+      new_bloc->prev = NIL_BLOC;
+    }
+
+  return new_bloc;
+}
+
+/* Calculate new locations of blocs in the list beginning with BLOC,
+   relocating it to start at ADDRESS, in heap HEAP.  If enough space is
+   not presently available in our reserve, call obtain for
+   more space.
+
+   Store the new location of each bloc in its new_data field.
+   Do not touch the contents of blocs or break_value.  */
+
+static int
+relocate_blocs (bloc_ptr bloc, heap_ptr heap, POINTER address)
+{
+  register bloc_ptr b = bloc;
+
+  /* No need to ever call this if arena is frozen, bug somewhere!  */
+  if (r_alloc_freeze_level)
+    abort();
+
+  while (b)
+    {
+      /* If bloc B won't fit within HEAP,
+	 move to the next heap and try again.  */
+      while (heap && address + b->size > heap->end)
+	{
+	  heap = heap->next;
+	  if (heap == NIL_HEAP)
+	    break;
+	  address = heap->bloc_start;
+	}
+
+      /* If BLOC won't fit in any heap,
+	 get enough new space to hold BLOC and all following blocs.  */
+      if (heap == NIL_HEAP)
+	{
+	  register bloc_ptr tb = b;
+	  register SIZE s = 0;
+
+	  /* Add up the size of all the following blocs.  */
+	  while (tb != NIL_BLOC)
+	    {
+	      if (tb->variable)
+		s += tb->size;
+
+	      tb = tb->next;
+	    }
+
+	  /* Get that space.  */
+	  address = obtain (address, s);
+	  if (address == 0)
+	    return 0;
+
+	  heap = last_heap;
+	}
+
+      /* Record the new address of this bloc
+	 and update where the next bloc can start.  */
+      b->new_data = address;
+      if (b->variable)
+	address += b->size;
+      b = b->next;
+    }
+
+  return 1;
+}
+
+#if 0 /* unused */
+/* Reorder the bloc BLOC to go before bloc BEFORE in the doubly linked list.
+   This is necessary if we put the memory of space of BLOC
+   before that of BEFORE.  */
+
+static void
+reorder_bloc (bloc_ptr bloc, bloc_ptr before)
+{
+  bloc_ptr prev, next;
+
+  /* Splice BLOC out from where it is.  */
+  prev = bloc->prev;
+  next = bloc->next;
+
+  if (prev)
+    prev->next = next;
+  if (next)
+    next->prev = prev;
+
+  /* Splice it in before BEFORE.  */
+  prev = before->prev;
+
+  if (prev)
+    prev->next = bloc;
+  bloc->prev = prev;
+
+  before->prev = bloc;
+  bloc->next = before;
+}
+#endif /* unused */
+
+/* Update the records of which heaps contain which blocs, starting
+   with heap HEAP and bloc BLOC.  */
+
+static void
+update_heap_bloc_correspondence (bloc_ptr bloc, heap_ptr heap)
+{
+  register bloc_ptr b;
+
+  /* Initialize HEAP's status to reflect blocs before BLOC.  */
+  if (bloc != NIL_BLOC && bloc->prev != NIL_BLOC && bloc->prev->heap == heap)
+    {
+      /* The previous bloc is in HEAP.  */
+      heap->last_bloc = bloc->prev;
+      heap->free = bloc->prev->data + bloc->prev->size;
+    }
+  else
+    {
+      /* HEAP contains no blocs before BLOC.  */
+      heap->first_bloc = NIL_BLOC;
+      heap->last_bloc = NIL_BLOC;
+      heap->free = heap->bloc_start;
+    }
+
+  /* Advance through blocs one by one.  */
+  for (b = bloc; b != NIL_BLOC; b = b->next)
+    {
+      /* Advance through heaps, marking them empty,
+	 till we get to the one that B is in.  */
+      while (heap)
+	{
+	  if (heap->bloc_start <= b->data && b->data <= heap->end)
+	    break;
+	  heap = heap->next;
+	  /* We know HEAP is not null now,
+	     because there has to be space for bloc B.  */
+	  heap->first_bloc = NIL_BLOC;
+	  heap->last_bloc = NIL_BLOC;
+	  heap->free = heap->bloc_start;
+	}
+
+      /* Update HEAP's status for bloc B.  */
+      heap->free = b->data + b->size;
+      heap->last_bloc = b;
+      if (heap->first_bloc == NIL_BLOC)
+	heap->first_bloc = b;
+
+      /* Record that B is in HEAP.  */
+      b->heap = heap;
+    }
+
+  /* If there are any remaining heaps and no blocs left,
+     mark those heaps as empty.  */
+  heap = heap->next;
+  while (heap)
+    {
+      heap->first_bloc = NIL_BLOC;
+      heap->last_bloc = NIL_BLOC;
+      heap->free = heap->bloc_start;
+      heap = heap->next;
+    }
+}
+
+/* Resize BLOC to SIZE bytes.  This relocates the blocs
+   that come after BLOC in memory.  */
+
+static int
+resize_bloc (bloc_ptr bloc, SIZE size)
+{
+  register bloc_ptr b;
+  heap_ptr heap;
+  POINTER address;
+  SIZE old_size;
+
+  /* No need to ever call this if arena is frozen, bug somewhere!  */
+  if (r_alloc_freeze_level)
+    abort();
+
+  if (bloc == NIL_BLOC || size == bloc->size)
+    return 1;
+
+  for (heap = first_heap; heap != NIL_HEAP; heap = heap->next)
+    {
+      if (heap->bloc_start <= bloc->data && bloc->data <= heap->end)
+	break;
+    }
+
+  if (heap == NIL_HEAP)
+    abort ();
+
+  old_size = bloc->size;
+  bloc->size = size;
+
+  /* Note that bloc could be moved into the previous heap.  */
+  address = (bloc->prev ? bloc->prev->data + bloc->prev->size
+	     : first_heap->bloc_start);
+  while (heap)
+    {
+      if (heap->bloc_start <= address && address <= heap->end)
+	break;
+      heap = heap->prev;
+    }
+
+  if (! relocate_blocs (bloc, heap, address))
+    {
+      bloc->size = old_size;
+      return 0;
+    }
+
+  if (size > old_size)
+    {
+      for (b = last_bloc; b != bloc; b = b->prev)
+	{
+	  if (!b->variable)
+	    {
+	      b->size = 0;
+	      b->data = b->new_data;
+            }
+	  else
+	    {
+	      safe_bcopy (b->data, b->new_data, b->size);
+	      *b->variable = b->data = b->new_data;
+            }
+	}
+      if (!bloc->variable)
+	{
+	  bloc->size = 0;
+	  bloc->data = bloc->new_data;
+	}
+      else
+	{
+	  safe_bcopy (bloc->data, bloc->new_data, old_size);
+	  memset (bloc->new_data + old_size, 0, size - old_size);
+	  *bloc->variable = bloc->data = bloc->new_data;
+	}
+    }
+  else
+    {
+      for (b = bloc; b != NIL_BLOC; b = b->next)
+	{
+	  if (!b->variable)
+	    {
+	      b->size = 0;
+	      b->data = b->new_data;
+            }
+	  else
+	    {
+	      safe_bcopy (b->data, b->new_data, b->size);
+	      *b->variable = b->data = b->new_data;
+	    }
+	}
+    }
+
+  update_heap_bloc_correspondence (bloc, heap);
+
+  break_value = (last_bloc ? last_bloc->data + last_bloc->size
+		 : first_heap->bloc_start);
+  return 1;
+}
+
+/* Free BLOC from the chain of blocs, relocating any blocs above it
+   and returning BLOC->size bytes to the free area. */
+
+static void
+free_bloc (bloc_ptr bloc)
+{
+  heap_ptr heap = bloc->heap;
+
+  if (r_alloc_freeze_level)
+    {
+      bloc->variable = (POINTER *) NIL;
+      return;
+    }
+
+  resize_bloc (bloc, 0);
+
+  if (bloc == first_bloc && bloc == last_bloc)
+    {
+      first_bloc = last_bloc = NIL_BLOC;
+    }
+  else if (bloc == last_bloc)
+    {
+      last_bloc = bloc->prev;
+      last_bloc->next = NIL_BLOC;
+    }
+  else if (bloc == first_bloc)
+    {
+      first_bloc = bloc->next;
+      first_bloc->prev = NIL_BLOC;
+    }
+  else
+    {
+      bloc->next->prev = bloc->prev;
+      bloc->prev->next = bloc->next;
+    }
+
+  /* Update the records of which blocs are in HEAP.  */
+  if (heap->first_bloc == bloc)
+    {
+      if (bloc->next != 0 && bloc->next->heap == heap)
+	heap->first_bloc = bloc->next;
+      else
+	heap->first_bloc = heap->last_bloc = NIL_BLOC;
+    }
+  if (heap->last_bloc == bloc)
+    {
+      if (bloc->prev != 0 && bloc->prev->heap == heap)
+	heap->last_bloc = bloc->prev;
+      else
+	heap->first_bloc = heap->last_bloc = NIL_BLOC;
+    }
+
+  relinquish ();
+  free (bloc);
+}
+
+/* Interface routines.  */
+
+/* Obtain SIZE bytes of storage from the free pool, or the system, as
+   necessary.  If relocatable blocs are in use, this means relocating
+   them.  This function gets plugged into the GNU malloc's __morecore
+   hook.
+
+   We provide hysteresis, never relocating by less than extra_bytes.
+
+   If we're out of memory, we should return zero, to imitate the other
+   __morecore hook values - in particular, __default_morecore in the
+   GNU malloc package.  */
+
+POINTER r_alloc_sbrk (ptrdiff_t size);
+POINTER
+r_alloc_sbrk (ptrdiff_t size)
+{
+  register bloc_ptr b;
+  POINTER address;
+
+  if (! r_alloc_initialized)
+    init_ralloc ();
+
+  if (! use_relocatable_buffers)
+    return (*real_morecore) (size);
+
+  if (size == 0)
+    return virtual_break_value;
+
+  if (size > 0)
+    {
+      /* Allocate a page-aligned space.  GNU malloc would reclaim an
+	 extra space if we passed an unaligned one.  But we could
+	 not always find a space which is contiguous to the previous.  */
+      POINTER new_bloc_start;
+      heap_ptr h = first_heap;
+      SIZE get = ROUNDUP (size);
+
+      address = (POINTER) ROUNDUP (virtual_break_value);
+
+      /* Search the list upward for a heap which is large enough.  */
+      while ((char *) h->end < (char *) MEM_ROUNDUP ((char *)address + get))
+	{
+	  h = h->next;
+	  if (h == NIL_HEAP)
+	    break;
+	  address = (POINTER) ROUNDUP (h->start);
+	}
+
+      /* If not found, obtain more space.  */
+      if (h == NIL_HEAP)
+	{
+	  get += extra_bytes + page_size;
+
+	  if (! obtain (address, get))
+	    return 0;
+
+	  if (first_heap == last_heap)
+	    address = (POINTER) ROUNDUP (virtual_break_value);
+	  else
+	    address = (POINTER) ROUNDUP (last_heap->start);
+	  h = last_heap;
+	}
+
+      new_bloc_start = (POINTER) MEM_ROUNDUP ((char *)address + get);
+
+      if (first_heap->bloc_start < new_bloc_start)
+	{
+	  /* This is no clean solution - no idea how to do it better.  */
+	  if (r_alloc_freeze_level)
+	    return NIL;
+
+	  /* There is a bug here: if the above obtain call succeeded, but the
+	     relocate_blocs call below does not succeed, we need to free
+	     the memory that we got with obtain.  */
+
+	  /* Move all blocs upward.  */
+	  if (! relocate_blocs (first_bloc, h, new_bloc_start))
+	    return 0;
+
+	  /* Note that (POINTER)(h+1) <= new_bloc_start since
+	     get >= page_size, so the following does not destroy the heap
+	     header.  */
+	  for (b = last_bloc; b != NIL_BLOC; b = b->prev)
+	    {
+	      safe_bcopy (b->data, b->new_data, b->size);
+	      *b->variable = b->data = b->new_data;
+	    }
+
+	  h->bloc_start = new_bloc_start;
+
+	  update_heap_bloc_correspondence (first_bloc, h);
+	}
+      if (h != first_heap)
+	{
+	  /* Give up managing heaps below the one the new
+	     virtual_break_value points to.  */
+	  first_heap->prev = NIL_HEAP;
+	  first_heap->next = h->next;
+	  first_heap->start = h->start;
+	  first_heap->end = h->end;
+	  first_heap->free = h->free;
+	  first_heap->first_bloc = h->first_bloc;
+	  first_heap->last_bloc = h->last_bloc;
+	  first_heap->bloc_start = h->bloc_start;
+
+	  if (first_heap->next)
+	    first_heap->next->prev = first_heap;
+	  else
+	    last_heap = first_heap;
+	}
+
+      memset (address, 0, size);
+    }
+  else /* size < 0 */
+    {
+      SIZE excess = (char *)first_heap->bloc_start
+		      - ((char *)virtual_break_value + size);
+
+      address = virtual_break_value;
+
+      if (r_alloc_freeze_level == 0 && excess > 2 * extra_bytes)
+	{
+	  excess -= extra_bytes;
+	  first_heap->bloc_start
+	    = (POINTER) MEM_ROUNDUP ((char *)first_heap->bloc_start - excess);
+
+	  relocate_blocs (first_bloc, first_heap, first_heap->bloc_start);
+
+	  for (b = first_bloc; b != NIL_BLOC; b = b->next)
+	    {
+	      safe_bcopy (b->data, b->new_data, b->size);
+	      *b->variable = b->data = b->new_data;
+	    }
+	}
+
+      if ((char *)virtual_break_value + size < (char *)first_heap->start)
+	{
+	  /* We found an additional space below the first heap */
+	  first_heap->start = (POINTER) ((char *)virtual_break_value + size);
+	}
+    }
+
+  virtual_break_value = (POINTER) ((char *)address + size);
+  break_value = (last_bloc
+		 ? last_bloc->data + last_bloc->size
+		 : first_heap->bloc_start);
+  if (size < 0)
+    relinquish ();
+
+  return address;
+}
+
+/* Allocate a relocatable bloc of storage of size SIZE.  A pointer to
+   the data is returned in *PTR.  PTR is thus the address of some variable
+   which will use the data area.
+
+   The allocation of 0 bytes is valid.
+   In case r_alloc_freeze is set, a best fit of unused blocs could be done
+   before allocating a new area.  Not yet done.
+
+   If we can't allocate the necessary memory, set *PTR to zero, and
+   return zero.  */
+
+POINTER r_alloc (POINTER *ptr, SIZE size);
+POINTER
+r_alloc (POINTER *ptr, SIZE size)
+{
+  bloc_ptr new_bloc;
+
+  if (! r_alloc_initialized)
+    init_ralloc ();
+
+  new_bloc = get_bloc (size);
+  if (new_bloc)
+    {
+      new_bloc->variable = ptr;
+      *ptr = new_bloc->data;
+    }
+  else
+    *ptr = 0;
+
+  return *ptr;
+}
+
+/* Free a bloc of relocatable storage whose data is pointed to by PTR.
+   Store 0 in *PTR to show there's no block allocated.  */
+
+void r_alloc_free (POINTER *ptr);
+void
+r_alloc_free (POINTER *ptr)
+{
+  register bloc_ptr dead_bloc;
+
+  if (! r_alloc_initialized)
+    init_ralloc ();
+
+  dead_bloc = find_bloc (ptr);
+  if (dead_bloc == NIL_BLOC)
+    abort ();
+
+  free_bloc (dead_bloc);
+  *ptr = 0;
+
+#ifdef emacs
+  refill_memory_reserve ();
+#endif
+}
+
+/* Given a pointer at address PTR to relocatable data, resize it to SIZE.
+   Do this by shifting all blocks above this one up in memory, unless
+   SIZE is less than or equal to the current bloc size, in which case
+   do nothing.
+
+   In case r_alloc_freeze is set, a new bloc is allocated, and the
+   memory copied to it.  Not very efficient.  We could traverse the
+   bloc_list for a best fit of free blocs first.
+
+   Change *PTR to reflect the new bloc, and return this value.
+
+   If more memory cannot be allocated, then leave *PTR unchanged, and
+   return zero.  */
+
+POINTER r_re_alloc (POINTER *ptr, SIZE size);
+POINTER
+r_re_alloc (POINTER *ptr, SIZE size)
+{
+  register bloc_ptr bloc;
+
+  if (! r_alloc_initialized)
+    init_ralloc ();
+
+  if (!*ptr)
+    return r_alloc (ptr, size);
+  if (!size)
+    {
+      r_alloc_free (ptr);
+      return r_alloc (ptr, 0);
+    }
+
+  bloc = find_bloc (ptr);
+  if (bloc == NIL_BLOC)
+    abort ();
+
+  if (size < bloc->size)
+    {
+      /* Wouldn't it be useful to actually resize the bloc here?  */
+      /* I think so too, but not if it's too expensive...  */
+      if ((bloc->size - MEM_ROUNDUP (size) >= page_size)
+          && r_alloc_freeze_level == 0)
+	{
+	  resize_bloc (bloc, MEM_ROUNDUP (size));
+	  /* Never mind if this fails, just do nothing...  */
+	  /* It *should* be infallible!  */
+	}
+    }
+  else if (size > bloc->size)
+    {
+      if (r_alloc_freeze_level)
+	{
+	  bloc_ptr new_bloc;
+	  new_bloc = get_bloc (MEM_ROUNDUP (size));
+	  if (new_bloc)
+	    {
+	      new_bloc->variable = ptr;
+	      *ptr = new_bloc->data;
+	      bloc->variable = (POINTER *) NIL;
+	    }
+          else
+	    return NIL;
+	}
+      else
+	{
+	  if (! resize_bloc (bloc, MEM_ROUNDUP (size)))
+	    return NIL;
+        }
+    }
+  return *ptr;
+}
+
+/* Disable relocations, after making room for at least SIZE bytes
+   of non-relocatable heap if possible.  The relocatable blocs are
+   guaranteed to hold still until thawed, even if this means that
+   malloc must return a null pointer.  */
+
+void r_alloc_freeze (long size);
+void
+r_alloc_freeze (long size)
+{
+  if (! r_alloc_initialized)
+    init_ralloc ();
+
+  /* If already frozen, we can't make any more room, so don't try.  */
+  if (r_alloc_freeze_level > 0)
+    size = 0;
+  /* If we can't get the amount requested, half is better than nothing.  */
+  while (size > 0 && r_alloc_sbrk (size) == 0)
+    size /= 2;
+  ++r_alloc_freeze_level;
+  if (size > 0)
+    r_alloc_sbrk (-size);
+}
+
+void r_alloc_thaw (void);
+void
+r_alloc_thaw (void)
+{
+
+  if (! r_alloc_initialized)
+    init_ralloc ();
+
+  if (--r_alloc_freeze_level < 0)
+    abort ();
+
+  /* This frees all unused blocs.  It is not too inefficient, as the resize
+     and bcopy is done only once.  Afterwards, all unreferenced blocs are
+     already shrunk to zero size.  */
+  if (!r_alloc_freeze_level)
+    {
+      bloc_ptr *b = &first_bloc;
+      while (*b)
+	if (!(*b)->variable)
+	  free_bloc (*b);
+	else
+	  b = &(*b)->next;
+    }
+}
+
+
+/* The hook `malloc' uses for the function which gets more space
+   from the system.  */
+#ifndef DOUG_LEA_MALLOC
+extern POINTER (*__morecore) (ptrdiff_t size);
+#endif
+
+/* Initialize various things for memory allocation. */
+
+void
+init_ralloc (void)
+{
+  if (r_alloc_initialized)
+    return;
+
+  r_alloc_initialized = 1;
+  real_morecore = (POINTER (*) (ptrdiff_t)) __morecore;
+  __morecore =
+#ifdef __GNUC__
+    (__typeof__ (__morecore))
+#endif
+    r_alloc_sbrk;
+
+  first_heap = last_heap = &heap_base;
+  first_heap->next = first_heap->prev = NIL_HEAP;
+  first_heap->start = first_heap->bloc_start
+    = virtual_break_value = break_value = (*real_morecore) (0);
+  if (break_value == NIL)
+    abort ();
+
+  page_size = PAGE;
+  extra_bytes = ROUNDUP (50000);
+
+#ifdef DOUG_LEA_MALLOC
+    mallopt (M_TOP_PAD, 64 * 4096);
+#else
+#if 0 /* Hasn't been synched yet */
+  /* Give GNU malloc's morecore some hysteresis
+     so that we move all the relocatable blocks much less often.  */
+  __malloc_extra_blocks = 64;
+#endif
+#endif
+
+  first_heap->end = (POINTER) ROUNDUP (first_heap->start);
+
+  /* The extra call to real_morecore guarantees that the end of the
+     address space is a multiple of page_size, even if page_size is
+     not really the page size of the system running the binary in
+     which page_size is stored.  This allows a binary to be built on a
+     system with one page size and run on a system with a smaller page
+     size.  */
+  (*real_morecore) (first_heap->end - first_heap->start);
+
+  /* Clear the rest of the last page; this memory is in our address space
+     even though it is after the sbrk value.  */
+  /* Doubly true, with the additional call that explicitly adds the
+     rest of that page to the address space.  */
+  memset (first_heap->start, 0, first_heap->end - first_heap->start);
+  virtual_break_value = break_value = first_heap->bloc_start = first_heap->end;
+  use_relocatable_buffers = 1;
+}
+
+#if defined (emacs) && defined (DOUG_LEA_MALLOC)
+
+/* Reinitialize the morecore hook variables after restarting a dumped
+   Emacs.  This is needed when using Doug Lea's malloc from GNU libc.  */
+void r_alloc_reinit (void);
+void
+r_alloc_reinit (void)
+{
+  /* Only do this if the hook has been reset, so that we don't get an
+     infinite loop, in case Emacs was linked statically.  */
+  if ( (POINTER (*) (ptrdiff_t)) __morecore !=  r_alloc_sbrk)
+    {
+      real_morecore = (POINTER (*) (ptrdiff_t)) __morecore;
+      __morecore =
+#ifdef __GNUC__
+	(__typeof__ (__morecore))
+#endif
+	r_alloc_sbrk;
+    }
+}
+#if 0
+#ifdef DEBUG
+
+void
+r_alloc_check (void)
+{
+  int found = 0;
+  heap_ptr h, ph = 0;
+  bloc_ptr b, pb = 0;
+
+  if (!r_alloc_initialized)
+    return;
+
+  assert (first_heap);
+  assert (last_heap->end <= (POINTER) sbrk (0));
+  assert ((POINTER) first_heap < first_heap->start);
+  assert (first_heap->start <= virtual_break_value);
+  assert (virtual_break_value <= first_heap->end);
+
+  for (h = first_heap; h; h = h->next)
+    {
+      assert (h->prev == ph);
+      assert ((POINTER) ROUNDUP (h->end) == h->end);
+#if 0 /* ??? The code in ralloc.c does not really try to ensure
+	 the heap start has any sort of alignment.
+	 Perhaps it should.  */
+      assert ((POINTER) MEM_ROUNDUP (h->start) == h->start);
+#endif
+      assert ((POINTER) MEM_ROUNDUP (h->bloc_start) == h->bloc_start);
+      assert (h->start <= h->bloc_start && h->bloc_start <= h->end);
+
+      if (ph)
+	{
+	  assert (ph->end < h->start);
+	  assert (h->start <= (POINTER)h && (POINTER)(h+1) <= h->bloc_start);
+	}
+
+      if (h->bloc_start <= break_value && break_value <= h->end)
+	found = 1;
+
+      ph = h;
+    }
+
+  assert (found);
+  assert (last_heap == ph);
+
+  for (b = first_bloc; b; b = b->next)
+    {
+      assert (b->prev == pb);
+      assert ((POINTER) MEM_ROUNDUP (b->data) == b->data);
+      assert ((SIZE) MEM_ROUNDUP (b->size) == b->size);
+
+      ph = 0;
+      for (h = first_heap; h; h = h->next)
+	{
+	  if (h->bloc_start <= b->data && b->data + b->size <= h->end)
+	    break;
+	  ph = h;
+	}
+
+      assert (h);
+
+      if (pb && pb->data + pb->size != b->data)
+	{
+	  assert (ph && b->data == h->bloc_start);
+	  while (ph)
+	    {
+	      if (ph->bloc_start <= pb->data
+		  && pb->data + pb->size <= ph->end)
+		{
+		  assert (pb->data + pb->size + b->size > ph->end);
+		  break;
+		}
+	      else
+		{
+		  assert (ph->bloc_start + b->size > ph->end);
+		}
+	      ph = ph->prev;
+	    }
+	}
+      pb = b;
+    }
+
+  assert (last_bloc == pb);
+
+  if (last_bloc)
+    assert (last_bloc->data + last_bloc->size == break_value);
+  else
+    assert (first_heap->bloc_start == break_value);
+}
+#endif /* DEBUG */
+#endif /* 0 */
+
+#endif
+
+#else /* HAVE_MMAP */
+
+/*
+   A relocating allocator built using the mmap(2) facility available
+   in some OSes.  Based on another version written by Paul Flinders,
+   from which code (and comments) are snarfed.
+
+   The OS should support mmap() with MAP_ANONYMOUS attribute, or have
+   /dev/zero.  It should support private memory mapping.
+
+   Paul Flinders wrote a version which works well for systems that
+   allow callers to specify (virtual) addresses to mmap().
+   Unfortunately, such a scheme doesn't work for certain systems like
+   HP-UX that have a system-wide virtual->real address map, and
+   consequently impose restrictions on the virtual address values
+   permitted.
+
+   NB: The mapping scheme in HP-UX is motivated by the inverted page
+   table design in some HP processors.
+
+   This alternate implementation allows for the addresses to be
+   optionally chosen by the system.  Fortunately, buffer allocation
+   doesn't insist upon contiguous memory which Flinders' scheme
+   provides, and this one doesn't.
+
+   We don't really provide for hysteresis here, but add some metering
+   to monitor how poorly the allocator actually works.  See the
+   documentation for `mmap-hysteresis'.
+
+   This implementation actually cycles through the blocks allocated
+   via mmap() and only sends it to free() if it wasn't one of them.
+   Unfortunately, this is O(n) in the number of mmapped blocks.  (Not
+   really, as we have a hash table which tries to reduce the cost.)
+   Also, this dereferences the pointer passed, so it would cause a
+   segfault if garbage was passed to it.  */
+
+#include <fcntl.h>
+#include <sys/mman.h>
+#include <stdio.h>
+
+typedef void *VM_ADDR;		/* VM addresses */
+static CONST VM_ADDR VM_FAILURE_ADDR = (VM_ADDR) -1; /* mmap returns this when it fails. */
+
+/* Configuration for relocating allocator. */
+
+/* #define MMAP_GENERATE_ADDRESSES */
+/* Define this if you want Emacs to manage the address table.
+   It is not recommended unless you have major problems with the
+   default scheme, which allows the OS to pick addresses. */
+
+/* USELESS_LOWER_ADDRESS_BITS defines the number of bits which can be
+   discarded while computing the hash, as they're always zero.  The
+   default is appropriate for a page size of 4096 bytes. */
+
+#define USELESS_LOWER_ADDRESS_BITS 12
+
+
+/* Size of hash table for inverted VM_ADDR->MMAP_HANDLE lookup */
+
+#define MHASH_PRIME 89
+
+
+/* Whether we want to enable metering of some ralloc performance.
+   This incurs a constant penalty for each mmap operation. */
+
+#define MMAP_METERING
+
+
+/* Rename the following to protect against a some smartness elsewhere.
+   We need access to the allocator used for non-mmap allocation
+   elsewhere, in case we get passed a handle that we didn't allocate
+   ourselves.  Currently, this default allocator is also used to
+   maintain local structures for relocatable blocks. */
+
+#define UNDERLYING_MALLOC   malloc
+#define UNDERLYING_FREE     free
+#define UNDERLYING_REALLOC  realloc
+
+/* MAP_ADDRCHOICE_FLAG is set to MAP_FIXED if MMAP_GENERATE_ADDRESSES
+   is defined, and MAP_VARIABLE otherwise.  Some losing systems don't
+   define the _FIXED/_VARIABLE flags, in which case it is set to 0 */
+
+#ifdef MMAP_GENERATE_ADDRESSES
+# ifdef MAP_FIXED
+#    define MAP_ADDRCHOICE_FLAG MAP_FIXED
+# endif
+#else /* !MMAP_GENERATE_ADDRESSES */
+# ifdef MAP_VARIABLE
+#    define MAP_ADDRCHOICE_FLAG MAP_VARIABLE
+# endif
+#endif /* MMAP_GENERATE_ADDRESSES */
+
+/* Default case. */
+#ifndef MAP_ADDRCHOICE_FLAG
+#  define MAP_ADDRCHOICE_FLAG 0
+#endif /* MAP_ADDRCHOICE_FLAG */
+
+#ifdef MAP_ANONYMOUS
+#  define MAP_FLAGS (MAP_PRIVATE | MAP_ADDRCHOICE_FLAG | MAP_ANONYMOUS)
+#else
+#  define MAP_FLAGS (MAP_PRIVATE | MAP_ADDRCHOICE_FLAG)
+#endif /* MAP_ANONYMOUS */
+
+
+/* (ptf): A flag to indicate whether we have initialized ralloc yet.  For
+   Emacs's sake, please do not make this local to malloc_init; on some
+   machines, the dumping procedure makes all static variables
+   read-only.  On these machines, the word static is #defined to be
+   the empty string, meaning that r_alloc_initialized becomes an
+   automatic variable, and loses its value each time Emacs is started up.
+
+   If we're using mmap this flag has three possible values
+   0 - initial value
+   1 - Normal value when running temacs. In this case buffers
+       are allocated using malloc so that any data that they
+       contain becomes part of the undumped executable.
+   2 - Normal value when running emacs */
+static int r_alloc_initialized = 0;
+
+/* (ptf): Macros for rounding.  Note that rounding to any value is possible
+   by changing the definition of PAGE. */
+#define PAGE (getpagesize ())
+#define PAGES_FOR(size) (((unsigned long int) (size) + page_size - 1)/page_size)
+#define ROUNDUP(size) ((unsigned long int)PAGES_FOR(size)*page_size)
+
+
+/* DEV_ZERO_FD is -1 normally, but for systems without MAP_ANONYMOUS
+   points to a file descriptor opened on /dev/zero */
+
+static int DEV_ZERO_FD = -1;
+
+
+/* We actually need a data structure that can be usefully structured
+   based on the VM address, and allows an ~O(1) lookup on an arbitrary
+   address, i.e. a hash table.  Maybe the XEmacs hash table can be
+   coaxed enough.  At the moment, we use lookup on a hash table to
+   decide whether to do an O(n) search on the malloced block list.
+   Addresses are hashed to a bucket modulo MHASH_PRIME. */
+
+
+/* We settle for a standard doubly-linked-list.  The dynarr type isn't
+   very amenable to deletion of items in the middle, so we conjure up
+   yet another stupid datastructure.  The structure is maintained as a
+   ring, and the singleton ring has the sole element as its left and
+   right neighbours. */
+
+static void init_MHASH_table (void); /* Forward reference */
+
+typedef struct alloc_dll
+{
+  size_t size;			/* #bytes currently in use */
+  size_t space_for;		/* #bytes we really have */
+  POINTER* aliased_address;	/* Address of aliased variable, to tweak if relocating */
+  VM_ADDR vm_addr;		/* VM address returned by mmap */
+  struct alloc_dll *left;	/* Left link in circular doubly linked list */
+  struct alloc_dll *right;
+} *MMAP_HANDLE;
+
+static MMAP_HANDLE mmap_start = 0; /* Head of linked list */
+static size_t page_size = 0;	/* Size of VM pages */
+static int mmap_hysteresis;	/* Should be size_t, really. */
+
+/* Get a new handle for a fresh block. */
+static MMAP_HANDLE
+new_mmap_handle (size_t nsiz)
+{
+  MMAP_HANDLE h = (MMAP_HANDLE) UNDERLYING_MALLOC( sizeof (struct alloc_dll));
+  if ( h == 0) return 0;
+  h->size = nsiz;
+  if (mmap_start == 0)
+    {
+      init_MHASH_table ();
+      mmap_start = h; mmap_start->left = h; mmap_start->right = h;
+    }
+  {
+    MMAP_HANDLE prev = mmap_start->left;
+    MMAP_HANDLE nex = mmap_start;
+
+    /* Four pointers need fixing. */
+    h->right = nex;
+    h->left = prev;
+    prev->right = h;
+    nex->left = h;
+  }
+  return h;
+}
+
+/* Find a handle given the aliased address using linear search. */
+static MMAP_HANDLE
+find_mmap_handle_lsearch (POINTER *alias)
+{
+  MMAP_HANDLE h = mmap_start;
+  if (h == 0) return 0;
+  do {
+    if (h->aliased_address == alias && *alias == h->vm_addr)
+      return h;
+    h = h->right;
+  } while( h != mmap_start );
+  return 0;			/* Bogus alias passed. */
+}
+
+/* Free a handle. */
+static void
+free_mmap_handle (MMAP_HANDLE h)
+{
+  MMAP_HANDLE prev = h->left;
+  MMAP_HANDLE nex = h->right;
+  if (prev == h || nex == h)	/* In fact, this should be && */
+    {				/* We're the singleton dll */
+      UNDERLYING_FREE( h );		/* Free the sole item */
+      mmap_start = 0; return;
+    }
+  else if (h == mmap_start)
+    {
+      mmap_start = nex;		/* Make sure mmap_start isn't bogus. */
+    }
+  prev->right = nex;
+  nex->left = prev;
+  UNDERLYING_FREE( h );
+}
+
+/* A simple hash table to speed up the inverted lookup of
+   VM_ADDR->MMAP_HANDLE. We maintain the number of hits for a
+   particular bucket.  We invalidate a hash table entry during block
+   deletion if the hash has cached the deleted block's address. */
+
+/* Simple hash check. */
+struct {
+  int n_hits;			/* How many addresses map to this? */
+  MMAP_HANDLE handle;		/* What is the current handle? */
+  VM_ADDR addr;			/* What is its VM address? */
+} MHASH_HITS[ MHASH_PRIME ];
+
+static void
+init_MHASH_table (void)
+{
+  int i = 0;
+  for (; i < MHASH_PRIME; i++)
+    {
+      MHASH_HITS[i].n_hits = 0;
+      MHASH_HITS[i].addr = 0;
+      MHASH_HITS[i].handle = 0;
+    }
+}
+
+/* Compute the hash value for an address. */
+static int
+MHASH (VM_ADDR addr)
+{
+#if (LONGBITS == 64)
+  unsigned long int addr_shift = (unsigned long int)(addr) >> USELESS_LOWER_ADDRESS_BITS;
+#else
+  unsigned int addr_shift = (unsigned int)(addr) >> USELESS_LOWER_ADDRESS_BITS;
+#endif
+  int hval = addr_shift % MHASH_PRIME; /* We could have addresses which are -ve
+					  when converted to signed ints */
+  return ((hval >= 0) ? hval : MHASH_PRIME + hval);
+}
+
+/* Add a VM address with its corresponding handle to the table. */
+static void
+MHASH_ADD (VM_ADDR addr, MMAP_HANDLE h)
+{
+  int kVal = MHASH( addr );
+  if (MHASH_HITS[kVal].n_hits++ == 0)
+    { /* Only overwrite the table if there were no hits so far. */
+      MHASH_HITS[kVal].addr = addr;
+      MHASH_HITS[kVal].handle = h;
+    }
+}
+
+/* Delete a VM address entry from the hash table. */
+static void
+MHASH_DEL (VM_ADDR addr)
+{
+  int kVal = MHASH( addr );
+  MHASH_HITS[kVal].n_hits--;
+  if (addr == MHASH_HITS[kVal].addr)
+    {
+      MHASH_HITS[kVal].addr = 0; /* Invalidate cache. */
+      MHASH_HITS[kVal].handle = 0;
+    }
+}
+
+/* End of hash buckets */
+
+/* Metering malloc performance. */
+#ifdef MMAP_METERING
+/* If we're metering, we introduce some extra symbols to aid the noble
+   cause of bloating XEmacs core size. */
+
+static Lisp_Object Qmmap_times_mapped;
+static Lisp_Object Qmmap_pages_mapped;
+static Lisp_Object Qmmap_times_unmapped;
+static Lisp_Object Qmmap_times_remapped;
+static Lisp_Object Qmmap_didnt_copy;
+static Lisp_Object Qmmap_pages_copied;
+static Lisp_Object Qmmap_average_bumpval;
+static Lisp_Object Qmmap_wastage;
+static Lisp_Object Qmmap_live_pages;
+static Lisp_Object Qmmap_addr_looked_up;
+static Lisp_Object Qmmap_hash_worked;
+static Lisp_Object Qmmap_addrlist_size;
+
+#define M_Map 0			/* How many times allocated? */
+#define M_Pages_Map 1		/* How many pages allocated? */
+#define M_Unmap 2		/* How many times freed? */
+#define M_Remap 3		/* How many times increased in size? */
+#define M_Didnt_Copy 4		/* How many times didn't need to copy? */
+#define M_Copy_Pages 5		/* Total # pages copied */
+#define M_Average_Bumpval 6	/* Average bump value */
+#define M_Wastage 7		/* Remaining (unused space) */
+#define M_Live_Pages 8		/* #live pages */
+#define M_Address_Lookup 9	/* How many times did we need to check if an addr is in the block? */
+#define M_Hash_Worked   10      /* How many times did the simple hash check work? */
+#define M_Addrlist_Size 11	/* What is the size of the XEmacs memory map? */
+
+#define N_Meterables 12		/* Total number of meterables */
+#define MEMMETER(x) {x;}
+#define MVAL(x) (meter[x])
+#define MLVAL(x) (make_int (meter[x]))
+static int meter[N_Meterables];
+
+DEFUN ("mmap-allocator-status", Fmmap_allocator_status, 0, 0, 0, /*
+Return some information about mmap-based allocator.
+
+mmap-times-mapped:    number of times r_alloc was called.
+mmap-pages-mapped:    number of pages mapped by r_alloc calls only.
+mmap-times-unmapped:  number of times r_free was called.
+mmap-times-remapped:  number of times r_re_alloc was called.
+mmap-didnt-copy:      number of times re-alloc did NOT have to move the block.
+mmap-pages-copied:    total number of pages copied.
+mmap-average-bumpval: average increase in size demanded to re-alloc.
+mmap-wastage:         total number of bytes allocated, but not currently in use.
+mmap-live-pages:      total number of pages live.
+mmap-addr-looked-up:  total number of times needed to check if addr is in block.
+mmap-hash-worked:     total number of times the simple hash check worked.
+mmap-addrlist-size:   number of entries in address picking list.
+*/
+       ())
+{
+  Lisp_Object result = Qnil;
+
+  result = cons3 (Qmmap_addrlist_size,	MLVAL (M_Addrlist_Size),   result);
+  result = cons3 (Qmmap_hash_worked,	MLVAL (M_Hash_Worked),	   result);
+  result = cons3 (Qmmap_addr_looked_up,	MLVAL (M_Address_Lookup),  result);
+  result = cons3 (Qmmap_live_pages,	MLVAL (M_Live_Pages),	   result);
+  result = cons3 (Qmmap_wastage,	MLVAL (M_Wastage),	   result);
+  result = cons3 (Qmmap_average_bumpval,MLVAL (M_Average_Bumpval), result);
+  result = cons3 (Qmmap_pages_copied,	MLVAL (M_Copy_Pages),	   result);
+  result = cons3 (Qmmap_didnt_copy,	MLVAL (M_Didnt_Copy),	   result);
+  result = cons3 (Qmmap_times_remapped,	MLVAL (M_Remap),	   result);
+  result = cons3 (Qmmap_times_unmapped,	MLVAL (M_Unmap),	   result);
+  result = cons3 (Qmmap_pages_mapped,	MLVAL (M_Pages_Map),	   result);
+  result = cons3 (Qmmap_times_mapped,	MLVAL (M_Map),		   result);
+
+  return result;
+}
+
+#else /* !MMAP_METERING */
+
+#define MEMMETER(x)
+#define MVAL(x)
+
+#endif /* MMAP_METERING */
+
+static MMAP_HANDLE
+find_mmap_handle (POINTER *alias)
+{
+  int kval  = MHASH( *alias );
+  MEMMETER( MVAL(M_Address_Lookup)++ )
+  switch( MHASH_HITS[kval].n_hits)
+    {
+    case 0:
+      MEMMETER( MVAL( M_Hash_Worked )++ )
+      return 0;
+
+    case 1:
+      if (*alias == MHASH_HITS[kval].addr)
+	{
+	  MEMMETER( MVAL( M_Hash_Worked) ++ );
+	  return MHASH_HITS[kval].handle;
+	}
+      /* FALL THROUGH */
+    default:
+      return find_mmap_handle_lsearch( alias );
+    } /* switch */
+}
+
+/*
+   Some kernels don't like being asked to pick addresses for mapping
+   themselves---IRIX is known to become extremely slow if mmap is
+   passed a ZERO as the first argument.  In such cases, we use an
+   address map which is managed local to the XEmacs process.  The
+   address map maintains an ordered linked list of (address, size,
+   occupancy) triples ordered by the absolute address.  Initially, a
+   large address area is marked as being empty.  The address picking
+   scheme takes bites off the first block which is still empty and
+   large enough.  If mmap with the specified address fails, it is
+   marked unavailable and not attempted thereafter.  The scheme will
+   keep fragmenting the large empty block until it finds an address
+   which can be successfully mmapped, or until there are no free
+   blocks of the given size left.
+
+   Note that this scheme, given its first-fit strategy, is prone to
+   fragmentation of the first part of memory earmarked for this
+   purpose. [ACP Vol I].  We can't use the workaround of using a
+   randomized first fit because we don't want to presume too much
+   about the memory map.  Instead, we try to coalesce empty or
+   unavailable blocks at any available opportunity.  */
+
+/* Initialization procedure for address picking scheme */
+static void Addr_Block_initialize(void);
+
+/* Get a suitable VM_ADDR via mmap */
+static VM_ADDR New_Addr_Block( SIZE sz );
+
+/* Free a VM_ADDR allocated via New_Addr_Block */
+static void Free_Addr_Block( VM_ADDR addr, SIZE sz );
+
+#ifdef MMAP_GENERATE_ADDRESSES
+/* Implementation of the three calls for address picking when XEmacs is incharge */
+
+/* The enum denotes the status of the following block. */
+typedef enum { empty = 0, occupied, unavailable } addr_status;
+
+typedef struct addr_chain
+{
+  POINTER addr;
+  SIZE sz;
+  addr_status flag;
+  struct addr_chain *next;
+} ADDRESS_BLOCK, *ADDRESS_CHAIN;
+/* NB: empty and unavailable blocks are concatenated. */
+
+static ADDRESS_CHAIN addr_chain = 0;
+/* Start off the address block chain with a humongous address block
+   which is empty to start with.  Note that addr_chain is invariant
+   WRT the addition/deletion of address blocks because of the assert
+   in Coalesce() and the strict ordering of blocks by their address
+   */
+static void Addr_Block_initialize()
+{
+  MEMMETER( MVAL( M_Addrlist_Size )++)
+  addr_chain = (ADDRESS_CHAIN) UNDERLYING_MALLOC( sizeof( ADDRESS_BLOCK ));
+  addr_chain->next = 0;		/* Last block in chain */
+  addr_chain->sz = 0x0c000000;	/* Size */
+  addr_chain->addr = (POINTER) (0x04000000 | DATA_SEG_BITS);
+  addr_chain->flag = empty;
+}
+
+/* Coalesce address blocks if they are contiguous.  Only empty and
+   unavailable slots are coalesced. */
+static void Coalesce_Addr_Blocks()
+{
+  ADDRESS_CHAIN p;
+  for (p = addr_chain; p; p = p->next)
+    {
+      while (p->next && p->flag == p->next->flag)
+	{
+	  ADDRESS_CHAIN np;
+	  np = p->next;
+
+	  if (p->flag == occupied) break; /* No cigar */
+
+	  /* Check if the addresses are contiguous. */
+	  if (p->addr + p->sz != np->addr) break;
+
+	  MEMMETER( MVAL( M_Addrlist_Size )--)
+	  /* We can coalesce these two. */
+	  p->sz += np->sz;
+	  p->next = np->next;
+	  assert( np != addr_chain ); /* We're not freeing the head of the list. */
+	  UNDERLYING_FREE( np );
+	}
+    } /* for all p */
+}
+
+/* Get an empty address block of specified size. */
+static VM_ADDR New_Addr_Block( SIZE sz )
+{
+  ADDRESS_CHAIN p = addr_chain;
+  VM_ADDR new_addr = VM_FAILURE_ADDR;
+  for (; p; p = p->next)
+    {
+      if (p->flag == empty && p->sz > sz)
+	{
+	  /* Create a new entry following p which is empty. */
+	  ADDRESS_CHAIN remainder = (ADDRESS_CHAIN) UNDERLYING_MALLOC( sizeof( ADDRESS_BLOCK ) );
+	  remainder->next = p->next;
+	  remainder->flag = empty;
+	  remainder->addr = p->addr + sz;
+	  remainder->sz = p->sz - sz;
+
+	  MEMMETER( MVAL( M_Addrlist_Size )++)
+
+	  /* Now make p become an occupied block with the appropriate size */
+	  p->next = remainder;
+	  p->sz = sz;
+	  new_addr = mmap( (VM_ADDR) p->addr, p->sz, PROT_READ|PROT_WRITE,
+			   MAP_FLAGS, DEV_ZERO_FD, 0 );
+	  if (new_addr == VM_FAILURE_ADDR)
+	    {
+	      p->flag = unavailable;
+	      continue;
+	    }
+	  p->flag = occupied;
+	  break;
+	}
+    }
+  Coalesce_Addr_Blocks();
+  return new_addr;
+}
+
+/* Free an address block.  We mark the block as being empty, and attempt to
+   do any coalescing that may have resulted from this. */
+static void Free_Addr_Block( VM_ADDR addr, SIZE sz )
+{
+  ADDRESS_CHAIN p = addr_chain;
+  for (; p; p = p->next )
+    {
+      if (p->addr == addr)
+	{
+	  if (p->sz != sz) abort(); /* ACK! Shouldn't happen at all. */
+	  munmap( (VM_ADDR) p->addr, p->sz );
+	  p->flag = empty;
+	  break;
+	}
+    }
+  if (!p) abort(); /* Can't happen... we've got a block to free which is not in
+		      the address list. */
+  Coalesce_Addr_Blocks();
+}
+#else /* !MMAP_GENERATE_ADDRESSES */
+/* This is an alternate (simpler) implementation in cases where the
+   address is picked by the kernel. */
+
+static void Addr_Block_initialize(void)
+{
+  /* Nothing. */
+}
+
+static VM_ADDR New_Addr_Block( SIZE sz )
+{
+  return mmap (0, sz, PROT_READ|PROT_WRITE, MAP_FLAGS,
+	       DEV_ZERO_FD, 0 );
+}
+
+static void Free_Addr_Block( VM_ADDR addr, SIZE sz )
+{
+  munmap ((caddr_t) addr, sz );
+}
+
+#endif /* MMAP_GENERATE_ADDRESSES */
+
+
+/* IMPLEMENTATION OF EXPORTED RELOCATOR INTERFACE */
+
+/*
+ r_alloc( POINTER, SIZE ): Allocate a relocatable area with the start
+ address aliased to the first parameter.
+ */
+
+POINTER r_alloc (POINTER *ptr, SIZE size);
+POINTER
+r_alloc (POINTER *ptr, SIZE size)
+{
+  MMAP_HANDLE mh;
+
+  switch(r_alloc_initialized)
+    {
+    case 0:
+      abort();
+    case 1:
+      *ptr = (POINTER) UNDERLYING_MALLOC(size);
+      break;
+    default:
+      mh = new_mmap_handle( size );
+      if (mh)
+	{
+	  SIZE hysteresis = (mmap_hysteresis > 0 ?  mmap_hysteresis  : 0);
+	  SIZE  mmapped_size = ROUNDUP( size + hysteresis );
+	  MEMMETER( MVAL(M_Map)++ )
+	  MEMMETER( MVAL(M_Pages_Map) += (mmapped_size/page_size) )
+	  MEMMETER( MVAL(M_Wastage) += mmapped_size - size )
+          MEMMETER( MVAL(M_Live_Pages) += (mmapped_size/page_size) )
+	  mh->vm_addr = New_Addr_Block( mmapped_size );
+	  if (mh->vm_addr == VM_FAILURE_ADDR) {
+	    free_mmap_handle( mh ); /* Free the loser */
+	    *ptr = 0;
+	    return 0;		/* ralloc failed due to mmap() failure. */
+	  }
+	  MHASH_ADD( mh->vm_addr, mh );
+	  mh->space_for = mmapped_size;
+	  mh->aliased_address = ptr;
+	  *ptr = (POINTER) mh->vm_addr;
+	}
+      else
+	*ptr = 0;		/* Malloc of block failed */
+      break;
+    }
+  return *ptr;
+}
+
+/* Free a bloc of relocatable storage whose data is pointed to by PTR.
+   Store 0 in *PTR to show there's no block allocated.  */
+
+void r_alloc_free (POINTER *ptr);
+void
+r_alloc_free (POINTER *ptr)
+{
+  switch( r_alloc_initialized) {
+    case 0:
+      abort();
+
+    case 1:
+      UNDERLYING_FREE( *ptr );		/* Certain this is from the heap. */
+      break;
+
+    default:
+      {
+	MMAP_HANDLE dead_handle = find_mmap_handle( ptr );
+	/* Check if we've got it. */
+	if (dead_handle == 0)	/* Didn't find it in the list of mmap handles */
+	  {
+	    UNDERLYING_FREE( *ptr );
+	  }
+	else
+	  {
+	    MEMMETER( MVAL( M_Wastage ) -= (dead_handle->space_for - dead_handle->size) )
+	    MEMMETER( MVAL( M_Live_Pages ) -= (dead_handle->space_for / page_size ))
+	    MEMMETER(MVAL(M_Unmap)++)
+	    MHASH_DEL( dead_handle->vm_addr );
+	    Free_Addr_Block( dead_handle->vm_addr, dead_handle->space_for );
+	    free_mmap_handle (dead_handle);
+	  }
+      }
+      break;
+    } /* r_alloc_initialized */
+  *ptr = 0;			/* Zap the pointer's contents. */
+}
+
+/* Given a pointer at address PTR to relocatable data, resize it to SIZE.
+
+   Change *PTR to reflect the new bloc, and return this value.
+
+   If more memory cannot be allocated, then leave *PTR unchanged, and
+   return zero.  */
+
+POINTER r_re_alloc (POINTER *ptr, SIZE sz);
+POINTER
+r_re_alloc (POINTER *ptr, SIZE sz)
+{
+  if (r_alloc_initialized == 0)
+    {
+      abort ();
+      return 0; /* suppress compiler warning */
+    }
+  else if (r_alloc_initialized == 1)
+    {
+      POINTER tmp = (POINTER) realloc(*ptr, sz);
+      if (tmp)
+	*ptr = tmp;
+      return tmp;
+    }
+  else
+    {
+      SIZE hysteresis = (mmap_hysteresis > 0 ?  mmap_hysteresis : 0);
+      SIZE actual_sz = ROUNDUP( sz + hysteresis );
+      MMAP_HANDLE h = find_mmap_handle( ptr );
+      VM_ADDR new_vm_addr;
+
+      if ( h == 0 )		/* Was allocated using malloc. */
+	{
+	  POINTER tmp = (POINTER) UNDERLYING_REALLOC(*ptr, sz);
+	  if (tmp)
+	    *ptr = tmp;
+	  return tmp;
+	}
+
+      MEMMETER(
+	       MVAL(M_Average_Bumpval) =
+	       (((double) MVAL(M_Remap) * MVAL(M_Average_Bumpval)) + (sz - h->size))
+	       / (double) (MVAL(M_Remap) + 1))
+      MEMMETER(MVAL(M_Remap)++)
+      if (h->space_for > sz)	/* We've got some more room */
+	{			/* Also, if a shrinkage was asked for. */
+	  MEMMETER( MVAL(M_Didnt_Copy)++ )
+          MEMMETER( MVAL(M_Wastage) -= (sz - h->size))
+	  /* We're pretty dumb at handling shrinkage.  We should check for
+	     a larger gap than the standard hysteresis allowable, and if so,
+	     shrink the number of pages.  Right now, we simply reset the size
+	     component and return. */
+	  h->size = sz;
+	  return *ptr;
+	}
+
+      new_vm_addr = New_Addr_Block( actual_sz );
+      if (new_vm_addr == VM_FAILURE_ADDR)
+	{/* Failed to realloc. */
+          /* *ptr = 0; */
+	  return 0;
+	}
+
+      MHASH_ADD( new_vm_addr, h );
+      /* We got a block OK: now we should move the old contents to the
+	 new address.  We use the old size of this block.  */
+      memmove(new_vm_addr, h->vm_addr, h->size);
+      MHASH_DEL( h->vm_addr );
+      Free_Addr_Block( h->vm_addr, h->space_for ); /* Unmap old area. */
+
+      MEMMETER( MVAL( M_Copy_Pages ) += (h->space_for/page_size) )
+      MEMMETER( MVAL( M_Live_Pages ) -= (h->space_for / page_size))
+      MEMMETER( MVAL( M_Live_Pages ) += (actual_sz / page_size))
+      MEMMETER( MVAL( M_Wastage ) -= (h->space_for - h->size))
+      MEMMETER( MVAL( M_Wastage ) += (actual_sz - sz) )
+
+      /* Update block datastructure. */
+      h->space_for = actual_sz;	/* New total space */
+      h->size = sz;		/* New (requested) size */
+      h->vm_addr = new_vm_addr;	/* New VM start address */
+      h->aliased_address = ptr;	/* Change alias to reflect block relocation. */
+      *ptr = (POINTER) h->vm_addr;
+      return *ptr;
+    }
+}
+
+
+/* Initialize various things for memory allocation.
+ */
+void
+init_ralloc (void)
+{
+  int i = 0;
+  if (r_alloc_initialized > 1)
+    return;	/* used to return 1 */
+
+  if (++r_alloc_initialized == 1)
+    return;	/* used to return 1 */
+
+  Addr_Block_initialize();	/* Initialize the address picker, if required. */
+  page_size = PAGE;
+  assert( page_size > 0 );	/* getpagesize() bogosity check. */
+
+#ifndef MAP_ANONYMOUS
+  DEV_ZERO_FD = open( "/dev/zero", O_RDWR );
+  if (DEV_ZERO_FD < 0)
+    /* Failed.  Perhaps we should abort here? */
+    return;	/* used to return 0 */
+#endif
+
+#ifdef MMAP_METERING
+  for(i = 0; i < N_Meterables; i++ )
+    {
+      meter[i] = 0;
+    }
+#endif /* MMAP_METERING */
+}
+
+void
+syms_of_ralloc (void)
+{
+#ifdef MMAP_METERING
+  defsymbol (&Qmmap_times_mapped, "mmap-times-mapped");
+  defsymbol (&Qmmap_pages_mapped, "mmap-pages-mapped");
+  defsymbol (&Qmmap_times_unmapped, "mmap-times-unmapped");
+  defsymbol (&Qmmap_times_remapped, "mmap-times-remapped");
+  defsymbol (&Qmmap_didnt_copy, "mmap-didnt-copy");
+  defsymbol (&Qmmap_pages_copied, "mmap-pages-copied");
+  defsymbol (&Qmmap_average_bumpval, "mmap-average-bumpval");
+  defsymbol (&Qmmap_wastage, "mmap-wastage");
+  defsymbol (&Qmmap_live_pages, "mmap-live-pages");
+  defsymbol (&Qmmap_addr_looked_up, "mmap-addr-looked-up");
+  defsymbol (&Qmmap_hash_worked, "mmap-hash-worked");
+  defsymbol (&Qmmap_addrlist_size, "mmap-addrlist-size");
+  DEFSUBR (Fmmap_allocator_status);
+#endif /* MMAP_METERING */
+}
+
+void
+vars_of_ralloc (void)
+{
+  DEFVAR_INT ("mmap-hysteresis", &mmap_hysteresis /*
+Extra room left at the end of an allocated arena,
+so that a re-alloc requesting extra space smaller than this
+does not actually cause a new arena to be allocated.
+
+A negative value is considered equal to zero.  This is the
+minimum amount of space guaranteed to be left at the end of
+the arena.  Because allocation happens in multiples of the OS
+page size, it is possible for more space to be left unused.
+*/ );
+  mmap_hysteresis = 0;
+}
+
+#endif /* HAVE_MMAP */