--- mlton-r6698.patched/runtime/gc/heap.c	2008-11-03 23:45:47.000000000 +0100
+++ mlton-r6698/runtime/gc/heap.c	2008-11-05 23:53:54.000000000 +0100
@@ -39,6 +39,7 @@
 size_t sizeofHeapDesired (GC_state s, size_t liveSize, size_t currentSize) {
   size_t liveWithMapsSize;
   size_t res;
+  size_t maxSize;
   float withMapsRatio;
 
   liveSize = align (liveSize, s->sysvals.pageSize);
@@ -82,6 +83,9 @@
     res = s->sysvals.ram;
   } else { /* Required live ratio. */
     res = liveSize * s->controls.ratios.markCompact;
+    /* Avoid overflow */
+    if (res < liveSize)
+      res = SIZE_MAX;
     /* If the current heap is bigger than res, then shrinking always
      * sounds like a good idea.  However, depending on what pages the
      * VM keeps around, growing could be very expensive, if it
@@ -104,6 +108,16 @@
       die ("Out of memory with max heap size %s.",
            uintmaxToCommaString(s->controls.maxHeap));
   }
+
+  /* Avoid overflow. */
+  maxSize = align(SIZE_MAX - s->sysvals.pageSize, s->sysvals.pageSize);
+  maxSize -= sizeofCardMapAndCrossMap(s, maxSize);
+  if (res > maxSize)
+    res = maxSize;
+  if (res < liveSize)
+    die ("Out of memory with system max heap size %s.", 
+	 uintmaxToCommaString(res));
+  
   if (DEBUG_RESIZING)
     fprintf (stderr, "%s = sizeofHeapDesired (%s, %s)\n",
              uintmaxToCommaString(res),