1 files changed, 31 insertions, 10 deletions

diff --git a/gcc/sbitmap.c b/gcc/sbitmap.c
index e581000e877..170d87df839 100644
--- a/gcc/sbitmap.c
+++ b/gcc/sbitmap.c
@@ -218,13 +218,26 @@ void
 sbitmap_difference (dst, a, b)
      sbitmap dst, a, b;
 {
-  unsigned int i, n = dst->size;
+  unsigned int i, dst_size = dst->size;
+  unsigned int min_size = dst->size;
   sbitmap_ptr dstp = dst->elms;
   sbitmap_ptr ap = a->elms;
   sbitmap_ptr bp = b->elms;
-
-  for (i = 0; i < n; i++)
-    *dstp++ = *ap++ & ~*bp++;
+  
+  /* A should be at least as large as DEST, to have a defined source.  */
+  if (a->size < dst_size)
+    abort ();
+  /* If minuend is smaller, we simply pretend it to be zero bits, i.e.
+     only copy the subtrahend into dest.  */
+  if (b->size < min_size)
+    min_size = b->size;
+  for (i = 0; i < min_size; i++)
+    *dstp++ = *ap++ & (~*bp++);
+  /* Now fill the rest of dest from A, if B was too short.
+     This makes sense only when destination and A differ.  */
+  if (dst != a && i != dst_size)
+    for (; i < dst_size; i++)
+      *dstp++ = *ap++;
 }
 
 /* Set DST to be (A and B).
@@ -658,27 +671,35 @@ dump_sbitmap (file, bmap)
 }
 
 void
-debug_sbitmap (bmap)
+dump_sbitmap_file (file, bmap)
+     FILE *file;
      sbitmap bmap;
 {
   unsigned int i, pos;
 
-  fprintf (stderr, "n_bits = %d, set = {", bmap->n_bits);
+  fprintf (file, "n_bits = %d, set = {", bmap->n_bits);
 
   for (pos = 30, i = 0; i < bmap->n_bits; i++)
     if (TEST_BIT (bmap, i))
       {
 	if (pos > 70)
 	  {
-	    fprintf (stderr, "\n");
+	    fprintf (file, "\n  ");
 	    pos = 0;
 	  }
 
-	fprintf (stderr, "%d ", i);
-	pos += 1 + (i >= 10) + (i >= 100);
+	fprintf (file, "%d ", i);
+	pos += 2 + (i >= 10) + (i >= 100) + (i >= 1000);
       }
 
-  fprintf (stderr, "}\n");
+  fprintf (file, "}\n");
+}
+
+void
+debug_sbitmap (bmap)
+     sbitmap bmap;
+{
+  dump_sbitmap_file (stderr, bmap);
 }
 
 void