(finish_struct): Promote unsigned bitfield to signed int

if the field isn't as wide as an int.

From-SVN: r4178

gcc/c-decl.c

@@ -5260,15 +5260,19 @@ finish_struct (t, fieldlist)
   /* Promote each bit-field's type to int if it is narrower than that.  */
   for (x = fieldlist; x; x = TREE_CHAIN (x))
     if (DECL_BIT_FIELD (x)
-	&& C_PROMOTING_INTEGER_TYPE_P (TREE_TYPE (x)))
+	&& (C_PROMOTING_INTEGER_TYPE_P (TREE_TYPE (x))
+	    || DECL_FIELD_SIZE (x) < TYPE_PRECISION (integer_type_node)))
       {
 	tree type = TREE_TYPE (x);
 
-      /* Preserve unsignedness if traditional or if not really any wider.  */
+	/* Preserve unsignedness if traditional
+	   or if not really getting any wider.  */
 	if (TREE_UNSIGNED (type)
 	    && (flag_traditional
-	      || (TYPE_PRECISION (type)
-		  == TYPE_PRECISION (integer_type_node))))
+		||
+		(TYPE_PRECISION (type) == TYPE_PRECISION (integer_type_node)
+		 &&
+		 DECL_FIELD_SIZE (x) == TYPE_PRECISION (integer_type_node))))
 	  TREE_TYPE (x) = unsigned_type_node;
 	else
 	  TREE_TYPE (x) = integer_type_node;