cvt.c (cp_convert_to_pointer): Handle NULL pointer conversions, even in complex…

cvt.c (cp_convert_to_pointer): Handle NULL pointer conversions, even in complex virtual base class hierarchies.

	* cvt.c (cp_convert_to_pointer): Handle NULL pointer
	conversions, even in complex virtual base class hierarchies.

From-SVN: r21626

gcc/cp/ChangeLog

+1998-08-07  Mark Mitchell  <mark@markmitchell.com>
+
+	* cvt.c (cp_convert_to_pointer): Handle a NULL pointer
+	conversions, even in complex virtual base class hierarchies.
+
 1998-08-06  Mark Mitchell  <mark@markmitchell.com>
 
 	* cp-tree.h (ENUM_TEMPLATE_INFO): New macro.

gcc/cp/cvt.c

@@ -154,7 +154,15 @@ cp_convert_to_pointer (type, expr)
 	  && TREE_CODE (TREE_TYPE (type)) == RECORD_TYPE
 	  && IS_AGGR_TYPE (TREE_TYPE (type))
 	  && IS_AGGR_TYPE (TREE_TYPE (intype))
-	  && TREE_CODE (TREE_TYPE (intype)) == RECORD_TYPE)
+	  && TREE_CODE (TREE_TYPE (intype)) == RECORD_TYPE
+	  /* If EXPR is NULL, then we don't need to do any arithmetic
+	     to convert it:
+
+	       [conv.ptr]
+
+	       The null pointer value is converted to the null pointer
+	       value of the destination type.  */
+	  && !integer_zerop (expr))
 	{
 	  enum tree_code code = PLUS_EXPR;
 	  tree binfo = get_binfo (TREE_TYPE (type), TREE_TYPE (intype), 1);

gcc/testsuite/g++.old-deja/g++.other/cast1.C

+// Build don't link:
+
+struct S0 { };
+struct S1 : virtual public S0 { };
+struct S2 : virtual public S0 { };
+
+struct S3 : public S1, public S2, virtual public S0
+{
+};
+
+void f(const S0*) {}
+
+void g()
+{
+  f(static_cast<S3*>(0));
+}