Fix PR c++/68711 - [6 regression] SEGV on an invalid offsetof of a member

of a virtual base.

gcc/testsuite/ChangeLog:
	* g++.dg/other/offsetof8.C: New test.

gcc/cp/ChangeLog:
	* typeck.c (build_class_member_access_expr): Strip NOPs before
        testing a potentially null operand for equality to zero.

From-SVN: r231437

gcc/cp/ChangeLog

+2015-12-08  Martin Sebor  <msebor@redhat.com>
+
+	PR c++/68711
+	* typeck.c (build_class_member_access_expr): Strip NOPs before
+        testing a potentially null operand for equality to zero.
+
 2015-12-07  Jakub Jelinek  <jakub@redhat.com>
 
 	PR c++/68760

gcc/cp/typeck.c

@@ -2358,8 +2358,11 @@ build_class_member_access_expr (cp_expr object, tree member,
       int type_quals;
       tree member_type;
 
-      null_object_p = (INDIRECT_REF_P (object)
-		       && integer_zerop (TREE_OPERAND (object, 0)));
+      if (INDIRECT_REF_P (object))
+	null_object_p =
+	  integer_zerop (tree_strip_nop_conversions (TREE_OPERAND (object, 0)));
+      else
+	null_object_p = false;
 
       /* Convert OBJECT to the type of MEMBER.  */
       if (!same_type_p (TYPE_MAIN_VARIANT (object_type),

gcc/testsuite/ChangeLog

+2015-12-08  Martin Sebor  <msebor@redhat.com>
+
+	PR c++/68711
+	* g++.dg/other/offsetof8.C: New test.
+
 2015-12-08  Nathan Sidwell  <nathan@acm.org>
 
 	* gcc.target/nvptx/trailing-init.c: New.

gcc/testsuite/g++.dg/other/offsetof8.C

+// PR c++/68711 - [5 regression] SEGV on an invalid offsetof of a member
+//                of a virtual base
+// { dg-do compile }
+
+struct A { int i; };
+
+struct B: virtual A { };
+
+int a[]  = {
+  !&((B*)0)->i,    // { dg-error "invalid access to non-static data member" }
+  __builtin_offsetof (B, i)   // { dg-error "invalid access to non-static" }
+};