re PR c++/41788 (-Wpacked option changes the layout of packed non-POD structs)

	PR c++/41788
	* class.c (layout_class_type): Set packed_maybe_necessary for packed
	non-PODs.

From-SVN: r156088

gcc/cp/ChangeLog

 2010-01-20  Jason Merrill  <jason@redhat.com>
 
+	PR c++/41788
+	* class.c (layout_class_type): Set packed_maybe_necessary for packed
+	non-PODs.
+
 	PR c++/41920
 	* semantics.c (build_lambda_object): Call mark_used on captured
 	variables.

gcc/cp/class.c

@@ -5216,6 +5216,11 @@ layout_class_type (tree t, tree *virtuals_p)
 		 build_decl (input_location,
 			     FIELD_DECL, NULL_TREE, char_type_node));
 
+  /* If this is a non-POD, declaring it packed makes a difference to how it
+     can be used as a field; don't let finalize_record_size undo it.  */
+  if (TYPE_PACKED (t) && !layout_pod_type_p (t))
+    rli->packed_maybe_necessary = true;
+
   /* Let the back end lay out the type.  */
   finish_record_layout (rli, /*free_p=*/true);
 

gcc/testsuite/ChangeLog

 2010-01-20  Jason Merrill  <jason@redhat.com>
 
+	PR c++/41788
+	* g++.dg/abi/packed1.C: New.
+
 	PR c++/41920
 	* g++.dg/cpp0x/lambda/lambda-warn1.C: New.
 

gcc/testsuite/g++.dg/abi/packed1.C

+// PR c++/41788
+// { dg-options "-Wpacked" }
+// { dg-do run }
+
+extern "C" void abort ();
+
+struct INNER {
+  virtual int foo() const { return 1; }
+} __attribute__ ((packed));
+
+struct OUTER {
+  char c;
+  INNER inner;
+} __attribute__ ((packed));
+
+int main()
+{
+  OUTER outer;
+  int s = sizeof(outer);
+  int o = (char *)&outer.inner - (char *)&outer;
+  if (s != sizeof (char) + sizeof (void*)
+      || o != sizeof (char))
+    abort ();
+}