re PR c++/13981 (Give message about incomplete class that might be implicitly upcasted.)

/cp
2014-05-08  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/13981
	* typeck.c (convert_for_assignment): Provide an inform for pointers
	to incomplete class types.

/testsuite
2014-05-08  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/13981
	* g++.dg/diagnostic/pr13981.C: New.

From-SVN: r210217

gcc/cp/ChangeLog

+2014-05-08  Paolo Carlini  <paolo.carlini@oracle.com>
+
+	PR c++/13981
+	* typeck.c (convert_for_assignment): Provide an inform for pointers
+	to incomplete class types.
+
 2014-05-07  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	PR c++/61083

gcc/cp/typeck.c

@@ -8094,6 +8094,14 @@ convert_for_assignment (tree type, tree rhs,
 		    default:
 		      gcc_unreachable();
 		  }
+	      if (TYPE_PTR_P (rhstype)
+		  && TYPE_PTR_P (type)
+		  && CLASS_TYPE_P (TREE_TYPE (rhstype))
+		  && CLASS_TYPE_P (TREE_TYPE (type))
+		  && !COMPLETE_TYPE_P (TREE_TYPE (rhstype)))
+		inform (DECL_SOURCE_LOCATION (TYPE_MAIN_DECL
+					      (TREE_TYPE (rhstype))),
+			"class type %qT is incomplete", TREE_TYPE (rhstype));
 	    }
 	  return error_mark_node;
 	}

gcc/testsuite/ChangeLog

+2014-05-08  Paolo Carlini  <paolo.carlini@oracle.com>
+
+	PR c++/13981
+	* g++.dg/diagnostic/pr13981.C: New.
+
 2014-05-08  Marc Glisse  <marc.glisse@inria.fr>
 
 	PR tree-optimization/59100

gcc/testsuite/g++.dg/diagnostic/pr13981.C

+// PR c++/13981
+
+struct A {};
+struct B;  // { dg-message "is incomplete" }
+
+void func( A *a );
+
+int main()
+{
+  B *b = 0;
+  func(b);  // { dg-error "cannot convert" }
+}