re PR c++/81061 (ICE modifying read-only variable)

/cp
2017-12-13  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/81061
	* typeck.c (cp_build_modify_expr): Upon cxx_readonly_error
	immediately return error_mark_node.

/testsuite
2017-12-13  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/81061
	* g++.dg/other/const5.C: New.

From-SVN: r255613

gcc/cp/ChangeLog

+2017-12-13  Paolo Carlini  <paolo.carlini@oracle.com>
+
+	PR c++/81061
+	* typeck.c (cp_build_modify_expr): Upon cxx_readonly_error
+	immediately return error_mark_node.
+
 2017-12-13  Nathan Sidwell  <nathan@acm.org>
 
 	PR c++/15272

gcc/cp/typeck.c

@@ -8037,8 +8037,7 @@ cp_build_modify_expr (location_t loc, tree lhs, enum tree_code modifycode,
     {
       if (complain & tf_error)
 	cxx_readonly_error (lhs, lv_assign);
-      else
-	return error_mark_node;
+      return error_mark_node;
     }
 
   /* If storing into a structure or union member, it may have been given a

gcc/testsuite/ChangeLog

+2017-12-13  Paolo Carlini  <paolo.carlini@oracle.com>
+
+	PR c++/81061
+	* g++.dg/other/const5.C: New.
+
 2017-12-13  Alexandre Oliva  <aoliva@redhat.com>
 	    Jakub Jelinek  <jakub@redhat.com>
 

gcc/testsuite/g++.dg/other/const5.C

+// PR c++/81061
+
+const int i = 0;
+
+void foo()
+{
+  (0, i) = 1;  // { dg-error "read-only" }
+}