Add RejectNegative for a c option.

	PR c/78933
	* g++.dg/pr78933.C: New test.
	PR c/78933
	* c.opt (strong-eval-order): Add RejectNegative keyword.

From-SVN: r243960

gcc/c-family/ChangeLog

+2016-12-29  Martin Liska  <mliska@suse.cz>
+
+	PR c/78933
+	* c.opt (strong-eval-order): Add RejectNegative keyword.
+
 2016-12-22  Jason Merrill  <jason@redhat.com>
 
 	Implement P0522R0, matching of template template arguments.

gcc/c-family/c.opt

@@ -1655,7 +1655,7 @@ Follow the C++17 evaluation order requirements for assignment expressions,
 shift, member function calls, etc.
 
 fstrong-eval-order=
-C++ ObjC++ Common Var(flag_strong_eval_order) Joined Enum(strong_eval_order) Init(-1)
+C++ ObjC++ Common Var(flag_strong_eval_order) Joined Enum(strong_eval_order) RejectNegative Init(-1)
 Follow the C++17 evaluation order requirements for assignment expressions,
 shift, member function calls, etc.
 

gcc/testsuite/ChangeLog

+2016-12-29  Martin Liska  <mliska@suse.cz>
+
+	PR c/78933
+	* g++.dg/pr78933.C: New test.
+
 2016-12-28  Uros Bizjak  <ubizjak@gmail.com>
 
 	PR target/78904

gcc/testsuite/g++.dg/pr78933.C

+// PR c/78933
+// { dg-do compile }
+// { dg-options "-fno-strong-eval-order" }