PR c++/84559 - ICE with constexpr VLA.

	* constexpr.c (ensure_literal_type_for_constexpr_object): Check
	for constexpr variable with VLA type.

From-SVN: r258015

gcc/cp/ChangeLog

+2018-02-26  Jason Merrill  <jason@redhat.com>
+
+	PR c++/84559 - ICE with constexpr VLA.
+	* constexpr.c (ensure_literal_type_for_constexpr_object): Check
+	for constexpr variable with VLA type.
+
 2018-02-26  Jakub Jelinek  <jakub@redhat.com>
 
 	PR c++/84558

gcc/cp/constexpr.c

@@ -112,6 +112,13 @@ ensure_literal_type_for_constexpr_object (tree decl)
 	      cp_function_chain->invalid_constexpr = true;
 	    }
 	}
+      else if (DECL_DECLARED_CONSTEXPR_P (decl)
+	       && variably_modified_type_p (type, NULL_TREE))
+	{
+	  error ("%<constexpr%> variable %qD has variably-modified type %qT",
+		 decl, type);
+	  decl = error_mark_node;
+	}
     }
   return decl;
 }

gcc/testsuite/g++.dg/ext/constexpr-vla5.C

+// PR c++/84559
+// { dg-do compile { target c++11 } }
+
+void foo(int i)
+{
+  constexpr char x[i] = "";	// { dg-error "" }
+}