--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/gcc.dg/pr65901.c	Fri Oct 27 22:46:09 2017 +0900
@@ -0,0 +1,16 @@
+/* PR c/65901 */
+/* { dg-do compile } */
+/* { dg-options "" } */
+
+struct S;
+enum E;
+union U;
+
+void
+foo (__builtin_va_list ap)
+{
+  __builtin_va_arg (ap, void);  /* { dg-error "second argument to .va_arg. is of incomplete type .void." } */
+  __builtin_va_arg (ap, struct S);  /* { dg-error "second argument to .va_arg. is of incomplete type .struct S." } */
+  __builtin_va_arg (ap, enum E);  /* { dg-error "second argument to .va_arg. is of incomplete type .enum E." } */
+  __builtin_va_arg (ap, union U);  /* { dg-error "second argument to .va_arg. is of incomplete type .union U." } */
+}