--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/gcc.dg/cpp/ucnid-7-utf8.c	Thu Feb 13 11:34:05 2020 +0900
@@ -0,0 +1,21 @@
+/* { dg-do compile } */
+/* { dg-options "-std=c99" } */
+
+/* When GCC reads UTF-8-encoded input into its internal UTF-8
+representation, it does not apply any transformation to the data, and
+in particular it makes no attempt to verify that the encoding is valid
+UTF-8.  Historically, if any non-ASCII characters were found outside a
+string or comment, they were treated as stray tokens and did not
+necessarily produce an error, e.g. if, as in this test, they disappear
+in the preprocessor.  Now that UTF-8 is also supported in identifiers,
+the basic structure of this process has not changed; GCC just treats
+invalid UTF-8 as a stray token.  This test verifies that the historical
+behavior is unchanged.  In the future, if GCC were changed, say, to
+validate the UTF-8 on input, then this test would no longer be
+appropriate.  */
+
+
+#define a b(
+#define b(x) q
+/* The line below contains invalid UTF-8.  */
+int a�);