--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/gcc.dg/cpp/19990407-1.c	Fri Oct 27 22:46:09 2017 +0900
@@ -0,0 +1,19 @@
+/* Regression test for a cpplib macro-expansion bug where
+   `@' becomes `@@' when stringified.  */
+
+/* { dg-do run } */
+
+#include <string.h>
+#include <stdlib.h>
+
+#define STR(x) #x
+
+char *a = STR(@foo), *b = "@foo";
+
+int
+main(void)
+{
+  if (strcmp (a, b))
+    abort ();
+  return 0;
+}