--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libgo/misc/cgo/test/issue18720.go	Fri Oct 27 22:46:09 2017 +0900
@@ -0,0 +1,28 @@
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package cgotest
+
+/*
+#define HELLO "hello"
+#define WORLD "world"
+#define HELLO_WORLD HELLO "\000" WORLD
+
+struct foo { char c; };
+#define SIZE_OF(x) sizeof(x)
+#define SIZE_OF_FOO SIZE_OF(struct foo)
+*/
+import "C"
+import "testing"
+
+func test18720(t *testing.T) {
+	if C.HELLO_WORLD != "hello\000world" {
+		t.Fatalf(`expected "hello\000world", but got %q`, C.HELLO_WORLD)
+	}
+
+	// Issue 20125.
+	if got, want := C.SIZE_OF_FOO, 1; got != want {
+		t.Errorf("C.SIZE_OF_FOO == %v, expected %v", got, want)
+	}
+}