From a9f1569e7bff932eada0c4c691123e3c1177b6f0 Mon Sep 17 00:00:00 2001
From: Volker Dobler <dr.volker.dobler@gmail.com>
Date: Thu, 11 Apr 2013 11:45:18 -0700
Subject: [PATCH] gc: escape unicode BOM in exported string literals

Fixes #5260.

R=golang-dev, minux.ma, 0xjnml, r
CC=golang-dev
https://golang.org/cl/8658043
---
 src/cmd/gc/fmt.c                  |  3 +++
 test/fixedbugs/issue5260.dir/a.go |  7 +++++++
 test/fixedbugs/issue5260.dir/b.go | 11 +++++++++++
 test/fixedbugs/issue5260.go       | 10 ++++++++++
 4 files changed, 31 insertions(+)
 create mode 100644 test/fixedbugs/issue5260.dir/a.go
 create mode 100644 test/fixedbugs/issue5260.dir/b.go
 create mode 100644 test/fixedbugs/issue5260.go

diff --git a/src/cmd/gc/fmt.c b/src/cmd/gc/fmt.c
index 8a14aa2df95..35f01a5c262 100644
--- a/src/cmd/gc/fmt.c
+++ b/src/cmd/gc/fmt.c
@@ -443,6 +443,9 @@ Zconv(Fmt *fp)
 			fmtrune(fp, '\\');
 			fmtrune(fp, r);
 			break;
+		case 0xFEFF: // BOM, basically disallowed in source code
+			fmtstrcpy(fp, "\\uFEFF");
+			break;
 		}
 	}
 	return 0;
diff --git a/test/fixedbugs/issue5260.dir/a.go b/test/fixedbugs/issue5260.dir/a.go
new file mode 100644
index 00000000000..5a2c99f65c7
--- /dev/null
+++ b/test/fixedbugs/issue5260.dir/a.go
@@ -0,0 +1,7 @@
+// Copyright 2013 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 a
+
+const BOM = "\uFEFF"
diff --git a/test/fixedbugs/issue5260.dir/b.go b/test/fixedbugs/issue5260.dir/b.go
new file mode 100644
index 00000000000..299b75e4a7c
--- /dev/null
+++ b/test/fixedbugs/issue5260.dir/b.go
@@ -0,0 +1,11 @@
+// Copyright 2013 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 main
+
+import "./a"
+
+func main() {
+	_ = a.BOM
+}
diff --git a/test/fixedbugs/issue5260.go b/test/fixedbugs/issue5260.go
new file mode 100644
index 00000000000..11fd5d04815
--- /dev/null
+++ b/test/fixedbugs/issue5260.go
@@ -0,0 +1,10 @@
+// rundir
+
+// Copyright 2013 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.
+
+// Issue 5260: Unicode BOM in exported string constant
+// cannot be read back during package import.
+
+package ignored