Merge from trunk revision 104c05c5284b7822d770ee51a7d91946c7e56d50.

3 files changed, 14 insertions, 1 deletions

diff --git a/libgo/go/bytes/boundary_test.go b/libgo/go/bytes/boundary_test.go
index ea84f1e..5a47526 100644
--- a/libgo/go/bytes/boundary_test.go
+++ b/libgo/go/bytes/boundary_test.go
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 //
+//go:build linux
 // +build linux
 
 package bytes_test
diff --git a/libgo/go/bytes/buffer.go b/libgo/go/bytes/buffer.go
index f19a4cf..549b077 100644
--- a/libgo/go/bytes/buffer.go
+++ b/libgo/go/bytes/buffer.go
@@ -275,7 +275,8 @@ func (b *Buffer) WriteByte(c byte) error {
 // included to match bufio.Writer's WriteRune. The buffer is grown as needed;
 // if it becomes too large, WriteRune will panic with ErrTooLarge.
 func (b *Buffer) WriteRune(r rune) (n int, err error) {
-	if r < utf8.RuneSelf {
+	// Compare as uint32 to correctly handle negative runes.
+	if uint32(r) < utf8.RuneSelf {
 		b.WriteByte(byte(r))
 		return 1, nil
 	}
diff --git a/libgo/go/bytes/buffer_test.go b/libgo/go/bytes/buffer_test.go
index fec5ef8..9c9b744 100644
--- a/libgo/go/bytes/buffer_test.go
+++ b/libgo/go/bytes/buffer_test.go
@@ -6,6 +6,7 @@ package bytes_test
 
 import (
 	. "bytes"
+	"fmt"
 	"io"
 	"math/rand"
 	"testing"
@@ -387,6 +388,16 @@ func TestRuneIO(t *testing.T) {
 	}
 }
 
+func TestWriteInvalidRune(t *testing.T) {
+	// Invalid runes, including negative ones, should be written as
+	// utf8.RuneError.
+	for _, r := range []rune{-1, utf8.MaxRune + 1} {
+		var buf Buffer
+		buf.WriteRune(r)
+		check(t, fmt.Sprintf("TestWriteInvalidRune (%d)", r), &buf, "\uFFFD")
+	}
+}
+
 func TestNext(t *testing.T) {
 	b := []byte{0, 1, 2, 3, 4}
 	tmp := make([]byte, 5)