1 files changed, 59 insertions, 1 deletions

diff --git a/libgo/go/io/multi_test.go b/libgo/go/io/multi_test.go
index 447e7f59635..70f2a48e9ea 100644
--- a/libgo/go/io/multi_test.go
+++ b/libgo/go/io/multi_test.go
@@ -14,6 +14,7 @@ import (
 	"runtime"
 	"strings"
 	"testing"
+	"time"
 )
 
 func TestMultiReader(t *testing.T) {
@@ -212,7 +213,7 @@ func (b byteAndEOFReader) Read(p []byte) (n int, err error) {
 	return 1, EOF
 }
 
-// In Go 1.7, this yielded bytes forever.
+// This used to yield bytes forever; issue 16795.
 func TestMultiReaderSingleByteWithEOF(t *testing.T) {
 	got, err := ioutil.ReadAll(LimitReader(MultiReader(byteAndEOFReader('a'), byteAndEOFReader('b')), 10))
 	if err != nil {
@@ -235,3 +236,60 @@ func TestMultiReaderFinalEOF(t *testing.T) {
 		t.Errorf("got %v, %v; want 1, EOF", n, err)
 	}
 }
+
+func TestMultiReaderFreesExhaustedReaders(t *testing.T) {
+	if runtime.Compiler == "gccgo" {
+		t.Skip("skipping finalizer test on gccgo with conservative GC")
+	}
+
+	var mr Reader
+	closed := make(chan struct{})
+	{
+		buf1 := bytes.NewReader([]byte("foo"))
+		buf2 := bytes.NewReader([]byte("bar"))
+		mr = MultiReader(buf1, buf2)
+		runtime.SetFinalizer(buf1, func(*bytes.Reader) {
+			close(closed)
+		})
+	}
+
+	buf := make([]byte, 4)
+	if n, err := ReadFull(mr, buf); err != nil || string(buf) != "foob" {
+		t.Fatalf(`ReadFull = %d (%q), %v; want 3, "foo", nil`, n, buf[:n], err)
+	}
+
+	runtime.GC()
+	select {
+	case <-closed:
+	case <-time.After(5 * time.Second):
+		t.Fatal("timeout waiting for collection of buf1")
+	}
+
+	if n, err := ReadFull(mr, buf[:2]); err != nil || string(buf[:2]) != "ar" {
+		t.Fatalf(`ReadFull = %d (%q), %v; want 2, "ar", nil`, n, buf[:n], err)
+	}
+}
+
+func TestInterleavedMultiReader(t *testing.T) {
+	r1 := strings.NewReader("123")
+	r2 := strings.NewReader("45678")
+
+	mr1 := MultiReader(r1, r2)
+	mr2 := MultiReader(mr1)
+
+	buf := make([]byte, 4)
+
+	// Have mr2 use mr1's []Readers.
+	// Consume r1 (and clear it for GC to handle) and consume part of r2.
+	n, err := ReadFull(mr2, buf)
+	if got := string(buf[:n]); got != "1234" || err != nil {
+		t.Errorf(`ReadFull(mr2) = (%q, %v), want ("1234", nil)`, got, err)
+	}
+
+	// Consume the rest of r2 via mr1.
+	// This should not panic even though mr2 cleared r1.
+	n, err = ReadFull(mr1, buf)
+	if got := string(buf[:n]); got != "5678" || err != nil {
+		t.Errorf(`ReadFull(mr1) = (%q, %v), want ("5678", nil)`, got, err)
+	}
+}