1 files changed, 46 insertions, 0 deletions
diff --git a/src/cmd/compile/internal/test/testdata/slice_test.go b/src/cmd/compile/internal/test/testdata/slice_test.go
new file mode 100644
index 0000000000..c134578034
--- /dev/null
+++ b/src/cmd/compile/internal/test/testdata/slice_test.go
@@ -0,0 +1,46 @@
+// Copyright 2018 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.
+
+// This test makes sure that t.s = t.s[0:x] doesn't write
+// either the slice pointer or the capacity.
+// See issue #14855.
+
+package main
+
+import "testing"
+
+const N = 1000000
+
+type X struct {
+	s []int
+}
+
+func TestSlice(t *testing.T) {
+	done := make(chan struct{})
+	a := make([]int, N+10)
+
+	x := &X{a}
+
+	go func() {
+		for i := 0; i < N; i++ {
+			x.s = x.s[1:9]
+		}
+		done <- struct{}{}
+	}()
+	go func() {
+		for i := 0; i < N; i++ {
+			x.s = x.s[0:8] // should only write len
+		}
+		done <- struct{}{}
+	}()
+	<-done
+	<-done
+
+	if cap(x.s) != cap(a)-N {
+		t.Errorf("wanted cap=%d, got %d\n", cap(a)-N, cap(x.s))
+	}
+	if &x.s[0] != &a[N] {
+		t.Errorf("wanted ptr=%p, got %p\n", &a[N], &x.s[0])
+	}
+}