1 files changed, 63 insertions, 0 deletions
diff --git a/test/fixedbugs/issue8606b.go b/test/fixedbugs/issue8606b.go
new file mode 100644
index 0000000000..448ea566f0
--- /dev/null
+++ b/test/fixedbugs/issue8606b.go
@@ -0,0 +1,63 @@
+// run
+
+// Copyright 2020 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 is an optimization check. We want to make sure that we compare
+// string lengths, and other scalar fields, before checking string
+// contents.  There's no way to verify this in the language, and
+// codegen tests in test/codegen can't really detect ordering
+// optimizations like this. Instead, we generate invalid strings with
+// bad backing store pointers but nonzero length, so we can check that
+// the backing store never gets compared.
+//
+// We use two different bad strings so that pointer comparisons of
+// backing store pointers fail.
+
+package main
+
+import (
+	"fmt"
+	"reflect"
+	"unsafe"
+)
+
+func bad1() string {
+	s := "foo"
+	(*reflect.StringHeader)(unsafe.Pointer(&s)).Data = 1 // write bad value to data ptr
+	return s
+}
+func bad2() string {
+	s := "foo"
+	(*reflect.StringHeader)(unsafe.Pointer(&s)).Data = 2 // write bad value to data ptr
+	return s
+}
+
+type SI struct {
+	s string
+	i int
+}
+
+type SS struct {
+	s string
+	t string
+}
+
+func main() {
+	for _, test := range []struct {
+		a, b interface{}
+	}{
+		{SI{s: bad1(), i: 1}, SI{s: bad2(), i: 2}},
+		{SS{s: bad1(), t: "a"}, SS{s: bad2(), t: "aa"}},
+		{SS{s: "a", t: bad1()}, SS{s: "b", t: bad2()}},
+		// This one would panic because the length of both strings match, and we check
+		// the body of the bad strings before the body of the good strings.
+		//{SS{s: bad1(), t: "a"}, SS{s: bad2(), t: "b"}},
+	} {
+		if test.a == test.b {
+			panic(fmt.Sprintf("values %#v and %#v should not be equal", test.a, test.b))
+		}
+	}
+
+}