From 069c397975b09edddce5af5e5e96fd86f7fe1cca Mon Sep 17 00:00:00 2001
From: Damian Gryski <damian@gryski.com>
Date: Mon, 6 Mar 2023 13:14:33 -0800
Subject: [PATCH] reflect: fix off-by-one in Zero sizing

Without this, pointers wouldn't be set to nil.  Add some tests.
---
 src/reflect/value.go      |  2 +-
 src/reflect/value_test.go | 22 ++++++++++++++++++++++
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/src/reflect/value.go b/src/reflect/value.go
index 92f87086..3f879e29 100644
--- a/src/reflect/value.go
+++ b/src/reflect/value.go
@@ -1083,7 +1083,7 @@ func init() {
 }
 
 func Zero(typ Type) Value {
-	if typ.Size() < unsafe.Sizeof(uintptr(0)) {
+	if typ.Size() <= unsafe.Sizeof(uintptr(0)) {
 		return Value{
 			typecode: typ.(*rawType),
 			value:    nil,
diff --git a/src/reflect/value_test.go b/src/reflect/value_test.go
index 7f26aa8a..08bd325a 100644
--- a/src/reflect/value_test.go
+++ b/src/reflect/value_test.go
@@ -266,6 +266,28 @@ func TestNamedTypes(t *testing.T) {
 	}
 }
 
+func TestZero(t *testing.T) {
+	s := "hello, world"
+	var sptr *string = &s
+	v := ValueOf(&sptr).Elem()
+	v.Set(Zero(v.Type()))
+
+	sptr = v.Interface().(*string)
+
+	if sptr != nil {
+		t.Errorf("failed to set a nil string pointer")
+	}
+
+	sl := []int{1, 2, 3}
+	v = ValueOf(&sl).Elem()
+	v.Set(Zero(v.Type()))
+	sl = v.Interface().([]int)
+
+	if sl != nil {
+		t.Errorf("failed to set a nil slice")
+	}
+}
+
 func addrDecode(body interface{}) {
 	vbody := ValueOf(body)
 	ptr := vbody.Elem()