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reflect: keep RO flags unchanged in Value.Addr

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Currently, Value.Addr collapses flagRO, which is a combination of
flagEmbedRO and flagStickyRO, to flagStickyRO. This causes exported
fields of unexported anonymous field from Value.Addr.Elem read only.

This commit fix this by keeping all bits of flagRO from origin
value in Value.Addr. This should be safe due to following reasons:
* Result of Value.Addr is not CanSet because of it is not CanAddr
   but not flagRO.
* Addr.Elem get same flagRO as origin, so it should behave same as
   origin in CanSet.

Fixes #32772.

Change-Id: I79e086628c0fb6569a50ce63f3b95916f997eda1
GitHub-Last-Rev: 78e280e6d0
GitHub-Pull-Request: golang/go#32787
Reviewed-on: https://go-review.googlesource.com/c/go/+/183937
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
Kezhu Wang 2020-05-04 02:28:39 +00:00 committed by Matthew Dempsky
parent a1ffbe9c69
commit 4c003f6b78
2 changed files with 40 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

35
src/reflect/all_test.go
View File

@ -350,6 +350,7 @@ func TestCanSetField(t *testing.T) {
}
type testCase struct {
// -1 means Addr().Elem() of current value
index []int
canSet bool
}
@ -360,17 +361,33 @@ func TestCanSetField(t *testing.T) {
val: ValueOf(&S1{}),
cases: []testCase{
{[]int{0}, false},
{[]int{0, -1}, false},
{[]int{0, 0}, false},
{[]int{0, 0, -1}, false},
{[]int{0, -1, 0}, false},
{[]int{0, -1, 0, -1}, false},
{[]int{0, 1}, true},
{[]int{0, 1, -1}, true},
{[]int{0, -1, 1}, true},
{[]int{0, -1, 1, -1}, true},
{[]int{1}, false},
{[]int{1, -1}, false},
{[]int{2}, true},
{[]int{2, -1}, true},
},
}, {
val: ValueOf(&S2{embed: &embed{}}),
cases: []testCase{
{[]int{0}, false},
{[]int{0, -1}, false},
{[]int{0, 0}, false},
{[]int{0, 0, -1}, false},
{[]int{0, -1, 0}, false},
{[]int{0, -1, 0, -1}, false},
{[]int{0, 1}, true},
{[]int{0, 1, -1}, true},
{[]int{0, -1, 1}, true},
{[]int{0, -1, 1, -1}, true},
{[]int{1}, false},
{[]int{2}, true},
},
@ -378,8 +395,15 @@ func TestCanSetField(t *testing.T) {
val: ValueOf(&S3{}),
cases: []testCase{
{[]int{0}, true},
{[]int{0, -1}, true},
{[]int{0, 0}, false},
{[]int{0, 0, -1}, false},
{[]int{0, -1, 0}, false},
{[]int{0, -1, 0, -1}, false},
{[]int{0, 1}, true},
{[]int{0, 1, -1}, true},
{[]int{0, -1, 1}, true},
{[]int{0, -1, 1, -1}, true},
{[]int{1}, false},
{[]int{2}, true},
},
@ -387,8 +411,15 @@ func TestCanSetField(t *testing.T) {
val: ValueOf(&S4{Embed: &Embed{}}),
cases: []testCase{
{[]int{0}, true},
{[]int{0, -1}, true},
{[]int{0, 0}, false},
{[]int{0, 0, -1}, false},
{[]int{0, -1, 0}, false},
{[]int{0, -1, 0, -1}, false},
{[]int{0, 1}, true},
{[]int{0, 1, -1}, true},
{[]int{0, -1, 1}, true},
{[]int{0, -1, 1, -1}, true},
{[]int{1}, false},
{[]int{2}, true},
},
@ -402,8 +433,12 @@ func TestCanSetField(t *testing.T) {
if f.Kind() == Ptr {
f = f.Elem()
}
if i == -1 {
f = f.Addr().Elem()
} else {
f = f.Field(i)
}
}
if got := f.CanSet(); got != tc.canSet {
t.Errorf("CanSet() = %v, want %v", got, tc.canSet)
}

5
src/reflect/value.go
View File

@ -269,7 +269,10 @@ func (v Value) Addr() Value {
if v.flag&flagAddr == 0 {
panic("reflect.Value.Addr of unaddressable value")
}
return Value{v.typ.ptrTo(), v.ptr, v.flag.ro() | flag(Ptr)}
// Preserve flagRO instead of using v.flag.ro() so that
// v.Addr().Elem() is equivalent to v (#32772)
fl := v.flag & flagRO
return Value{v.typ.ptrTo(), v.ptr, fl | flag(Ptr)}
}
// Bool returns v's underlying value.