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reflect: keep RO flags unchanged in Value.Addr #32787

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reflect: keep RO flags unchanged in Value.Addr #32787

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48e8569
reflect: error if Value.Addr().Elem.CanSet() diff from Value.CanSet()
kezhuw Jun 25, 2019
808aaea
reflect: inherit all bits of flagRO in Value.Addr()
kezhuw Jun 25, 2019
78e280e
fixup: Change code comment according to code reviewer request
kezhuw May 4, 2020
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37 changes: 36 additions & 1 deletion src/reflect/all_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -350,6 +350,7 @@ func TestCanSetField(t *testing.T) {
}

type testCase struct {
// -1 means Addr().Elem() of current value
index []int
canSet bool
}
Expand All @@ -360,35 +361,65 @@ 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},
},
}, {
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},
},
}, {
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},
},
Expand All @@ -402,7 +433,11 @@ func TestCanSetField(t *testing.T) {
if f.Kind() == Ptr {
f = f.Elem()
}
f = f.Field(i)
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)
Expand Down
5 changes: 4 additions & 1 deletion src/reflect/value.go
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Original file line number Diff line number Diff line change
Expand Up @@ -257,7 +257,10 @@ 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.
Expand Down