Thanks for your answer :), even though the original question has been
deleted.
I've used the reflect.NewAt to allocate a new memory at the same address of
the unexported field's reflect.Value, it seems work.
for unexported not nil field
if !v.CanSet() {
v = reflect.NewAt(v.Type(), unsafe.Pointer(v.UnsafeAddr())).Elem()
}
for unexported nil field
// since v is nil value, v.Elem() will be zero value
// and zero value is not addressable or settable, we
// need allocate a new settable v at the same address
v = reflect.NewAt(v.Type(), unsafe.Pointer(v.UnsafeAddr())).Elem()
newv := reflect.New(v.Type().Elem())
v.Set(newv)
在 2017年7月26日星期三 UTC+8上午9:08:50，Ian Lance Taylor写道：
>
> On Sun, Jul 23, 2017 at 12:46 AM, feilengcui008 <feilen...@gmail.com
> <javascript:>> wrote:
> > Hi, all:
> > I'm writing a little fuzz tool for struct using reflect package, and
> > came across the following case, but didn't find any way to solve it
> >
> >
> > type TestStruct struct {
> > a *int // unexported nil ptr field, how to modify it?
> > b int // unexported not ptr field, can be modified using
> > reflect.NewAt
> > C *int // exported nil ptr field, can be modified using
> > reflect.New and value.Set
> > }
> >
> > ts := &TestStruct {} // a is nil ptr and not exported
> > fieldA := reflect.ValueOf(ts).Elem().Field(0)
> > // how to modify the value of a using the reflect value fieldA?
>
> In general you can not use reflect to set unexported fields. If that
> were possible, then any package could use reflect to defeat the name
> hiding used by any other package, which would make name hiding much
> less useful.
>
> Ian
>
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