通过函数将指针设置为nil

Question

There is a function that sets a pointer to a nil value:

func nilSetter(x *int) {
    x = nil
}

I have such snippet of code:

i := 42
fmt.Println(&i)
nilSetter(&i)
fmt.Println(&i)

Which prints:

0xc42008a000
0xc42008a000

While I expect:

0xc42008a000
nil

I know that it happens because function nilSetter just copy address and sets to nil that copy.

But how can I do it correctly?

Answer 1

The only way to achieve that is with a pointer to a pointer. And it's pretty clunky so it's probably not what you want:

func nilSetter(x **int) {
    *x = nil
}

func main() {
    x := 2
    xp := &x

    fmt.Println(xp)
    nilSetter(&xp)
    fmt.Println(xp)

}

// Output:
// 0x10414020
// <nil>