Question

I am trying to create a map of addresses of objects that I create with the time at which it is allocated. The key is the address returned by the call to new(). How do I get the address returned by new()?

type T struct{a, b int }

func main(){

        var t int64 = time.Nanoseconds()
        memmap := make(map[uint8]int64)
        fmt.Printf("%d\n", t)
        var ptr *T = new(T)
        ptr.a = 1
        ptr.b = 2
        fmt.Printf("%d %d %p %T\n", ptr.a, ptr.b, ptr, ptr)
        //memmap[ptr] = t //gives error
        //var temp uint8 = ptr//gives error
}

Please tell me what should be the type of the key field in the map so that I can store the address returned by new()? I plan to use new() with different types, get the allocated address and map it with the creation time.

Answer 1

You can use the type Pointer from the unsafe package, but that is, the package name implies it, unsafe. The address itself is a opaque thing and there’s only little use in actually using a address value alone for a map, better use a tuple of type and address. That’s what unsafe.Reflect does provide you. The package reflect offers you the function UnsafeAddr and a lot more.

I suggest you read the package documentation for reflect and unsafe packages.