Can't add weak ref feature?

[ClarkGuan]

I heard that can use runtime.SetFinalizer function implement WEAK REF feature.

[nilium]

That wouldn't cover weak references, just finalization.

In order to correctly implement weak references in go-lua, the Lua GC (or some variation of it) would have to be implemented. Right now, go-lua relies on the Go GC, which does not support weak references, to manage memory.

Going back to finalizers, they're something that could be supported if the GC were implemented (via a metatable with a gc metamethod on userdata, same as Lua 5.2). In any case, it wouldn't make sense to use Go GC finalizers (and using them should be mostly discouraged).

[ClarkGuan]

Please forgive me my poor English!
Yes, I know what you mean about finalization. What i saw is something like the CODE BELOW:

`
import (
"fmt"
"runtime"
"sync/atomic"
"unsafe"
)

type WeakRef struct {
t uintptr
d uintptr
}

func NewWeakRef(v interface{}) WeakRef {
i := ([2]uintptr)(unsafe.Pointer(&v))
w := &WeakRef{^i[0], ^i[1]}
runtime.SetFinalizer((*uintptr)(unsafe.Pointer(i[1])), func(_ *uintptr) {
atomic.StoreUintptr(&w.d, 0)
w.t = 0
})
return w
}

func (w WeakRef) Get() (v interface{}) {
t := w.t
d := atomic.LoadUintptr(&w.d)
if d != 0 {
i := ([2]uintptr)(unsafe.Pointer(&v))
i[0] = ^t
i[1] = ^d
}
return
}
`

convert Go pointer to uintptr which not prevent Go object from being collected by GC. Here runtime.SetFinalizer I think only provide a chance to notify us "oh, it has been collected".