golang的copyCheck.check如何检测对象复制？

Question

How golang's copyCheck.check detect object copying?

// copyChecker holds back pointer to itself to detect object copying.
type copyChecker uintptr

func (c *copyChecker) check() {
    if uintptr(*c) != uintptr(unsafe.Pointer(c)) &&
        !atomic.CompareAndSwapUintptr((*uintptr)(c), 0, uintptr(unsafe.Pointer(c))) &&
        uintptr(*c) != uintptr(unsafe.Pointer(c)) {
        panic("sync.Cond is copied")
    }
}

Answer 1

When it's created, it sets its value to its own address. To check if it's been copied, it compares its address to the stored value. If it's been copied, its address will be different, but the value will be the same, so it will no longer be pointing to itself.