skiplist/node_alloc_amd64.go
func debugMarkFree(n *Node) {
	var block []byte
	l := int(nodeTypes[n.level].Size())
	sh := (*reflect.SliceHeader)(unsafe.Pointer(&block))
	sh.Data = uintptr(unsafe.Pointer(n))
	sh.Len = l
	sh.Cap = l

	copy(block, freeBlockContent)
}
func debugMarkFree(n *Node) {
	var block []byte
	l := int(nodeTypes[n.level].Size())
	sh := (*reflect.SliceHeader)(unsafe.Pointer(&block))
	sh.Data = uintptr(unsafe.Pointer(n))
	sh.Len = l
	sh.Cap = l

	copy(block, freeBlockContent)
}
// Fill free blocks with a const
// This can help debugging of memory reclaimer bugs