code: func (t *Collection) freeNodeLoc(nloc *nodeLoc) {
  	if nloc == nil || nloc == empty_nodeLoc {
  		return
  	}
  	if nloc.next != nil {
  		panic("double free nodeLoc")
  	}
  	nloc.loc = unsafe.Pointer(nil)
  	nloc.node = unsafe.Pointer(nil)
  
  	freeNodeLocLock.Lock()
  	nloc.next = freeNodeLocs
  	freeNodeLocs = nloc
  	allocStats.CurFreeNodeLocs++
  	allocStats.FreeNodeLocs++
  	t.allocStats.FreeNodeLocs++
  	freeNodeLocLock.Unlock()
  }
docs: // Assumes that the caller serializes invocations.