一个mem内存管理类,用链表管理所有申请的内存,申请时,请用XNEW1向内存管理对象申请,这样退出时会自动检查是否有内存忘了释放,并提醒作者-a mem memory management category, with all chain management application memory, applications, Please XNEW1 object to the memory management application, this withdrawal will automatically check whether a memory forgotten release, and to remind the author