内存的申请和分配并没有成功，但程序员却使用了它。一些新手经常会犯这种错误，他们并不会留意到内存没有分配成功。判断指针的值是否为NULL可以有效地避免这种错误。-Application and allocation of memory and did not succeed, but the programmers are using it. Some novices are often guilty of this error, they will not notice that the suc