新建，删除，malloc &自由

2021-12-24 00:00:00 memory-management malloc c++ new-operator free

这个问题是在一次采访中问我的:

This question was asked to me in an interview:

在 C++ 中，

  1. 如果我们使用 malloc 分配内存并使用 delete 来释放分配的内存会怎样?
  2. 如果我们使用 new 分配内存并使用 free 释放它会怎样?
  1. what if we allocate memory using malloc and use delete to free that allocated memory?
  2. what if we allocate the memory using new and free it using free?

如果在代码中使用上述东西，我们会面临哪些问题?

What are the problems that we would face if the above things are used in the code?

我的回答是没有区别.我这样说对吗?

My answer was there is no difference. Was I right in saying so?

推荐答案

如果你这样做，你会遇到未定义的行为.永远不要尝试.尽管 new 可能通过 malloc() 实现，而 delete 可能通过 free() 实现，但不能保证它们确实是这样实现的并且用户也可以自行决定重载new和delete.您可能会遇到堆损坏.

If you do so you will run into undefined behavior. Never try that. Although new might be implemented through malloc() and delete might be implemented through free() there's no guarantee that they are really implemented that way and also the user can overload new and delete at his discretion. You risk running into heap corruption.

除此之外不要忘记，当您调用 malloc() 时，您将获得原始内存 - 没有调用构造函数 - 当您调用 free() 时没有析构函数被调用.这也可能导致程序的未定义行为和不正常运行.

Other than that don't forget that when you call malloc() you get raw memory - no constructor is invoked - and when you call free() no destructor is invoked. This can as well lead to undefined behavior and improper functioning of the program.

底线是...永远不要这样做.

The bottom line is... never do this.

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