有没有在C程序中调用'自由'为同一指针两次任何伤害？ [英] Is there any harm in calling 'free' for the same pointer twice in a C program?

问题描述

如果我有一个C程序，如：

If I have a c program, like:

SomeTypePtr my_type;
my_type = malloc(sizeof(someType));

/* do stuff */

free(my_type);

/* do a bunch of more stuff */

free(my_type);

是'自由'的，要求my_type做任何伤害？我调用free（my_type）后，确实指针变成一个空指针再次？

Does the calling of 'free' for my_type do any harm? After I call free(my_type), does the pointer become a null pointer once again?

推荐答案

解除分配与免费的内存区域不会使指针NULL的内容。假设你有为int * A =的malloc（sizeof的（INT））和 A 的 0xdeadbeef 和执行免费（一）然后执行后 A 仍然包含 0xdeadbeef 但免费调用这个内存地址后没有给你更多的保留。像你这样的东西已经租下一个单位与使用了一段时间的malloc ，返回平通过免费，那么你可能有一个重复键为平，但它不是为您保留。

Deallocating a memory area with free does not make the contents of the pointer NULL. Suppose that you have int *a = malloc (sizeof (int)) and a has 0xdeadbeef and you execute free (a) then after execution a still contains 0xdeadbeef but after the free call this memory address is no more reserved for you. Something like you have rented a flat with malloc used for some time, returned the flat by free then you might have a duplicate key for the flat, but it is not reserved for you.

做一个免费上会造成双重释放内存损坏已经免费 D内存。

Doing a free on an already freed memory will result in double free memory corruption.

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