Double Free-崩溃或不崩溃 [英] Double Free - crash or no crash
本文介绍了Double Free-崩溃或不崩溃的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
有人可以解释一下为什么连续两次释放a会导致崩溃，但是先释放a，然后释放b，然后再释放a不会崩溃吗?
Can someone explain me why freeing a twice in a row causes a crash, but freeing a first, then b, and then a again does not crash?
我知道一个free会将堆块插入到一个双链接的free列表中.释放两次将在空闲列表中两次插入相同的块.但是为什么会发生崩溃?
I know that a free will insert the heap chunk in a double linked free list. Freeing twice would insert the same chunk twice in the free list. But why is the crash happening?
int *a = malloc(8);
int *b = malloc(8);
free(a);
// free(a); // Would crash!
free(b);
free(a); // No crash.
推荐答案
在C语言中，未定义的行为就是这样:未定义.可能发生任何事情.
Because in C lingo, undefined behavior is just that: undefined. Anything might happen.
另请参见man 3 free:
[…]如果以前已经调用过
free(ptr)，则会发生未定义的行为.
[…] if
free(ptr)has already been called before, undefined behavior occurs.
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