我们如何能够重新分配存储器后访问指针？

问题描述

按我的理解，

免费（）来释放我们之前分配使用malloc内存。

在我下面的代码片段，我释放我已经分配的内存。但我可以释放，即使后访问指针？它是如何可能的？

如何免费内部工作？

 ＃包括LT＆;＆iostream的GT;
使用命名空间std;诠释的main（）
{
   为int * p =（INT *）malloc的（的sizeof（INT））;
   * p = 17;
   自由（对）;
   * p值= * P + 1;
   的printf（\\ n释放内存::％天后，* P）;
   返回0;
}
 

解决方案

您当然可以继续使用 P 呼叫后免费（P）并没有什么会阻止你。然而，结果将完全不确定的和未predictable。它的工作原理只是运气。这就是所谓的在许多节目作品后免费 。

相当不错

As per my understanding,

free() is used to deallocate the memory that we allocated using malloc before.

In my following snippet, I have freed the memory i have allocated. But i was able to access the pointer even after freeing? How it is possible?

How free works internally?

#include<iostream>
using namespace std;

int main()
{
   int *p=(int *)malloc(sizeof(int));
   *p=17;
   free(p);
   *p=*p+1;
   printf("\n After freeing memory :: %d ",*p );
   return 0;
}

解决方案

You can certainly continue to use p after calling free(p) and nothing will stop you. However the results will be completely undefined and unpredictable. It works by luck only. This is a common programming error called "use after free" which works in many programs for literally years without "problems" -- until it causes a problem.

There are tools which are quite good at finding such errors, such as Valgrind.

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