Some great answers here. To add another perspective to this question, I'll address a case where memory leak is not only acceptable but desirable: in Windows drivers environment the developer provides a set of callbacks that are being run by the OS whenever required. One of the callbacks is a 'Shutdown' callback, which runs prior to system being shut off/restarted. Unlike standard situations, not only memory release is not necessary (system will be off in a moment), it's even discouraged - to make the shutdown as fast as possible and prevent the overhead of memory management.

I'm going to give the unpopular but practical answer that it's always wrong to free memory unless doing so will reduce the memory usage of your program. For instance a program that makes a single allocation or series of allocations to load the dataset it will use for its entire lifetime has no need to free anything. In the more common case of a large program with very dynamic memory requirements (think of a web browser), you should obviously free memory you're no longer using as soon as you can (for instance closing a tab/document/etc.), but there's no reason to free anything when the user selects clicks "exit", and doing so is actually harmful to the user experience.

为什么?释放内存需要接触内存。即使您的系统的malloc实现碰巧没有在分配的内存块附近存储元数据，您也可能会遍历递归结构，只是为了找到所有需要释放的指针。

Now, suppose your program has worked with a large volume of data, but hasn't touched most of it for a while (again, web browser is a great example). If the user is running a lot of apps, a good portion of that data has likely been swapped to disk. If you just exit(0) or return from main, it exits instantly. Great user experience. If you go to the trouble of trying to free everything, you may spend 5 seconds or more swapping all the data back in, only to throw it away immediately after that. Waste of user's time. Waste of laptop's battery life. Waste of wear on the hard disk.

这不仅仅是理论上的。每当我发现自己加载了太多的应用程序，磁盘开始抖动时，我甚至不会考虑点击“退出”。我以最快的速度到达一个终端，输入killall -9…因为我知道"退出"只会让情况更糟。

我看到了和所有场景问题一样的问题，比如:当程序改变时，会发生什么?突然，这个小内存泄漏被调用了1000万次，而程序的结尾在不同的地方，所以它很重要?如果它在库中，那么请向库维护者记录错误，不要在您自己的代码中泄漏。

首先，让我们把定义更正一下。内存泄漏是指动态分配内存，例如使用malloc()，并且所有对内存的引用都在没有相应的free的情况下丢失。制作一个简单的方法是这样的:

#define BLK ((size_t)1024)
while(1){
    void * vp = malloc(BLK);
}

注意，每次在while(1)循环中，分配1024(+开销)字节，并将新地址分配给vp;没有指向之前malloc 'Ed块的剩余指针。这个程序保证运行到堆用完为止，并且没有办法恢复任何malloc'ed内存。内存从堆中“泄漏”出来，再也看不见了。

你所描述的，听起来就像

int main(){
    void * vp = malloc(LOTS);
    // Go do something useful
    return 0;
}

你分配内存，使用它直到程序结束。这不是内存泄漏;它不会损害程序，并且当程序终止时，所有的内存将被自动清除。

一般来说，应该避免内存泄漏。首先，因为就像你头顶上的高度和飞机库里的燃料一样，已经泄漏且无法恢复的内存是无用的;其次，在一开始就正确编码，不泄漏内存，比后来发现内存泄漏要容易得多。

最佳实践是始终释放所分配的空间，特别是在编写旨在在整个系统正常运行期间运行的内容时，即使在退出之前进行清理。

这是一个非常简单的规则。以无泄漏为目标进行编程，可以很容易地发现新的泄漏。你会卖给别人一辆你自己造的车吗?你知道它一熄火就会喷到地上?：）

清理函数中的一些if () free()调用是廉价的，为什么不使用它们呢?

规则很简单:如果你用完了一些内存，就清理它。 有时，即使我们稍后需要一些实例，但我们注意到我们会大量使用内存，所以它会影响性能，因为交换到磁盘，我们可以将数据存储到磁盘文件中，然后重新加载它们，有时这种技术会优化你的程序。