如何检查内存的释放

Question

如何检查指针p指向的内存是否已成功释放？

Answer 1

In few words: you can't.

Check out tools like Valgrind to help you debugging memory leaks issues.

Some other things you should consider:

• Use smart pointers so that you don't have do think about memory management,
• Set your pointers to 0 after you free them, so that a further delete has no effect,
• Use standard classes ( vector , ...) instead of rolling your own,
• Finally, don't use pointers (actually you almost can)

Answer 2

抱歉，很简短的回答“你不能”

Answer 3

使用IBM Rational Purify工具检查内存的正确释放。

Answer 4

Define successfully! Define deallocated!

After deallocating memory (whether it is free or delete) you must not use that pointer again. All other assumptions are irrelevant.

After all, you call the C/C++ runtime to deallocate memory, but the C/C++ runtime also calls functions of the operating system to free the page. You could even have a custom memory allocator on top of the C/C++ runtime that eg uses caching to implement a faster memory allocation algorithm.

All of these layers may keep the deallocated memory for themselves (because of fragmentation or just because they like to keep it to themselves) or may tell the underlying layer to deallocate it. Anything can happen, just don't use that pointer anymore.

Answer 5

Exception handling. Ie try/catch blocks.

Answer 6

1. Some tools which are doing static code analysis can point some problems regarding the memory deallocation.
2. Use valgrind to check whether you have memory leaks
3. Avoid raw pointers - use smart pointers instead

Answer 7

In C++, you can safely assume deallocation never fails. Destructors must not throw exceptions, and the actual memory reserved should never fail to be released, so given those two points, nothing can go wrong.

However, if you delete a pointer that has already been deleted, your program will probably crash. This isn't a problem with deallocation itself though - the original delete worked successfully. It's a problem with your program's memory management if it tries to delete a pointer twice, but that's rarely necessary with modern STL and smart pointers like std::vector , std::unique_ptr , etc...