How do you detect/avoid Memory leaks in your (Unmanaged) code?
In unmanaged C/C++ code, what are the best practices to detect memory leaks? And coding guidelines to avoid? (As if it's that simple ;)
We have used a bit of a silly way in the past: having a counter increment for every memory allocation call and decrement while freeing. At the end of the program, the counter value should be zero.
I know this is not a great way and there are a few catches. (For instance, if you are freeing memory which was allocated by a platform API call, your allocation count will not exactly match your freeing count. Of course, then we incremented the counter when calling API calls that allocated memory.)
I am expecting your experiences, suggestions and maybe some references to tools which simplify this.
如果你的C / C ++代码可以移植到* nix，那么很少有东西比Valgrind更好。
If you are using Visual Studio, Microsoft provides some useful functions for detecting and debugging memory leaks.
I would start with this article: https://msdn.microsoft.com/en-us/library/x98tx3cf(v=vs.140).aspx
Here is the quick summary of those articles. First, include these headers:
#define _CRTDBG_MAP_ALLOC
#include <stdlib.h>
#include <crtdbg.h>
Then you need to call this when your program exits:
_CrtDumpMemoryLeaks();
Alternatively, if your program does not exit in the same place every time, you can call this at the start of your program:
_CrtSetDbgFlag ( _CRTDBG_ALLOC_MEM_DF | _CRTDBG_LEAK_CHECK_DF );
Now when the program exits all the allocations that were not free'd will be printed in the Output Window along with the file they were allocated in and the allocation occurrence.
This strategy works for most programs. However, it becomes difficult or impossible in certain cases. Using third party libraries that do some initialization on startup may cause other objects to appear in the memory dump and can make tracking down your leaks difficult. Also, if any of your classes have members with the same name as any of the memory allocation routines( such as malloc ), the CRT debug macros will cause problems.
There are other techniques explained in the MSDN link referenced above that could be used as well.
In C++: use RAII. Smart pointers like std::unique_ptr, std::shared_ptr, std::weak_ptr are your friends.
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