How do you detect/avoid Memory leaks in your (Unmanaged) code? [closed]

Question

If your C/C++ code is portable to *nix, few things are better than Valgrind.

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.

As a C++ Developer here's some simply guidelines:

1. Use pointers only when absolutely necessary
2. If you need a pointer, doublecheck if a SmartPointer is a possibility
3. Use the GRASP Creator pattern.

As for the detection of memory leaks personally I've always used Visual Leak Detector and find it to be very useful.

I've been using DevStudio for far too many years now and it always amazes me just how many programmers don't know about the memory analysis tools that are available in the debug run time libraries. Here's a few links to get started with:

Tracking Heap Allocation Requests - specifically the section on Unique Allocation Request Numbers

_CrtSetDbgFlag

_CrtSetBreakAlloc

Of course, if you're not using DevStudio then this won't be particularly helpful.

I’m amazed no one mentioned DebugDiag for Windows OS.
It works on release builds, and even at the customer site.
(You just need to keep your release version PDBs, and configure DebugDiag to use Microsoft public symbol server)