Debugging Win32 API Apps for Memory Leaks

Question

I was reading up on how to go about finding memory leaks with the C++ new operator and the standard CRT malloc function on a Win32 application.

I added some stuff for working with windows sockets and I wanted to include crtdbg.h only if running in debug mode, along with some other defines. So I ended up piecing this together into my stdafx.cpp as my standard pre-compiled header:

// stdafx.h : include file for standard system include files,
// or project specific include files that are used frequently, but
// are changed infrequently
//

#pragma once

#include "targetver.h"

#define WIN32_LEAN_AND_MEAN             // Exclude rarely-used stuff from Windows headers
// Windows Header Files:
#include <windows.h>

// C RunTime Header Files
#include <stdlib.h>
#include <malloc.h>
#include <memory.h>
#include <tchar.h>

// Windows Sockets
#include <winsock2.h>
#pragma comment(lib,"ws2_32.lib")


// If running in debug mode we need to use this library to check for memory leaks, output will be in DEBGUG -> WINDOWS -> OUTPUT
// http://msdn.microsoft.com/en-us/library/x98tx3cf.aspx
#ifdef _DEBUG   
    //http://stackoverflow.com/questions/8718758/using-crtdumpmemoryleaks-to-display-data-to-console
    #ifndef DBG_NEW      
        #define DBG_NEW new ( _NORMAL_BLOCK , __FILE__ , __LINE__ )      
        #define new DBG_NEW   
    #endif
    #define _CRTDBG_MAP_ALLOC
    #include <crtdbg.h>
#endif  // _DEBUG

I also intended to put these lines just before the exit point of my program:

#ifdef _DEBUG  
    _CrtSetReportMode( _CRT_ERROR, _CRTDBG_MODE_DEBUG );
    _CrtSetReportMode( _CRT_WARN, _CRTDBG_MODE_DEBUG );
    _CrtDumpMemoryLeaks(); 
#endif

Anyways, it appears to compile but I get some strange warning:

warning C4005: '_malloca': macro redefinition

From the crtdbg.h. Is this due to the wrong ordering of the headers in the stdafx.h, or is this normal? Also, am I on the right track for detecting memory leaks in Win32 apps or is there something else I should be using in Visual Studio?

Answer 1

From the crtdbg.h. Is this due to the wrong ordering of the headers in the stdafx.h, or is this normal?

Perhaps this article can help you. Notice this part :

For the CRT functions to work correctly, the #include statements must follow the order shown here.

---

You could use Visual Leak Detector for finding leaks involved with missing delete for new operator as others mentioned. I had good experience with it, but I usually tend to triple-check if in my code every new has corresponding delete call.

---

Also, am I on the right track for detecting memory leaks in Win32 apps or is there something else I should be using in Visual Studio?

The other type of memory leaks are GDI leaks. These usually happen when you do not restore the device context into original state or you forget to delete the GDI object.

For those leaks I use GDIView. Its usage is well described but if you have any questions leave a comment.

You might find this article useful.

Of course, there are lots of good tools out there, this is just my suggestion.

Hopefully this helps.

Best regards.