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harshman_chris

Debugging Memory Leaks in Visual Studio 2010 (c++)

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I am trying to debug memory leaks in my game application, which consists of a executable and a dynamic-link library.

 

This is the code I have added following some msdn pages. 

 

#define _CRTDBG_MAP_ALLOC
#include <stdlib.h>
#include <crtdbg.h>

#define DEBUG_NEW new(_NORMAL_BLOCK, __FILE__, __LINE__)
#define new DEBUG_NEW

int WINAPI WinMain(HINSTANCE hInstance,
					HINSTANCE hPrevInstance,
					LPSTR lpCmdLine,
					int nCmdShow)
{
	_CrtSetDbgFlag ( _CRTDBG_ALLOC_MEM_DF | _CRTDBG_LEAK_CHECK_DF );
	_CrtSetReportMode( _CRT_ERROR, _CRTDBG_MODE_DEBUG );

	init();

	int result = loop();

	deInit();

	return result;
}

 

 

My Output looks like this though:

 

Detected memory leaks!
Dumping objects ->
{298045} normal block at 0x0B0AB5F0, 32 bytes long.
 Data: <Threshold: 0.800> 54 68 72 65 73 68 6F 6C 64 3A 20 30 2E 38 30 30 
{298037} normal block at 0x0B0A3B30, 8 bytes long.
 Data: <        > 10 B3 0A 0B 00 00 00 00 
{298020} normal block at 0x0B0AB0E8, 32 bytes long.
 Data: <Middle Grey: 0.1> 4D 69 64 64 6C 65 20 47 72 65 79 3A 20 30 2E 31 
{298012} normal block at 0x0B0A3C60, 8 bytes long.
 Data: <        > C0 AF 0A 0B 00 00 00 00

 

 

As far as I know I should be getting file and line numbers at this point, I did fine something earlier on gamedev that talked about this, but it didn't seem to resolve my issue and the post was quite old.

 

So how can I get better information about debugging these memory leaks?

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If there's always a leak reported at the same request number (e.g. 298012), you can define a custom allocation callback function to give you more information on the leak (you register these with _CrtSetAllocHook()).

 

If you then break on a specific request, the call stack will show you exactly where the leak occurred.

 

_CrtSetAllocHook(crtDebugMemAllocHook);

 

 

static int crtDebugMemAllocHook(int allocType, void *userData, size_t size, int blockType, long requestIndex, const unsigned char *fileName, int lineIndex){
 
   if(requestIndex == 298012) //break;
 
   return true;
}

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I like to output the pointers of anything that could potentially have a memory leak, and then match it up with the CRT output.

For example, my log file may have something like this:
[3/31/2013 13:10:10:461] --------------- pWindow: 004BD750
[3/31/2013 13:10:10:461] --------------- pController: 004754B8
[3/31/2013 13:10:10:461] --------------- pMouse: 004BD6C0
[3/31/2013 13:10:10:461] --------------- pKeyboard: 004C08E8
and if CRT says 004BD750 has a memory leak, then I know where to go to fix it.

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Something you might want to try instead of MSVC's built in leak detector functions is Visual Leak Detector.

 
Tried it and I like I seem, it is still hard to understand what some of the leaks mean though.


VLD should take you directly to the allocation that isn't being freed. That's the best anything can do for you.

Are you not using smart pointers?

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I use this type of implementation for this: http://www.flipcode.com/archives/How_To_Find_Memory_Leaks.shtml

Doesn't work on malloc etc.

 

It will make your code really slow, but the awesome thing is.. you can add some extra functionality:

-Record when the memory block was allocated.

-Reset you memory-track-table

-Output the table when you like to a file

-etc.

Edited by Vlad86

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