Memory leak finder

9loong 2008-11-28

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Sample Image - Memory_leak_finder.jpg

Introduction

Have you ever had a memory leak? Wished you knew where you allocated it and how? Is your boss cheap and refuses to buy Boundchecker or another debugging tool?

Here is the solution for you. A memory leak detector compiled directly into your code. It reports memory leaks with call stack of the allocation down to a user defined depth.

As an add-on, it does simple checks of the memory before and after the memory block, to track buffer overwrites.

Usage

Include tracealloc.cpp in your project. Define DETECT_LEAKS in the project settings. Compile. Run your application. Memory leaks are reported into your debug output window when the application terminates. Just click the memory leak and the correct file and line will be shown.

You can find further instructions in the source code.

How is it done?

The code overrides operator new and operator delete. For each allocation made, the code allocates extra space for tracking, call stack and no-mans-land. The current call stack is fetched and remembered, finally the code puts the newly allocated block in a linked list and the requested memory is returned.

When a memory block is deleted, the header is found and checked for buffer overwrites. The memory block is then removed from the linked list and deallocated.

When the program terminates, the global memory tracker object is deleted. The destructor traverses the linked list for memory blocks that isn’t deleted (= leaked memory). It then fetches symbol information for the call stacks and dumps the information in the debug console.

Limitations

The code is Microsoft Visual Studio and Win32 specific. It requires a debug build. The code is C++ specific. It handles new/delete but not malloc/free. The code will run slower with leak detection active (roughly at half normal debug build speed).

Finally

I want to thank Zoltan Csizmadia who wrote ExtendedTrace. I have used parts of his code for stack walking and symbol lookups.

I also want to thank the Code Project community. I have found many solutions or pointers in the right direction here. I hope I have given something back with this contribution.

Thank you!