Detect memory leak by overload new operator?

Question

I'm finding the memory leak in my program, I tried the following guide from Microsoft

http://msdn.microsoft.com/en-us/library/e5ewb1h3%28v=vs.90%29.aspx

But there are some memory leak report items, don't have the source file name and line of code.

I tried to use VLD, but the VLD don't show the file name on call stack, although I did any step in the guides on internet.

From the memory leak report of VLD, I can see the size of block leaked. So I have the idea. Assume that I can overload the operator new, and debug on it, maybe I can detect where memory leak occurred by the special break point as code below.

void* operator new (size_t size)
{
    if(size = 1107)
    {
        int temp = 0; //Put the break point here
    }
    void *p = malloc(size);
    return p;
}

But I can't overload the operator new, because I an error when compiling the program:

Error   166 error LNK2005: "void * __cdecl operator new(unsigned __int64,char *,unsigned int)" (??2@YAPEAX_KPEADI@Z) already defined in CommonGlobal.obj    E:\TIN HOC\Learning\Chuong Tring Dao Tao\Working\Main_Code\Mystic\branches\DVRServer\Common\Message.obj Common

Someone can tell me how to overload the operator new, for debugging in it?

Answer 1

The linker complains about redefinition of the operator new. You probably defined that function in a header file that is included in multiple files (at least in CommonGlobal.cpp and Message.cpp). Either move it to a source file or add an inline specifier to it. If you define the operator new is in source file, make sure it is in only one source file - it applies to all calls to the operator new in all of your source files.

Also the if(size = 1107) is suspicious - it will always break and always allocates a memory of size 1107. Change it to if(size == 1107) if you want to break when the size is equal to 1107. Under Windows you can also call __debugbreak() which breaks into debugger without need to place a breakpoint manually, but you can't expect it to work under different complier than Visual C++.

And for the Visual Leak Detector: did you see a message like Visual Leak Detector Version 2.4RC2 installed message in VS's output window and console? If not, switch active configuration from Release to Debug or #define VLD_FORCE_ENABLE before inclusion of vld.h.

Answer 2

Please include new

#include <new>

and, how Karoly mentiond, change the line if(size = 1107) to

if(size == 1107)

then the program works.