FIX: Using Run-Time Type Info May Cause Memory Leak Report

ID: Q140670

The information in this article applies to:

Microsoft Visual C++, 32-bit Editions, versions 4.0, 4.1

SYMPTOMS

When exiting a debug application that uses run-time type information (RTTI) and calls the 'name' member function of the type_info class, Visual C++ reports "Detected memory leaks!" in the output window.

CAUSE

When you call the 'name' member function of the type_info class, it incorrectly allocates a _NORMAL_BLOCK buffer to hold the type name. This can cause a memory leak to be reported incorrectly when you run a debug version of the program.

RESOLUTION

The reported memory leak can be ignored.

STATUS

Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article. This problem was corrected in Visual C++, 32-bit Edition, version 4.2.

MORE INFORMATION

When you call the 'name' member function of the type_info and then later call _CrtDumpMemoryLeaks, memory leaks are incorrectly reported. The following sample code demonstrates the problem.

Sample Code


/* Compile options needed: /D_DEBUG
*/ 

#include <typeinfo.h>
#include <iostream.h>
#include <crtdbg.h>

struct test {};

void main()
{
    test t;
    typeid(t).name();
    _CrtDumpMemoryLeaks();
}

You would see messages similar to the following in the debug tab of the output window:


   Loaded symbols for 'E:\WINNT35\system32\MSVCR40D.DLL'
   Detected memory leaks!
   Dumping objects ->
   {44} normal block at 0x002D2390, 12 bytes long.
   Data: <struct test > 73 74 72 75 63 74 20 74 65 73 74 00
   Object dump complete.
   The program 'E:\temp\Text1.exe' has exited with code 1 (0x1).

NOTE: If you are using the 'name' member function within an MFC application, the leaks will be reported even if you do not explicitly call _CrtDumpMemoryLeaks. MFC calls this function automatically when the application terminates.

Additional query words: kbVC400bug 4.00 4.10 vcfixlist420

Keywords : kbCRT kbVC
Version : 4.00 4.10
Platform : NT WINDOWS
Issue type :