BUG: _MBCS String Functions of the MSVCRT.DLL file (version 6.1.8637.0) Is Slower than Earlier Versions

1. Rebuild the application to statically link to the run-time library. The static library does not have the performance delay with MBCS string functions on Windows 2000 and Windows ME.
2. Modify the application to be Unicode compatible on Windows 2000. For example, use _ttoi(argv[1]) in the sample code located in the "More Information" section of this article instead of atoi(argv[1]). Rebuild the application with the _UNICODE manifest instead of _MBCS. If the application uses the MFC, the Unicode version of the MFC library is used by default. Refer to the MSDN library for more information about Unicode programming.
3. If your application only uses single-byte character set (SBCS), rebuild the application without the _MBCS manifest. If the application uses the MFC CString functions, you will still encounter this MBCS problem because MFC is built with _MBCS by default. The following are two possible work arounds for this case:
   • Add \MFC\SRC\Strex.cpp to your project, and then compile it without _MBCS. The Strex.cpp file implements the CString functions. This may not work if your application uses the MFC library indirectly when other DLL's that are used by your application use MFC CString functions.
   • Rebuild the MFC library with MBCS=0. Add the MFC42.LIB file to the "Ignore Libraries" project setting, and then link your custom MFC library with your application. Refer to technician note TN033 for "Rebuilding the MFC DLL" procedures.

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Steps to Reproduce the Behavior

• Create a Win32 Console Application project with the following code:
  

  #include <windows.h>
  #include <tchar.h>
  #include <process.h>
  #include <stdio.h>
  
  unsigned int __stdcall threadfunc(void *)
  {
      for (int v = 0; v <= 10000000; ++v)
  	_istspace(' ');
  	return 0;
  }
  
  int main(int argc, char **argv)
  {
      if (argc != 2)
  	{
  		printf("Usage: <appname.exe> <# of threads>\n");
  		exit(1);
  	}
  
      int nthreads = atoi(argv[1]);
      //int nthreads = _ttoi(argv[1]);  //UNICODE version
  
      HANDLE *handles = new HANDLE[nthreads];
  	unsigned int *threadID = new unsigned int[nthreads];
  
      for (int i = 0; i < nthreads; ++i) {
  	handles[i] = (HANDLE) _beginthreadex(NULL, 0, &threadfunc, NULL, 0, &threadID[i]);
      }
  
      WaitForMultipleObjects(nthreads, handles, TRUE, INFINITE);
  
  	delete [] handles;
  	delete [] threadID;
  
      return 0;
  }
  						

  
  
• Build the application using the Multithreaded DLL run-time library Msvcrt.dll file. The project is built with the _MBCS processor directive by default and _istspace() is mapped to _ismbcspace(). This application runs slower on Windows 2000 and Windows ME than on Windows NT 4.0 and Windows 9x.

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