KnowledgeBase Archive

An Archive of Early Microsoft KnowledgeBase Articles

View on GitHub

Q166504: PRB: MFC and CRT Must Match in debug/release and static/dynamic

Article: Q166504
Product(s): Microsoft C Compiler
Version(s): winnt:2.0,2.1,2.2,4.0,4.1,4.2,5.0,6.0
Operating System(s): 
Keyword(s): kbnokeyword kbCRT kbMFC kbVC200 kbVC210 kbVC220 kbVC400 kbVC410 kbVC420 kbVC500 kbVC600
Last Modified: 04-AUG-2001

-------------------------------------------------------------------------------
The information in this article applies to:

- The Microsoft Foundation Classes (MFC), used with:
   - Microsoft Visual C++, 32-bit Editions, versions 2.0, 2.1, 2.2, 4.0, 4.1 
   - Microsoft Visual C++, 32-bit Enterprise Edition, version 4.2 
   - Microsoft Visual C++, 32-bit Professional Edition, version 4.2 
   - Microsoft Visual C++, 32-bit Enterprise Edition, version 5.0 
   - Microsoft Visual C++, 32-bit Professional Edition, version 5.0 
   - Microsoft Visual C++, 32-bit Enterprise Edition, version 6.0 
   - Microsoft Visual C++, 32-bit Professional Edition, version 6.0 
   - Microsoft Visual C++, 32-bit Learning Edition, version 6.0 
-------------------------------------------------------------------------------

SYMPTOMS
========

When the MFC and CRT (C Run-Time) libraries do not match in debug/release or in
static/dynamic, you get errors such as the following when linking:

  nafxcwd.lib(appcore.obj) : error LNK2001: unresolved external symbol ___argc

Many other strange problems may erupt during build or runtime: memory corruption,
memory leaks, complaints from the debug C Run-Time libraries during run-time,
and more.

CAUSE
=====

When building an MFC application or DLL, you need to insure that all relevant
libraries are in sync:

- If you have selected to build an application using MFC in the Shared Library,
  then you must also use the dynamic version of the C Run-Time (MSVCRT.DLL).

- If you have selected to build a debug MFC application, then you must also use
  the debug version of the C Run-Time. Similarly, release MFC applications must
  use the non-debug version of the C Run-Time.

- If your debug MFC application uses extension DLLs, every extension DLL must
  be a debug build as well. Again, release apps must match release extension
  DLLs. The type of C Run-Time library is fixed. Extension DLLs and the
  applications which use them must all use MFC in the shared library, which
  requires the dynamic DLL version of the C Run-Time.

- If you are linking to any static libraries that also link to MFC or the CRT,
  you should ensure that every static library shares the same properties
  (debug/release, CRT-static/dynamic) as the application.

RESOLUTION
==========

To change the type of C Run-Time library used by an application or DLL, go to
the Build/Project settings property sheet and switch to the C/C++ tab. On the
C/C++ page, choose the "Code Generation" category. Change the value of the "Use
run-time library" listbox. Pay careful attention to make this specific for each
configuration; only one configuration, such as "Win32 (80x86) Debug," should be
selected when you change this value.

  Debug, shared library MFC applications - "Debug Multithreaded Dll."

  Release, shared library MFC applications - "Multithread Dll."

  Debug, static library MFC applications - "Debug Multithreaded."

  Release, static library MFC applications - "Multithreaded."

STATUS
======

This behavior is by design.

REFERENCES
==========

For additional information on C Run-Time options and MFC, please see the
following articles in the Microsoft Knowledge Base:

  Q126646 PRB: Error Msg: LNK2001 on __beginthreadex and __endthreadex

  Q128641 The /Mx Compiler Options and the LIBC, LIBCMT, MSVCRT Libs

(c) Microsoft Corporation 1999, All Rights Reserved.
Contributions by Jason Strayer, Microsoft Corporation


Additional query words:

======================================================================
Keywords          : kbnokeyword kbCRT kbMFC kbVC200 kbVC210 kbVC220 kbVC400 kbVC410 kbVC420 kbVC500 kbVC600 kbGrpDSMFCATL 
Technology        : kbAudDeveloper kbMFC
Version           : winnt:2.0,2.1,2.2,4.0,4.1,4.2,5.0,6.0
Issue type        : kbprb

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.