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
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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
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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:
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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
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