FIX: LNK2001 on AfxSocketInit When Using __stdcall Default (135336)
The information in this article applies to:
- The Microsoft Foundation Classes (MFC), when used with:
- Microsoft Visual C++, 32-bit Professional Edition 2.1
This article was previously published under Q135336 SYMPTOMS
An MFC sockets application that uses a default calling convention of
__stdcall receives the following error:
<module name>.obj : error LNK2001: unresolved external symbol
"?AfxSocketInit@@YGHPAUWSAData@@@Z
(int _stdcall AfxSocketInit(struct WSAData *))"
CAUSE
The AfxSocketInit function is declared in AFXSOCK.H as follows:
BOOL AfxSocketInit(WSADATA* lpwsaData = NULL);
Note that it has no modifiers on the name of the function. Because of this,
the function calling conventions used by the compiler for this function
will be whatever the command-line setting is.
Because MFC is built with the default __cdecl calling convention, the
AfxSocketInit function has its name decorated according to this convention.
If your application is built with the __stdcall calling convention, then
the function will be decorated according to this convention.
Your code is effectively trying to call a function by a different name than
the one that exists in the MFC library (due to the different name
decoration), so the linker cannot resolve your reference.
RESOLUTION
Because MFC is built with the default calling convention of __cdecl, your
application needs to have the AfxSocketInit declaration specifying this.
Modify the declaration of AfxSocketInit in the header file AFXSOCK.H. This
file is installed by default in the directory: \MSVC20\MFC\INCLUDE
Change the declaration of AfxSocketInit from:
BOOL AfxSocketInit(WSADATA* lpwsaData = NULL);
To:
BOOL __cdecl AfxSocketInit(WSADATA* lpwsaData = NULL);
After making the change to this declaration, rebuild the .CPP file in your
project that contains the call to AfxSocketInit. Note that you won't need
to rebuild MFC because the MFC libraries have been built with this function
being marked as __cdecl.
STATUS
Microsoft has confirmed this to be a bug in the Microsoft products listed
at the beginning of this article. This bug was corrected in Visual C++, 32-
bit edition, version 4.0.
REFERENCES
For more information on how to track down LNK2001 errors, please use the
Help file.
| Modification Type: | Major | Last Reviewed: | 10/24/2003 |
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| Keywords: | kbBug kbfix kbNoUpdate kbVC400fix kbWinsock KB135336 |
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