FIX: Function Prototypes in comutil.h Missing Calling Convention

• Microsoft Visual C++, 32-bit Editions, version 5.0

SYMPTOMS

Unresolved external errors may occur when you compile with a default calling convention of __fastcall (/Gr) or __stdcall (/Gz) and call ConvertStringToBSTR or ConvertBSTRToString.

CAUSE

The prototypes are missing the __cdecl calling convention, which is the calling convention of these functions in comsupp.lib.

RESOLUTION

Build with __cdecl as the default calling convention. Do not build with __fastcall or __stdcall as the default calling convention.

STATUS

Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article. This bug has been corrected in Visual Studio 97 Service Pack 1.

For additional information about the Visual Studio 97 Service Pack 1, please see the following article in the Microsoft Knowledge Base:

Q170365 INFO: Visual Studio 97 Service Packs - What, Where, and Why

MORE INFORMATION

Sample Code

   //compile options needed: /Gr or /Gz
   #include <comutil.h>
   int main()
   {
       char sz[]="hello";
       _bstr_t b;
       b = _com_util::ConvertStringToBSTR(sz);
       char * p = _com_util::ConvertBSTRToString(b);
       return 1;
   } 

   error LNK2001: unresolved external symbol "char * __fastcall
   _com_util::ConvertBSTRToString(unsigned short *)"
   (?ConvertBSTRToString@_com_util@@YIPADPAG@Z) 

   error LNK2001: unresolved external symbol "unsigned short * __fastcall
   _com_util::ConvertStringToBS
   TR(char const *)" (?ConvertStringToBSTR@_com_util@@YIPAGPBD@Z) 

Additional query words: LNK2001

Keywords : kbcode kbVC500bug kbVS97sp1fix
Version : 5.0
Platform : NT WINDOWS
Issue type : kbbug