PRB: Conflict with EOF and GetUserName Using #import on RDO

 Last reviewed: August 7, 1997
Article ID: Q167542
The information in this article applies to:
  • Microsoft Visual C++, 32-bit Editions, version 5.0

SYMPTOMS

With #import, you can generate classes that encapsulate the typelib of database API's such as Remote Data Objects (RDO) within a windows application. For example: 

   // Excerpt from STDAFX.H
   #include <afxwin.h>         // MFC core and standard components
   ...
   #import "C:\winnt\system32\msrdo20.dll" no_namespace
When you use #import for RDO, you may receive these errors. The first is for a conflict with the ResultSet.EOF property, and the second is for the Environment.GetUserName method. 

   error C2629: unexpected 'short ('
   error C2238: unexpected token(s) preceding ';'

   error C2535: 'class _bstr_t
   _rdoEnvironment::GetUserNameA(void)':
                member function already defined or declared
   error C2084: function 'class bstr_t
                _rdoEnvironment::GetUserNameA(void)'
                already has a body

CAUSE

In this case, two separate problems are creating the four compiler errors.

"EOF" Property and #import

Within an application that uses STDIO.H, IOS.H or STREAMB.H (including AFXWIN.H ), EOF has already been defined as a constant (-1). #import defines the EOF property for RDO's Resultset object. At compile time, this generates the C2629/C2238 errors on this line of generated code in the MSRDO20.TLH file: 

   VARIANT_BOOL EOF;
This line is attempting to define a variable, but EOF has already been defined as -1. So the above line of code parses to: 

   short -1;
Which will not compile because -1 is not a valid variable name.

GetUserName and #import

The compiler errors C2535 and C2084 are an indication that Msrdo20.dll's typelib is using a name that is mapped by #define to another name that's also used. In this case, the _rdoEnvironment interface has properties UserName and UserNameA. #import creates property get methods for GetUserName and GetUserNameA. However, there's a GetUserName Win32 API that the system headers #define to GetUserNameA (or GetUserNameW for Unicode). That means, after preprocessing, the compiler sees two definitions for _rdoEnvironment::GetUserNameA.

RESOLUTION

To correct both problems, the rename clause will be used as follows: 

   #import "C:\winnt\system32\msrdo20.dll" \
            no_namespace \
            rename( "EOF", "_EOF" ) \
            rename("UserNameA", "_UserNameA")
This time, it'll compile without error. If you look at _rdoEnvironment in Msrdo20.tlh, you'll now see properties UserName and _UserNameA, with propget methods GetUserName and Get_UserNameA.

Note that the rename attribute renames UserNameA, not GetUserNameA. That's because rename must be applied to an actual name from the typelib, and only UserNameA, not GetUserNameA, appears there. Instead, GetUserNameA is a name synthesized by the #import mechanism. 

Keywords          : MfcDatabase RDOALL RDOVC
Version           : 5.0
Platform          : NT WINDOWS
Issue type        : kbprb

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Last reviewed: August 7, 1997
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