PRB: Conflict with EOF and GetUserName Using #import on RDO (167542)

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 will 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: 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.