PRB: C2065/C2064 Errors when Using Win32 APIs in MFC Program

The information in this article applies to:

• The Microsoft Foundation Classes (MFC), included with: Microsoft Visual C++, 32-bit Edition, versions 4.0, 4.1

SYMPTOMS

Using some Win32 APIs, such as PurgeComm() and RegFlushKey(), in an AppWizard generated application will cause C2065 and C2064 compilation errors. For example, a call to the PurgeComm() function will produce the following errors:

   error C2065: 'PurgeComm' : undeclared identifier
   error C2064: term does not evaluate to a function

CAUSE

In Visual C++ 4.x, AppWizard automatically adds a macro definition for VC_EXTRALEAN to the project's precompiled header. Its purpose is to help speed up compilation by excluding less-frequently used declarations from the various Windows header files.

When VC_EXTRALEAN is defined in the precompiled header, the following SDK symbols get defined in afxv_w32.h:

   #define WIN32_EXTRA_LEAN
   #define NOSERVICE
   #define NOMCX
   #define NOIME
   #define NOSOUND
   #define NOCOMM
   #define NOKANJI
   #define NORPC
   #define NOPROXYSTUB
   #define NOIMAGE
   #define NOTAPE

   #ifndef NO_ANSIUNI_ONLY
   #ifdef _UNICODE
   #define UNICODE_ONLY
   #else
   #define ANSI_ONLY
   #endif
   #endif //!NO_ANSIUNI_ONLY

RESOLUTION

One solution is to remove the #define VC_EXTRALEAN line from stdafx.h. This keeps the Communication, Registry, and other areas of the Win32 APIs that are not directly used by MFC in the project.

An alternative is to replace the "#define VC_EXTRALEAN" line with the set of #define lines listed above, and then selectively remove those #define's that should not be included. For instance, if the Communication APIs are called, you may have all the #define lines listed above except the "#define NOCOMM" line in the stdafx.h.

STATUS

This behavior is by design.

MORE INFORMATION

For complete information on what the macros listed above exclude, search the windows.h and afxv_w32.h files for the symbols.