PRB: Error C4226 and Defining WIN32 (122306)

SYMPTOMS

Compiling a source file that includes WINDOWS.H generates many C4226 errors, such as:

C:\MSVC20\INCLUDE\olebase.h (8954) : error C4226: nonstandard extension used : '__export' is an obsolete keyword

...

C:\MSVC20\INCLUDE\oleauto.h(293) : error C4226: nonstandard extension used : '__huge' is an obsolete keyword

...

C:\MSVC20\INCLUDE\ole2.h(4818) : error C4226: nonstandard extension used : '__export' is an obsolete keyword

Including these header files individually causes the same problem.

CAUSE

A number of the OLE header files that are included in the WINDOWS.H file require WIN32 to be defined. While _WIN32 is defined for you, WIN32 is not. Because WIN32 is not defined, the header file logic assumes that the definitions are for 16-bit Windows-based applications and uses the __export and __huge keywords.

RESOLUTION

Here are three possible way to define WIN32:

Define WIN32 before the WINDOWS.H file is included.

   #define WIN32
   #include <windows.h>

Define WIN32 in a compiler switch. From the command line, use /DWIN32. In the development environment, follow these following steps:
1. Choose Settings from the Projects menu, and click the C/C++ tab.
2. Select the Preprocessor category.
3. Add WIN32 to the Preprocessor Definitions field of the dialog box.
Add the following lines to the beginning of the WINDOWS.H file:
```
   #if( defined (_WIN32) && !defined (WIN32) )
   #define WIN32
   #endif
						
```
NOTE: This will not take care of the case where individual OLE header files are included in an application.

MORE INFORMATION

This problem will most likely occur when building console applications.

NOTE: Although this was by design, this behavior was changed in Microsoft Visual C++, 32-bit Edition, version 4.0.