PRB: C2632 Caused by Including WINDOWS.H First

The information in this article applies to:

• The Microsoft Foundation Classes (MFC) included with:

      - Microsoft C/C++ version 7.0
      - Microsoft Visual C++ for Windows, versions 1.0 and 1.5
  

SYMPTOMS

Compiling a source file that explicitly includes WINDOWS.H followed by a Microsoft Foundation Classes (MFC) header file such as AFX.H may produce errors such as:

   c2632 'long' followed by 'long' is illegal

CAUSE

This error occurs as a result of MFC using STRICT type checking by default. STRICT type checking is not used in WINDOWS.H unless you define STRICT as a preprocessor symbol before including the header file.

Specifically, WINDOWS.H has the following statement:

   #ifdef STRICT
   typedef signed long LONG;
   #else
   #define LONG long
   #endif

   typedef long LONG;   // 32-bit signed number

   typedef long long;   // 32-bit signed number

RESOLUTION

Include WINDOWS.H after the MFC header files or not at all. AFXWIN.H automatically includes WINDOWS.H, so it is normally not necessary to explicitly include it in your source code.

Another way to avoid this error is to define STRICT as a preprocessor symbol before including WINDOWS.H. This will ensure that LONG is type defined as signed long rather than simply long.

MORE INFORMATION

MFC Technical Note 12 "Using Windows 3.1 Robustness Features" contains additional information on STRICT type checking and other Windows 3.1 robustness features.

Sample Code

/* Compile options needed:  /D_WINDOWS */

/*
#define STRICT    // Remove comments from this line to avoid errors.
*/

#include <windows.h> // Or, reverse order of these statements.
#include <afx.h>