KB164150 - DOC: C4237 Online Help Contains Wrong Information on "bool"

SUMMARY

If you include the header OAIDL.H, note that this header defines both bool and boolval. To avoid this warning and prevent possible compatibility problems with future versions of Visual C++, your code should use the boolval definition instead of the bool definition.

error C2065: 'bool' : undeclared identifier

MORE INFORMATION

In Visual C++ 4.2, the keywords bool, true, and false are declared in the header file yvals.h. By including this file in your program, you can use the keywords bool, true, and false. Since the standard C++ header files (that is, iostream, ostream, etc.) automatically include yvals.h, if you use any of these header files you can use bool, true, and false. If you are also including windows.h, then make sure that windows.h is included above yvals.h or the standard C++ header files, otherwise the C4237 warning appears. This happens because yvals.h disables the C4237 warning with a #pragma statement.

The following programs compile without errors in Visual C++ 4.2.

Sample Code

   /* Compile options needed:none
   */ 

   #include <windows.h>
   #include <iostream>

   void main(void){
   bool x;
   BOOL Y;

   x=true;
   Y=FALSE;

   }

   Or,

   #include <windows.h>
   #include <yvals.h>

   void main(void){
   bool x;
   BOOL Y;

   x=true;
   Y=FALSE;

   }