__HIDE_FORBIDDEN_NAMES

 The ANSI C standard specifies exactly what identifiers in the
 normal name space are declared by the standard header files.  A
 compiler is not free to declare additional identifiers in a header
 file unless the identifiers follow defined rules (the identifier
 must begin with an underscore followed by an uppercase letter or
 another underscore).

 When you compile with VSI C using any values of /STANDARD that set
 strict C standard conformance (ANSI89, MIA, C99, and LATEST),
 versions of the standard header files are included that hide many
 identifiers that do not follow the rules.  The header file
 <stdio.h>, for example, hides the definition of the macro TRUE.
 The compiler accomplishes this by predefining the macro
 __HIDE_FORBIDDEN_NAMES for the above-mentioned /STANDARD values.

 You can use the command line qualifier
 /UNDEFINE="__HIDE_FORBIDDEN_NAMES" to prevent the compiler from
 predefining this macro, thus including macro definitions of the
 forbidden names.

 The header files are modified to only define additional VAX C names
 if __HIDE_FORBIDDEN_NAMES is undefined.  For example, <stdio.h>
 might contain the following:

         #ifndef __HIDE_FORBIDDEN_NAMES
         #define TRUE    1
         #endif