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#undef                   Remove a Macro Definition

 #undef  identifier

    This directive removes the current definition of the macro named
    identifier.

      Notes:    To remove the definition of a macro with arguments,
                specify the macro name only. Do not include the argument
                list.

                If identifier is not currently defined as a macro, no
                error occurs.

                Macro definitions can also be removed using the compile-
                time switches /U and /u.