VMS Help CC, Messages, SUBINVALIDCHR  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 Message        Parameter substitution produced an invalid character
                constant.

 Description    In certain modes, the compiler will replace
                identifiers found within a character constant if they
                match a macro argument name.  This form of "old-style
                stringization" is provided for compatibility with
                older C compilers.  This message is output if this
                replacement forms an invalid character constant.

 User Action    Modify the macro argument so that a valid character
                constant is formed.