Message        An apparent UCN escape sequence was encountered, but
                UCNs are not supported in this language mode.  The
                backslash will be ignored.

 Description    Universal Character Name (UCN) escape sequences were
                added to C in the C99 standard.  The language mode of
                the current compilation does not process UCNs, so
                they will be treated as unrecognized escape
                sequences, which ignore the backslash.

 User Action    Compile in a mode that processes UCNs (C99, or the
                default "relaxed" mode), or remove the backslash.
                Relying on apparent escape sequences to be
                unrecognized is not good practice.