$ rcsdiff -wu -r .* 2>&1 | histring -f '^RCS file.*'

RCS file: RCS/.aliases_cs,v
rcsdiff: RCS/.aliases_cs,v: Symbolic name `(P' is undefined.
rcsdiff: RCS/.bash_logout,v: No such file or directory
===================================================================
RCS file: RCS/.bash_profile_,v
rcsdiff: RCS/.bash_profile_,v: Symbolic name `,T' is undefined.
===================================================================
RCS file: RCS/.bash_profile_su,v
retrieving revision 1.4
diff -wu -r1.4 .bash_profile_su
===================================================================
RCS file: RCS/.bash_rc,v
rcsdiff: RCS/.bash_rc,v: Symbolic name `(P' is undefined.
[...]

Why are the "symbolic name undefined" problems?

The problem occurs when there is more than one file on the rcsdiff command line. I.e., rcsdiff file1 file2 file3… From file2 and on, the "symbolic name undefined" error will occur.

Solution: have to compare files individually, not all in one line.

Like this:

gen_file_list | xargsi rcsdiff -wU -r {}