I added support for multibyte coding systems. The new magic variable is slime-net-coding-system. Currently there are 3 possible values for the coding system: iso-8859-1-unix, utf-8-unix, and emacs-mule-unix. At startup, Emacs tells the Lisp implementation which coding system to use and same encoding is used for the rest of the session. Not all Lisps implementations support all coding systems. The situations is as follows:
CMUCL, OpenMCL: support only iso-8859-1-unix. SBCL, CLISP: can be used with iso-8859-1-unix or utf-8-unix. Allegro: supports all three.
LispWorks and ABCL support only iso-8859-1-unix because I didn't know how to set the external-format for socket streams in those Lisps.
Of course, the Emacs version must support the coding system too. GNU Emacs 20 and 21 support emacs-mule. utf-8 is probably only available in CVS Emacs or CVS XEmacs. AFAIK, no XEmacs has no support for emacs-mule.
If you use a multibyte encoding in GNU Emacs, it is important that you set default-enable-multibyte-characters to t. That's default, so most people don't have to worry about it.
No change is needed for people who don't care about multibyte characters. Everything should work as before (modulo bugs).
Helmut.