Incompatible changes coming!

[Moon at MIT-AI (David A. Moon)]

Lisp machine system 18 and microcode 555, which must be used together,
contain some incompatible changes.  Most of these probably only affect
system programs, which have been fixed, but they are being announced in
case any users have programs which would be affected.

This system is installed on CADR1 and CADR6.  It will be installed on
all the other machines in a few days, so if you are going to have trouble
with the new system please find out before then.

The function-calling microcode has been extensively revised.  The ^ and EXPT
functions should now work completely.  However, any user programs (hopefully
there are none) that use the macros in LISPM2;SGDEFS (stack-group and pdl
formats) will need to be at least recompiled and possibly revised. 

The way the microcode treats multiple values has been changed as the first
step of making multiple values "work right".  More about this later.   Any
programs that return multiple values should be recompiled; they will still
work in system 18 due to a kludge in the microcode, but they will crash the
system in system 19, because the compiler wasn't really generating the right
code.  Programs that receive multiple values returned by other functions
have no problem.  Use of the MULTIPLE-VALUE-CALL macro, and of crockish code
sequences involving %OPEN-CALL-BLOCK, should no longer be necessary. 

The format of the item-list in a menu has been changed.  Consult the
documentation in the front of the file LISPM2;MENU.  If you have a program
that uses menus and uses other than simple a-lists as item lists, you
will need to change.

The :RUBOUT-HANDLER stream operation has been changed.  A new argument has
been added in front of the existing arguments, which is an alist of options.
Normally you want to supply NIL. 

The RUBOUT-HANDLER-CONTROL-CHARACTER-HOOK has been flushed.  Presumably
no one is using it.

If you need help converting your programs, and if this message isn't
sufficient help, please consult me.