A question about ignoring IGNORE

[Beng-Hong Lim <BHLim@jasper.palladian.com>]

    Date: Wed, 18 Nov 87 11:17 EST
    From: Jeffrey Mark Siskind <Qobi@ZERMATT.LCS.MIT.EDU>

    If I have a macro which expands into some lisp code which contains
    local variable definitions (either through LET or DEFUN etc.)
    and I don't know or care whether all such variables will be used
    by any particular expansion of the macro, I run into the
    following annoying problem. The compiler will complain and issue
    warnings that the variables are unused, but if I declare them
    as (DECLARE (IGNORE FOO)) and the variables are unused then
    the compiler will complain and issue a warning that the variables
    are used. It turns out to be to much of a pain for me to
    determine whether a given variable is used and conditionally
    include its binding in the expanded output of the macro. So
    as the old saying goes, how do I avoid being "Damned if you
    do, and damned if you don't"? What I really want is something
    like (DECLARE (I-DONT-CARE-IF-IT-IS-UNUSED FOO)).
	    Jeff


You can't use a declaration in this case if you want to avoid the
warnings.  Best you can do is "use" the variables e.g.  by saying
(PROGN A B C) where A, B, and C are the local variables that may or
may not be used.  You then hope that the compiler is smart enough to
ignore the PROGN. (On the Symbolics it is.)  Or if you want something
more semantically pleasing than PROGN, then use (IGNORE A B C) on
Symbolics which macroexpands to (PROGN A B C). 

Beng.