From: Dave Dyer
Subject: Can C return strings to Allegro?
Date: Thu, 09 Jun 1994 18:35:28 +0000
Message-ID: <19940609181602.3.DDYER@GOYA.triple-i.com>

    Date: Thu, 9 Jun 1994 07:01 PDT
    From: Ronald S. Chong <······@dip.eecs.umich.edu>

    hi all:

    i'm fumbling around trying to learn foreign functions calls to c.  the
    :return-type keyword argument for ff:defforeign doesn't have a value
    that would permit strings to returned from the c function.  how is
    this typically done.  thanks.

    /r/

It looks like you're referring to allegro.  There's a
c-string-to-lisp-string function.  A little macrology can conceal this
deficiency from the enduser:

(macroexpand-1 '(ffc:def-ffun foo (a) :return-type :string))

(PROGN (FOREIGN-FUNCTIONS:DEFFOREIGN 'FOO%INTERNAL
         :LANGUAGE :C
         :RETURN-TYPE ':INTEGER
         :ENTRY-POINT '"foo"
         :PROTOTYPE T
         ...)
       (DEFUN FOO (FFC::ARG1)
         (LET ((FFC::V #))
           (UNLESS (EQL FFC::V 0)
             (FOREIGN-FUNCTIONS:CHAR*-TO-STRING FFC::V))))
	)