GNU bug report logs - #72313
31.0.50; Warning about cl-member possibly being undefined when using cl-pushnew

Previous Next

Full log

View this message in rfc822 format

From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: Tassilo Horn <tsdh <at> gnu.org>
Cc: 72313 <at> debbugs.gnu.org
Subject: bug#72313: 31.0.50; Warning about cl-member possibly being undefined when using cl-pushnew
Date: Sat, 27 Jul 2024 03:01:32 -0400

> --8<---------------cut here---------------start------------->8---
> ;;  -*- lexical-binding: t; -*-
> (eval-when-compile
>   (require 'cl-lib))
>
> (defun foo ()
>   (let ((s (list 'a 'b)))
>     (cl-pushnew (list 1 2 3)
>                 s
>                 :test (lambda (_a _b) nil))))
> --8<---------------cut here---------------end--------------->8---

    (macroexpand-all '(cl-pushnew (list 1 2 3) s :test (lambda (_a _b) nil)))
=>
    (setq s
     (let* ((va (list 1 2 3)))
       (if (cl-member va s :test #'(lambda (_a _b) nil)) s (cons va s))))

> My assumption is that (eval-when-compile (require 'cl-lib)) should be
> fine when using only macros from cl-lib which in turn should expand to
> cl-free code,

That's not the case here (and a few other places).
In the past, I've moved some of this kind of code to `cl-preloaded`, so
as to make things easier for programmers (to avoid them having to know
which CL macros emit code which calls CL functions (and when)), but
there are still cases like above, yes.

In practice most complex macros are often best served by emitting code
which itself calls helper functions (e.g. `cl-defstruct` used to not
call a function but I changed it to call `cl-struct-define`).


        Stefan

Previous Next

GNU bug tracking system
Copyright (C) 1999 Darren O. Benham, 1997,2003 nCipher Corporation Ltd, 1994-97 Ian Jackson.