GNU bug report logs - #27016
possible bug in `defsetf'

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From: Michael Heerdegen <michael_heerdegen <at> web.de>
To: npostavs <at> users.sourceforge.net
Cc: 27016 <at> debbugs.gnu.org, Stefan Monnier <monnier <at> iro.umontreal.ca>, Rafael D Sorkin <rsorkin <at> perimeterinstitute.ca>
Subject: bug#27016: possible bug in `defsetf'
Date: Mon, 03 Jul 2017 13:25:57 +0200

npostavs <at> users.sourceforge.net writes:

> I hope someone will correct me if I've gotten mixed up again, but I
> believe the byte-compiled case already works fine:
>
>     ~/src/emacs$ cat bug-27016-defsetf.el
>     (require 'cl)
>
>     (defvar pair nil)
>     (setq pair (cons 3 4))
>     (when nil
>       (defalias 'foobar 'cons)
>       (defsetf foobar setcar))
>     ~/src/emacs$ emacs -Q -batch -f batch-byte-compile bug-27016-defsetf.el
>
>     In toplevel form:
>     bug-27016-defsetf.el:1:1:Warning: cl package required at runtime
>     bug-27016-defsetf.el:3:1:Warning: global/dynamic var ‘pair’ lacks a prefix
>     ~/src/emacs$ emacs -Q -batch -l bug-27016-defsetf.elc --eval '(setf (foobar pair) 0)'
>     Symbol’s function definition is void: \(setf\ foobar\)

Yes - if you use two separate Emacs instances.  The defsetf gets
evaluated in the Emacs that is used to compile the code
(unconditionally).

So what you state is not suspicious for a problem with a surprising side
effect when performing macroexpansion, right?


Michael.

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