From: Philipp Stephani <p.stephani2@gmail.com>
To: Sean Devlin <spd@toadstyle.org>
Cc: 43601@debbugs.gnu.org
Subject: bug#43601: 27.1; Macroexpansion bug in `push'
Date: Fri, 25 Sep 2020 11:35:35 +0200 [thread overview]
Message-ID: <CAArVCkRpBMTKoxofqNEGpHy2D1z+v2OXFcZ2TQw4L-MxupvSzA@mail.gmail.com> (raw)
In-Reply-To: <33F8870E-E0A5-43EC-98A2-7EF3DA2CCD53@toadstyle.org>
Am Fr., 25. Sept. 2020 um 00:56 Uhr schrieb Sean Devlin <spd@toadstyle.org>:
>
> Hi folks,
>
> I believe I've found a macroexpansion bug in the `push' macro. Open a
> new instance of Emacs and evaluate the following form in the scratch
> buffer:
>
> (macroexpand '(push (list 'x)
> (cdr my-list)))
>
> The result (with some reformatting) is this:
>
> (let* ((v (list 'x))
> (v my-list))
> (setcdr v
> (cons v
> (cdr v))))
>
> Both values are bound to `v', so the former is shadowed by the latter.
These are different uninterned symbols:
(let ((print-gensym t) (print-circle t))
(print (macroexpand '(push (list 'x) (cdr my-list))))
nil)
⇒ (let* ((#2=#:v (list 'x)) (#1=#:v my-list)) (setcdr #1# (cons #2# (cdr #1#))))
In general, if you see a "weird" expansion like this, bind
print-gensym to non-nil to see the uninterned symbols.
next prev parent reply other threads:[~2020-09-25 9:35 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-24 22:54 bug#43601: 27.1; Macroexpansion bug in `push' Sean Devlin
[not found] ` <handler.43601.B.160098811131831.ack@debbugs.gnu.org>
2020-09-24 23:17 ` bug#43601: Acknowledgement (27.1; Macroexpansion bug in `push') Sean Devlin
2020-09-25 5:56 ` bug#43601: 27.1; Macroexpansion bug in `push' Phil Sainty
2020-09-25 9:35 ` Philipp Stephani [this message]
2020-09-25 9:40 ` Lars Ingebrigtsen
2020-09-26 15:05 ` Lars Ingebrigtsen
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