From: Pip Cet <pipcet@gmail.com>
To: 46834@debbugs.gnu.org
Subject: bug#46834: 28.0.50; byte-compiling the standard counter closure fails
Date: Sun, 28 Feb 2021 19:57:59 +0000 [thread overview]
Message-ID: <CAOqdjBeBwgTtTrrecExPb-toa54t6Vm6USO4F0fwWWYN62UYVw@mail.gmail.com> (raw)
In-Reply-To: <CAOqdjBcPE7Uff9eFf+ERQMDojecLLEdaqgVt8xHnRLdb-EVbgQ@mail.gmail.com>
[-- Attachment #1: Type: text/plain, Size: 1339 bytes --]
On Sun, Feb 28, 2021 at 6:08 PM Pip Cet <pipcet@gmail.com> wrote:
> (My apologies if this is well-known, documented, or plain stupid on my
> part, but I think it's an interesting gotcha. Feel free to close
> immediately in those cases.)
>
> Steps to reproduce from emacs -Q:
> Evaluate the following in a lexically-bound Emacs Lisp buffer:
>
> (byte-compile (let ((l 0)) (lambda () (cl-incf l))))
>
> Expected result:
>
> A byte code object which will increment its return value by one every
> time it is called.
>
> Actual result:
>
> A byte code object which always returns 1.
So, investigating a little, byte-compile--reify-function does not do,
and as far as I can tell has never done, what it claims to do in its
docstring.
(byte-compile--reify-function (let ((x 0)) (lambda () (cl-incf x))))
=> (lambda nil (let ((x '0)) (setq x (1+ x))))
Obviously, the closure generated on the LHS is not equivalent to that
generated by evaluating the RHS.
Also, while we're there:
(byte-compile--reify-function (let ((x 0)) (let ((x 1)) (lambda ()
x)))) => (lambda nil (let ((x '1) (x '0)) x))
The closure on the LHS returns 1 (correctly); the transformed closure
generated by evaluating the RHS returns 0.
Patch attached. I've looked through the generated bytecode for all of
lisp/ and there appear to be no significant differences.
Pip
[-- Attachment #2: 0001-Compile-closures-that-modify-their-bound-vars-correc.patch --]
[-- Type: application/x-patch, Size: 1448 bytes --]
next prev parent reply other threads:[~2021-02-28 19:57 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-28 15:04 bug#46834: 28.0.50; byte-compiling the standard counter closure fails Pip Cet
2021-02-28 19:57 ` Pip Cet [this message]
2021-02-28 20:34 ` Pip Cet
2021-03-01 14:23 ` Stefan Monnier
2021-03-01 15:01 ` Pip Cet
2021-03-01 16:02 ` Stefan Monnier
2021-03-02 7:00 ` Lars Ingebrigtsen
2021-03-02 7:31 ` Pip Cet
2021-03-02 7:34 ` Lars Ingebrigtsen
2021-03-02 7:36 ` Pip Cet
2021-03-02 13:16 ` Eli Zaretskii
2021-03-02 13:19 ` Pip Cet
2021-03-02 13:48 ` Eli Zaretskii
2021-03-01 13:16 ` Lars Ingebrigtsen
2021-03-01 14:34 ` Stefan Monnier
2021-03-01 15:16 ` Pip Cet
2021-03-01 16:15 ` Stefan Monnier
2021-03-01 16:41 ` Pip Cet
2021-03-01 17:01 ` Stefan Monnier
2021-03-01 17:13 ` Pip Cet
2021-03-01 16:31 ` Eli Zaretskii
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
List information: https://www.gnu.org/software/emacs/
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CAOqdjBeBwgTtTrrecExPb-toa54t6Vm6USO4F0fwWWYN62UYVw@mail.gmail.com \
--to=pipcet@gmail.com \
--cc=46834@debbugs.gnu.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://git.savannah.gnu.org/cgit/emacs.git
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).