From: Stefan Monnier via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
To: Alan Mackenzie <acm@muc.de>
Cc: Michael Heerdegen <michael_heerdegen@web.de>,
Lars Ingebrigtsen <larsi@gnus.org>,
54079@debbugs.gnu.org
Subject: bug#54079: 29.0.50; Method dispatching eratically fails
Date: Wed, 09 Mar 2022 13:06:11 -0500 [thread overview]
Message-ID: <jwv35jrui02.fsf-monnier+emacs@gnu.org> (raw)
In-Reply-To: <YijnIA12P7xs8dlV@ACM> (Alan Mackenzie's message of "Wed, 9 Mar 2022 17:42:56 +0000")
>> I don't understand the scenario you're thinking of.
>> Are you thinking of something like `(eval-when-compile (byte-compile ...))?
> Yes.
>> Does that ever happen in real life?
> Probably exceedingly seldomly.
> What's to be gained by not catering to this unusual case? What do we
> lose?
We lose making it work right for the 99% other cases that *do* occur?
>> >> And why bother stripping the result of `byte-compile-eval`?
>> > Because it might be the result of evaluating a defun (or defvar or
>> > defconst).
>
>> AFAIK sympos should only appear within the compiler pipeline between the
>> "read" and the "emit resulting bytecode". They may be passed to various
>> functions and macros along the way, but I can't think of any scenario
>> where they'd end up returned by `(byte-compile-)eval`.
>
>> > This was the situation which gave rise to the bug.
>
>> Could you give some details about how it played out?
>> [ Either here or as a comment in the code. ]
>
> Michael byte compiled cl-generic.el. This created cl-generic.elc
> correctly, but also left uncompiled forms in the function cells of the
> symbols defun'd inside an eval-{when,and}-compile. These forms
> contained symbols with positions.
Hmm... we're talking about stripping the result of `byte-compile-eval`.
This function is only used for `eval-when-compile`, not `eval-and-compile`.
And nothing in your above description indicates that the sympos appeared
in the resulting value of `eval-when-compile` (as opposed to appearing
in the slot of functions and variables that were set during the course
of the evaluation).
>> >> Fundamentally, `eval` should always strip before doing its job.
>> > Except when what it's evaluating is a defun, defmacrro, defsubst, etc.
>> Why?
> Because that evaluated form might later be byte compiled, and the SWPs
> will be needed for that.
I don't understand the scenario you're thinking of.
Are thinking of a case like:
- something causes the execution of (eval '(defun foo ...))
- the user types `M-x byte-compile RET foo RET`
If so, then:
- I don't think we should care about this case because it's extremely
rare and fundamentally broken (the symbol's function cell contains
a function *value* (i.e. a closure) and not a function's source code,
so in general we need `byte-compile--reify-function` which implements
a heuristic to go back to something like a source form, which can
break in various ways in corner cases).
- If we don't strip before calling the `M-x byte-compile` then the code
may/will bisbehave because of the presence of the sympos.
Stefan
next prev parent reply other threads:[~2022-03-09 18:06 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-21 0:12 bug#54079: 29.0.50; Method dispatching eratically fails Michael Heerdegen
2022-02-21 1:14 ` Michael Heerdegen
2022-03-04 16:12 ` Lars Ingebrigtsen
2022-02-21 3:16 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2022-02-21 4:21 ` Michael Heerdegen
2022-02-22 23:55 ` Michael Heerdegen
2022-02-23 0:27 ` Michael Heerdegen
2022-02-23 0:47 ` Michael Heerdegen
2022-03-04 2:08 ` Michael Heerdegen
2022-03-04 19:11 ` Alan Mackenzie
2022-03-05 16:37 ` Alan Mackenzie
2022-03-05 17:57 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2022-03-05 19:00 ` Alan Mackenzie
2022-03-05 23:01 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2022-03-05 18:19 ` Eli Zaretskii
2022-03-05 19:07 ` Alan Mackenzie
2022-03-06 2:19 ` Michael Heerdegen
2022-03-08 19:28 ` Alan Mackenzie
2022-03-08 19:53 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2022-03-08 20:48 ` Alan Mackenzie
2022-03-08 21:03 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2022-03-09 17:42 ` Alan Mackenzie
2022-03-09 18:06 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors [this message]
2022-03-09 20:32 ` Alan Mackenzie
2022-03-09 22:04 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2022-03-11 22:01 ` Alan Mackenzie
2022-03-12 4:23 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2022-03-13 16:49 ` Alan Mackenzie
2022-03-14 12:10 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2022-03-09 4:10 ` Michael Heerdegen
2022-03-09 17:29 ` Alan Mackenzie
2022-03-16 1:44 ` Michael Heerdegen
2022-03-16 11:52 ` Alan Mackenzie
2022-03-16 19:22 ` Michael Heerdegen
2022-03-17 2:58 ` Michael Heerdegen
2022-03-16 19:29 ` Alan Mackenzie
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