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bug#54079: 29.0.50; Method dispatching eratically fails
From: |
Stefan Monnier |
Subject: |
bug#54079: 29.0.50; Method dispatching eratically fails |
Date: |
Wed, 09 Mar 2022 13:06:11 -0500 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/29.0.50 (gnu/linux) |
>> 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
- bug#54079: 29.0.50; Method dispatching eratically fails, (continued)
bug#54079: 29.0.50; Method dispatching eratically fails, Eli Zaretskii, 2022/03/05
bug#54079: 29.0.50; Method dispatching eratically fails, Michael Heerdegen, 2022/03/05
- bug#54079: 29.0.50; Method dispatching eratically fails, Alan Mackenzie, 2022/03/08
- bug#54079: 29.0.50; Method dispatching eratically fails, Stefan Monnier, 2022/03/08
- bug#54079: 29.0.50; Method dispatching eratically fails, Alan Mackenzie, 2022/03/08
- bug#54079: 29.0.50; Method dispatching eratically fails, Stefan Monnier, 2022/03/08
- bug#54079: 29.0.50; Method dispatching eratically fails, Alan Mackenzie, 2022/03/09
- bug#54079: 29.0.50; Method dispatching eratically fails,
Stefan Monnier <=
- bug#54079: 29.0.50; Method dispatching eratically fails, Alan Mackenzie, 2022/03/09
- bug#54079: 29.0.50; Method dispatching eratically fails, Stefan Monnier, 2022/03/09
- bug#54079: 29.0.50; Method dispatching eratically fails, Alan Mackenzie, 2022/03/11
- bug#54079: 29.0.50; Method dispatching eratically fails, Stefan Monnier, 2022/03/11
- bug#54079: 29.0.50; Method dispatching eratically fails, Alan Mackenzie, 2022/03/13
- bug#54079: 29.0.50; Method dispatching eratically fails, Stefan Monnier, 2022/03/14
bug#54079: 29.0.50; Method dispatching eratically fails, Michael Heerdegen, 2022/03/08
bug#54079: 29.0.50; Method dispatching eratically fails, Alan Mackenzie, 2022/03/09
bug#54079: 29.0.50; Method dispatching eratically fails, Michael Heerdegen, 2022/03/15
bug#54079: 29.0.50; Method dispatching eratically fails, Alan Mackenzie, 2022/03/16