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: Eli Zaretskii <eliz@gnu.org>, 67455@debbugs.gnu.org
Subject: bug#67455: (Record source position, etc., in doc strings, and use this in *Help* and backtraces.)
Date: Sun, 07 Apr 2024 23:16:13 -0400 [thread overview]
Message-ID: <jwvsezwegsq.fsf-monnier+emacs@gnu.org> (raw)
In-Reply-To: <ZhJ8Ltr3DuuAyFOD@ACM> (Alan Mackenzie's message of "Sun, 7 Apr 2024 10:57:50 +0000")
> Pretending the problem doesn't exist won't solve it. In the ;POS...
> structures for a lambda, there are two pointers - one to the definition
> of the lambda, the other to the point of use.
Fancy. Could you give me an example where I see this in play?
[ To help me understand also what you mean by "definition of the
lambda" and "point of use"? ]
I looked around but all I could see where position info like
[foo foo.el 41 nil]
which point to "the definition" of the function.
>> BTW, AFAIK the above is conceptually what the byte-compiler does (except
>> it performs a few more transformations between `macroexp--expand-all`
>> and `strip-all-symbol-positions`).
> It is a bad idea to conflate these two radically different uses of SWPs.
In what way are they radically different uses of SWPs?
>> Is it the case that `cl-defmethod` generates a function whose source
>> position (partly) points to `generic.el:403` if `cl-generic.el` was
>> interpreted but not if it compiled?
> No, the intention is that the source positions are independent of whether
> the code is compiled.
Good. So why do the interpreted and compiled cases need to be
"radically different uses of SWPs"?
>> > (defmacro foo (lambda bar)
>> > `(cons ,lambda ,bar))
>
>> > expands to
>
>> > (macro closure (t) (lambda bar) ";POS^^^A^A^A [foo *scratch* 158 nil]
>> > " (list 'cons lambda bar))
>
>> IIUC your reader will make the `lambda` formal argument into an SWP.
>> Where is that SWP stripped?
>
> In macroexp--expand-all in the "guard arm" near the end.
How? `macroexp--expand-all` will not be passed this `lambda` because
it's not an *expression*.
`eval-buffer` of a buffer containing the above defmacro does:
1 -> (macroexp--expand-all (defalias 'foo (cons 'macro #'{foo} (lambda (#<symbol lambda at 46> bar) ";POS\x01\x01 [foo foo.el 41 nil]\n" `(cons ,lambda ,bar)))))
| 2 -> (macroexp--expand-all 'foo)
| 2 <- macroexp--expand-all: 'foo
| 2 -> (macroexp--expand-all (cons 'macro #'{foo} (lambda (#<symbol lambda at 46> bar) ";POS\x01\x01 [foo foo.el 41 nil]\n" `(cons ,lambda ,bar))))
| | 3 -> (macroexp--expand-all 'macro)
| | 3 <- macroexp--expand-all: 'macro
| | 3 -> (macroexp--expand-all #'{foo} (lambda (#<symbol lambda at 46> bar) ";POS\x01\x01 [foo foo.el 41 nil]\n" `(cons ,lambda ,bar)))
| | | 4 -> (macroexp--expand-all ";POS\x01\x01 [foo foo.el 41 nil]\n")
| | | 4 <- macroexp--expand-all: ";POS\x01\x01 [foo foo.el 41 nil]\n"
| | | 4 -> (macroexp--expand-all `(cons ,lambda ,bar))
| | | | 5 -> (macroexp--expand-all 'cons)
| | | | 5 <- macroexp--expand-all: 'cons
| | | | 5 -> (macroexp--expand-all lambda)
| | | | 5 <- macroexp--expand-all: lambda
| | | | 5 -> (macroexp--expand-all bar)
| | | | 5 <- macroexp--expand-all: bar
| | | 4 <- macroexp--expand-all: (list 'cons lambda bar)
| | 3 <- macroexp--expand-all: #'{foo} (lambda (#<symbol lambda at 46> bar) ";POS\x01\x01 [foo foo.el 41 nil]\n" (list 'cons lambda bar))
| 2 <- macroexp--expand-all: (cons 'macro #'{foo} (lambda (#<symbol lambda at 46> bar) ";POS\x01\x01 [foo foo.el 41 nil]\n" (list 'cons lambda bar)))
1 <- macroexp--expand-all: (defalias 'foo (cons 'macro #'{foo} (lambda (#<symbol lambda at 46> bar) ";POS\x01\x01 [foo foo.el 41 nil]\n" (list 'cons lambda bar))))
So we see that indeed it returns code where the formal argument `lambda`
is (incorrectly) a SYMPOS. Yet somehow the sympos is stripped after
macroexpansion somewhere since `(symbol-function 'foo)` shows the
resulting function doesn't have any symposes in it.
>> > so it is clear this case is getting handled OK. I'm afraid I can't
>> > point out the exact place in the code at the moment where this is
>> > getting done.
>> I think it would be good to know, so as to be able to decide whether
>> it'll indeed always work right, or we just got lucky this time.
> See above.
Yes, please, see above 🙂
>> Could you explain what you think makes it intrinsically complex?
> The mass of detail that needs dealing with that Emacs has collected over
> the decades. As a counter question, why do you think the exercise ought
> to be simple (assuming you do think this)?
Because you solved the hard part when you added the symposes for the compiler.
Stefan
next prev parent reply other threads:[~2024-04-08 3:16 UTC|newest]
Thread overview: 65+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-26 14:30 bug#67455: Record source position, etc., in doc strings, and use this in *Help* and backtraces Alan Mackenzie
2023-12-04 17:36 ` Alan Mackenzie
2023-12-04 18:33 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-12-04 21:32 ` Alan Mackenzie
2023-12-04 21:56 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-12-04 22:30 ` Alan Mackenzie
2023-12-04 22:59 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-12-15 18:23 ` Alan Mackenzie
2023-12-15 23:12 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
[not found] ` <handler.67455.B.170100905232659.ack@debbugs.gnu.org>
2024-03-04 15:38 ` bug#67455: (Record source position, etc., in doc strings, and use this in *Help* and backtraces.) Alan Mackenzie
2024-03-09 21:36 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-03-10 16:02 ` Alan Mackenzie
2024-03-10 17:19 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-03-10 19:22 ` Alan Mackenzie
2024-03-10 21:03 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-03-24 11:04 ` Alan Mackenzie
2024-03-25 18:23 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-03-25 21:03 ` Alan Mackenzie
2024-03-25 22:10 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-03-26 9:48 ` Alan Mackenzie
2024-03-26 13:40 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-03-26 16:55 ` Alan Mackenzie
2024-03-26 19:40 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-03-26 20:21 ` Alan Mackenzie
2024-03-26 20:42 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-03-27 3:35 ` Alan Mackenzie
2024-03-27 12:23 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-03-27 22:00 ` Alan Mackenzie
2024-03-26 20:30 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-03-26 21:13 ` Drew Adams
2024-03-27 10:04 ` Alan Mackenzie
2024-03-27 12:22 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-03-27 21:43 ` Alan Mackenzie
2024-03-28 16:25 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-03-28 16:48 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-03-30 9:10 ` Alan Mackenzie
2024-03-30 9:53 ` Alan Mackenzie
2024-03-31 2:22 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-04-07 11:35 ` Alan Mackenzie
2024-04-08 2:19 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-04-08 2:56 ` Alan Mackenzie
2024-04-10 8:53 ` Alan Mackenzie
2024-03-30 11:03 ` Alan Mackenzie
2024-03-31 2:54 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-04-07 10:57 ` Alan Mackenzie
2024-04-08 3:16 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors [this message]
2024-04-08 8:32 ` Alan Mackenzie
2024-04-08 12:00 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-06-02 13:38 ` Alan Mackenzie
2024-06-03 4:52 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-06-05 15:01 ` Alan Mackenzie
2024-03-10 22:27 ` Alan Mackenzie
2024-03-11 0:50 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-03-13 10:54 ` Alan Mackenzie
2024-03-13 11:52 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-03-19 16:18 ` Alan Mackenzie
2024-03-19 20:47 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-03-19 21:40 ` Alan Mackenzie
2024-03-19 22:32 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-03-24 11:21 ` Alan Mackenzie
2024-06-01 17:40 ` Alan Mackenzie
2024-06-01 18:01 ` Eli Zaretskii
2024-06-01 18:15 ` Eli Zaretskii
2024-06-01 18:17 ` Alan Mackenzie
2024-06-01 23:14 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
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