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From: Alan Mackenzie <acm@muc.de>
To: Stefan Monnier <monnier@iro.umontreal.ca>
Cc: 59213@debbugs.gnu.org
Subject: bug#59213: Emacs 29: Edebug fails to instrument a parameter whose name begins with _
Date: Mon, 14 Nov 2022 10:28:29 +0000	[thread overview]
Message-ID: <Y3IYTSTtOBZSRZ3z@ACM> (raw)
In-Reply-To: <jwvfsemi499.fsf-monnier+emacs@gnu.org>

Hello, Stefan.

On Sun, Nov 13, 2022 at 22:53:12 -0500, Stefan Monnier wrote:
> > In Emacs 29 (not started with -Q, but...),

> > I instrumented for edebug a function which looked like:

> >     (defun c-trim-found-types (beg end _old-len) ....)

> > , the compilation being with lexical-binding: t.

> > During the edebug session, I attempted

> >     e _old-len RET.

> The behavior depends on where you are in the *Backtrace* buffer, because
> each line in the backtrace can be in a different lexical scope.
> So please clarify on which line you were when you did the above.

I wasn't in the backtrace.  I was stepping through the code in edebug.

More precisely, with this defun:

    (defun add (a b _c)
      (+ a b))

, instrument it for edebug.  Call M-: (add 1 2 6).

The source code with active edebug now looks like:

    (defun add (a b _c)
    =>(+ a b))

..  e a now returns 1.  e b returns 2.  e _c gives the error message:

    Error: Symbol's value as variable is void: _c

..  I repeat, this is a bug.  It should have returned 6.

> > Instead of giving me the value of _old-len (which was 3) it gave the
> > error message

> >     Error: Symbol's value as variable is void: _old-len

> > ..  This is a bug.

> Could be.  Or could be that you were trying to use `_old-len` in
> a lexical context where there is no such variable.

_c is in the same lexical context as a and b, surely?

> > Just because a function doesn't use a particular argument (here

> I think the leading underscore is purely incidental and you'd get the
> same behavior with `beg` and `end`.

No, beg and end returned their values.  I admit I'm speculating about the
leading underscore, but I still say there's a bug, somewhere here.

>         Stefan

-- 
Alan Mackenzie (Nuremberg, Germany).





  reply	other threads:[~2022-11-14 10:28 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-11-12  9:35 bug#59213: Emacs 29: Edebug fails to instrument a parameter whose name begins with _ Alan Mackenzie
2022-11-14  2:48 ` Michael Heerdegen
2022-11-14  3:53 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2022-11-14 10:28   ` Alan Mackenzie [this message]
2022-11-14 12:50     ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2022-11-14 12:56     ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-02-10 18:51       ` Alan Mackenzie
2023-02-10 22:05         ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-02-11  7:26           ` Eli Zaretskii
2023-02-13  3:26             ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-02-13 12:54               ` Eli Zaretskii
2023-02-11 11:17           ` Alan Mackenzie
2023-02-14 21:47             ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-02-14 22:19         ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-02-18 18:08           ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-02-18 18:46           ` Alan Mackenzie
2023-02-20 22:21             ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2022-11-15 13:08   ` Eli Zaretskii

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