GNU bug report logs - #26847
26.0.50; Using edebug-step-in on a macro switches to go-mode

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Gemini Lasswell <gazally <at> runbox.com>
To: bug-gnu-emacs <at> gnu.org
Subject: 26.0.50; Using edebug-step-in on a macro switches to go-mode
Date: Mon, 08 May 2017 14:06:21 -0700

edebug-step-in doesn't behave well when you try to use it on a
macro. For an example, enter the following code in *scratch*:
  
(setq my-things nil)
(defun my-try-thing (thing)
  (push thing my-things))

Then:

M-x eval-buffer RET
navigate to my-try-thing and C-u C-M-x
M-: (my-try-thing 'a) RET
i

Result: Edebug exits and code runs to completion, result printed in
minibuffer.

Then navigate to my-try-thing again and C-M-x

Result: Edebug activates with the debugger prompt in `push'.

Stepping into macros would have made sense before eager
macro-expansion, but now by the time Edebug instruments the code the
macro has already run. Probably the simplest thing to do here is to
have edebug-step-in signal an error if asked to step into a macro. The
documentation for edebug-step-in also should be updated to remove
mention of stepping into macros.

Message #8 received at 26847 <at> debbugs.gnu.org (full text, mbox):

From: Dmitry Gutov <dgutov <at> yandex.ru>
To: Gemini Lasswell <gazally <at> runbox.com>, 26847 <at> debbugs.gnu.org
Subject: Re: bug#26847: 26.0.50; Using edebug-step-in on a macro switches to
 go-mode
Date: Wed, 10 May 2017 01:23:39 +0300

On 09.05.2017 0:06, Gemini Lasswell wrote:

> Stepping into macros would have made sense before eager
> macro-expansion, but now by the time Edebug instruments the code the
> macro has already run. Probably the simplest thing to do here is to
> have edebug-step-in signal an error if asked to step into a macro. The
> documentation for edebug-step-in also should be updated to remove
> mention of stepping into macros.

Since nobody has complained about this problem by now, it's probably the 
easiest solution indeed.

However, I wonder if we could inhibit eager macro-expansion when a 
function is being instrumented by edebug. Its definition is being 
re-evaluated at that time, right?

I don't know if we have a good way to do that, though. Or if adding one 
ends up being easy to maintain.

Message #11 received at 26847 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: Gemini Lasswell <gazally <at> runbox.com>
Cc: 26847 <at> debbugs.gnu.org
Subject: Re: bug#26847: 26.0.50; Using edebug-step-in on a macro switches to
 go-mode
Date: Sun, 20 Oct 2019 23:41:03 +0200

Gemini Lasswell <gazally <at> runbox.com> writes:

> edebug-step-in doesn't behave well when you try to use it on a
> macro. For an example, enter the following code in *scratch*:
>
> (setq my-things nil)
> (defun my-try-thing (thing)
>   (push thing my-things))
>
> Then:
>
> M-x eval-buffer RET
> navigate to my-try-thing and C-u C-M-x
> M-: (my-try-thing 'a) RET
> i
>
> Result: Edebug exits and code runs to completion, result printed in
> minibuffer.

I'm unable to reproduce this in Emacs 27.  When I hit `i', I'm then
edebugging the `push' macro, and then I can step through it, and then
I'm back to stepping through my-try-thing.

Are you still seeing this bug in Emacs 27?

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

Message #16 received at 26847 <at> debbugs.gnu.org (full text, mbox):

From: Gemini Lasswell <gazally <at> runbox.com>
To: Lars Ingebrigtsen <larsi <at> gnus.org>
Cc: 26847 <at> debbugs.gnu.org
Subject: Re: bug#26847: 26.0.50;
 Using edebug-step-in on a macro switches to go-mode
Date: Sun, 20 Oct 2019 22:18:54 -0700

Lars Ingebrigtsen <larsi <at> gnus.org> writes:

> I'm unable to reproduce this in Emacs 27.  When I hit `i', I'm then
> edebugging the `push' macro, and then I can step through it, and then
> I'm back to stepping through my-try-thing.
>
> Are you still seeing this bug in Emacs 27?

In Emacs 26, eager macro expansion happened when instrumenting code for
Edebug using eval-defun.  In current master, it's not getting done.
Looking at (symbol-function 'my-try-thing) in both versions will show
you the difference.

The lack of macroexpansion doesn't only happen when instrumenting for
Edebug.  If you evaluate a function definition with eval-buffer or
eval-last-sexp then macroexpansion is done, but if you evaluate it with
eval-defun with or without the universal argument, then no
macroexpansion happens. This is a change from Emacs 26, and is masking
the original bug.

If you use these steps to reproduce, with the same sample code:

M-x edebug-all-defs RET
M-x eval-buffer RET
M-: (my-try-thing 'a) RET
i

then the original bug still occurs.

Message #19 received at 26847 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: Gemini Lasswell <gazally <at> runbox.com>
Cc: 26847 <at> debbugs.gnu.org
Subject: Re: bug#26847: 26.0.50; Using edebug-step-in on a macro switches to
 go-mode
Date: Mon, 21 Oct 2019 21:35:20 +0200

Gemini Lasswell <gazally <at> runbox.com> writes:

> If you use these steps to reproduce, with the same sample code:
>
> M-x edebug-all-defs RET
> M-x eval-buffer RET
> M-: (my-try-thing 'a) RET
> i
>
> then the original bug still occurs.

Yup.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

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