bug#13061: 24.3.50; regressions: 1) Redefining a function should cancel `debug-on-entry', 2) doc

bug#13061: 24.3.50; regressions: 1) Redefining a function should cancel `debug-on-entry', 2) doc

[Drew Adams]

1.
 
emacs -Q

(defun foo (&optional n)
  (interactive "p")
  (forward-char n))
 
M-x debug-on-entry RET foo RET
 
M-x foo ; enters the debugger
 
Then C-M-x on the defun above, to redefine foo.
 
M-x foo ; STILL enters the debugger

You can even add a doc string or make another change, then C-M-x, and you will
STILL enter the debugger when `foo' is invoked.
 
Redefining foo should cancel the `debug-on-entry'.  See (elisp)
`Function Debugging':
 
  *Warning:* if you redefine a function after using `debug-on-entry'
  on it, the code to enter the debugger is discarded by the
  redefinition.  In effect, redefining the function cancels the
  break-on-entry feature for that function.
 
This feature has now been broken.  Please restore it.
 
It is a hell of a lot easier to hit C-M-x on foo's definition than it is
to do `M-x cancel-debug-on-entry RET foo RET'.
 

2. In the Elisp manual, this should NOT be a *Warning*.  This is an
intentional, longstanding FEATURE, not something bad to be warned about.
 
And this WAS NOT a *Warning* but a simple *Note*, prior to Emacs 22.  This
mania of introducing "*WARNING*" everywhere really should stop.
 
This occurrence is a second regression.  "*Note*", and its attendant
sanity, should be restored here.
 
It would not be surprising if some misguided soul removed this feature
of debug cancellation by function redefinition precisely because of a
misunderstanding introduced by this *Warning*, thinking that this is not
a feature but something bad - a bug to be "fixed".
 
Far from being warned, as if this were about some bug workaround, users
should be positively informed about this feature.  That's what the
original *Note* was for: to draw their attention to this positively, not
to warn them about it as if it were something to avoid.
 
 
 
In GNU Emacs 24.3.50.1 (i386-mingw-nt5.1.2600)
 of 2012-11-19 on MS-W7-DANI
Bzr revision: 110950 monnier@iro.umontreal.ca-20121119182725-5p6w4wjimm7epggr
Windowing system distributor `Microsoft Corp.', version 5.1.2600
Configured using:
 `configure --with-gcc (4.7) --no-opt --enable-checking --cflags
 -Ic:/emacs/libs/libXpm-3.5.10/include -Ic:/emacs/libs/libXpm-3.5.10/src
 -Ic:/emacs/libs/libpng-1.2.37-lib/include -Ic:/emacs/libs/zlib-1.2.5
 -Ic:/emacs/libs/giflib-4.1.4-1-lib/include
 -Ic:/emacs/libs/jpeg-6b-4-lib/include
 -Ic:/emacs/libs/tiff-3.8.2-1-lib/include
 -Ic:/emacs/libs/libxml2-2.7.8-w32-bin/include/libxml2
 -Ic:/emacs/libs/gnutls-3.0.9-w32-bin/include
 -Ic:/emacs/libs/libiconv-1.9.2-1-lib/include'
 

bug#13061: 24.3.50; regressions: 1) Redefining a function should cancel `debug-on-entry',2) doc

[Drew Adams]

1. I really hope this regression gets fixed soon.  It's quite annoying that
redefining a function does not cancel `debug-on-entry' for it.


2. Wrt the recent abuse by Emacs Dev of the term "Warning": Think about the
terms they use for hurricanes and such, situations which are FAR more serious
than what Emacs has to deal with:

a. The first level of making people aware is called an "Advisory".

b. "Warning" is used only for a much higher level involving imminent danger.

The equivalent of "advisory" wrt documentation is generally "Note", "Notice", or
"Attention".  You are just drawing attention to a statement, without a
connotation of danger.

Emacs doc should stop being so alarmist, generally.  And in the case of this
bug, it is downright perverted to "warn" about a positive feature.

bug#13061: 24.3.50; regressions: 1) Redefining a function should cancel`debug-on-entry',2) doc

[Drew Adams]

Could someone please take a look at this bug?

It is so simple to hit C-M-x when debugging and modifiying a function that has
`debug-on-entry'.  Doing that should (obviously) cancel opening the debugger on
entry.  This has always been the behavior in Emacs, and it should be a
no-brainer.

(I'm not saying that how to fix it is a no-brainer - just the fact that the sane
behavior should be restored.)

Thx.

> I really hope this regression gets fixed soon.  It's quite 
> annoying that redefining a function does not cancel
> `debug-on-entry' for it.

bug#13061: 24.3.50; regressions: 1) Redefining a function should cancel`debug-on-entry',2) doc

[Michael Heerdegen]

"Drew Adams" <drew.adams@oracle.com> writes:

> It is so simple to hit C-M-x when debugging and modifiying a function
> that has `debug-on-entry'.  Doing that should (obviously) cancel
> opening the debugger on entry.  This has always been the behavior in
> Emacs, and it should be a no-brainer.

Just one comment from another user: I like the opposite (that is, the
new) behavior.  It always annoyed me that e.g. loading file sources
canceled any according `debug-on-entry' in effect.  I prefer to use
`cancel-debug-on-entry' explicitly.

Maybe the behavior could be made configurable?


Regards,

Michael.

bug#13061: 24.3.50; regressions: 1) Redefining a function should cancel`debug-on-entry',2) doc

[Drew Adams]

> > It is so simple to hit C-M-x when debugging and modifiying 
> > a function that has `debug-on-entry'.  Doing that should
> > (obviously) cancel opening the debugger on entry.  This has
> > always been the behavior in Emacs, and it should be a no-brainer.
> 
> Just one comment from another user: I like the opposite (that is, the
> new) behavior.  It always annoyed me that e.g. loading file sources
> canceled any according `debug-on-entry' in effect.  I prefer to use
> `cancel-debug-on-entry' explicitly.
> 
> Maybe the behavior could be made configurable?

+1 - users use Emacs differently.

But the default behavior should be the longstanding behavior.
There is no reason to change that.

bug#13061: 24.3.50; regressions: 1) Redefining a function shouldcancel`debug-on-entry',2) doc

[Drew Adams]

> > > It is so simple to hit C-M-x when debugging and modifiying
> > > a function that has `debug-on-entry'.  Doing that should
> > > (obviously) cancel opening the debugger on entry.  This has
> > > always been the behavior in Emacs, and it should be a no-brainer.
> >
> > Just one comment from another user: I like the opposite (that is, the
> > new) behavior.  It always annoyed me that e.g. loading file sources
> > canceled any according `debug-on-entry' in effect.  I prefer to use
> > `cancel-debug-on-entry' explicitly.
> >
> > Maybe the behavior could be made configurable?
> 
> +1 - users use Emacs differently.
> 
> But the default behavior should be the longstanding behavior.
> There is no reason to change that.

FWIW, I'm OK with the new behavior, even as the default behavior.

(I do think the behavior should be user configurable, however.  And
I think it is best not to change the default behavior, especially
without polling users.)

[And this bug should NOT have been merged with bug #17902, which
simply points out that the new behavior is not reflected in the doc.]