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bug#30186: 27.0.50; Password is not hidden in read-passwd
From: |
Alan Mackenzie |
Subject: |
bug#30186: 27.0.50; Password is not hidden in read-passwd |
Date: |
Sat, 27 Jan 2018 11:37:13 +0000 |
User-agent: |
Mutt/1.7.2 (2016-11-26) |
Hello, Eli.
On Sat, Jan 27, 2018 at 11:40:36 +0200, Eli Zaretskii wrote:
> > Date: Fri, 26 Jan 2018 20:00:27 +0000
> > Cc: juri@linkov.net, 30186@debbugs.gnu.org
> > From: Alan Mackenzie <acm@muc.de>
> > Do you have any opinion on my suggestion:
> > > > Perhaps an alternative would be for Emacs to provide a flag which
> > > > indicates to a before/after-change-function whether the current
> > > > change is a "proper" change or merely a text property change.
> > > > Change hook functions could then test this flag and, for example,
> > > > refrain from doing anything for a text property change.
> I'm not sure it would be possible to provide such a flag. Did you
> look at the internals involved, and if so, can you tell where do we
> know which kind of change caused the hooks to run?
I envisage adding an extra boolean argument to prepare_to_modify_buffer,
and to signal_after_change. When called from the text property
routines, that argument would be true, otherwise it would be false.
The essence of this argument would be a guarantee that the change is not
going to alter the buffer text. There may be other primitives besides
text properties for which we could set this argument.
> I also don't understand the problem you have in CC Mode with
> text-property changes. Can you elaborate on that?
Yes. In a largish CC Mode file, mark the entire buffer, kill-ring-save,
and append it after itself, with
C-x h, M-w, M->, C-y
. In buffer-undo-list there are no entries for text property changes.
Before the with-silent-modifications was put in, there were many such
entries. Assume this in the next paragraph
Now undo this latest change with C-_. Each of the entries for text
property changes wants to invoke CC Mode's
before/after-change-functions, which would make the operation slow.
(But see below.)
The workaround (currently in Emacs) for this, back in 2015, was to put
with-silent-modifications around the text property manipulations in
remove-yank-excluded-properties. This prevents these manipulations
getting into the undo list, but also stops read-passwd from working
properly.
I now see there is a second workaround, in CC Mode itself, where
c-before-change and c-after-change use backtrace-frame to check the
primitive invoking them, and do nothing if that primitive is, e.g.,
put-text-property. This is not an elegant workaround.
So, I'm changing my mind, after looking into it a bit more. Removing
the with-silent-modifications from remove-yank-excluded-properties would
not slow down undo in CC Mode buffers noticeably. It might slow down
other modes which make extensive use of before/after-change-functions.
The extra flag for the change hooks might still be a good idea. It no
longer seems pertinent for solving the current bug, though.
--
Alan Mackenzie (Nuremberg, Germany).
- bug#30186: 27.0.50; Password is not hidden in read-passwd, (continued)
- bug#30186: 27.0.50; Password is not hidden in read-passwd, Glenn Morris, 2018/01/22
- bug#30186: 27.0.50; Password is not hidden in read-passwd, Glenn Morris, 2018/01/22
- bug#30186: 27.0.50; Password is not hidden in read-passwd, Juri Linkov, 2018/01/22
- bug#30186: 27.0.50; Password is not hidden in read-passwd, Juri Linkov, 2018/01/23
- bug#30186: 27.0.50; Password is not hidden in read-passwd, Alan Mackenzie, 2018/01/25
- bug#30186: 27.0.50; Password is not hidden in read-passwd, Juri Linkov, 2018/01/25
- bug#30186: 27.0.50; Password is not hidden in read-passwd, Alan Mackenzie, 2018/01/26
- bug#30186: 27.0.50; Password is not hidden in read-passwd, Eli Zaretskii, 2018/01/26
- bug#30186: 27.0.50; Password is not hidden in read-passwd, Alan Mackenzie, 2018/01/26
- bug#30186: 27.0.50; Password is not hidden in read-passwd, Eli Zaretskii, 2018/01/27
- bug#30186: 27.0.50; Password is not hidden in read-passwd,
Alan Mackenzie <=
- bug#30186: 27.0.50; Password is not hidden in read-passwd, Eli Zaretskii, 2018/01/27
- bug#30186: 27.0.50; Password is not hidden in read-passwd, Alan Mackenzie, 2018/01/27
- bug#30186: 27.0.50; Password is not hidden in read-passwd, Juri Linkov, 2018/01/27
- bug#30186: 27.0.50; Password is not hidden in read-passwd, Alan Mackenzie, 2018/01/27
- bug#30186: 27.0.50; Password is not hidden in read-passwd, martin rudalics, 2018/01/27
- bug#30186: 27.0.50; Password is not hidden in read-passwd, Alan Mackenzie, 2018/01/27
- bug#30186: 27.0.50; Password is not hidden in read-passwd, martin rudalics, 2018/01/30
bug#30186: 27.0.50; Password is not hidden in read-passwd, Glenn Morris, 2018/01/21