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bug#7728: 24.0.50; GDB backtrace from abort
From: |
Eli Zaretskii |
Subject: |
bug#7728: 24.0.50; GDB backtrace from abort |
Date: |
Sun, 09 Jan 2011 23:18:14 +0200 |
Ping!
This is a bug that I think we should fix for Emacs 23.3.
> Date: Sat, 01 Jan 2011 20:02:17 +0200
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: 7728@debbugs.gnu.org
>
> > From: Stefan Monnier <monnier@iro.umontreal.ca>
> > Cc: Drew Adams <drew.adams@oracle.com>, 7728@debbugs.gnu.org
> > Date: Sat, 25 Dec 2010 15:35:31 -0500
> >
> > If selected_window is nil because of Fset_window_configuration, then it
> > is presumably nil for all the intervening and some of the subsequent
> > code, and I suspect fixing it earlier in the call chain will be
> > preferable: e.g., it doesn't make sense to "display_and_set_cursor" in
> > the "selected_window = nil" case.
>
> After some looking around, I'm sorry to report that I don't see how to
> do that. Here are the details:
>
> We set selected_window to nil as a semi-kludgey way of preventing
> select-window from storing in the old selected window the value of
> point of the buffer that has been restored into that window.
> select-window has this code:
>
> sf = SELECTED_FRAME ();
> if (XFRAME (WINDOW_FRAME (w)) != sf)
> {
> XFRAME (WINDOW_FRAME (w))->selected_window = window;
> /* Use this rather than Fhandle_switch_frame
> so that FRAME_FOCUS_FRAME is moved appropriately as we
> move around in the state where a minibuffer in a separate
> frame is active. */
> Fselect_frame (WINDOW_FRAME (w), norecord);
> /* Fselect_frame called us back so we've done all the work already. */
> eassert (EQ (window, selected_window));
> return window;
> }
> else
> sf->selected_window = window;
>
> /* Store the current buffer's actual point into the
> old selected window. It belongs to that window,
> and when the window is not selected, must be in the window. */
> if (!NILP (selected_window))
> {
> ow = XWINDOW (selected_window);
> if (! NILP (ow->buffer))
> set_marker_both (ow->pointm, ow->buffer,
> BUF_PT (XBUFFER (ow->buffer)),
> BUF_PT_BYTE (XBUFFER (ow->buffer)));
> }
>
> selected_window = window;
>
> The last `if' clause is what we want to bypass, when we restore window
> configuration as the last part of save-window-excursion. Note that
> select-window stores the right value into selected_window right after
> that, but the call to Fselect_frame that crashes happens before that,
> so selected_window is still nil.
>
> Now, the sequence of calls leading to the crash inside Fselect_frame
> is as follows:
>
> Fselect_frame
> -> do_switch_frame
> -> Fredirect_frame_focus
> -> w32_frame_rehighlight / XTframe_rehighlight
> -> x_frame_rehighlight
> -> frame_highlight
> -> x_update_cursor
> -> update_cursor_in_window_tree
> -> update_window_cursor
> -> display_and_set_cursor
> -> erase_phys_cursor
> -> window_text_bottom_y
> -> die
>
> My conclusion after studying this is that everything that happens
> below Fselect_frame is reasonable: we switch to the frame and redraw
> the cursor in all of its windows. In particular,
> update_cursor_in_window_tree simply walks the entire window tree of
> the newly selected frame. I don't see how we can avoid any of this
> when selected_window is nil, because selected_window has nothing to do
> with the windows that are being processed. None of these functions
> even references selected_window, which is TRT. The first place that
> does reference selected_window is the CURRENT_MODE_LINE_HEIGHT macro
> used in window_text_bottom_y, and that leads to the abort.
>
> So I see 2 ways to prevent this particular problem:
>
> 1) Handle the case of selected_window == Qnil in
> CURRENT_MODE_LINE_FACE_ID.
>
> 2) Change the code of Fset_window_configuration and Fselect_window,
> to have some other way of preventing the latter from storing point
> in the old selected window, without setting selected_window to
> nil.
>
> Any other ideas are welcome.
>
- bug#7728: 24.0.50; GDB backtrace from abort, Eli Zaretskii, 2011/01/01
- bug#7728: 24.0.50; GDB backtrace from abort,
Eli Zaretskii <=
- bug#7728: 24.0.50; GDB backtrace from abort, Stefan Monnier, 2011/01/11
- bug#7728: 24.0.50; GDB backtrace from abort, Eli Zaretskii, 2011/01/11
- bug#7728: 24.0.50; GDB backtrace from abort, Drew Adams, 2011/01/11
- bug#7728: 24.0.50; GDB backtrace from abort, Eli Zaretskii, 2011/01/11
- bug#7728: 24.0.50; GDB backtrace from abort, Drew Adams, 2011/01/12
- bug#7728: 24.0.50; GDB backtrace from abort, Eli Zaretskii, 2011/01/12
- bug#7728: 24.0.50; GDB backtrace from abort, Drew Adams, 2011/01/12
- bug#7728: 24.0.50; GDB backtrace from abort, Drew Adams, 2011/01/12
- bug#7728: 24.0.50; GDB backtrace from abort, Drew Adams, 2011/01/12