GNU bug report logs - #6284
Crash in w32_wnd_proc at frame deletion

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Jason Rumney <jasonr <at> gnu.org>
Cc: tracker <at> debbugs.gnu.org
Subject: bug#6284: closed (Crash in w32_wnd_proc at frame deletion)
Date: Fri, 08 Jul 2011 12:55:03 +0000

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Your message dated Fri, 08 Jul 2011 20:53:47 +0800
with message-id <87box5ndb8.fsf <at> gnu.org>
and subject line Re: bug#6284: Crash in w32_wnd_proc at frame deletion
has caused the GNU bug report #6284,
regarding Crash in w32_wnd_proc at frame deletion
to be marked as done.

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help-debbugs <at> gnu.org.)


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From: Lennart Borgman <lennart.borgman <at> gmail.com>
To: Emacs Bugs <bug-gnu-emacs <at> gnu.org>
Subject: Crash in w32_wnd_proc at frame deletion
Date: Thu, 27 May 2010 19:44:27 +0200

Now I finally got a backtrace of this crash. Thanks for the (harsh)
reminders about running under gdb.

Here is part of the backtrace

  Program received signal SIGSEGV, Segmentation fault.
  [Switching to Thread 1836.0xef8]
  0x011cc376 in w32_wnd_proc (hwnd=0x1001ac, msg=32, wParam=1049004,
      lParam=33554433) at w32fns.c:4351
  4351              if (f->output_data.w32->hourglass_p && !menubar_in_use
  (gdb) bt
  #0  0x011cc376 in w32_wnd_proc (hwnd=0x1001ac, msg=32, wParam=1049004,
      lParam=33554433) at w32fns.c:4351
  #1  0x7e418734 in USER32!GetDC () from C:\WINDOWS\system32\user32.dll
  #2  0x001001ac in ?? ()
  #3  0x00000020 in ?? ()
  #4  0x001001ac in ?? ()
  #5  0x02000001 in ?? ()
  #6  0x011c9291 in post_character_message (hwnd=0x11c9291, msg=1049004,
      wParam=32, lParam=1049004, dwmodifiers=33554433) at w32fns.c:3049
  #7  0x7e418816 in USER32!GetDC () from C:\WINDOWS\system32\user32.dll
  #8  0x011c9291 in post_character_message (hwnd=0x0, msg=18649745,
      wParam=1049004, lParam=32, dwmodifiers=1049004) at w32fns.c:3049
  #9  0x7e428ea0 in USER32!DefWindowProcW () from C:\WINDOWS\system32\user32.dll
  #10 0x00000000 in ?? ()

  Lisp Backtrace:
  "delete-frame" (0x82af44)

It looks like the important part is line 4351. I tried to look at f:

  (gdb) print f
  $1 = (struct frame *) 0x0
  (gdb) print f->output_data
  Cannot access memory at address 0x104

Does this mean that f might be gone here and that there should be a
test for this?

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From: Jason Rumney <jasonr <at> gnu.org>
To: Lennart Borgman <lennart.borgman <at> gmail.com>
Cc: Juanma Barranquero <lekktu <at> gmail.com>, Eli Zaretskii <eliz <at> gnu.org>,
	6284-done <at> debbugs.gnu.org
Subject: Re: bug#6284: Crash in w32_wnd_proc at frame deletion
Date: Fri, 08 Jul 2011 20:53:47 +0800

Lennart Borgman <lennart.borgman <at> gmail.com> writes:

> New patch. I missed one place in the previous patch and this just hit me.
>
> It is great running under the debugger and finally being able to find
> and fix those bugs I have wondered about quite long now but have not
> had time to fix before.
>
> The only problem now is how to get them installed. As I said elsewhere
> I currently have no checkout from savannah so I can't checkin the
> patches myself AFAIK. Should I get a second checkout from savannah for
> this, or?

I fixed the two locations where a bug could conceivably occur.  Others
were either #ifdef'ed out, or already protected against dereferencing
the non-existent frame struct.

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