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Date: Sun, 22 Dec 1996 19:26:43 -0800
Message-Id: <199612230326.TAA13902@xemacs.eng.sun.com>
From: Martin Buchholz <mrb@Eng.Sun.COM>
To: Steven L Baur <steve@miranova.com>
Cc: Stig <stig@hackvan.com>, Douglas Keller <dkeller@vnet.ibm.com>,
        XEmacs Beta Test <xemacs-beta@xemacs.org>
Subject: xlwscrollbar crash
Reply-To: Martin Buchholz <mrb@Eng.Sun.COM>
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There's a class of XEmacs crashes that someone at Sun was finally able
to reproduce.  The stacktrace typically contains xlwscrollbar.c:timer,
but the crash could occur anywhere.

After some investigation, it turns out that xlwscrollbar.c calls
XtAppAddTimeOut to later call `timer' with the address of the
scrollbar widget instance structure.  Unfortunately, widgets get
destroyed occasionally, and the timeout doesn't get removed, so
`timer' might end up reading and modifying de-allocated, or worse,
re-allocated memory.  The best tool for reproducing this crash is
clicking and dragging furiously in the file dialog box, then selecting
a file.

Steven: at ftp.xemacs.org:~mrb, find 3 source files for xlwscrollbar
that should replace those files in both 20.0 and 19.15 without any
changes.

As usual, I have trouble resisting the urge to `beautify' the code, so
much of the code for these files has changed.

Doug: Your name appears as the author.  Surprisingly, since you're not
a Lucid guy.

Doug & Stig: Is anyone other than me maintaining the Lucid Widget
Library anymore?

Martin

