Comment 32 for bug 1046244

Now that Qt 4.8.3 (the first upstream Qt version to include this patch) is in Arch Linux, the problem occurs there too. For me, it caused both plasma-desktop and kwin to segfault on startup, thus making KDE almost unusable. (As a temporary measure to prevent these from crashing, I reverted to Qt 4.8.2.)
https://bugs.archlinux.org/task/31654

There's also an Ubuntu bug report which looks it it might be caused by this patch:
https://bugs.launchpad.net/ubuntu/+source/qt4-x11/+bug/1045755

This patch actually appears to have originated 2 years ago in the upstream WebKit SVN repository:
http://trac.webkit.org/changeset/62799
https://bugs.webkit.org/show_bug.cgi?id=41641
But it wasn't until August this year that it migrated from WebKit's JavaScriptCore to the copy of JavaScriptCore in the QtScript module of Qt:
http://qt.gitorious.org/qt/qtscript/commit/79ebd39d0d4846cb911ae122d2059e5add568d7e
http://qt.gitorious.org/qt/qt/commit/ada98493bbfbd9af0d0b593017e29d39bcd3495e
https://bugreports.qt-project.org/browse/QTBUG-23871

Maybe it would be worth reporting the problem to the upstream WebKit developers?