7-button mouse (dual wheel) makes emacs crash

[David Monniaux]

[You may have already received this message; I resend it since I do not
know whether it has reached you, we experienced some mail problems here
and some outgoing mail was not delivered.]

In GNU Emacs 20.5.1 (i386-redhat-linux-gnu, X toolkit)
 of Tue Feb 22 2000 on porky.devel.redhat.com
configured using `configure  --prefix=/usr --libexecdir=/usr/lib 
--sharedstatedir=/var --with-gcc --with-pop --with-x-toolkit 
i386-redhat-linux-gnu'

Running XFree86 4.0.1 on Linux, I wanted to use the second wheel on my mouse
and bind it to mouse buttons 6 and 7 (the first being bound to 4 and
5). xev shows button events correctly.

In emacs, moving the second wheel (thus pressing virtual buttons 6 and
7) make emacs get immediately a segmentation fault and core dump.

I know that the X protocol was not supposed to support more than 5
buttons, but I count this as a bug since in any case emacs should not
segfault.

Perhaps adding support for mice with many buttons would be nice: the
second wheel could be used to scroll the buffer
horizontally. Currently, it's possible to make the first one scroll it
vertically.