Aki Vehtari <Aki.Vehtari(a)hut.fi> writes in xemacs-beta(a)xemacs.org:
Btw. gud.el in XEmacs is dated 1993 and gud.el in emacs-20.3 is
dated 1998. Unfortunately gud.el in emacs-20.3 does not work in
XEmacs and I don't know much work it would need to make it work and
I've done the initial port of gud.el to XEmacs. It mostly works, but
it sorely lacks the functionality in gdbsrc.el. Making a gudsrc.el
mode is on my list of things to do.
It was in
when I was on the 'net.
It was delayed integration into the XEmacs packages pending 21.0
I also have a ported cua-mode.el to integrate.
NOTE: The gud.el and cua-mode.el XEmacs portings are courtesy of
Altrasoft, Inc. Thank you Altrasoft.
 I have a report that my port does not work on Solaris with dbx.