From Ian Campbell – http://lists.xensource.com/archives/html/xen-devel/2010-08/msg00728.html
The last in-tree user of the xc_ptrace functionality was removed in
user: Ian Jackson <Ian.Jackson@eu.citrix.com>
date: Fri Jul 02 17:46:01 2010 +0100
tools/debugger/gdb: Remove gdb
This code is not maintained, does not work properly, and no-one is
using it. Delete it, following discussion on xen-devel.
and has now been replaced with gdbsx.
We are having trouble tracking down all of the contributors to the ptrace code in libxc (as part of the effort to relicense libxc under the LGPL, see  or ) and if this functionality is no longer required it would be simplest to remove it. I will follow up shortly with a patch to disable the build by default and the code will be removed shortly unless anyone objects. If you have an out-of-tree project which is using this functionality (specifically the functions xc_register_event_handler()
xc_ptrace() and xc_waitdomain()) then please tell us ASAP.