xlibmesa-dri-dbg 6.8.2-10.4 (amd64 binary) in ubuntu hoary

 Debugging versions of chipset-specific DRI modules are provided by this
 package. They are installed in /usr/X11R6/lib/modules/dri/debug and can be
 used by placing that directory in the LIBGL_DRIVERS_PATH environment variable
 when the code to be debugged is executed.
 .
 Non-programmers will likely have little use for this package. See the
 xlibmesa-dri package for further information.