libc6-xen 2.15-0ubuntu10.18 (i386 binary) in ubuntu precise

 Contains the standard libraries that are used by nearly all programs on
 the system. This package includes shared versions of the standard C
 library and the standard math library, as well as many others.
 .
 This set of libraries is optimized for the Xen hypervisor, and will be
 selected instead when running under Xen.