[ root@desktop ] megabaks # grep glibc /etc/portage/package.mask
>sys-libs/glibc-2.13-r1
[ root@desktop ] megabaks # emerge -pvuDN world
...
[ebuild UD] sys-libs/glibc-2.12.2 [2.13-r1] USE="glibc-omitfp nls -debug -gd (-hardened) (-multilib) -profile (-selinux) -vanilla" 16,009 kB
...
[ root@desktop ] megabaks # grep glibc /etc/portage/package.mask
>=sys-libs/glibc-2.13-r2
[ root@desktop ] megabaks # emerge -pvuDN world
...
[ebuild UD] sys-libs/glibc-2.12.2 [2.13-r1] USE="glibc-omitfp nls -debug -gd (-hardened) (-multilib) -profile (-selinux) -vanilla" 16,009 kB
...
[ root@desktop ] megabaks #