sys-libs/glibc-2.5-r3 fails while patching if USE contains "hardened" due it needs the patch file "files/2.6/glibc-2.6-gentoo-stack_chk_fail.c".
This file is not available on Funtoo's portage, so it must be added for those users who uses the "hardened" USE flag.
Link to Gentoo's CVS file: http://sources.gentoo.org/cgi-bin/viewvc.cgi/gentoo-x86/sys-libs/glibc/files/2.6/glibc-2.6-gentoo-stack_chk_fail.c