Gentoo's Bugzilla –
Attachment 270401 Details for
Bug 363935sys-kernel/gentoo-source-2.6.38-r2 - with gcc 4.6.0 - /usr/src/linux-2.6.38-gentoo-r2/arch/powerpc/include/asm/pgtable-ppc64.h:260:16: error: variable ‘old’ set but not used [-Werror=unused-but-set-variable]