From toolchain.eclass: 1990 ewarn "You might want to review the GCC upgrade guide when moving between" 1991 ewarn "major versions (like 4.2 to 4.3):" 1992 ewarn "https://wiki.gentoo.org/wiki/Upgrading_GCC" Wiki says: "If you are upgrading GCC then you do not need to do anything except switch compiler version and rebuild libtool:" But with the new auto-switching behaviour this is incorrect, you just need to 'emerge -u gcc' and it'll auto-upgrade (since it removes <gcc-4.9) And now behaviour is inconsistent, 4.8->4.9 autoswitches, 4.9->5.3 doesn't.
it doesn't remove old versions in all scenarios, nor does that mean the upgrading guide shouldn't be consulted
