Ubuntu 15.10, the Wily Werewolf, will closely follow Debian in its GCC 5 compiler upgrade and libstdc++6 ABI updates. They hope to have everything settled for Ubuntu 15.10 to avoid any big tool-chain changes during the Ubuntu 16.04 LTS cycle.

Hours after iterating the plans for GCC 5 and libstdc++6 in Debian unstable by month's end, Matthias Klose sent out a similar email to the Ubuntu-devel list.

Ubuntu/Debian package maintainers are encouraged to start testing -- and fixing any problems -- right away rather than waiting for GCC 5 to roll-out in the main archive. GCC 5 has many new compiler features but its change in defaulting to C++11 and the libstdc++6 ABI breakage makes this upgrade a bit more hairy than usual.