https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64967
--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> --- (In reply to Jakub Jelinek from comment #2) > Or drop the gnu-versioned-namespace support altogether. I'd like to do that ... maybe for GCC 6 though. It seems a bit late now to remove it without deprecation. > Anyway, if you don't, bumping it to _8 and always using the new ABI sounds > like a good plan to me. That proved quite difficult. My plan for now is to simply force --disable-libstdcxx-dual-abi when gnu-versioned-namespace is in use, so it bootstraps and can be used, just without the new GCC 5 hotness.