https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80943
--- Comment #3 from Barry Revzin <barry.revzin at gmail dot com> --- This is CWG 2327 (http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#2327). It's still active, but gcc/clang's behavior (printing 2) seems like the superior choice.
