https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79118
--- Comment #8 from Niall Douglas <s_gccbugzilla at nedprod dot com> --- (In reply to Marek Polacek from comment #7) > I'm giving up; there's just too much C++. Thanks for looking into it. You should know that the above code works without issue on clang and VS2017 (with C++ 14 constexpr enabled too!). In your reduced test case I don't think you're packing the storage and the type of storage into a single byte. That's what the original does, and appears to be the cause of the ICE on GCC: use of bitfields in constexpr. It certainly should not be the case that the constexpr is accessing storage not initialised by constexpr e.g. a bit 8 when valid bits are 0 ... 7. Niall
