GCC error with fallback uint128_t

[moiwi]

With ce93a66 I get this error with 32 bit GCC 8.1:

t:\fmt.org\fmt\format.h: In instantiation of 'To fmt::v8::detail::bit_cast(const From&) [with To = fmt::v8::detail::uint128_t; From = long double]':
t:\fmt.org\fmt\format-inl.h:261:36:   required from 'constexpr bool fmt::v8::detail::fp::assign(Float) [with Float = long double; typename std::enable_if<std::integral_constant<bool, (((sizeof (Float) == sizeof (unsigned int)) || (sizeof (Float) == (2 * sizeof (unsigned int)))) || (std::numeric_limits<_Tp>::digits == 64))>::value, int>::type <anonymous> = 0]'
t:\fmt.org\fmt\format-inl.h:245:66:   required from 'constexpr fmt::v8::detail::fp::fp(Float) [with Float = long double]'
t:\fmt.org\fmt\format-inl.h:2264:30:   required from 'int fmt::v8::detail::format_float(T, int, fmt::v8::detail::float_specs, fmt::v8::detail::buffer<char>&) [with T = long double]'
../../fmt.org/src/format.cc:111:64:   required from here
t:\fmt.org\fmt\format.h:293:28: error: static assertion failed: size mismatch
   static_assert(sizeof(To) == sizeof(From), "size mismatch");
                 ~~~~~~~~~~~^~~~~~~~~~~~~~~
t:\fmt.org\fmt\format.h:298:14: warning: 'void* memcpy(void*, const void*, size_t)' copying an object of non-trivial type 'class fmt::v8::detail::uint128_t' from an array of 'const long double' [-Wclass-memaccess]
   std::memcpy(&to, &from, sizeof(to));
   ~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
In file included from t:\fmt.org\fmt\format.h:50,
                 from t:\fmt.org\fmt\format-inl.h:29,
                 from ../../fmt.org/src/format.cc:8:
t:\fmt.org\fmt\core.h:393:7: note: 'class fmt::v8::detail::uint128_t' declared here
 class uint128_t {
       ^~~~~~~~~

(plus an initialization order warning:

t:\fmt.org\fmt\core.h: In constructor 'constexpr fmt::v8::detail::uint128_t::uint128_t(uint64_t)':
t:\fmt.org\fmt\core.h:395:17: warning: 'fmt::v8::detail::uint128_t::hi_' will be initialized after [-Wreorder]
   uint64_t lo_, hi_;
                 ^~~
t:\fmt.org\fmt\core.h:395:12: warning:   'uint64_t fmt::v8::detail::uint128_t::lo_' [-Wreorder]
   uint64_t lo_, hi_;
            ^~~
t:\fmt.org\fmt\core.h:399:13: warning:   when initialized here [-Wreorder]
   constexpr uint128_t(uint64_t value = 0) : hi_(0), lo_(value) {}
             ^~~~~~~~~

)

Originally posted by @moiwi in #2771 (comment)

[vitaut]

Oops. Looks like long double is 96-bit in this configuration. Here's a tentative workaround: 532a69a.

[moiwi]

Yes, works for me. Thank you!