https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123167
--- Comment #6 from Jonathan Wakely <redi at gcc dot gnu.org> --- Putting it another way, the platform ABI says that long double is 80-bit on x86_64. If you change that, you are creating a new, incompatible platform. At that point, it's your job to provide a suitable libc (you can't use glibc) and to rebuild libstdc++.so for your custom platform.
