Indeed. And in cases like those, the application and any libraries it uses have to either agree on which time_t size to use, or perform the same rewriting as li

Indeed. And in cases like those, the application and any libraries it uses have to either agree on which time_t size to use, or perform the same rewriting as libc does. Getting libc on board is merely the first step. The same goes for _FILE_OFFSET_BITS for obvious reasons (though embedding an off_t is probably somewhat less common). Nobody said this would be easy. OpenBSD's "ABIs are for breaking"-approach resulted in them fixing this very problem almost 10 years ago: https://marc.info/?l=openbsd-cvs&m=137637321205010&w=2 https://marc.info/?l=openbsd-cvs&m=137637321205010&w=2.