20 Library introduction [library]

20.5 Library-wide requirements [requirements]

20.5.4 Constraints on programs [constraints] Reserved names [reserved.names] Types [extern.types]

For each type T from the C standard library,180 the types ​::​T and std​::​T are reserved to the implementation and, when defined, ​::​T shall be identical to std​::​T.
These types are clock_­t, div_­t, FILE, fpos_­t, lconv, ldiv_­t, mbstate_­t, ptrdiff_­t, sig_­atomic_­t, size_­t, time_­t, tm, va_­list, wctrans_­t, wctype_­t, and wint_­t.