16 Library introduction [library]

16.5 Library-wide requirements [requirements]

16.5.4 Constraints on programs [constraints]

16.5.4.3 Reserved names [reserved.names]

16.5.4.3.4 Types [extern.types]

For each type T from the C standard library, the types ​::​T and std​::​T are reserved to the implementation and, when defined, ​::​T shall be identical to std​::​T.