31 Input/output library [input.output]

31.12 File systems [filesystems]

31.12.2 Conformance [fs.conformance] Operating system dependent behavior conformance [fs.conform.os]

Behavior that is specified as being operating system dependent is dependent upon the behavior and characteristics of an operating system.
The operating system an implementation is dependent upon is implementation-defined.
It is permissible for an implementation to be dependent upon an operating system emulator rather than the actual underlying operating system.