fcntl is as specified in
ISO POSIX (2003),
but with differences as listed below.
According to the Single UNIX
Specification, only an application sets
fcntl flags, for example
O_LARGEFILE. However, this specification
also allows an implementation to set O_LARGEFILE
in the case where the system default behavior matches the
O_LARGEFILE behavior,
for example if sizeof(off_t) is 8.
Thus, calling fcntl with the
F_GETFL command may return
O_LARGEFILE as well as flags explicitly
set by the application.