Constant __O_SYNC

pub const __O_SYNC: i32 = 0o400_0000; // 1_048_576i32

Available on crate feature dep_nc only.

Before Linux 2.6.33 only O_DSYNC semantics were implemented, but using the O_SYNC flag.

We continue to use the existing numerical value for O_DSYNC semantics now, but using the correct symbolic name for it.

This new value is used to request true Posix O_SYNC semantics.

It is defined in this strange way to make sure applications compiled against new headers get at least O_DSYNC semantics on older kernels.

This has the nice side-effect that we can simply test for O_DSYNC wherever we do not care if O_DSYNC or O_SYNC is used.

Note: __O_SYNC must never be used directly.