Christoph Hellwig wrote:
On Fri, Jun 19, 2009 at 10:22:07PM -0400, m a wrote:
This patch replaces O_SYNC with O_FSYNC. These two flags do the same
thing, but only O_FSYNC is available in Mac OS 10.3 and under. It
only
replaces O_SYNC if it doesn't exist. This patch allows the file
block-raw-posix.c to compile on Mac OS 10.3. This is my first time
submitting a patch, so there might have been a few mistakes made.
But O_SYNC is a standard posix flag, while O_FSYNC appears to be
a BSD extension. Also the actual code uses O_DSYNC anyway, which
also is in Posix but not actually natively supported by some OSes,
e.g. Linux (but still provided in libc there).
If O_FSYNC and O_SYNC do the same thing, and O_SYNC is used anywhere,
there's no harm in this for portability:
#if !defined(O_SYNC) && defined(O_FSYNC)
#define O_SYNC O_FSYNC
#endif
The patch assumes O_FSYNC is defined if O_SYNC isn't, which is wrong.
/* OS X does not have O_DSYNC */
#ifndef O_DSYNC
#define O_DSYNC O_SYNC
So if the code here is correct and Darwin is the only supported OS
where
O_DSYNC is missing we could just replace the O_SYNC in the last line
with O_FSYNC.
I agree, though the comment might be misleading, if there's another
supported OS without O_DSYNC.
-- Jamie