fsync() is not called for messages written to maildir

[Safari]

It can take as much as 30s (or more) till the OS really flushes the buffers if fsync() is not called.

Besides, maildir format is not reliable if you do not use fsync.

[brendan]

(In [5d46ad49d04a]) fsync maildir/mh messages on commit. Closes #2962.

[Safari]

You should call fflush before fsync. May I suggest something: add function safe_fclose_fsync into lib.c and call safe_fclose_fsync instead of safe_fclose in mh.c.

Then it's also easy to call safe_fclose_fsync when for example saving attachments...

int safe_fclose_fsync (FILE **f)
{
  int r = 0;

  if (*f) {
    if (fflush(*f) == EOF || ((fsync(fileno(*f)) == -1) && errno != EINVAL)) {
      r = -1;
      fclose (*f);
    } else {
      r = fclose (*f);
    }
  }

  *f = NULL;
  return r;
}

[brendan]

You're right. I'll push a fix momentarily.

[brendan]

(In [50cc55e95be6]) fflush before fsync and close. Closes #2962 again.