> -----Original Message-----
> From: Jeff King [mailto:p...@peff.net]
> Sent: Friday, February 10, 2017 4:15 PM
> To: David Turner <david.tur...@twosigma.com>
> Cc: git@vger.kernel.org; pclo...@gmail.com; Junio C Hamano
> <gits...@pobox.com>
> Subject: Re: [PATCH v5] gc: ignore old gc.log files
> 
> > @@ -76,10 +78,30 @@ static void git_config_date_string(const char
> > *key, const char **output)  static void process_log_file(void)  {
> >     struct stat st;
> > -   if (!fstat(get_lock_file_fd(&log_lock), &st) && st.st_size)
> > +   if (fstat(get_lock_file_fd(&log_lock), &st)) {
> > +           /*
> > +            * Perhaps there was an i/o error or another
> > +            * unlikely situation.  Try to make a note of
> > +            * this in gc.log along with any existing
> > +            * messages.
> > +            */
> > +           FILE *fp;
> > +           int saved_errno = errno;
> > +           fp = fdopen(log_lock.tempfile.fd, "a");
> 
> We usually use xfdopen() to handle (unlikely) errors rather than segfaulting. 
>  But
> I think you'd actually want fdopen_lock_file(), which attaches the fd to the
> tempfile for flushing and cleanup purposes.
> 
> That said, I'm not sure I understand why you're opening a new stdio 
> filehandle.
> We know that stderr already points to our logfile (that's how content gets 
> there
> in the first place). If there's a problem with the file or the descriptor, 
> opening a
> new filehandle around the same descriptor won't help.
> 
> Speaking of stderr, I wonder if this function should be calling
> fflush(stderr) before looking at the fstat result. There could be contents 
> buffered
> there that haven't been written out yet (not from child processes, but perhaps
> ones written in this process itself).
> Probably unlikely in practice, since stderr is typically unbuffered by 
> default.

Process_log_file_at_exit calls fflush.  Will fix the other.

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