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Re: Question about the use of _newlib_flockfile_* in newlib
On Dec 18 09:38, Bin.Cheng wrote:
> On Mon, Dec 17, 2012 at 9:56 PM, Corinna Vinschen <vinschen@redhat.com> wrote:
> > On Dec 17 21:42, Bin.Cheng wrote:
> >> On Mon, Dec 17, 2012 at 6:53 PM, Corinna Vinschen <vinschen@redhat.com> wrote:
> >> > On Dec 17 10:06, Bin.Cheng wrote:
> >> >> Hi,
> >> >> I have two questions on _newlib_flockfile_*.
> >> >> 1.
> >> >> _fputc_r calls _putc_r to do the job, but both of them calls
> >> >> _newlib_flockfile_*. Is it OK? Why if it is.
> >> >
> >> > I'm not quite sure, but I think the reason is that putc and, in analogy,
> >> > _putc_r might be defined as macro. Newlib doesn't do that by default
> >> > for _putc_r, but target-specific code could.
> >> >
> >> >> 2. In most functions, the macro ORIENT() is guarded by
> >> >> _newlib_flockfile_*, but it is not in _puts_r. Anything special or
> >> >> just missed something?
> >> >
> >> > I had a look into the CVS annotation and it seems that this is not about
> >> > ORIENT, but about the fact that the __sfvwrite_r call in _puts_r was
> >> > never guarded by a flockfile/funlockfile (the predecessor of
> >> > _newlib_flockfile_start/_newlib_flockfile_end).
> >> Yes.
> >> >
> >> > I don't know why, though. Jeff?
> >>
> >> Another problem.
> >> In function _fwrite_r, there is code like:
> >>
> >> _newlib_flockfile_start (fp);
> >> ORIENT (fp, -1);
> >> if (__sfvwrite_r (ptr, fp, &uio) == 0)
> >> {
> >> _newlib_flockfile_exit (fp);
> >> return count;
> >> }
> >> _newlib_flockfile_end (fp);
> >> return (n - uio.uio_resid) / size;
> >>
> >> I think _newlib_flockfile_exit and _newlib_flockfile_end are
> >> mis-placed with each other, right?
> >
> > No, that's correct. See libc/stdio/local.h.
> I am a little confused. Yes, the expanded code of the two macros are
> same, but the literal meaning of them are as commented:
No, the expanded code is not the same. Look again. It's not about
the success or failure but only about leaving a critical section
earlier than through _newlib_flockfile_end.
Corinna
--
Corinna Vinschen
Cygwin Project Co-Leader
Red Hat