From: Jeff King <peff@peff.net>
Date: Mon, 13 Sep 2021 19:03:10 GMT
Subject: Re: [PATCH] refs/files-backend: remove unused open mode parameter
Message-ID: <YT+gbhnKmd0nlpxG@coredump.intra.peff.net>
In-Reply-To: <xmqqilz4fi86.fsf@gitster.g>

On Mon, Sep 13, 2021 at 11:22:49AM -0700, Junio C Hamano wrote:

> Han-Wen Nienhuys <hanwen@google.com> writes:
> 
> > On Thu, Sep 9, 2021 at 11:46 PM René Scharfe <l.s.r@web.de> wrote:
> >>
> >> We only need to provide a mode if we are willing to let open(2) create
> >> the file, which is not the case here, so drop the unnecessary parameter.
> >
> > I was #today years old when I learned that C supports (a limited form
> > of) function signature overloading.
> 
> I do not think it is that kind of magic.
> 
> Like printf(3) that allows its early parameter to affect the way how
> its later parameters are recognised, it just allows the flags word
> to decide if it needs to grab one extra mode_t out of va_list or
> not, which can be done as a plain vanilla varargs function, i.e.
> 
> 	extern int open(const char *path, int flags, ...);

Yes, you can see some examples (complete with interesting subtleties) in
wrapper.c:xopen() and compat/open.c:git_open_with_retry(). :)

-Peff