Re: [PATCH 1/2] inline constant return from error() function

From: Jeff King <peff@peff.net>
Date: May 7, 2014, 03:02 UTC
Message-ID: <20140507030254.GC20726@sigill.intra.peff.net>
In-Reply-To: <xmqqppjqczhq.fsf@gitster.dls.corp.google.com>

On Tue, May 06, 2014 at 03:29:37PM -0700, Junio C Hamano wrote:

Show 9 quoted lines

> > We can work around this by encapsulating the constant return
> > value in a static inline function, as gcc specifically
> > avoids complaining about unused function returns unless the
> > function has been specifically marked with the
> > warn_unused_result attribute.
> 
> That's kind of W*A*T magic, and I generally try to avoid magic, as
> long as it solves your "can we make both -O2 with new compilers and
> -O3 happy?" I wouldn't complain ;-)

I agree it's rather magical, but I think it's something we can count on. Certainly turning on warn_unused_result for every function would be a catastrophe for most code bases, and I don't expect gcc to do it. It's possible it would eventually grow smart to say "eh, I inlined this and realized that you don't use the return value", but I think that would be similarly a bad idea.

And it does work with -O2 and -O3 with both gcc-4.9 and clang in my tests.

-Peff