From: Jeff King <peff@peff.net>
Date: Fri, 17 Feb 2017 20:54:42 GMT
Subject: Re: [PATCH] tempfile: avoid "ferror | fclose" trick
Message-ID: <20170217205442.wnldfsxbj3dnnqvj@sigill.intra.peff.net>
In-Reply-To: <64eedabd-c0de-a7e0-8d98-ad23a9625b45@alum.mit.edu>

On Fri, Feb 17, 2017 at 11:42:25AM +0100, Michael Haggerty wrote:

> On 02/17/2017 09:07 AM, Jeff King wrote:
> > [...]
> > That's similar to what I wrote earlier, but if we don't mind overwriting
> > errno unconditionally, I think just:
> > 
> >   errno = EIO; /* covers ferror(), overwritten by failing fclose() */
> >   err |= ferror(fp);
> >   err |= fclose(fp);
> > 
> > does the same thing.
> 
> True; I'd forgotten the convention that non-failing functions are
> allowed to change errno. Your solution is obviously simpler and faster.

I guess we are simultaneously assuming that it is OK to munge errno on
success in our function, but that fclose() will not do so. Which seems a
bit hypocritical. Maybe the "if" dance is better.

-Peff