netdev - Re: Lots of new warnings with gcc-7.1.1

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Date:   Wed, 12 Jul 2017 15:10:10 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Arnd Bergmann <arnd@...db.de>
Cc:     Tejun Heo <tj@...nel.org>, Jean Delvare <jdelvare@...e.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Sathya Prakash <sathya.prakash@...adcom.com>,
        "James E.J. Bottomley" <jejb@...ux.vnet.ibm.com>,
        the arch/x86 maintainers <x86@...nel.org>,
        xen-devel <xen-devel@...ts.xenproject.org>,
        linux-block <linux-block@...r.kernel.org>,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        IDE-ML <linux-ide@...r.kernel.org>,
        "linux-fbdev@...r.kernel.org" <linux-fbdev@...r.kernel.org>,
        Network Development <netdev@...r.kernel.org>
Subject: Re: Lots of new warnings with gcc-7.1.1

On Tue, Jul 11, 2017 at 03:35:15PM -0700, Linus Torvalds wrote:
> [ Very random list of maintainers and mailing lists, at least
> partially by number of warnings generated by gcc-7.1.1 that is then
> correlated with the get_maintainers script ]
> 
> So I upgraded one of my boxes to F26, which upgraded the compiler to gcc-7.1.1
> 
> Which in turn means that my nice clean allmodconfig compile is not an
> unholy mess of annoying new warnings.

I asked Arnd about this the other day on IRC as I've hit this as well on
the stable releases, and it's really annoying.  He mentioned that he had
lots of these warnings fixed, but didn't push most of the changes out
yet.  Arnd, any repo with them in it that we could look at?

> Normally I hate the stupid new warnings, but this time around they are
> actually exactly the kinds of warnings you'd want to see and that are
> hard for humans to pick out errors: lots of format errors wrt limited
> buffer sizes.
> 
> At the same time, many of them *are* annoying. We have various limited
> buffers that are limited for a good reason, and some of the format
> truncation warnings are about numbers in the range {0-MAX_INT], where
> we definitely know that we don't need to worry about the really big
> ones.
> 
> After all, we're using "snprintf()" for a reason - we *want* to
> truncate if the buffer is too small.

Yeah, that's the warnings in the USB core code, we "know" this will not
happen, and we are using snprintf() for that reason as well, I don't
know how to fool gcc into the fact that it's all ok here.

> Anyway, it would be lovely if some of the more affected developers
> would take a look at gcc-7.1.1 warnings. Right now I get about three
> *thousand* lines of warnings from a "make allmodconfig" build, which
> makes them a bit overwhelming.

I only have 310 when building the 4.12.0 release with 7.1.1, I wonder if
Fedora turned more warnings on in their compiler release, I'm running
Arch here:
	$ gcc --version
	gcc (GCC) 7.1.1 20170621

thanks,

greg k-h