netdev - Re: [PATCH] pkt_sched: QFQ Plus: fair-queueing service at DRR cost

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Date:	Tue, 20 Nov 2012 10:44:00 -0800
From:	Stephen Hemminger <shemminger@...tta.com>
To:	David Miller <davem@...emloft.net>
Cc:	paolo.valente@...more.it, jhs@...atatu.com,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	rizzo@....unipi.it, fchecconi@...il.com
Subject: Re: [PATCH] pkt_sched: QFQ Plus: fair-queueing service at DRR cost

On Tue, 20 Nov 2012 13:15:16 -0500 (EST)
David Miller <davem@...emloft.net> wrote:

> From: Stephen Hemminger <shemminger@...tta.com>
> Date: Tue, 20 Nov 2012 10:09:58 -0800
> 
> > On Tue, 20 Nov 2012 13:02:02 -0500 (EST)
> > David Miller <davem@...emloft.net> wrote:
> > 
> >> From: Stephen Hemminger <shemminger@...tta.com>
> >> Date: Tue, 20 Nov 2012 09:53:04 -0800
> >> 
> >> > There are actually lots of bogus warnings than seem to only occur
> >> > because gcc 4.4 does a bad job of checking. Later versions are fixed
> >> > and don't generate warnings.
> >> > 
> >> > My preference is to not add the unnecessary initialization because
> >> > if you get in the habit of doing it. The whole purpose of the uninitialized
> >> > check is lost. 
> >> 
> >> Try again, this was with gcc-4.7.2-2 on Fedora.
> >> 
> >> There are too many preconditions, across multiple basic block, which
> >> together ensure the skb is in fact initialized at the point in
> >> question and the compiler simply isn't sophisticated enough to see
> >> that.
> > 
> > Weird, it compiles  clean on x86-84 on Debian.
> > gcc-4.7.real (Debian 4.7.2-4) 4.7.2
> 
> Fedora backports a lot more stuff into gcc than Debian does.

Probably. that's it. Plus Fedora has more gcc maintainers.

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