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

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Message-Id: <20121120.130202.1918742054229219388.davem@davemloft.net>
Date:	Tue, 20 Nov 2012 13:02:02 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	shemminger@...tta.com
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

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.
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