linux-kernel - Re: [PATCH 01/12] extarray: define helpers for arrays defined in linker scripts

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Message-ID: <20161017083315.GA29322@worktop.vlan200.pylonone.local>
Date:   Mon, 17 Oct 2016 10:33:15 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Vegard Nossum <vegard.nossum@...cle.com>
Cc:     linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.cz>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        "Luis R . Rodriguez" <mcgrof@...nel.org>, stable@...r.kernel.org,
        Ming Lei <ming.lei@...onical.com>,
        Steven Rostedt <srostedt@...hat.com>
Subject: Re: [PATCH 01/12] extarray: define helpers for arrays defined in
 linker scripts

On Sun, Oct 16, 2016 at 05:16:05PM +0200, Vegard Nossum wrote:
> The test in this loop:
> 
> 	for (b_fw = __start_builtin_fw; b_fw != __end_builtin_fw; b_fw++) {
> 
> was getting completely compiled out by my gcc, 7.0.0 20160520. The result
> was that the loop was going beyond the end of the builtin_fw array and
> giving me a page fault when trying to dereference b_fw->name.
> 
> This is because __start_builtin_fw and __end_builtin_fw are both declared
> as (separate) arrays, and so gcc conludes that b_fw can never point to
> __end_builtin_fw.
> 

Urgh, isn't that the kind of 'optimizations' we should shoot in the head
for the kernel? Just like the -fno-strict-aliassing crap?