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

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Date:   Wed, 19 Oct 2016 13:31:16 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Richard Biener <rguenther@...e.de>
Cc:     "Luis R. Rodriguez" <mcgrof@...nel.org>,
        Vegard Nossum <vegard.nossum@...cle.com>,
        Jiri Slaby <jslaby@...e.cz>, linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        stable@...r.kernel.org, Ming Lei <ming.lei@...onical.com>,
        Steven Rostedt <srostedt@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Cesar Eduardo Barros <cesarb@...arb.eti.br>,
        Michael Matz <matz@...e.de>,
        David Miller <davem@...emloft.net>,
        Guenter Roeck <linux@...ck-us.net>,
        Fengguang Wu <fengguang.wu@...el.com>,
        Borislav Petkov <bp@...en8.de>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        Kees Cook <keescook@...omium.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 01/12] extarray: define helpers for arrays defined in
 linker scripts

On Wed, Oct 19, 2016 at 01:11:31PM +0200, Richard Biener wrote:
> For C++ these kind of warnings trigger whenever abstraction penalty
> is removed.  Like the typical
> 
>  template <int i> foo () { if (i) { <code> } }
> 
> triggering for a hypothetical -Wdead-code for i == 0.  The kernel
> is known for its "C" abstraction stuff and I can believe that
> such -W flag would trigger for cases where abstraction is removed.

Sure, we very much rely on dead code elimination and constant
propagation all over the place. I was mostly thinking about the specific
case where it was triggered by alias analysis. I'm not sure how often
we'd trigger that.