linux-kernel - Re: [PATCH] HID: simplify code in fetch

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Message-ID: <20241015205953.GH29862@gate.crashing.org>
Date: Tue, 15 Oct 2024 15:59:53 -0500
From: Segher Boessenkool <segher@...nel.crashing.org>
To: Nathan Chancellor <nathan@...nel.org>
Cc: Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Jiri Kosina <jikos@...nel.org>,
        Benjamin Tissoires <bentiss@...nel.org>, linux-input@...r.kernel.org,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev, paulmck@...nel.org,
        sfr@...b.auug.org.au, jpoimboe@...nel.org,
        linux-toolchains@...r.kernel.org
Subject: Re: [PATCH] HID: simplify code in fetch_item()

On Tue, Oct 15, 2024 at 12:26:04PM -0700, Nathan Chancellor wrote:
> On Tue, Oct 15, 2024 at 11:28:26AM -0700, Dmitry Torokhov wrote:
> > Oh well, if our toolchain does not like "unreachable()" then we can
> > simply remove it - the switch does cover all possible values and the
> > "return" statement should be valid even if compiler somehow decides that
> > "switch" statement can be skipped.
> > 
> > If you can send a patch that would be great.
> 
> Done, thanks a lot for the input!
> 
> https://lore.kernel.org/20241015-hid-fix-fetch_item-unreachable-v1-1-b131cd10dbd1@kernel.org/

There also is -funreachable-traps, which the kernel might want to use
(with that option every builtin_unreachablei() is compiled to a trap
instruction, instead of that the compiler just thinks "Aha!  This can
never happen!", and optimise based on that).


Segher