linux-kernel - Re: older gccs and case labels producing integer constants

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Date:   Tue, 5 Apr 2022 12:39:20 +0000 (UTC)
From:   Michael Matz <matz@...e.de>
To:     Peter Zijlstra <peterz@...radead.org>
cc:     Borislav Petkov <bp@...en8.de>, linux-toolchains@...r.kernel.org,
        Richard Biener <rguenther@...e.de>,
        lkml <linux-kernel@...r.kernel.org>
Subject: Re: older gccs and case labels producing integer constants

Hey,

On Tue, 5 Apr 2022, Peter Zijlstra wrote:

> > sound/usb/midi.c: In function ‘snd_usbmidi_out_endpoint_create’:
> > sound/usb/midi.c:1389:2: error: case label does not reduce to an integer constant
> >   case (((0xfc08) << 16) | (0x0101)):
> >   ^~~~
> 
> IIRC GCC-8 fixed a bunch of -wrapv issues. Could be this is one of them 
> I suppose.

Or better said, later GCCs returned back to the old behaviour of rejecting 
this only with -pedantic even in the presence of -fsanitize.  But 
pedantically speaking (ahem!) it really isn't conforming c99 (which the 
compilation flags claim) , and in this case it seems easy enough to make 
the construct actually be conforming in the kernel sources, so that should 
perhaps be done?

Ciao,
Michael.