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

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Message-ID: <pn935o4p-82sn-275n-s793-r85qr8q85o9r@fhfr.qr>
Date:   Tue, 5 Apr 2022 13:37:26 +0200 (CEST)
From:   Richard Biener <rguenther@...e.de>
To:     Borislav Petkov <bp@...en8.de>
cc:     linux-toolchains@...r.kernel.org, Michael Matz <matz@...e.de>,
        lkml <linux-kernel@...r.kernel.org>
Subject: Re: older gccs and case labels producing integer constants

On Tue, 5 Apr 2022, Borislav Petkov wrote:

> On Tue, Apr 05, 2022 at 12:06:45PM +0200, Richard Biener wrote:
> > Wird auch mit gcc 11 rejected.  Kanns sein dass mit gcc 7 andere
> > compiler flags genommen werden?
> 
> Found it:
> 
> $ gcc -fsanitize=shift -c switch.c
> switch.c: In function ‘foo’:
> switch.c:10:7: error: case label does not reduce to an integer constant
>        case (((0xfc08) << 16) | (0x0101)):;
> 
> $ gcc --version
> gcc (SUSE Linux) 7.4.1 20190905 [gcc-7-branch revision 275407]
> Copyright (C) 2017 Free Software Foundation, Inc.
> 
> Something not fully backported?

Probably early vs. late folding change in the frontend.  So yes,
don't use -fsanitize=... ;)

Richard.

-- 
Richard Biener <rguenther@...e.de>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Ivo Totev; HRB 36809 (AG Nuernberg)