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

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Message-ID: <YkwQ6+tIH8GQpuct@zn.tnic>
Date:   Tue, 5 Apr 2022 11:50:35 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     linux-toolchains@...r.kernel.org
Cc:     Michael Matz <matz@...e.de>, Richard Biener <rguenther@...e.de>,
        lkml <linux-kernel@...r.kernel.org>
Subject: older gccs and case labels producing integer constants

Hi folks,

I'm starting to see failures like this on allmodconfig builds:

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)):
  ^~~~

(The case statement is a macro but it evaluates to what I have there)

and that thing fails with

$ gcc --version
gcc (SUSE Linux) 7.5.0

although it doesn't have any problems building with newer compilers.

I'm presuming older gccs consider those case statements signed ints and
the following fixes it:

  case ((((unsigned int)0xfc08) << 16) | (0x0101)):

and I guess we can whack the couple of occurrences but what I'm
wondering is why does this work with newer gccs?

Thx.

-- 
Regards/Gruss,
    Boris.

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