linux-kernel - Re: [PATCH] vgaswitcheroo: Fix error checking in vga_switcheroo_register_audio

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Message-ID: <f608a3b5-320a-4194-bd03-cf08be04c317@stanley.mountain>
Date: Wed, 19 Feb 2025 19:04:54 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Jani Nikula <jani.nikula@...ux.intel.com>
Cc: Jim Qu <Jim.Qu@....com>, Lukas Wunner <lukas@...ner.de>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
	Takashi Iwai <tiwai@...e.de>, dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
	Su Hui <suhui@...china.com>
Subject: Re: [PATCH] vgaswitcheroo: Fix error checking in
 vga_switcheroo_register_audio_client()

On Wed, Feb 19, 2025 at 05:17:56PM +0200, Jani Nikula wrote:
> On Wed, 19 Feb 2025, Dan Carpenter <dan.carpenter@...aro.org> wrote:
> > The "id" variable is an enum and in this context it's treated as an
> > unsigned int so the error handling can never trigger.
> 
> When would that be true with GCC?

The C standard give compilers a lot of flexibility with regards to enums.

But in terms of GCC/Clang then enums default to unsigned int, if you
declare one as negative then they become signed int.  If they don't fit
in int, then they become u64 etc.

enum u32_values {
	zero,
};

enum s32_values {
	minus_one = -1,
	zero,
};

enum u64_values {
	big = 0xfffffffffUL;
};

regards,
dan carpenter