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Date: Thu, 18 Jul 2019 13:16:34 +0300
From: Dan Carpenter <dan.carpenter@oracle.com>
Subject: Re: Packed struct size issue
Message-ID: <20190718093322.GD3111@kadam>
References: <20190717134234.GA5551@movementarian.org>
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To: John Levon <levon@movementarian.org>
Cc: smatch@vger.kernel.org, andy@omniosce.org, sparse@vger.kernel.org

On Wed, Jul 17, 2019 at 02:42:34PM +0100, John Levon wrote:
> 
> Andy Fiddaman discovered:
> 
> $ cat ./test.c
> #include <stdio.h>
> #include <stdint.h>
> 
> struct t1 {
>         uint8_t                 critical_warning;
>         uint16_t                temperature;
>         uint8_t                 available_spare;
> } __packed;
> 
> _Static_assert(sizeof(struct t1) == 4, "bad size for t1");
> 

I've added Sparse mailing list to the CC.

It looks like the packed attribute is broken on upstream Sparse (from
April) as well and I would prefer if they fixed it and I pulled in their
fix.  It's probably better to use __attribute__((packed)) instead of the
__packed macro in the test code.

regards,
dan carpenter