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From: Dan Carpenter <dan.carpenter@oracle.com>
To: Fengguang Wu <fengguang.wu@intel.com>
Cc: "Rafał Miłecki" <zajec5@gmail.com>,
	"John W. Linville" <linville@tuxdriver.com>,
	kbuild-all@01.org, "Christopher Li" <sparse@chrisli.org>,
	Linux-Sparse <linux-sparse@vger.kernel.org>
Subject: Re: [wireless-next:master 70/102] drivers/net/wireless/b43/phy_ht.c:338:35: sparse: cast truncates bits from constant value (ffff3fff becomes 3fff)
Date: Tue, 16 Sep 2014 10:20:35 +0300	[thread overview]
Message-ID: <20140916072035.GG17875@mwanda> (raw)
In-Reply-To: <20140916021718.GB16455@localhost>

On Tue, Sep 16, 2014 at 10:17:18AM +0800, Fengguang Wu wrote:
> I could disable this warning in my reports, but CC sparse authors
> first to check if there are more elegant solutions.

int main(void)
{
        printf("%x\n", (unsigned short)~(0xc00));   // <-- ok
        printf("%x\n", (unsigned short)~(0xc000));  // <-- complains

        return 0;
}

test.c:10:40: warning: cast truncates bits from constant value (ffff3fff becomes 3fff)

The reason the first one is ok is because we don't complain if the
truncated bits are purely sign bits.  I feel like it should apply to the
second statement as well.  If we're only masking out 0xffff then don't
complain.

regards,
dan carpenter


      reply	other threads:[~2014-09-16  7:21 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <541742fe.FxHiltLcSOUDGDDj%fengguang.wu@intel.com>
     [not found] ` <CACna6ryGg4NY2ecDjCKckXk8QXSJWVpbWWtdya9JRB618G92wQ@mail.gmail.com>
2014-09-16  2:17   ` [wireless-next:master 70/102] drivers/net/wireless/b43/phy_ht.c:338:35: sparse: cast truncates bits from constant value (ffff3fff becomes 3fff) Fengguang Wu
2014-09-16  7:20     ` Dan Carpenter [this message]

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