From: Wei Liu <wei.liu2@citrix.com>
To: Jan Beulich <JBeulich@suse.com>
Cc: Juergen Gross <jgross@suse.com>,
xen-devel <xen-devel@lists.xenproject.org>,
Olaf Hering <olaf@aepfle.de>,
Paul Durrant <paul.durrant@citrix.com>,
Wei Liu <wei.liu2@citrix.com>
Subject: Re: bogus wrap check in xen-netback
Date: Wed, 25 Apr 2018 11:31:25 +0100 [thread overview]
Message-ID: <20180425103125.kllxadyujbqbiamq@citrix.com> (raw)
In-Reply-To: <5AE057BE02000078001BE50B@prv1-mh.provo.novell.com>
On Wed, Apr 25, 2018 at 04:26:06AM -0600, Jan Beulich wrote:
> >>> On 25.04.18 at 12:06, <wei.liu2@citrix.com> wrote:
> > On Wed, Apr 25, 2018 at 11:04:26AM +0200, Olaf Hering wrote:
> >> Am Wed, 25 Apr 2018 09:59:23 +0100
> >> schrieb Wei Liu <wei.liu2@citrix.com>:
> >>
> >> > Do you have the full diff of your changes?
> >>
> >> Not right now. But without 'val', or val being uint, the same error happens
> > in f():
> >>
> >> #include <stdio.h>
> >> void f(void)
> >> {
> >> unsigned short req_prod = 0, req_cons = 65400;
> >> unsigned short val;
> >> val = req_prod - req_cons;
> >> printf("req_prod - req_cons %u\n", val);
> >> printf("req_prod - req_cons %x\n", val);
> >> }
> >
> > What Jan said.
> >
> > Integer promotion makes unsigned short into unsigned int first then do
> > the calculation.
>
> Not exactly - it promotes to plain (i.e. signed) int.
My bad. Yes, they are converted to int, not unsigned int.
Wei.
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next prev parent reply other threads:[~2018-04-25 10:31 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-25 7:19 bogus wrap check in xen-netback Olaf Hering
2018-04-25 7:28 ` Juergen Gross
2018-04-25 7:39 ` Olaf Hering
2018-04-25 8:59 ` Wei Liu
2018-04-25 9:04 ` Olaf Hering
2018-04-25 9:48 ` Jan Beulich
2018-04-25 10:06 ` Wei Liu
2018-04-25 10:26 ` Jan Beulich
2018-04-25 10:31 ` Wei Liu [this message]
2018-04-25 10:35 ` Olaf Hering
2018-04-25 10:47 ` Wei Liu
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