From: "Richard W.M. Jones" <rjones@redhat.com>
To: Peter Maydell <peter.maydell@linaro.org>
Cc: Kevin Wolf <kwolf@redhat.com>, Jeff Cody <jcody@redhat.com>,
QEMU Developers <qemu-devel@nongnu.org>,
Stefan Hajnoczi <stefanha@redhat.com>,
Alexander Graf <agraf@suse.de>
Subject: Re: [Qemu-devel] [PATCH] block: Explicitly specify 'unsigned long long' for VHDX 64-bit constants
Date: Fri, 14 Mar 2014 15:57:42 +0000 [thread overview]
Message-ID: <20140314155742.GU1346@redhat.com> (raw)
In-Reply-To: <CAFEAcA9M1W6w0KR5MA1AbA3dACdjd9PYfjQXH2ySiVf1iM3zRg@mail.gmail.com>
On Fri, Mar 14, 2014 at 03:38:55PM +0000, Peter Maydell wrote:
> On 14 March 2014 15:36, Richard W.M. Jones <rjones@redhat.com> wrote:
> > On Fri, Mar 14, 2014 at 06:50:37AM -0400, Jeff Cody wrote:
> >> On 32-bit hosts, some compilers will warn on too large integer constants
> >> for constants that are 64-bit in length. Explicitly put a 'ULL' suffix
> >> on those defines.
> >> -#define VHDX_FILE_SIGNATURE 0x656C696678646876 /* "vhdxfile" in ASCII */
> >> +#define VHDX_FILE_SIGNATURE 0x656C696678646876ULL /* "vhdxfile" in ASCII */
> >
> > I think it's better to use this C99-defined feature (from <stdint.h>):
> >
> > #define VHDX_FILE_SIGNATURE UINT64_C(0x656C696678646876)
>
> Why? It's longer and we barely use it anywhere else
> in the codebase, whereas we use the ULL suffix all
> over the place...
It's permitted for unsigned long long to be longer than 64 bits. The
UINT64_C() macro will always return a 64 bit int constant. Yup, it's
not likely and for this particular macro it wouldn't matter. (And I'm
not going to get into language-lawyering ...)
Rich.
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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next prev parent reply other threads:[~2014-03-14 15:58 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-03-14 10:50 [Qemu-devel] [PATCH] block: Explicitly specify 'unsigned long long' for VHDX 64-bit constants Jeff Cody
2014-03-14 15:25 ` Stefan Hajnoczi
2014-03-14 15:36 ` Richard W.M. Jones
2014-03-14 15:38 ` Peter Maydell
2014-03-14 15:57 ` Richard W.M. Jones [this message]
2014-03-14 16:26 ` Laszlo Ersek
2014-03-14 16:51 ` Richard W.M. Jones
2014-03-14 17:27 ` Laszlo Ersek
2014-03-14 17:49 ` Richard W.M. Jones
2014-03-14 18:16 ` Laszlo Ersek
2014-03-14 16:17 ` Laszlo Ersek
2014-03-14 16:26 ` Peter Maydell
2014-03-14 16:35 ` Laszlo Ersek
2014-03-14 16:36 ` Laszlo Ersek
2014-03-14 17:08 ` Peter Maydell
2014-03-14 17:42 ` Laszlo Ersek
2014-03-14 18:22 ` Peter Maydell
2014-03-14 18:49 ` Laszlo Ersek
2014-03-14 18:57 ` Laszlo Ersek
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