From: Richard Henderson <rth@twiddle.net>
To: Jes Sorensen <Jes.Sorensen@redhat.com>
Cc: Doug Ledford <dledford@redhat.com>,
neilb@suse.de, joe.lawrence@stratus.com,
linux-raid@vger.kernel.org
Subject: Re: [PATCH 1/2] Fix sign extension of bitmap_offset in super1.c
Date: Thu, 26 Apr 2012 08:32:36 -0700 [thread overview]
Message-ID: <4F996A94.3060509@twiddle.net> (raw)
In-Reply-To: <4F9968F0.30805@redhat.com>
On 04/26/12 08:25, Jes Sorensen wrote:
> Just checking mdadm.h and bswap32() is defined like this:
>
> #define bswap_32(x) (((x) & 0x000000ffU) << 24 | \
> ((x) & 0xff000000U) >> 24 | \
> ((x) & 0x0000ff00U) << 8 | \
> ((x) & 0x00ff0000U) >> 8)
>
> so I am not 100% sure just swapping to an s32 in the struct will work on
> big endian systems? Will the 0x000000ffU not force the conversion back
> to unsigned or what happens in this case?
This is actually semi-complicated. c89 or c99 rules? X already of a
type larger than unsigned int?
But if X is signed int, this entire expression will always be unsigned.
You're certainly better off with a cast as we discussed on irc.
r~
next prev parent reply other threads:[~2012-04-26 15:32 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-26 15:12 [PATCH 0/2] Solve problem adding internal bitmaps to 1.0 arrays Jes.Sorensen
2012-04-26 15:12 ` [PATCH 1/2] Fix sign extension of bitmap_offset in super1.c Jes.Sorensen
2012-04-26 15:18 ` Doug Ledford
2012-04-26 15:21 ` Jes Sorensen
2012-04-26 15:25 ` Jes Sorensen
2012-04-26 15:32 ` Richard Henderson [this message]
2012-04-26 15:35 ` Doug Ledford
2012-04-26 15:36 ` Jes Sorensen
2012-04-29 23:55 ` NeilBrown
2012-04-26 15:12 ` [PATCH 2/2] Introduce sysfs_set_num_signed() and use it to set bitmap/offset Jes.Sorensen
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