From mboxrd@z Thu Jan  1 00:00:00 1970
From: Harvey Harrison <harvey.harrison-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Subject: Re: [PATCH 1/8] kernel: add common infrastructure for unaligned
	access
Date: Thu, 10 Apr 2008 15:06:23 -0700
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To: David Howells <dhowells-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Cc: Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>, linux-arch <linux-arch-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>

On Thu, 2008-04-10 at 23:01 +0100, David Howells wrote:
> Harvey Harrison <harvey.harrison-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> 
> > > Actually, you probably _ought_ to have casts, but it should look like this:
> > > 
> > > 	return (u16)p[0] | (u16)p[1] << 8;
> > 
> > I've been looking at that thinking I needed something different, I
> > believe it is ok as u8 will expand to int when shifted... correct?  Or
> > do I actually need the cast on each p[] term...anyone?
> 
> Hmmm... I think you may be right:
> 
> 	#include <stdio.h>
> 
> 	int main()
> 	{
> 		unsigned char x;
> 		printf("%u, %u\n", sizeof(x), sizeof(x << 8));
> 		return 0;
> 	}
> 
> Says:
> 
> 	1, 4
> 
> In which case, the cast you do have is superfluous, and casting the retrievals
> is unnecessary.

Expands to int, not unsigned int, I think that cast is still needed?

Harvey

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Subject: Re: [PATCH 1/8] kernel: add common infrastructure for unaligned
	access
From: Harvey Harrison <harvey.harrison@gmail.com>
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On Thu, 2008-04-10 at 23:01 +0100, David Howells wrote:
> Harvey Harrison <harvey.harrison@gmail.com> wrote:
> 
> > > Actually, you probably _ought_ to have casts, but it should look like this:
> > > 
> > > 	return (u16)p[0] | (u16)p[1] << 8;
> > 
> > I've been looking at that thinking I needed something different, I
> > believe it is ok as u8 will expand to int when shifted... correct?  Or
> > do I actually need the cast on each p[] term...anyone?
> 
> Hmmm... I think you may be right:
> 
> 	#include <stdio.h>
> 
> 	int main()
> 	{
> 		unsigned char x;
> 		printf("%u, %u\n", sizeof(x), sizeof(x << 8));
> 		return 0;
> 	}
> 
> Says:
> 
> 	1, 4
> 
> In which case, the cast you do have is superfluous, and casting the retrievals
> is unnecessary.

Expands to int, not unsigned int, I think that cast is still needed?

Harvey