linux-kernel - Re: [announce] new tree: "fix all build warnings, on all configs"

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Date:	Mon, 20 Oct 2008 09:49:24 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Ingo Molnar <mingo@...e.hu>, Roland Dreier <rdreier@...co.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"David S. Miller" <davem@...emloft.net>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	linux-kernel@...r.kernel.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Thomas Gleixner <tglx@...utronix.de>,
	David Howells <dhowells@...hat.com>
Subject: Re: [announce] new tree: "fix all build warnings, on all configs"

Linus Torvalds wrote:
> 
> The old code was correct. Your code is shit. And you didn't fix 
> _anything_.
> 
>>  	case 5:
>>  		*(int *)to = *(int *)from;
>> -		*((short *)to + 3) = *((short *)from + 3);
>> +		*((char *)(to + 3)) = *((char *)(from + 3));
>>  		return to;
> 
> Are you just making changes by randomly inserting and deleting characters 
> until you don't see warnings? Or what?
> 
> That thing is supposed to be a 5-byte memcpy. Not a "take a random byte 
> from a random location and move it to another random location". That would 
> be "randcpy()", not "memcpy()".
> 

That is not a 5-byte memcopy.  In *either* version!

In the "before" case, it copies bytes 0, 1, 2, 3, 6 and 7.
In the "after" case, it copies bytes 0, 1 and 2.

Presumably it *should* be:

	*((char *)to + 4) = *((char *)from + 4);

	-hpa
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