To: linux-kernel@vger.kernel.org
From: Alexander Clouter <alex@digriz.org.uk>
Subject: Re: [PATCH]exit.c: support larger exit code
Date: Mon, 9 Aug 2010 09:25:49 +0100
Message-ID: <dlq4j7-0tp.ln1@chipmunk.wormnet.eu>
References: <14414B36FFA0F1418CB707361EAA199A0194FB16@CNBEEXC006.nsn-intra.net>
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"Zhang, Wei-Jovi (NSN - CN/Hangzhou)" <wei-jovi.zhang@nsn.com> wrote:
> 
> I think this is just a convention of userspace program. if program 
> want to obey this convention, it should be use one-byte limition exit 
> code, I agree this. so this mail thread's subject should change to "if 
> program use exit code with not want to obey the convention, kernel 
> should return which value?"
>
I do have to agree with you on this point, although I stand by my 
thoughts on *how* you should be using the exit code.  Whilst writing my 
post I was thinking why in C is it 'int main()' and not 'u8 main()'.

A dig around with my Googlefu and on Wackipedia gave me nothing 
either...

One thing I can think of why the kernel is forcing a one byte return 
code is that:
 * guarantee there is no endian issue; hard to pull off though but I 
	guess that exit code could travel across IP to another 
	architecture
 * stop people abusing the exitcode :)

There is probably a deeper reason as errno.h/errno-base.h all seem to be 
one byte return codes too.  I'm starting to ponder if that top three 
bytes are meant to carry some other information?

Cheers

-- 
Alexander Clouter
.sigmonster says: Make sure your code does nothing gracefully.

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