linux-kernel - Re: [PATCH 7/7] asm-generic: suppress sparse warning in ioctl.h

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Message-ID: <alpine.LFD.1.00.0804021752040.14670@woody.linux-foundation.org>
Date:	Wed, 2 Apr 2008 17:57:54 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Harvey Harrison <harvey.harrison@...il.com>
cc:	Al Viro <viro@...IV.linux.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 7/7] asm-generic: suppress sparse warning in ioctl.h

On Wed, 2 Apr 2008, Harvey Harrison wrote:
>
> 1 ? 0 : x
> 
> is not valid in contexts where C requires integer constant expressions.
> Index in static array initializer is one of those.

So I don't much like this one, because (a) we could just make sparse 
accept it and (b) gcc _does_ accept it and gives us nicer error messages. 

Well, maybe "nicer" is wrong (because it's a link-time one), but at least 
not a _totally_ misleading one.

What does "division by zero" mean as an error message? Also, if I recall 
correctly, last time we tried something like this (admittedly long ago), 
some compilers would actually make it a run-time error, not a compile-time 
one - it would simply refuse optimize the 1/0 into a value at all, and 
just generate a run-time divide.

So I'm not even sure that all versions of gcc will even complain at all 
(although it might have been icc).

			Linus
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