linux-kernel - Re: [PATCH] arm64: traps: Mark __le16, __le32, _

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Message-ID: <20170221110355.GD300@arm.com>
Date:   Tue, 21 Feb 2017 11:03:56 +0000
From:   Will Deacon <will.deacon@....com>
To:     Luc Van Oostenryck <luc.vanoostenryck@...il.com>
Cc:     Mark Rutland <mark.rutland@....com>,
        Stephen Boyd <stephen.boyd@...aro.org>,
        Catalin Marinas <catalin.marinas@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Punit Agrawal <punit.agrawal@....com>,
        linux-sparse@...r.kernel.org
Subject: Re: [PATCH] arm64: traps: Mark __le16, __le32, __user variables
 properly

On Mon, Feb 20, 2017 at 10:33:45PM +0100, Luc Van Oostenryck wrote:
> I just checked this and I'm not very sure what's best.
> Sparse is very well aware of the '...' to specify a range
> in an array initializer or in switch-case. The warning
> is there only because those entries are later overridden
> with some value.
> When checking what GCC is doing in this situation is saw
> that by default even in cases like:
> 	static in ref[] = {
> 		[1] = 1,
> 		[2] = 2,
> 	};
> GCC doesn't issue a warning. You need to use the flag
> -Woverride-init for that. But then you also have a warning
> for our current case:
> 	static in foo[] = {
> 		[0 ... 3] = 1,
> 		[0] = 2,
> 	};
> 
> It's easy enough to patch sparse to not issue a warning when the
> override concerns a range (which would be perfect for the situation here),
> Controlled or not by a new warning flag. But I'm far from convinced
> that all uses of such "ranged-initialization" is used for default values
> that may be later overridden.

How about not warning only when the overridden range covers the entire
length of the array? The only broken case I can think of that slips
through the cracks then is if somebody typoed the range so that it
accidentally covered the whole array and therefore suppressed the override
warning.

Will