linux-kernel - Re: [PATCH 6/9] drivers/net/wireless/iwlwifi/iwl-4965.c: Correct use of ! and &

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Date:	Wed, 5 Mar 2008 09:55:49 +0100 (CET)
From:	Julia Lawall <julia@...u.dk>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Christopher Li <sparse@...isli.org>, yi.zhu@...el.com,
	linux-wireless@...r.kernel.org,
	ipw3945-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org,
	Harvey Harrison <harvey.harrison@...il.com>,
	Alexander Viro <viro@....linux.org.uk>,
	linux-sparse@...r.kernel.org, Josh Triplett <josh@...edesktop.org>
Subject: Re: [PATCH 6/9] drivers/net/wireless/iwlwifi/iwl-4965.c: Correct
 use of ! and &

There are some legitimate uses of !x & y which are actually of the form !x 
& !y, where x and y are function calls.  That is a not particularly 
elegant way of getting both x and y to be evaluated and then combining the 
results using "and".  If such code is considered acceptable, then perhaps 
the sparse patch should be more complicated.

julia

> Al's patch is:
> 
> +                       if (op == '&' && expr->left->type == EXPR_PREOP &&
> +                           expr->left->op == '!')
> +                               warning(expr->pos, "dubious: !x & y");
> 
> i think there might be similar patterns: "x & !y", "!x | y", "x | !y" ?
> 
> 	Ingo
> 
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