From mboxrd@z Thu Jan  1 00:00:00 1970
From: Roland Dreier <rdreier@cisco.com>
Subject: Re: [PATCH v2] fs: O_* bit numbers uniqueness check
Date: Tue, 05 Jan 2010 23:30:31 -0800
Message-ID: <adad41nvgfc.fsf@roland-alpha.cisco.com>
References: <20100106065526.GB11368@localhost>
	<adahbqzvhgn.fsf@roland-alpha.cisco.com>
	<20100106071817.GA24428@localhost>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Cc: Andrew Morton <akpm@linux-foundation.org>,
	David Miller <davem@davemloft.net>,
	Stephen Rothwell <sfr@canb.auug.org.au>,
	Al Viro <viro@zeniv.linux.org.uk>,
	Christoph Hellwig <hch@infradead.org>,
	Eric Paris <eparis@redhat.com>,
	LKML <linux-kernel@vger.kernel.org>,
	"linux-fsdevel\@vger.kernel.org" <linux-fsdevel@vger.kernel.org>
To: Wu Fengguang <fengguang.wu@intel.com>
Return-path: <linux-kernel-owner+glk-linux-kernel-3=40m.gmane.org-S1755568Ab0AFHaf@vger.kernel.org>
In-Reply-To: <20100106071817.GA24428@localhost> (Wu Fengguang's message of
	"Wed, 6 Jan 2010 15:18:17 +0800")
Sender: linux-kernel-owner@vger.kernel.org
List-Id: linux-fsdevel.vger.kernel.org


 > Yeah, I chose the boot time check because of hweight32()..

One could do something like

#define HWEIGHT32(x) (!!((x) & (1u <<  0)) +
		      !!((x) & (1u <<  1)) +
//...
		      !!((x) & (1u << 31)));

that would probably work with BUILD_BUG_ON().

But as I said maybe it's too ugly.

 - R.