linux-kernel - Re: [PATCH v2] fs: O_* bit numbers uniqueness check

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Date:	Tue, 05 Jan 2010 23:30:31 -0800
From:	Roland Dreier <rdreier@...co.com>
To:	Wu Fengguang <fengguang.wu@...el.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	David Miller <davem@...emloft.net>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Al Viro <viro@...iv.linux.org.uk>,
	Christoph Hellwig <hch@...radead.org>,
	Eric Paris <eparis@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"linux-fsdevel\@vger.kernel.org" <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH v2] fs: O_* bit numbers uniqueness check


 > 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.
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