From: "Américo Wang" <xiyou.wangcong@gmail.com>
To: Rofail Qu <rofail@gmail.com>
Cc: linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: A simple question of sys_
Date: Mon, 20 Sep 2010 15:48:38 +0800 [thread overview]
Message-ID: <20100920074838.GB5503@cr0.nay.redhat.com> (raw)
In-Reply-To: <AANLkTintKaxaAKarDPFgpDLQMVomhThYtZecp5R5Mi62@mail.gmail.com>
On Fri, Sep 17, 2010 at 02:58:30PM +0800, Rofail Qu wrote:
>How to use macro IS_ERR() ?
>
>It defines as,
>...
>#define IS_ERR_VALUE(x) unlikely((x) >= (unsigned long)-MAX_ERRNO)
>static inline long __must_check IS_ERR(const void *ptr)
>{
> return IS_ERR_VALUE((unsigned long)ptr);
>}
>...
>so when pass x as a pointer and x>=-MAX_ERRNO (including NULL or any
>valid address),
>IS_ERR() will return true!
NULL is not an error pointer, you missed the cast to unsigned long.
>IS_ERR(x) seems to use on judge if "x" is a valid error number, right?
>
Strictly speaking, it checks if 'x' is an error pointer.
next prev parent reply other threads:[~2010-09-20 7:44 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-17 6:58 Rofail Qu
2010-09-17 18:55 ` Randy Dunlap
2010-09-20 8:34 ` Rofail Qu
2010-09-20 15:28 ` Randy Dunlap
2010-09-20 7:48 ` Américo Wang [this message]
2010-09-20 8:28 ` Rofail Qu
2010-09-21 7:53 ` Américo Wang
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