From: Ingo Molnar <mingo@elte.hu>
To: Bart Van Assche <bart.vanassche@gmail.com>
Cc: Julia Lawall <julia@diku.dk>, Christopher Li <sparse@chrisli.org>,
yi.zhu@intel.com, linux-wireless@vger.kernel.org,
ipw3945-devel@lists.sourceforge.net,
linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org,
Harvey Harrison <harvey.harrison@gmail.com>,
Alexander Viro <viro@ftp.linux.org.uk>,
linux-sparse@vger.kernel.org,
Josh Triplett <josh@freedesktop.org>
Subject: Re: [PATCH 6/9] drivers/net/wireless/iwlwifi/iwl-4965.c: Correct use of ! and &
Date: Wed, 5 Mar 2008 13:36:42 +0100 [thread overview]
Message-ID: <20080305123641.GA2365@elte.hu> (raw)
In-Reply-To: <e2e108260803050430o317d3e0dyed50e86cc4569746@mail.gmail.com>
* Bart Van Assche <bart.vanassche@gmail.com> wrote:
> If someone writes (!x & !y) instead of (!x && !y) because both x and y
> have to be evaluated, this means that both x and y have side effects.
> Please keep in mind that the C language does not specify whether x or
> y has to be evaluated first, so if x and y have to be evaluated in
> that order, an expression like (!x & !y) can be the cause of very
> subtle bugs. I prefer readability above brevity.
such expressions _must_ be written as:
ret1 = x();
ret2 = y();
if (ret1 && ret2)
...
any side-effects are totally un-obvious when they are in expressions and
someone doing cleanups later on could easily change the '&' to '&&' and
introduce a bug.
Ingo
next prev parent reply other threads:[~2008-03-05 12:37 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-02-26 20:44 [PATCH 6/9] drivers/net/wireless/iwlwifi/iwl-4965.c: Correct use of ! and & Julia Lawall
2008-02-26 22:47 ` Tomas Winkler
2008-02-27 0:59 ` John W. Linville
2008-03-05 6:38 ` Ingo Molnar
2008-03-05 6:49 ` Christopher Li
2008-03-05 7:02 ` Ingo Molnar
2008-03-05 7:09 ` Harvey Harrison
2008-03-05 8:19 ` Ingo Molnar
2008-03-05 12:13 ` Derek M Jones
2008-03-05 8:55 ` Julia Lawall
2008-03-05 12:20 ` Ingo Molnar
2008-03-05 12:30 ` Bart Van Assche
2008-03-05 12:36 ` Ingo Molnar [this message]
2008-03-05 12:35 ` Julia Lawall
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