linux-kernel - Re: A CodingStyle suggestion

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Message-Id: <20070203164042.237f156b.randy.dunlap@oracle.com>
Date:	Sat, 3 Feb 2007 16:40:42 -0800
From:	Randy Dunlap <randy.dunlap@...cle.com>
To:	Roland Dreier <rdreier@...co.com>
Cc:	"Ahmed S. Darwish" <darwish.07@...il.com>,
	Richard Knutsson <ricknu-0@...dent.ltu.se>,
	linux-kernel@...r.kernel.org
Subject: Re: A CodingStyle suggestion

On Sat, 03 Feb 2007 16:21:18 -0800 Roland Dreier wrote:

>  > Good catch :). A small grep of `access_ok' reveals that it's always used in the 
>  > form of:
>  > if (!access_ok()) { .. }
>  > 
>  > I can conclude that verbal/imperative methods like `kmalloc, add_work' be 
>  > checked as:
>  > ret = do_work();
>  > if (ret) { ... }
>  > and predicate methods like `acess_ok, pci_dev_present' be checked like:
>  > if (!access_ok) { ... }
>  > if (pci_dev_present) { ...}
>  > 
>  > Any comments ?
> 
> I don't think that's really the distinction that matters.  I think
> really the issue is that assignment within an if is hard to read, so
> 
> 	ret = foo(a, b);
>         if (ret) { ... }
> 
> is clearly preferred to
> 
> 	if ((ret = foo(a,b))) { ... }
> 
> However, in my opinion something like
> 
> 	if (foo(a,b)) { ... }
> 
> if perfectly fine if the return value of foo is not needed anywhere
> else.  In other words, there's no sense introducing a temporary
> variable to hold the return value if you're never going to do anything
> with it other than check it on the next line.

I agree with Roland's comments here.

And with Tim's about side effects.

---
~Randy
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