linux-kernel - Re: [PATCH 1/6] staging: android: binder: Remove some funny && usage

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Date:	Wed, 17 Jun 2009 09:31:16 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Daniel Walker <dwalker@...o99.com>
CC:	Greg Kroah-Hartman <greg@...ah.com>,
	Brian Swetland <swetland@...gle.com>, arve@...roid.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/6] staging: android: binder: Remove some funny	&&	usage

On 06/17/09 09:08, Daniel Walker wrote:
> On Wed, 2009-06-17 at 08:28 -0700, Jeremy Fitzhardinge wrote:
>    
>> I have a general code-cleanup rule to
>> convert:
>>
>> 	foo = false;
>> 	if (something_is_true())
>> 		foo = true;
>>
>> to
>>
>> 	foo = something_is_true();
>>      
>
> Above seems more like a speed up, rather than a clean up. I would think
> it's likely fine for a lot of cases tho.
>    

The compiler should be smart enough to generate identical code in both 
cases.  I think the second is better because it more directly expresses 
what you're trying to do: you have a boolean predicate, and you're 
assigning it to a boolean variable.  The if() form has the same effect, 
but couches it in terms of control flow which is just obfuscation.

> I was hoping Brian could explain this. I also added Arve (the author) to
> the CC list. Maybe they can explain the purpose of the subsystem.
>    

Also, what its usermode ABI is, how stable it is, whether its generally 
useful, does it have glibc/other library support, etc.  Would you ever 
want to use this in a non-Android context?

> Was this a recent change to C99, cause my compiler still doesn't know
> about it .. I also see a couple places in the kernel where bool is
> getting typedef'ed or somehow declared..
>    

The C99 type has some stupid name like "_Bool", but the kernel typedefs 
it to bool everywhere.

     J
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