[prev in list] [next in list] [prev in thread] [next in thread] 

List:       kde-core-devel
Subject:    Re: Krazy: prefix vs. postfix ++ and -- operators
From:       Matthew Dawson <matthew () mjdsystems ! ca>
Date:       2011-01-11 18:09:59
Message-ID: 201101111310.04949.matthew () mjdsystems ! ca
[Download RAW message or body]


On Tuesday 11 January 2011 12:36:49 Artur de Souza wrote:
> 
> Quoting Rafa? Mi?ecki <zajec5@gmail.com>:
> > Doesn't compiler optimize than anyway, when possible (like inside
> > for)? I was told that when I tried using post incr. in kernel.
> 
> You're right. Most of the compilers take care of that today, so you  
> don't have to worry about this anymore.
> Of course you can defend one or another based on code readability and  
> coding style, but performance-wise it shouldn't be a problem with  
> modern compilers.
> 
> Cheers,
> 
Compilers can only optimize away this code when then can guarantee that no side \
effects occur.  For things like iterators, this can be very hard unless the whole \
iterator is inline and the compiler can verify this.  For instance, a simplistic \
iterators post incr.: Iterator operator++(Iterator){
	Iterator temp = *this;
	++(*this);
	return temp;
}

Which incurs the assignment operator.

Of course, for standard types the compiler can optimize this away.  For C this means \
the compiler can optimize all post incr. as there is no operator overloading, thus \
why the kernel developers don't care.

Matthew


["signature.asc" (application/pgp-signature)]

[prev in list] [next in list] [prev in thread] [next in thread]