[Scummvm-devel] Being memory & speed efficient when dealing with C++ objects

[Philip Kendall]

On Sat, Jun 03, 2006 at 06:21:13PM +0200, Max Horn wrote:
> Hi there,
> 
> the following might be old news to some of you, but maybe a few  
> people out there can learn something from this, so I thought I post  
> it here anyway.
> 
> When dealing with objects in C++, one has to be careful if one wants  
> to be speed and memory efficient. C++ has this habit of copying  
> objects in places were you might not expect it. Especially if you are  
> from a Java / Python / other GC collected background.
> 
> Consider this statement:
>    String myStr = someOtherString;
> This is in fact equivalent to
>    String myStr;
>    myStr = someOtherString;
> In other words, it will first create the string object myStr (on the  
> stack). *Then* it will invoke the assignment operator, overriding the  
> default value of myStr.

Are you sure about this? Stroustrup gives the example of

int main ()
{
	string s = "Newton";	// string initalized (using copy constructor)
	s = g(s)
}

(Section 11.7, "Essential Operators" in my edition). My very quick tests
with g++ would appear to confirm this behaviour.

Cheers,

Phil

-- 
"I don't want a used ride. I want my motorcycle." "It's just a machine."
"It's an extension of my soul... if there is such a thing."
                        Max and Original Cindy: Dark Angel: 411 on the DL