About ref used for performance reasons with struct

[Ali Çehreli]

On 02/11/2013 04:31 PM, jerro wrote:
 >> To be honest, up until recently, I mistakenly thought the compiler DID
 >> do this. (Yea, my mistake.)
 >>
 >> Is it possible I had confused structs with static arrays? Do static
 >> arrays do that?
 >
 > Maybe you were thinking about named return value optimization (which
 > applies to return values, not parameters)?

There is a corresponding optimization for parameters, which can be 
applied only in some cases.

The related guideline in C++ is this: If you are going to make a copy of 
the parameter inside the function anyway, take the parameter by-value. 
Here is a related article:

   http://cpp-next.com/archive/2009/08/want-speed-pass-by-value/

Especially this part: "Also, although the compiler is normally required 
to make a copy when a function parameter is passed by value (so 
modifications to the parameter inside the function can’t affect the 
caller), it is allowed to elide the copy, and simply use the source 
object itself, when the source is an rvalue."

Ali