tiny problem for cc

[blueshake]

hi,guys

I see that some codes in cc like this one.

e.g.

Code Select Expand

void functionname (const classname& var)
{
      classname localvar = var;
     ......

}



here,in the function body functionname, why it make a copy for "var".


if want to make a copy for "var",why not use it in this way??

Code Select Expand

void functionname (const classname var)
{
      //classname localvar = var;
     ......

}

correct me if I am wrong,thanks.

[oBFusCATed]

Why do you care?
Some people say that the second way of doing it might be faster ( http://cpp-next.com/archive/2009/08/want-speed-pass-by-value/ ).

[blueshake]

Thanks for your reply.

I am going to rewrite the cc search function,but I see that in some funciton body it make a copy for the function arguments,I dont know why it was used here,
e.g.

the function arguments (var) here.
is it relatived to something(like thread-safe or else)?

if not,I will omit it in my new cc search function.

[Loaden]

RVO optimization capability is very limited!

[thomas]

There might be no particular reason at all, or it might be not wanting to change the function's signature for SDK compatibility at a later time.