Re: [Boost-users] shared_ptr as reference argument

19 Mar 2009

      What about RVO and NRVO?

You still can bind a temporary to a const reference. This is a simple
example on how it is possible to do optimizations. Or am I mistaken?

Example:

std::string foo();

void bar()
{
   std::string const& bound_temporary = foo();

   std::cout << bound_temporary;
}

whereas this is invalid:

void invalid_bar()
{
   std::string& bound_temporary = foo(); //will not work, but AFAIK some
compilers support it
}

So compilers can do optimizations based on constness.

Regards,
Ovanes

On Fri, Mar 20, 2009 at 12:15 AM, Emil Dotchevski
wrote:
...
On Thu, Mar 19, 2009 at 3:49 PM, Ovanes Markarian
 wrote:
...
For boost::shared_ptr it's the same. Nothing is copied in both cases.
Some
compilers might (which is under doubt) optimize it better. Since const is
an
additional information for them, that the object is not going to change
within the called function.
Const in a reference is merely part of the type safety system.
Compilers can not do optimizations based on the constness of a
reference, all they can do is report errors.
Emil Dotchevski
Reverge Studios, Inc.
http://www.revergestudios.com/reblog/index.php?n=ReCode