On 09/09/2011 08:23 AM, leon zadorin wrote:
Hi everyone.
Just started looking-into/reading-on c++0x rvalue refs and would like
clarification on the following code being compiled by gcc v 4.6.1 (on
freebsd 8.2 release, amd64):
#include<iostream>
struct init {};
struct x {
template<typename InitPolicy>
void
init_from(InitPolicy const& x)
{
::std::cout<< "by ref\n";
}
template<typename InitPolicy>
void
init_from(InitPolicy&& x)
{
::std::cout<< "by rvalue ref possibly stealing resources held by x\n";
}
};
int
main()
{
x x1;
init i;
x1.init_from(i);
return 0;
}
compiled with:
c++ -std=c++0x main.cc
produces:
"by rvalue ref possibly stealing resources held by x"
From various experiments, the above 'x1.init_from(i)' binds as
'x1.init_from<init&>(i)' [as opposed to 'x1.init_from<init>(i)]... but
even if so -- I was wondering how does this correlate with the
following quote from wiki on c++11:
http://en.wikipedia.org/wiki/C%2B%2B0x#Rvalue_references_and_move_constructors
"... A named variable will never be considered to be an rvalue even if
it's declared as such; in order to get an rvalue, the function
template std::move<T>() should be used ..."
I am most likely missing something simple here (just starting to read
no rval refs...)
What you are missing is that the '&&' modifier for an argument to a
*template* function has a different meaning than it does for a regular
function.
--
Kevin P. Fleming
Digium, Inc. | Director of Software Technologies
Jabber: kfleming@xxxxxxxxxx | SIP: kpfleming@xxxxxxxxxx | Skype: kpfleming
445 Jan Davis Drive NW - Huntsville, AL 35806 - USA
Check us out at www.digium.com & www.asterisk.org
