On Sat, 30 Jun 2012, Steven Watanabe wrote:
On 06/30/2012 11:08 AM, John Maddock wrote:
The safe solution is returning Number, not Number&&. If Dave reads this message, he can probably point us to previous discussions about this. Being able to return Number&& would be great...
Can you explain why it's unsafe given that we know that the value returned is an rvalue ref already?
I'm guessing that it has something to do with temporary lifetimes?
I think so. Trying to find back how some people managed to convince me it was unsafe, all I managed to find right now is a statement by Dave that Howard generally advised against function returning rvalue references... One easy issue I can see (in code right in front of me) is: const NT& result=a*d-b*c; Using const references instead of plain variables is something that quite a number of people do, and which (I think) would fail if operator- returned a reference. Note that it also means that the unary operator+ (which I hope noone ever uses) is "unsafe" in a number of libraries. -- Marc Glisse