David Abrahams wrote:
The example below shows a technique for perfect forwarding that seems to work with GCC 3.3.1. rvalues are always moved automatically, and lvalues are copied. [...] may have missed something. *If* my example actually works other than this case, I'd like to try to get the rule lifted, and soon! This is by no means the cleanest route to move semantics, but it's probably the smallest "language extension" we'd ever need to get it, and might even be possible before C++0x
I already mentioned during the improved auto_ptr discussions that I'm not smart enough to use the new trick in order to introduce move semantics. It seems that you amazingly did it!
Except for one rather important case, it works with Comeau (errors only in strict mode). The important case that causes the error clearly violates 12.2/1 of the standard, but see below.
The problem with reference binding using conversion operator/constructor(i.e. X const& r = X()) is addressed in active DR #291 (see Mr. Adamczyk note) and AFAICT it was discussed during the MoJo days. IMHO the current standard explicitly allows it (per 8.5.3/5/2/1) and EDG is not very consistent about it: auto_ptr<Base> const& r = auto_ptr<Derived>(); // accepted by EDG auto_ptr<Base> const& r = auto_ptr<Base>(); // rejected by EDG Thank you, Rani