[Bug libstdc++/42593] [c++0x] [4.5 Regression] std::bind not assignable to std::function

["redi at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #3 from redi at gcc dot gnu dot org  2010-01-03 15:07 -------
>From a quick look, I think the problem is that std::function now uses perfect
forwarding, but std::bind doesn't yet.
So invoking the function passes an rvalue to _Bind::operator() which fails to
bind to _Args&
Previously, std::function took its arguments by value, and
_Bind::operator()(_Args&...) bound an lvalue reference to that by-value
parameter:
      return _M_invoker(_M_functor, __args...);

Now it does this:

      return _M_invoker(_M_functor, std::forward<_ArgTypes>(__args)...);

and so the rvalue cannot bind to _Args&

This will be fixed when std::bind supports rvalue references. I was going to
finish those changes after updating <future>, but I have been delayed by some
unexpected events and am away from my home PC which contains my work in
progress.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42593