[Bug c++/52901] invalid rvalue reference

[marc.glisse at normalesup dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52901

Marc Glisse <marc.glisse at normalesup dot org> changed:

           What    |Removed                     |Added
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                 CC|                            |marc.glisse at normalesup
                   |                            |dot org

--- Comment #3 from Marc Glisse <marc.glisse at normalesup dot org> 2012-04-08 15:32:45 UTC ---
(In reply to comment #2)
> > X&& f() {
> >         X x;
> >         return std::move(x);
> > }
> 
> This function is unsafe, it returns a reference to a local variable. You
> probably meant it to return X not X&&
> 
> It is effectively the same as:
> 
> X& f() {
>    X x;
>    return x;
> }
> 
> (except G++ warns about that, because it's simpler)

Maybe this could be taken as a RFE for a warning with std::move? Many people
learning C++11 are bound to try similar things. g++ warns for

return X();
return static_cast<X&&>(x);

but not

return std::move(x);

I expect the case of std::move to be important enough that if doing a generic
warning is too hard, special-casing std::move could be worth the trouble
(assuming it is easier).