[Bug c++/53990] wrong "optimisation": automatic variable doesn't removed at fuction exit

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53990

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|wrong-code                  |accepts-invalid
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID
           Severity|major                       |normal

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> 2012-07-17 06:00:37 UTC ---
>Is this optimization in C++ standard?

Yes it is the named return value optimization which is part of the C++
standard.

>        A[2] = E[1];  //it works. but should it work?

This code is valid but most likely does not do what you want it to do.
In that it creates a temporary variable (a rvalue) to hold A[2].  Then it calls
operator= on that rvalue (which is valid).