std::ios_base::operator=

From cppreference.com
< cpp‎ | io‎ | ios base
private :
ios_base& operator= ( const ios_base& ) ;
(until C++11)
public :
ios_base& operator= ( const ios_base& ) = delete;
(since C++11)

The copy assignment operator is private(until C++11) deleted(since C++11)

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR Applied to Behavior as published Correct behavior
LWG 50 C++98 the copy assignment operator was not specified specified as private