From cppreference.com
private:ios_base(constios_base&); (1)(until C++11)public:ios_base(constios_base&)=delete;(since C++11)protected:ios_base(); (2) 1) The copy constructor is private(until C++11)deleted(since C++11): streams are not copyable.
2) The default constructor is protected: only derived classes may construct std::ios_base. The internal state is undefined after the construction. The derived class must call
to complete initialization before first use or before destructor; otherwise the behavior is undefined.
Notes
The same applies to the constructors of the next class in the I/O hierarchy,
. Further-derived classes (
and
) are always constructed with a concrete stream buffer object and call
, possibly more than once, to complete initialization of their virtual base.
Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
DR Applied to Behavior as published Correct behavior
C++98 the copy constructor was not specified specified as private
C++98 the behavior of destroying a std::ios_base
object before calling its
was not clear the behavior is
undefined in this case
C++98 initialization did not need to be completed before first use also needs to be completed