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std::ios_base::ios_base

(1) 
private:
ios_base( const ios_base& );
 (until C++11) 
public:
ios_base( const ios_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 std::basic_ios::init() 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, std::basic_ios. Further-derived classes (std::istream and std::ostream) are always constructed with a concrete stream buffer object and call std::basic_ios::init(), 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
LWG 50 C++98 the copy constructor was not specified specified as private
LWG 220 C++98 the behavior of destroying a std::ios_base
object before calling its init() was not clear		 the behavior is
undefined in this case
LWG 1249 C++98 initialization did not need to be completed before first use also needs to be completed

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