explicit basic_ostream( std::basic_streambuf<CharT, Traits>* sb );
basic_ostream( const basic_ostream& rhs ) = delete;
(2) (since C++11)
basic_ostream( basic_ostream&& rhs );
(3) (since C++11)

1) Constructs the basic_ostream object, assigning initial values to the base class by calling basic_ios::init(sb).

2) The copy constructor is protected, and is deleted. Output streams are not copyable.

3) The move constructor uses basic_ios<CharT, Traits>::move(rhs) to move all basic_ios members, except for the rdbuf(), from rhs into *this. This move constructor is protected: it is called by the move constructors of movable output stream classes std::basic_ofstream and std::basic_ostringstream, which know how to correctly move the associated streambuffer.


sb - streambuffer to use as output sequence
rhs - basic_ostream to initialize from


Because basic_ios::init(sb) sets badbit when sb is a null pointer, and because basic_ostream::sentry does nothing if the stream is already in a failed state, writing to a stream constructed from a null pointer sb is a no-op.


#include <sstream>
#include <utility>
#include <iostream>
int main()
    // ERROR: copy ctor is deleted
//  std::ostream myout(std::cout);
    // OK: shares buffer with cout
    std::ostream myout(std::cout.rdbuf());
    // ERROR: move constructor is protected
//  std::ostream s2(std::move(std::ostringstream() << 7.1));    
    // OK: move ctor called through the derived class
    std::ostringstream s2(std::move(std::ostringstream() << 7.1)); 
    myout << s2.str() << '\n';
    std::ostream dev_null{nullptr}; // see Notes above
    dev_null << "no-op";



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