27.ostream.unformatted.stdcxx-626.cpp

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#include <cassert>
#include <ostream>
 
int sync_calls;
 
struct MyBuf: std::streambuf
{
    virtual int sync () {
        ++sync_calls;
        return -1;
    }
};
 
 
int main ()
{
    MyBuf buf;
 
    std::ostream os (&buf);
 
    // verify that ostream::flush() doesn't call streambuf::sync()
    // when the state of the stream isn't good
 
    os.setstate (os.badbit);
 
    os.flush ();
 
    assert (0 == sync_calls);
 
    os.setstate (os.eofbit);
 
    os.flush ();
 
    assert (0 == sync_calls);
 
    os.setstate (os.failbit);
 
    os.flush ();
 
    assert (0 == sync_calls);
 
    return 0;
}