#include <ostream>
#include <cassert>
int seekpos_called = 0;
template <class CharT>
struct testbuf
: public std::basic_streambuf<CharT>
{
typedef std::basic_streambuf<CharT> base;
testbuf() {}
protected:
typename base::pos_type
seekpos(typename base::pos_type sp, std::ios_base::openmode which)
{
++seekpos_called;
assert(which == std::ios_base::out);
return sp;
}
};
int main()
{
{
std::ostream os((std::streambuf*)0);
assert(&os.seekp(5) == &os);
assert(seekpos_called == 0);
}
{
testbuf<char> sb;
std::ostream os(&sb);
assert(&os.seekp(10) == &os);
assert(seekpos_called == 1);
assert(os.good());
assert(&os.seekp(-1) == &os);
assert(seekpos_called == 2);
assert(os.fail());
}
}