std::basic_ios<CharT,Traits>:: rdstate

#include <iostream>
#include <sstream>
int main()
{
    std::ostringstream stream;
    if (stream.rdstate()== std::ios_base::goodbit)
        std::cout << "stream state is goodbit\n";
    stream.setstate(std::ios_base::eofbit);
    // 检查状态恰好为 eofbit（无 failbit 且无 badbit）
    if (stream.rdstate() == std::ios_base::eofbit)
        std::cout << "stream state is eofbit\n";
}