View Compilation Error

0_0_16936875_17495.cpp: In function 'int main()':
0_0_16936875_17495.cpp:48:52: error: cannot pass objects of non-trivially-copyable type 'std::string {aka class std::basic_string<char>}' through '...'
                           printf("%s + %s = ",s1,s2);
                                                    ^
0_0_16936875_17495.cpp:48:52: error: cannot pass objects of non-trivially-copyable type 'std::string {aka class std::basic_string<char>}' through '...'