/in/foo.cc: In function 'int canlink(std::__cxx11::string, std::__cxx11::string)':
/in/foo.cc:7:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i = 1; i < min(str1.length(), str2.length()); i++) {//重叠长度从1开始，直到最短的字符串长度-1（因为不能包含）
                    ~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/in/foo.cc: At global scope:
/in/foo.cc:27:6: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
 main() {
      ^