foo.cc: In function 'int sti(std::string)':
foo.cc:7:25: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
    7 |         for(int i = 0;i < a.length();i++)
      |                       ~~^~~~~~~~~~~~
foo.cc: In function 'std::string stradd(std::string, std::string)':
foo.cc:16:9: error: 'ret1' was not declared in this scope
   16 |         ret1 = a.length() >= b.length() ? a : b;
      |         ^~~~
foo.cc:17:9: error: 'ret2' was not declared in this scope
   17 |         ret2 = b.length() > a.length() ? a : b;
      |         ^~~~
foo.cc: In function 'std::string strmult(std::string, std::string)':
foo.cc:41:9: error: 'ret' was not declared in this scope
   41 |         ret = "0";
      |         ^~~
foo.cc: In function 'int main()':
foo.cc:58:18: error: no 'operator++(int)' declared for postfix '++' [-fpermissive]
   58 |                 t++;
      |                 ~^~

[Hydro](https://hydro.ac)提供评测服务