foo.cc: In function ‘int main()’:
foo.cc:9:26: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::__cxx11::basic_string<char>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
    9 |         for (int i = 0;i < line.length();i++)
      |                        ~~^~~~~~~~~~~~~~~
foo.cc:12:34: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::__cxx11::basic_string<char>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   12 |                 for (int j = 0;j < strf.length() && i <= line.length() - strf.length();j++)
      |                                ~~^~~~~~~~~~~~~~~
foo.cc:12:55: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::__cxx11::basic_string<char>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   12 |                 for (int j = 0;j < strf.length() && i <= line.length() - strf.length();j++)
      |                                                     ~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
foo.cc:15:31: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::__cxx11::basic_string<char>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   15 |                         if (j == strf.length() - 1)
      |                             ~~^~~~~~~~~~~~~~~~~~~~