foo.cc: In function 'void Test()':
foo.cc:11:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   11 |  for (int i = 0; i < a.length(); i++)
      |                  ~~^~~~~~~~~~~~
foo.cc:16:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   16 |    for (j = 0; j < a1.length(); j++)
      |                ~~^~~~~~~~~~~~~
foo.cc:24:10: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   24 |    if (j == a1.length())
      |        ~~^~~~~~~~~~~~~~

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