foo.cc: In function 'int func(int, std::__cxx11::string)':
foo.cc:36:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int j = i; j < str.size(); j++)
                     ~~^~~~~~~~~~~~
foo.cc: In function 'int main()':
foo.cc:22:23: warning: 'index' may be used uninitialized in this function [-Wmaybe-uninitialized]
     for (int i = 0; i <= index; i++)
                     ~~^~~~~~~~

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