foo.cc: In function 'int f(std::string)':
foo.cc:5:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
    5 |         for(int i=0;i<a.size();i++){
      |                     ~^~~~~~~~~
foo.cc:19:20: warning: 's' may be used uninitialized [-Wmaybe-uninitialized]
   19 |                 sum+=s;
      |                 ~~~^~~
foo.cc:6:21: note: 's' was declared here
    6 |                 int s;
      |                     ^

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