/in/foo.cc: In function 'int findFirstNonZero(std::string&)':
/in/foo.cc:38:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   38 |     for (int i = 0; i < str.length(); i++) {
      |                     ~~^~~~~~~~~~~~~~
/usr/bin/ld: /usr/lib/gcc/x86_64-linux-gnu/12/../../../x86_64-linux-gnu/Scrt1.o: in function `_start':
(.text+0x17): undefined reference to `main'
collect2: error: ld returned 1 exit status