foo.cc: In function 'int main()':
foo.cc:20:14: warning: format '%d' expects argument of type 'int', but argument 2 has type 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wformat=]
   20 |     printf("%d\n", v.size());
      |             ~^     ~~~~~~~~
      |              |           |
      |              int         std::vector<int>::size_type {aka long unsigned int}
      |             %ld

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