/in/foo.cc: In function 'int main()':
/in/foo.cc:7:29: warning: format '%d' expects argument of type 'int', but argument 2 has type '__gnu_cxx::__enable_if<true, double>::__type' {aka 'double'} [-Wformat=]
    7 |                 printf("OK %d",log2(n+1));
      |                            ~^  ~~~~~~~~~
      |                             |      |
      |                             int    __gnu_cxx::__enable_if<true, double>::__type {aka double}
      |                            %f