/in/foo.cc:12:26: warning: multi-character character constant [-Wmultichar]
   12 |     const int max_val = 1'000'000;
      |                          ^~~~~
/in/foo.cc: In function 'void precompute_primes()':
/in/foo.cc:12:26: error: expected ',' or ';' before '\x303030'
/in/foo.cc: In function 'bool is_prime_ll(ll)':
/in/foo.cc:29:15: warning: comparison of integer expressions of different signedness: 'int' and 'll' {aka 'long long unsigned int'} [-Wsign-compare]
   29 |         if (p > sqrt_x) break;
      |             ~~^~~~~~~~