/in/foo.cc: In function 'int main()':
/in/foo.cc:5:9: warning: empty parentheses were disambiguated as a function declaration [-Wvexing-parse]
    5 | thread t();
      |         ^~
/in/foo.cc:5:9: note: remove parentheses to default-initialize a variable
    5 | thread t();
      |         ^~
      |         --
/in/foo.cc:5:9: note: or replace parentheses with braces to value-initialize a variable
/in/foo.cc:6:3: error: request for member 'join' in 't', which is of non-class type 'std::thread()'
    6 | t.join();
      |   ^~~~