foo.cc: In function ‘int main()’:
foo.cc:5:13: warning: unused variable ‘a’ [-Wunused-variable]
    5 |         int a,b,c;
      |             ^
foo.cc:5:17: warning: unused variable ‘c’ [-Wunused-variable]
    5 |         int a,b,c;
      |                 ^