foo.cc: In function ‘int main()’:
foo.cc:16:30: warning: unused variable ‘c’ [-Wunused-variable]
   16 |                         bool c=0;
      |                              ^
foo.cc:20:17: error: ‘c’ was not declared in this scope
   20 |                 c=1;
      |                 ^
foo.cc:21:20: error: ‘c’ was not declared in this scope
   21 |                 if(c)
      |                    ^