/in/foo.c: In function 'prime':
/in/foo.c:6:23: error: 'false' undeclared (first use in this function)
   if (num < 2) return false;
                       ^~~~~
/in/foo.c:6:23: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:12:12: error: 'true' undeclared (first use in this function)
     return true;
            ^~~~
/in/foo.c:4:6: warning: unused variable 'count' [-Wunused-variable]
  int count=0;
      ^~~~~
/in/foo.c:13:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^