/in/ex3.c: In function 'ex3':
/in/ex3.c:12:13: error: format '%f' expects argument of type 'double', but argument 2 has type 'root {aka struct _root}' [-Werror=format=]
  printf("%.5f\n%.5f",myroot(a,b,c));
          ~~~^        ~~~~~~~~~~~~~
/in/ex3.c:12:19: error: format '%f' expects a matching 'double' argument [-Werror=format=]
  printf("%.5f\n%.5f",myroot(a,b,c));
                ~~~^
/in/ex3.c: In function 'myroot':
/in/ex3.c:20:9: error: suggest parentheses around arithmetic in operand of '^' [-Werror=parentheses]
  d = b^2-4*a*c;
        ~^~~~~~
/in/ex3.c:17:12: error: unused variable 'x2' [-Werror=unused-variable]
  double x1,x2;
            ^~
/in/ex3.c:17:9: error: unused variable 'x1' [-Werror=unused-variable]
  double x1,x2;
         ^~
cc1: all warnings being treated as errors