/in/foo.c: In function 'main':
/in/foo.c:5:28: warning: variable 'q' set but not used [-Wunused-but-set-variable]
 {double a,b,c,disc,x1,x2,p,q;
                            ^
/in/foo.c:5:26: warning: variable 'p' set but not used [-Wunused-but-set-variable]
 {double a,b,c,disc,x1,x2,p,q;
                          ^
/in/foo.c:10:2: warning: 'x1' is used uninitialized in this function [-Wuninitialized]
  printf("x1=%7.2f\nx2=%7.2f\n",x1,x2);
  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/in/foo.c:10:2: warning: 'x2' is used uninitialized in this function [-Wuninitialized]