/in/ex1.c: In function 'main':
/in/ex1.c:5:19: error: 'x2' may be used uninitialized in this function [-Werror=maybe-uninitialized]
     dist=sqrt((x2 - x1)*(x2 - x1)*(y2 - y1)*(y2 - y1));
               ~~~~^~~~~
/in/ex1.c:15:17: note: 'x2' was declared here
     float x1,y1,x2,y2,dist;
                 ^~
cc1: all warnings being treated as errors