/in/foo.c: In function 'main':
/in/foo.c:6:9: warning: 'xmin' is used uninitialized in this function [-Wuninitialized]
  if(xmin>xmax) {t=xmin;xmin=xmax;xmax=t;}
     ~~~~^~~~~
/in/foo.c:6:9: warning: 'xmax' is used uninitialized in this function [-Wuninitialized]
/in/foo.c:10:2: warning: 'sum' may be used uninitialized in this function [-Wmaybe-uninitialized]
  printf("%d",sum);
  ^~~~~~~~~~~~~~~~