/in/foo.c: In function 'qiu2':
/in/foo.c:30:20: warning: variable 'min' set but not used [-Wunused-but-set-variable]
  int big,small,max,min,z;
                    ^~~
/in/foo.c: In function 'main':
/in/foo.c:71:4: warning: operation on 'b3' may be undefined [-Wsequence-point]
  b3=b3/=max;
  ~~^~~~~~~~
/in/foo.c: In function 'qiu1':
/in/foo.c:25:5: warning: 'z' may be used uninitialized in this function [-Wmaybe-uninitialized]
  min=x*y/max;
  ~~~^~~~~~~~
/in/foo.c: In function 'qiu2':
/in/foo.c:50:9: warning: 'z' may be used uninitialized in this function [-Wmaybe-uninitialized]
  return max;
         ^~~
/in/foo.c: In function 'main':
/in/foo.c:70:4: warning: 'z' may be used uninitialized in this function [-Wmaybe-uninitialized]
  a3=a3/max;
  ~~^~~~~~~
/in/foo.c:25:5: warning: 'z' may be used uninitialized in this function [-Wmaybe-uninitialized]
  min=x*y/max;
  ~~~^~~~~~~~
/in/foo.c:6:24: note: 'z' was declared here
  int big,small,max,min,z;
                        ^