/in/foo.c: In function 'main':
/in/foo.c:6:4: warning: statement with no effect [-Wunused-value]
  k1<=k2;
  ~~^~~~
/in/foo.c:7:9: warning: zero-length gnu_printf format string [-Wformat-zero-length]
  printf("");
         ^~
/in/foo.c:9:7: warning: statement with no effect [-Wunused-value]
  for(i>=k1;i<=k2;i++)
      ~^~~~
/in/foo.c:6:4: warning: 'k1' is used uninitialized in this function [-Wuninitialized]
  k1<=k2;
  ~~^~~~
/in/foo.c:6:4: warning: 'k2' is used uninitialized in this function [-Wuninitialized]
/in/foo.c:16:2: warning: 'sum' may be used uninitialized in this function [-Wmaybe-uninitialized]
  printf("%d",sum);
  ^~~~~~~~~~~~~~~~
/in/foo.c:9:19: warning: 'i' may be used uninitialized in this function [-Wmaybe-uninitialized]
  for(i>=k1;i<=k2;i++)
                  ~^~