/in/foo.cc: In function 'int main()':
/in/foo.cc:6:13: warning: 'c' is used uninitialized in this function [-Wuninitialized]
  while(c>'9'||c<'0')
        ~~~~~^~~~~~~
/in/foo.cc:5:19: note: 'c' was declared here
  int s=0,f=1;char c;
                   ^
/in/foo.cc:5:19: warning: 'c' may be used uninitialized in this function [-Wmaybe-uninitialized]
/in/foo.cc:5:19: warning: 'c' may be used uninitialized in this function [-Wmaybe-uninitialized]