/in/foo.cc:25:5: warning: multi-character character constant [-Wmultichar]
  to[' $']='$ ';
     ^~~~
/in/foo.cc:25:11: warning: multi-character character constant [-Wmultichar]
  to[' $']='$ ';
           ^~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:25:11: warning: overflow in implicit constant conversion [-Woverflow]
/in/foo.cc:31:42: warning: array subscript has type 'char' [-Wchar-subscripts]
         while(S[i+len[i]]==to[S[i-len[i]]]) len[i]++;
                                          ^
/in/foo.cc:25:9: warning: array subscript is above array bounds [-Warray-bounds]
  to[' $']='$ ';
  ~~~~~~~^