/in/foo.cc: In function 'int main()':
/in/foo.cc:53:20: warning: array subscript has type 'char' [-Wchar-subscripts]
   extend(ref[str[i]]);
                    ^
/in/foo.cc:60:31: warning: array subscript has type 'char' [-Wchar-subscripts]
    if (t[pos].trans[ref[str[j]]])
                               ^
/in/foo.cc:65:32: warning: array subscript has type 'char' [-Wchar-subscripts]
     pos=t[pos].trans[ref[str[j]]];
                                ^
/in/foo.cc:69:41: warning: array subscript has type 'char' [-Wchar-subscripts]
     while (pos&&!t[pos].trans[ref[str[j]]])
                                         ^
/in/foo.cc:76:32: warning: array subscript has type 'char' [-Wchar-subscripts]
     pos=t[pos].trans[ref[str[j]]];
                                ^