Compilare: user.c: In function ‘add’: user.c:23:3: warning: array subscript has type ‘char’ [-Wchar-subscripts] if(p->fii[s[k]] == &nul){ ^ user.c:24:5: warning: array subscript has type ‘char’ [-Wchar-subscripts] p->fii[s[k]] = (nod*) malloc(sizeof(nod)); ^ user.c:25:5: warning: array subscript has type ‘char’ [-Wchar-subscripts] *(p->fii[s[k]]) = nul; ^ user.c:27:3: warning: array subscript has type ‘char’ [-Wchar-subscripts] return add(p->fii[s[k]], s, k + 1, d); ^ user.c: In function ‘main’: user.c:89:5: warning: array subscript has type ‘char’ [-Wchar-subscripts] while(p != &root && p->fii[x] == &nul) ^ user.c:91:5: warning: array subscript has type ‘char’ [-Wchar-subscripts] if(p->fii[x] != &nul) ^ user.c:92:7: warning: array subscript has type ‘char’ [-Wchar-subscripts] p = p->fii[x]; ^ user.c:70:8: warning: ignoring return value of ‘fgets’, declared with attribute warn_unused_result [-Wunused-result] fgets(s, MAXL + 2, in); ^ user.c:72:9: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] fscanf(in, "%d ", &n); ^ user.c:77:10: warning: ignoring return value of ‘fgets’, declared with attribute warn_unused_result [-Wunused-result] fgets(cuv, MAXC + 2, in); ^