Compilare: main.c: In function 'add': main.c:36:18: warning: array subscript has type 'char' [-Wchar-subscripts] if (node->child[ch] == NULL) { ^ main.c:37:18: warning: array subscript has type 'char' [-Wchar-subscripts] node->child[ch] = &mem[alloc_cnt++]; ^ main.c:38:18: warning: array subscript has type 'char' [-Wchar-subscripts] node->child[ch]->parent = node; ^ main.c:41:21: warning: array subscript has type 'char' [-Wchar-subscripts] node = node->child[ch]; ^ main.c: In function 'rm': main.c:54:21: warning: array subscript has type 'char' [-Wchar-subscripts] node = node->child[ch]; ^ main.c:60:14: warning: array subscript has type 'char' [-Wchar-subscripts] node->child[ch] = 0; ^ main.c: In function 'query': main.c:116:21: warning: array subscript has type 'char' [-Wchar-subscripts] node = node->child[ch]; ^ main.c: In function 'prefix': main.c:130:21: warning: array subscript has type 'char' [-Wchar-subscripts] node = node->child[ch]; ^ main.c: In function 'main': main.c:185:17: warning: unused variable 'buf' [-Wunused-variable] char line[32], buf[32]; ^~~ main.c: In function 'rm': main.c:65:1: warning: control reaches end of non-void function [-Wreturn-type] } ^ main.c: In function 'main': main.c:188:5: warning: ignoring return value of 'freopen', declared with attribute warn_unused_result [-Wunused-result] freopen( "trie.in", "r", stdin ); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ main.c:189:2: warning: ignoring return value of 'freopen', declared with attribute warn_unused_result [-Wunused-result] freopen( "trie.out", "w", stdout ); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ main.c:192:2: warning: ignoring return value of 'fgets', declared with attribute warn_unused_result [-Wunused-result] fgets(line, 32, stdin); ^~~~~~~~~~~~~~~~~~~~~~ main.c:208:3: warning: ignoring return value of 'fgets', declared with attribute warn_unused_result [-Wunused-result] fgets(line, 32, stdin); ^~~~~~~~~~~~~~~~~~~~~~