Compilare: main.c: In function 'add': main.c:53:18: warning: array subscript has type 'char' [-Wchar-subscripts] if (node->child[ch] == NULL) { ^ main.c:54:18: warning: array subscript has type 'char' [-Wchar-subscripts] node->child[ch] = mem + alloc_cnt++; ^ main.c:55:18: warning: array subscript has type 'char' [-Wchar-subscripts] node->child[ch]->parent = node; ^ main.c:58:21: warning: array subscript has type 'char' [-Wchar-subscripts] node = node->child[ch]; ^ main.c: In function 'rm': main.c:71:21: warning: array subscript has type 'char' [-Wchar-subscripts] node = node->child[ch]; ^ main.c:77:14: warning: array subscript has type 'char' [-Wchar-subscripts] node->child[ch] = 0; ^ main.c: In function 'query': main.c:119:21: warning: array subscript has type 'char' [-Wchar-subscripts] node = node->child[ch]; ^ main.c: In function 'prefix': main.c:133:21: warning: array subscript has type 'char' [-Wchar-subscripts] node = node->child[ch]; ^ main.c: In function 'main': main.c:156:17: warning: unused variable 'buf' [-Wunused-variable] char line[32], buf[32]; ^~~ main.c: In function 'rm': main.c:82:1: warning: control reaches end of non-void function [-Wreturn-type] } ^ main.c: In function 'main': main.c:159:5: warning: ignoring return value of 'freopen', declared with attribute warn_unused_result [-Wunused-result] freopen( "trie.in", "r", stdin ); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ main.c:160:2: warning: ignoring return value of 'freopen', declared with attribute warn_unused_result [-Wunused-result] freopen( "trie.out", "w", stdout ); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ main.c:163:2: warning: ignoring return value of 'fgets', declared with attribute warn_unused_result [-Wunused-result] fgets(line, 32, stdin); ^~~~~~~~~~~~~~~~~~~~~~ main.c:179:3: warning: ignoring return value of 'fgets', declared with attribute warn_unused_result [-Wunused-result] fgets(line, 32, stdin); ^~~~~~~~~~~~~~~~~~~~~~