Compilare: main.c:13:6: warning: return type of 'main' is not 'int' [-Wmain] void main() { ^~~~ main.c: In function 'main': main.c:22:18: warning: implicit declaration of function 'calloc' [-Wimplicit-function-declaration] hashtable[i] = calloc(1300, sizeof(unsigned int)); ^~~~~~ main.c:22:18: warning: incompatible implicit declaration of built-in function 'calloc' main.c:22:18: note: include '<stdlib.h>' or provide a declaration of 'calloc' main.c:44:28: warning: implicit declaration of function 'realloc' [-Wimplicit-function-declaration] hashtable[index] = realloc(hashtable[index], j<<3); ^~~~~~~ main.c:44:28: warning: incompatible implicit declaration of built-in function 'realloc' main.c:44:28: note: include '<stdlib.h>' or provide a declaration of 'realloc' main.c:15:21: warning: unused variable 'flag' [-Wunused-variable] unsigned int n, o, flag; ^~~~ main.c:16:2: warning: ignoring return value of 'freopen', declared with attribute warn_unused_result [-Wunused-result] freopen("hashuri.in", "r", stdin); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ main.c:17:2: warning: ignoring return value of 'freopen', declared with attribute warn_unused_result [-Wunused-result] freopen("hashuri.out", "w", stdout); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ main.c:26:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &N); ^~~~~~~~~~~~~~~ main.c:30:3: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result] scanf("%u %u", &o, &n); ^~~~~~~~~~~~~~~~~~~~~~