Compilare: user.c: In function ‘hash_clear’: user.c:43: warning: implicit declaration of function ‘memset’ user.c:43: warning: incompatible implicit declaration of built-in function ‘memset’ user.c: In function ‘main’: user.c:126: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result user.c:127: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result