Compilare: user.c: In function ‘add’: user.c:22:5: warning: implicit declaration of function ‘malloc’ [-Wimplicit-function-declaration] p->next = (item*)malloc(sizeof(item)); ^ user.c:22:22: warning: incompatible implicit declaration of built-in function ‘malloc’ [enabled by default] p->next = (item*)malloc(sizeof(item)); ^