Compilare: user.c: In function ‘push’: user.c:10:33: warning: implicit declaration of function ‘malloc’ [-Wimplicit-function-declaration] struct Node* temp = (struct Node*)malloc(sizeof(struct Node)); ^ user.c:10:39: warning: incompatible implicit declaration of built-in function ‘malloc’ [enabled by default] struct Node* temp = (struct Node*)malloc(sizeof(struct Node)); ^ user.c: In function ‘pop’: user.c:19:5: warning: implicit declaration of function ‘free’ [-Wimplicit-function-declaration] free(temp); ^ user.c:19:5: warning: incompatible implicit declaration of built-in function ‘free’ [enabled by default] user.c: In function ‘main’: user.c:36:8: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("par.in", "r", stdin); ^ user.c:37:8: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("par.out", "w", stdout); ^ user.c:39:6: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &N); ^