Compilare: user.c: In function ‘main’: user.c:25: warning: implicit declaration of function ‘malloc’ user.c:25: warning: incompatible implicit declaration of built-in function ‘malloc’ user.c:39: warning: implicit declaration of function ‘free’ user.c:39: warning: incompatible implicit declaration of built-in function ‘free’ user.c:24: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result user.c:27: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result