Compilare: user.c: In function 'main': user.c:12: warning: conversion lacks type at end of format user.c:12: warning: too many arguments for format user.c:13: warning: implicit declaration of function 'calloc' user.c:13: warning: incompatible implicit declaration of built-in function 'calloc' user.c:24: warning: conversion lacks type at end of format user.c:24: warning: too many arguments for format user.c:58: warning: implicit declaration of function 'free'