Compilare: user.c: In function ‘var_new’: user.c:22:2: warning: implicit declaration of function ‘strdup’ [-Wimplicit-function-declaration] var->key = strdup(key); ^ user.c:22:11: warning: assignment makes pointer from integer without a cast [enabled by default] var->key = strdup(key); ^ user.c:23:13: warning: assignment makes pointer from integer without a cast [enabled by default] var->value = strdup(value); ^ user.c: In function ‘main’: user.c:134:9: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("convertor.out", "w", stdout); ^