Compilare: user.c: In function ‘cmmdc’: user.c:17:1: warning: control reaches end of non-void function [-Wreturn-type] } ^ user.c: In function ‘main’: user.c:21:12: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("cmmdc.in","r",stdin); ^ user.c:22:12: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("cmmdc.out","w",stdout); ^ user.c:24:6: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&a,&b); ^