strange no error within C# application

Question

I have a c# application in which i have this code :

 public static void Main()
        {
            int i = 2147483647;
            int j = i+1;
            Console.WriteLine(j);
            Console.ReadKey();
        }

The result is : -2147483648

I know that every integer must be < 2147483648. So

• Why I don't have a compilation or runtime error? like in this exemple

• What is the reason of the negative sign?

thanks

Answer 1

The compiler defaults to unchecked arithmetic; you have simply overflown and looped around, thanks to two's-complement storage.

This fails at runtime:

public static void Main()
{
    int i = 2147483647;
    int j = checked((int)(i + 1)); // <==== note "checked"
    Console.WriteLine(j);
    Console.ReadKey();
}

This can also be enabled globally as a compiler-switch.