[BUG] CRepr zero-sized structs aren't zero-sized

[zerkawei]

Marking a zero-sized struct with CRepr adds a byte to it making its size no longer 0.

[CRepr]
public struct Foo {}
sizeof(Foo); // 1

I encountered this bug when trying to use System.Net.Socket where SockAddr_in inherits from SockAddr and therefore is offset by a byte and it breaks bind.

Here's a repro to observe the bug in action.

using System;
namespace Repro;

[CRepr]
public struct Foo {}

[CRepr]
public struct Bar : Foo
{
	public uint8 value1;
	public uint8 value2;
}

[CRepr]
public struct FooBar
{
	public uint8 value1;
	public uint8 value2;
}

public class Program
{
	public static void Main()
	{
		Bar bar;
		bar.value1 = 1;
		bar.value2 = 2;
		Console.WriteLine("bar : {}, {}", bar.value1, bar.value2); // bar : 1, 2

		FooBar foo = *(FooBar*)&bar;
		Console.WriteLine("foo : {}, {}", foo.value1, foo.value2); // foo : 0, 1

		Console.Read();
	}
}