tcgetattr Marshalling fun for .Net 5

Program.cs

using System;
using System.Runtime.InteropServices;

namespace SysRplSerialPort
{
    [StructLayout(LayoutKind.Explicit)]
    public struct TermiosStruct
    {
        [MarshalAs(UnmanagedType.U4), FieldOffset(0)]
        public uint c_iflag;

        [MarshalAs(UnmanagedType.U4), FieldOffset(4)]
        public uint c_oflag;

        [MarshalAs(UnmanagedType.U4), FieldOffset(8)]
        public uint c_cflag;

        [MarshalAs(UnmanagedType.U4), FieldOffset(12)]
        public uint c_lflag;

        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 33), FieldOffset(16)]
        public byte[] c_cc;

        [MarshalAs(UnmanagedType.U4), FieldOffset(52)]
        public uint c_ispeed;

        [MarshalAs(UnmanagedType.U4), FieldOffset(56)]
        public uint c_ospeed;

        public static TermiosStruct Default
        {
            get => new TermiosStruct { c_cc = new byte[33] };
        }
    }

    class Program
    {
        [DllImport("libc", CallingConvention = CallingConvention.Cdecl, EntryPoint = "tcgetattr")]
        public static extern int tcgetattr(int fd, ref TermiosStruct term);

        [DllImport("libc", EntryPoint = "open")]
        private static extern int open(string fileName, int mode);
        [DllImport("libc", EntryPoint = "ioctl", SetLastError = true)]
        private static extern int ioctl(int fd, int request, int data);
        [DllImport("libc", EntryPoint = "read", SetLastError = true)]
        private static extern int read(int handle, byte[] data, int length);
        [DllImport("libc", EntryPoint = "write", SetLastError = true)]
        private static extern int write(int handle, byte[] data, int length);

        // constants for i2c
        private static int O_RDWR = 2;
        private static int O_NOCTTY = 0400;

        static void Main(string[] args)
        {
            Console.WriteLine("Hello World!");

            var term = TermiosStruct.Default;
            // this writes 33 correctly
            Console.WriteLine(term.c_cc.Length);
            tcgetattr(open("/dev/ttyS0", O_RDWR | O_NOCTTY), ref term);
            // exception here as c_cc is now null
            Console.WriteLine(term.c_cc.Length);
        }
    }
}