UnsafeSampleBehaviour.cs

using Unity.IL2CPP.CompilerServices;
using UnityEngine;


[Il2CppSetOption(Option.NullChecks, false)]
unsafe sealed class UnsafeSampleBehaviour : MonoBehaviour
{
    struct Point
    {
        public int x;
        public int y;
    }

    Point[] points = new Point[]
    {
        new Point(){y = 1},
        new Point(){y = 2},
        new Point(){y = 3},
    };

    unsafe void Awake()
    {
        // 配列のアドレスを固定
        int length = points.Length;
        fixed (Point* px = points)
        {
            // アクセス先をズラして構造体の中身を直接書き換えていく
            for (Point* p = px; p != px + length; ++p)
            {
                p->x = p->y;
            }
        }

        //　特定の構造体の中身を書き換える
        fixed (Point* p = &points[2]) { p->x = 12; }
    }

    [Il2CppSetOption(Option.ArrayBoundsChecks, false)]
    void Start()
    {
        for (int i = 0; i < points.Length; i++)
            Debug.Log(points[i].x);
    }
}