string_marshalling.cs

#if HOGEHOGE

    struct FullName
    {
        [MarshalAs(UnmanagedType.LPStr)] public string first;
        [MarshalAs(UnmanagedType.LPStr)] public string last;
    }

    [DllImport(_dll)]
    static extern uint get_full_length(in FullName name);

    void RunFullNameTest()
      => Debug.Log(get_full_length(
           new FullName { first = "Keijiro", last = "Takahashi" }));

#else

    struct FullName
    {
        public IntPtr first;
        public IntPtr last;
    }

    [DllImport(_dll)]
    static extern uint get_full_length(in FullName name);

    void RunFullNameTest()
    {
        var p1 = Marshal.StringToHGlobalAnsi("Keijiro");
        var p2 = Marshal.StringToHGlobalAnsi("Takahashi");
        Debug.Log(get_full_length(new FullName { first = p1, last = p2 }));
        Marshal.FreeHGlobal(p1);
        Marshal.FreeHGlobal(p2);
    }

#endif