Question

帮助

在C ++中

    #pragma pack(push,1) 
typedef struct SIGMPGroup{
  int temp;
  char name[50]; //name of group
  int port; 
  char addr[50]; //network address "229."
  //int ttl;          //
  //int loop;         // 0 - no loop back, 1 - loop back

  SIGMPGroup():
  temp(0),
  port(0)
  //ttl(-1),
  //loop(0)
  {}
};
#pragma pack(pop)

C＃

public static SIGMPGroup DTIGMPGroup = new SIGMPGroup { temp = 56, name = "Example",port = 4000 };
   [StructLayout(LayoutKind.Explicit, Pack = 1, CharSet = CharSet.Ansi, Size = 108)]
   public struct SIGMPGroup{
     [FieldOffset(0)] 
     public int temp;
     [ FieldOffset(4), MarshalAs(UnmanagedType.ByValTStr,SizeConst=50)]
     public string name; //name of group
     [FieldOffset(54)]
     public int port;

     [FieldOffset(58), MarshalAs(UnmanagedType.ByValTStr, SizeConst = 50)]
     public string addr;

   }

    [DllImport(Eth_DLL, CallingConvention = CallingConvention.Cdecl)]
    public static extern void Leave(ref SIGMPGroup data);

   ImportFunctionEth.Leave(ref ImportFunctionEth.DTIGMPGroup);

运行后我有错误：无法从程序集“ConsoleApplication1，Version = 1.0.0.0，Culture = neutral，PublicKeyToken = null”加载类型“SIGMPGroup”，因为它包含偏移58处的对象字段，该字段未正确对齐或重叠字段不表示对象。

如果代码

 [FieldOffset(58), MarshalAs(UnmanagedType.ByValTStr, SizeConst = 50)]
 public string addr;

删除，全部工作。为什么？

只能像这样工作

   [StructLayout(LayoutKind.Sequential, Pack = 1, CharSet = CharSet.Ansi)]
   public struct SIGMPGroup{

     public int temp;
     [  MarshalAs(UnmanagedType.ByValTStr,SizeConst=50)]
     public string name; //name of group

     public int port;

     [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 50)]
     public string addr;

   }

Answer 1

不太确定该错误是什么，CLR似乎想要保持结构blittable出于某种神秘的原因。它肯定不是，字符串破坏了。最终错误是由端口字段引起的，它是错误的，违反了.NET内存模型的承诺，即 int 等简单类型的更新是原子的。它的偏移量被推到56，并与第二个字符串重叠。

StructLayout.Explicit可能很古怪，你可以提供很多帮助。通过不帮助简单解决：

[StructLayout(LayoutKind.Sequential, Pack = 1, CharSet = CharSet.Ansi)]
public struct SIGMPGroup {
    public int temp;
    [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 50)]
    public string name; //name of group
    public int port;
    [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 50)]
    public string addr;
}

...
Debug.Assert(Marshal.SizeOf(typeof(SIGMPGroup) == 108);   // fine

将带有2个C ++的数组导出到C＃中

1 个答案: