使用非托管 C++ DLL 的 AccessViolationException

Question

我第一次尝试在 C# 应用程序中使用非托管 C++ DLL ("res_lib")。我已使用 cppsharp 生成 PInvoke 代码：例如，我尝试调用的 functions/methods 之一是 get_system_snapshot。在 .h 文件中，这被定义为

SYS_INT SYS_ERR get_system_snapshot(SNAPSHOT_PARMS* snapshotp);

SYS_INT 和 SYS_ERR 等同于 int32_t。 SNAPSHOT_PARMS 是

typedef struct SNAPSHOT_PARMS
{
    SYS_ULONG   size;
    SYS_UINT    count;
    SYS_CHAR    serial_no[600];
} SYS_PACK_DIRECTIVE SYS_SNAPSHOT_PARMS;

cppsharp 已将其转换为以下代码片段：

DllImport

[SuppressUnmanagedCodeSecurity]
[DllImport("res_lib", CallingConvention = CallingConvention.StdCall,
                EntryPoint="get_system_snapshot")]       
   internal static extern int GetSystemSnapshot(IntPtr snapshotp);

对象

 public unsafe partial class SNAPSHOT_PARMS : IDisposable
    {
 [StructLayout(LayoutKind.Explicit, Size = 608)]
  public partial struct __Internal
    {
        [FieldOffset(0)]
        internal uint size;

        [FieldOffset(4)]
        internal uint count;

        [FieldOffset(8)]
        internal fixed sbyte serial_no[600];

        [SuppressUnmanagedCodeSecurity]
        [DllImport("res_lib", CallingConvention = global::System.Runtime.InteropServices.CallingConvention.ThisCall,
            EntryPoint="??0SNAPSHOT_PARMS@@QAE@ABU0@@Z")]
        internal static extern global::System.IntPtr cctor(global::System.IntPtr instance, global::System.IntPtr _0);
    }
}

 public SNAPSHOT_PARMS()
        {
             __Instance = Marshal.AllocHGlobal(sizeof(global::res_lib.SNAPSHOT_PARMS.__Internal));         
            __ownsNativeInstance = true;
            NativeToManagedMap[__Instance] = this;
        }

主要代码

  static void Main(string[] args)
        {
            SNAPSHOT_PARMS p = new SNAPSHOT_PARMS();
            var result = res_lib.res_lib.GetSystemSnapshot(p);
        }

 public static unsafe int GetSystemSnapshot(global::res_lib.SNAPSHOT_PARMS snapshotp)
        {         
            var __arg0 = ReferenceEquals(snapshotp, null) ? global::System.IntPtr.Zero : snapshotp.__Instance;
            var __ret = __Internal.GetSystemSnapshot(out __arg0);
            return __ret;
        }

调用函数时，我得到了臭名昭著的：

Attempted to read or write protected memory. This is often an indication that other memory is corrupt.

我尝试将 CallingConvention 从 StdCall 更改为 Cdecl，将 [In] 和 [Out] 引入 DllImport 等，但都无济于事。任何人都可以看出代码有任何明显的错误吗 - 很明显，这对我来说是全新的，也许我对 cppsharp 生成不需要调整的代码的要求有点高。

EDIT 原始 C++ 文档有一个示例，其中结构由

初始化

#define INIT_STRUCT(struct_p) { memset(struct_p, 0, sizeof(*(struct_p))); (struct_p)->size = sizeof(*(struct_p)); }

并被使用

 SNAPSHOT_PARMS snapshot_parms;
 SYS_ERR result;

 INIT_STRUCT(&snapshot_parms);
result = get_system_snapshot(&snapshot_parms);

Answer 1

根据 C++ 声明，这应该足够了：

[StructLayout(LayoutKind.Sequential)]
unsafe struct SNAPSHOT_PARMS {
    public int size;
    public int count;
    public fixed byte serial_no[600];
}

[DllImport("res_lib", EntryPoint = "get_system_snapshot")]
static extern int GetSystemSnapshot(ref SNAPSHOT_PARMS snapshot);

用作

var s = new SNAPSHOT_PARMS { size = Marshal.SizeOf<SNAPSHOT_PARMS>() };
int result = GetSystemSnapshot(ref s);
// check result, use s

使用非托管 C++ DLL 的 AccessViolationException

AccessViolationException using unmanaged C++ DLL

c#

pinvoke