Question

我有一个用C ++编写的DLL，其中包含导出函数，该函数具有一个函数指针，可用作回调函数。

// C++ 
DllExport unsigned int DllFunctionPointer( unsigned int i, unsigned int (*TimesThree)( unsigned int number ) ) {
    return TimesThree( i )  ; 
}

我有一个CSharp应用程序，我想用它来调用DLL函数。

// C#
public unsafe delegate System.UInt32 CallBack( System.UInt32 number ); 
class Program
{
    [DllImport("SimpleDLL.dll")]
    public static extern System.UInt32 DllFunctionPointer( System.UInt32 i, CallBack cb) ;

    static unsafe void Main(string[] args)
    {
        System.UInt32 j = 3;
        System.UInt32 jRet = DllFunctionPointer(j, CallBack );
        System.Console.WriteLine("j={0}, jRet={1}", j, jRet); 
    }

    static System.UInt32 CallBack( System.UInt32 number ) {
        return number * 3 ; 
    }
}

上述代码的问题是应用程序崩溃时出现以下错误消息。

'CallingACallbackFromADLL.vshost.exe' (Managed (v4.0.30319)): Loaded 'C:\XXXX\CallingACallbackFromADLL.exe', Symbols loaded.
Managed Debugging Assistant 'PInvokeStackImbalance' has detected a problem in 'C:\XXXX\CallingACallbackFromADLL.vshost.exe'.
Additional Information: A call to PInvoke function 'CallingACallbackFromADLL!CallingACallbackFromADLL.Program::DllFunction' has unbalanced the stack. This is likely because the managed PInvoke signature does not match the unmanaged target signature. Check that the calling convention and parameters of the PInvoke signature match the target unmanaged signature.

The program '[9136] CallingACallbackFromADLL.vshost.exe: Managed (v4.0.30319)' has exited with code 1073741855 (0x4000001f).

我不确定下一步该做什么。

我的问题是：

调用包含C＃应用程序的Callback指针的C ++ DLL函数的正确方法是什么。

Answer 1

这是因为默认情况下调用C#中函数的约定为__stdcall，但C/C++默认为__cdecl，因此您应该更改函数的调用约定，如下所示：

[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
public delegate void TimesTree( uint frame );
[DllImport("SimpleDLL.dll")]
public static extern System.UInt32 DllFunctionPointer( uint i,
    [MarshalAs(UnmanagedType.FunctionPtr)] TimesTree callback ) ;

static unsafe void Main(string[] args)
{
    // ...
    System.UInt32 jRet = DllFunctionPointer(j, CallBack );
    // ...
}

调用包含C＃函数指针的DLL函数

1 个答案: