Question

托管的 PInvoke 签名与非托管的目标签名不匹配??

我用C#调用C++写的DLL，为什么有这个问题？

对 PInvoke 函数“test2!test2.Form1::Add”的调用导致堆栈不对称。原因可能是托管的 PInvoke 签名与非托管的目标签名不匹配。请检查 PInvoke 签名的调用约定和参数与非托管的目标签名是否匹配。

C++头文件

//head.h

// Returns a + b
extern "C" _declspec(dllexport) double Add(double a, double b);

// Returns a - b
extern "C" _declspec(dllexport) double Subtract(double a, double b);

// Returns a * b
extern "C" _declspec(dllexport) double Multiply(double a, double b);

// Returns a / b
// Throws DivideByZeroException if b is 0
extern "C" _declspec(dllexport) double Divide(double a, double b);

C++源文件

// sourcefile

#include "Head.h"

#include <stdexcept>

using namespace std;

extern "C" _declspec(dllexport) double Add(double a, double b)
{
return a + b;
}

extern "C" _declspec(dllexport) double Subtract(double a, double b)
{
return a - b;
}

extern "C" _declspec(dllexport) double Multiply(double a, double b)
{
return a * b;
}

extern "C" _declspec(dllexport) double Divide(double a, double b)
{
if (b == 0)
{
throw new invalid_argument("b cannot be zero!");
}
return a / b;
}

C#中调用

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;
using System.Windows.Forms;

namespace test2
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}

[DllImport("Dll.dll")]
public static extern double Add(double a, double b);
[DllImport("Dll.dll")]
public static extern double Subtract(double a, double b);

private void button1_Click(object sender, EventArgs e)
{
double a=8.525,b=6.168;
label1.Text += Convert.ToString(Add(a, b));
}
}
}

请问问题在哪，我看了类似的问题，都是long类型在C++中跟C#中不同导致的，我这个呢？

Answer 1

[DllImport("Dll.dll")]

改为[DllImport("Dll.dll", CallingConvention=CallingConvention.Cdecl)]
DllImport的CallingConvention的属性,默认值是CallingCovention.Stdcall, 此处更改成Cdecl(c/c++默认调用方式)就可以了。