托管C#代码未发生非托管调用 [英] Unamanaged call is not happening from the managed C# code

问题描述

我正在从托管代码中调用非托管函数.但是未托管的呼叫不会发生.

I am calling unamanaged function from the managed code. But Unamanaged call is not happening.

托管的C#代码: (通过Visual C#->控制台应用程序创建了一个项目(最简单)) 样品测试:

Managed C# code: (Created a project (Sampletest) from Visual C# -> Console App) Sampletest:

namespace Sampletest
{
    class Program
    {
        const string Dllpath2 = @"C:\Users\apc\source\repos\Sampletest\SampleDll\Debug\SampleDll.dll";
        [DllImport(Dllpath2, EntryPoint = @"IsUPSPresent", CallingConvention = CallingConvention.Cdecl)]
        public static extern Boolean IsUPSPresent();
        static void Main(string[] args)
        {
            var test = IsUPSPresent();

            Console.ReadKey();
        }
    }
}

非托管C ++代码:

(从Visual C ++-> Windows桌面->动态链接库创建了一个dll项目(SampleDll)

(Created a dll project (SampleDll) from Visual C++ -> Windows Desktop -> Dynamic Link Library)

在SampleDll.cpp中有"IsUPSPresent()"定义

"IsUPSPresent()" definition is there in SampleDll.cpp

#include "stdafx.h"

BOOL IsUPSPresent()
{
    BOOL    bRetValue = FALSE;

    return bRetValue;
}

但是，当我们进行非托管调用时，首先要转到非托管代码中存在的dllmain.cpp文件.

But when we are making unmanaged call, first it is going to dllmain.cpp file present in unmanaged code.

#include "stdafx.h"

BOOL APIENTRY DllMain( HMODULE hModule,
                       DWORD  ul_reason_for_call,
                       LPVOID lpReserved
                     )
{
    switch (ul_reason_for_call)
    {
    case DLL_PROCESS_ATTACH:
    case DLL_THREAD_ATTACH:
    case DLL_THREAD_DETACH:
    case DLL_PROCESS_DETACH:
        break;
    }
    return TRUE;
}

那么它就不会

BOOL IsUPSPresent()函数

BOOL IsUPSPresent() function

并返回到"var test = IsUPSPresent();"处的托管调用.

and comming back to the managed call at "var test = IsUPSPresent();"

显示错误"Sampletest.exe中的0x7705D6C7(ntdll.dll)出现未处理的异常:0xC0000096:特权指令.

showing the error "Unhandled exception at 0x7705D6C7 (ntdll.dll) in Sampletest.exe: 0xC0000096: Privileged instruction.

我所做的设置:

对于C#项目，

Debug->选择启用本机代码调试"

Debug-> Selected "Enable native code debugging"

然后我选择了调试"，"x86"

And I selected "Debug", "x86"

请帮助我解决此问题.

推荐答案

您必须使用__declspec(dllexport)属性声明IsUPSPresent或使用.def文件.另外，要克服C ++名称修饰的问题，您的定义必须在C ++代码中为extern "C".

You have to declare IsUPSPresent using the __declspec(dllexport) attribute or use a .def-file. Also, to overcome C++ name mangling, your definition has to be extern "C" in C++-code.

extern "C" {
    BOOL __declspec(dllexport) IsUPSPresent()
    {
        BOOL bRetValue = FALSE;
        return bRetValue;
    }
}

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