Can't find PInvoke DLL - BUG?

问题

I have got Windows mobile GPS third party application.That is C++ code which code contain GPS automatic enabling/disabling facility.

I want to make dll. That also i did. When the user click invoice (C# code) GPS (C++) have to find.

This is my source Code GPS.cpp

      extern "C"      //No name mangling
      __declspec(dllexport) 
      #include "GPS.h"

      #include "stdafx.h"
      #include "RF PWR.h"
      #include "RF PWRDlg.h"
      #include "widioctl.h"

     #ifdef _DEBUG
     #define new DEBUG_NEW
     #endif

      void CaptureGPS()
     {
    HANDLE hDrv = CreateFile(TEXT("FNC1:"), GENERIC_READ | GENERIC_WRITE,
                            0, NULL, OPEN_EXISTING,              FILE_ATTRIBUTE_NORMAL, NULL);
if (0 == DeviceIoControl(hDrv, IOCTL_WID_GPS_ON, NULL, 0, NULL, 0, NULL, NULL))
{
    RETAILMSG(1, (L"IOCTL_WID_RFID_ON Failed !! \r\n")); return;
}
CloseHandle(hDrv);
}

& this is the GPS.h

class Adder
 {
    public:
       Adder(){;};
       ~Adder(){;};
       void CaptureGPS();
 };

This is my Source : http://pastie.org/3436376

It say can't find entry point CaptureGPS in PInvoke RF PWF.dll

Please anybody help me out this..

What is the issues...

回答1:

Let me explain first, what you've written

extern "C"      //No name mangling
__declspec(dllexport) 
#include "GPS.h"

will expand after preprocessing to

extern "C"      //No name mangling
__declspec(dllexport) 
class Adder
{
    public:
       Adder(){;};
       ~Adder(){;};
       void CaptureGPS();
};

It means, you are:

attempting to make class Adder C-style struct (and while it is not possible due to class Adder is not POD, extern "C" simply ignored)

attempting export a variable of class Adder, if it would defined after class definition, like:

extern "C"      //No name mangling
__declspec(dllexport) 
class Adder
{
    public:
       Adder(){;};
       ~Adder(){;};
       void CaptureGPS();
} variable;

But it is no any variable defined, so __declspec(dllexport) simply ignored.

Note, that you declared some methods in class Adder but not defined them. It is ok, while you do not try to use class Adder. Also note, that your void CaptureGPS() has nothing with void Adder::CaptureGPS(), it is just separate function.

What I think, you should do

It seems, you want just export void CaptureGPS();

If it is, you should add to your header file:

extern "C" __declspec(dllexport) void CaptureGPS();

Than, CaptureGPS() will be exported and you will be able to call it with pinvoke

回答2:

MSDN has an article that covers writing DLL function for P/Invoking and checking the exported names via dumpbin. It was written specifically for the Compact Framework, so it's very relevant to what you're doing.

That said, why are you creating a DLL for this anyway? Why not just P/Invoke CreateFile, DeviceIoControl and CloseHandle directly from your C# app? There's another MSDN article that covers using Stream Interface Drivers from managed code in the Compact Framework as well.

来源：https://stackoverflow.com/questions/9410197/cant-find-pinvoke-dll-bug

标签

c++

visual-c++

windows-mobile