C / C++ / MFC

Re: error while importing the static class member from dll

18-Feb-08 22:00

This is the error message

error LNK2001: unresolved external symbol "public: static int CMyClass::nValue" (?nValue@CMyClass@@2HA)

CPallini18-Feb-08 22:08

CPallini

18-Feb-08 22:08

I already showed you a working sample and suggested the proper settings for your application, please review the latters.
BTW Can you see the DLL exported int with Dependency Walker?
Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong.
-- Iain Clarke

Re: error while importing the static class member from dll

Prasanth M V18-Feb-08 22:24

Re: error while importing the static class member from dll

18-Feb-08 22:24

Hi,

I think u are speaking abt another thread that i launched day before yesterday.
Unfortunately that thread lost, i do not how that happend.
So i could not see your reply.

Expeting more help on this topic

Thanks
Prasanth

Rajesh R Subramanian18-Feb-08 22:35

Rajesh R Subramanian

18-Feb-08 22:35

Prasanth M V wrote:
Unfortunately that thread lost, i do not how that happend.

The Lost Thread ^

Nobody can give you wiser advice than yourself. - Cicero
.·´¯`·->Rajesh<-·´¯`·.
Codeproject.com: Visual C++ MVP

Re: error while importing the static class member from dll

Prasanth M V18-Feb-08 23:42

Re: error while importing the static class member from dll

18-Feb-08 23:42

I have gone though ur help.It seems that we are in the same path.
But there is still error.
Is there anything related with machine configuration?\
I am Win XP Sp2

Or any other library dependency?

Thanks
Prasanth M V

CPallini18-Feb-08 22:38

CPallini

18-Feb-08 22:38

The following is a working sample:
DLL header

#ifdef CPPDLL_EXPORTS
#define CPPDLL_API __declspec(dllexport)
#else
#define CPPDLL_API __declspec(dllimport)
#endif

class CPPDLL_API CCppDll {
public:
	CCppDll(void);
	~CCppDll(void);
	// TODO: add your methods here.

	static int nValue;
};

DLL source

// DLLMain stuff omitted
CCppDll::CCppDll()
{
	return;
}
CCppDll::~CCppDll()
{
	return;
}
int CCppDll::nValue = 0;

Application source

#include "stdafx.h"
#include "..\\..\\CppDLL\\CppDLL\CppDLL.h"

int _tmain(int argc, _TCHAR* argv[])
{
	CCppDll::nValue =5;
}

It works fine on my system (VS 2005, Win XP).

Have you checked again your client project settings? What about the little test with Dependency Walker?

Smile | :)

Re: error while importing the static class member from dll

Prasanth M V19-Feb-08 0:07

Re: error while importing the static class member from dll [modified]

19-Feb-08 0:07

,

I have just gone through your Dll implementation code.
I think we both moving with same implementation.
But still there is error in my PC.

My Build environment details is as follows:

OS – Win XP SP2
IDE – Microsoft Visual 6.0(c++)

I tested the same implementation in another PC which has the same configuration, but the same error.

Thanks
Prasanth M V

Rajkumar R19-Feb-08 0:15

Rajkumar R

19-Feb-08 0:15

this can occur if u donot define the nValue in ur DLL, but ur code shows u defined the variable,

I see two possibility,

1) u may be linking to wrong export library, that can happen if u r moving projects, but given fixed path.

2) ur error message shows it is not dllimport, it is normal class declaration,
if dllimport then following can be the error message

error LNK2001: unresolved external symbol "__declspec(dllimport) public: static int CMyClass::nValue" (__imp_?nValue@CMyClass@@2HA)

not this

error LNK2001: unresolved external symbol "public: static int CMyClass::nValue" (?nValue@CMyClass@@2HA)

this can happen if ur using different header file, other than that used in DLL project which doesnot have the dllimport keyword

modified on Tuesday, February 19, 2008 7:23 AM

vfw.h and capDlgVideoDisplay

Tomice18-Feb-08 21:05

Tomice

18-Feb-08 21:05

Hi.

I have 2 web cameras connected to my PC.

capGetDriverDescription retreives:
Microsoft WDM Image Capture (Win32)

The capDlgVideoDisplay macro displays a dialog box in which I can choose between 2 web cameras.

How to switch between web cameras from my code (not using capDlgVideoDisplay macro)?
Or how to enumerate capturing devices and then select one?

Thank you in advance!
TomazZ

Re: vfw.h and capDlgVideoDisplay

Mark Salsbery19-Feb-08 8:18

Mark Salsbery

19-Feb-08 8:18

You can't with VFW.

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Saving a bitmap image in visual C++ 2003

MozhdehQeraati18-Feb-08 20:34

18-Feb-08 20:34

I want to save a bitmap image in Visual C++ 2003.I use the save method of the bitmap class of Gdiplus this way:

Gdiplus :: bitmap mybitmap;
mybitmap.save (L"C:\myFolder\",&bmpClsid);

But I get a win32Error.

Thanks in advance.

Hamid_RT18-Feb-08 20:43

Hamid_RT

18-Feb-08 20:43

Did you try with CImage class? it has save method.

MozhdehQeraati18-Feb-08 21:01

18-Feb-08 21:01

I want to use GDIPlus:: Image.

Rajkumar R18-Feb-08 21:03

Rajkumar R

18-Feb-08 21:03

MozhdehQeraati wrote:
mybitmap.save (L"C:\myFolder\",&bmpClsid);

file path error?

something like L"C:\\myFolder\\image1.bmp"

MozhdehQeraati18-Feb-08 21:22

18-Feb-08 21:22

i Test with this format but get win32error.

Prasanth M V18-Feb-08 21:56

18-Feb-08 21:56

Hi,

Did u start the GDI + engine?

ULONG_PTR m_gdiplusToken;
GdiplusStartupInput gdiplusStartupInput;

GdiplusStartup(&m_gdiplusToken, &gdiplusStartupInput, NULL);

Bitmap *pBitmap = Bitmap::FromFile(/*File name*/);

CLSID Clsid = {0};
GetEncoderClsid(L"image/bmp", &Clsid))

CString strFilePath = "C://1.bmp";
pBitmap->Save(strFilePath.AllocSysString(),&Clsid);

GdiplusShutdown(m_gdiplusToken);

Prasanth M V
Software Engineer.

Rajkumar R18-Feb-08 22:12

Rajkumar R

18-Feb-08 22:12

I would like to know the value of win32 error.

GINA

MozhdehQeraati18-Feb-08 20:28