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DLL Blues, Where did I go Wrong???

I am trying to create a dll file.  I have about 40 functions that I want to store in a DLL file and make calls sto them from other msv 7.1C++  programs.  So looked at some examples and decided to try one first before going to a large one. I tried 3 exsamples and always got a linking error when I tried to call one of the functions in the dll file i created.  Pls hlelp me find out where I am going wrong.  Here is a sample of the last code that I wrote.  The dll file complies fine but to program to make a call to it does not.  I used the mfc wizard to create the wizard and added the functions. I commented  where I added my code lines.  Could you please Debus this one or send me a sample of one that works so I can use it as a template???  I want to pass strings and numerical values to the calling applications.   Thanks in advance for your assistance.  I will be passing string and numbers in my functions.

DLL Program

the H File
// The following ifdef block is the standard way of creating macros which make exporting
// from a DLL simpler. All files within this DLL are compiled with the TESTDLL_EXPORTS
// symbol defined on the command line. this symbol should not be defined on any project
// that uses this DLL. This way any other project whose source files include this file see
// TESTDLL_API functions as being imported from a DLL, whereas this DLL sees symbols
// defined with this macro as being exported.
#ifdef TESTDLL_EXPORTS
#define TESTDLL_API __declspec(dllexport)
#else
#define TESTDLL_API __declspec(dllimport)
#endif

// This class is exported from the TESTDLL.dll
class TESTDLL_API CTESTDLL {
public:
     CTESTDLL(void);
     // TODO: add your methods here.
};

extern TESTDLL_API int nTESTDLL;

TESTDLL_API int fnTESTDLL(void);


 the CPP file

// TESTDLL.cpp : Defines the entry point for the DLL application.
//

#include "stdafx.h"
#define TESTDLL_EXPORTS  // I added this line  *******************
#include "TESTDLL.h"
BOOL APIENTRY DllMain( HANDLE 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;
}

// This is an example of an exported variable
TESTDLL_API int nTESTDLL=0;

// This is an example of an exported function.
TESTDLL_API int fnTESTDLL(void)
{
     return 42;
}

// This is the constructor of a class that has been exported.
// see TESTDLL.h for the class definition
CString CTESTDLL::CTESTDLL()
{
     return "Test message.";
}

///////////////////////////////////    The program that calls the Dll

the H Files
// TestCall.h : main header file for the PROJECT_NAME application
//

#pragma once

#ifndef __AFXWIN_H__
     #error include 'stdafx.h' before including this file for PCH
#endif

#include "resource.h"          // main symbols


// CTestCallApp:
// See TestCall.cpp for the implementation of this class
//

class CTestCallApp : public CWinApp
{
public:
     CTestCallApp();

// Overrides
     public:
     virtual BOOL InitInstance();

// Implementation

     DECLARE_MESSAGE_MAP()
};

extern CTestCallApp theApp;

// TestCallDlg.h : header file
//

#pragma once


// CTestCallDlg dialog
class CTestCallDlg : public CDialog
{
// Construction
public:
     CTestCallDlg(CWnd* pParent = NULL);     // standard constructor

// Dialog Data
     enum { IDD = IDD_TESTCALL_DIALOG };

     protected:
     virtual void DoDataExchange(CDataExchange* pDX);     // DDX/DDV support


// Implementation
protected:
     HICON m_hIcon;

     // Generated message map functions
     virtual BOOL OnInitDialog();
     afx_msg void OnSysCommand(UINT nID, LPARAM lParam);
     afx_msg void OnPaint();
     afx_msg HCURSOR OnQueryDragIcon();
     DECLARE_MESSAGE_MAP()
};
 The CPP Files

// TestCall.cpp : Defines the class behaviors for the application.
//

#include "stdafx.h"
#include "TestCall.h"
#include "TestCallDlg.h"

#ifdef _DEBUG
#define new DEBUG_NEW
#endif


// CTestCallApp

BEGIN_MESSAGE_MAP(CTestCallApp, CWinApp)
     ON_COMMAND(ID_HELP, CWinApp::OnHelp)
END_MESSAGE_MAP()


// CTestCallApp construction

CTestCallApp::CTestCallApp()
{
     // TODO: add construction code here,
     // Place all significant initialization in InitInstance
}


// The one and only CTestCallApp object

CTestCallApp theApp;


// CTestCallApp initialization

BOOL CTestCallApp::InitInstance()
{
     // InitCommonControls() is required on Windows XP if an application
     // manifest specifies use of ComCtl32.dll version 6 or later to enable
     // visual styles.  Otherwise, any window creation will fail.
     InitCommonControls();

     CWinApp::InitInstance();

     AfxEnableControlContainer();

     // Standard initialization
     // If you are not using these features and wish to reduce the size
     // of your final executable, you should remove from the following
     // the specific initialization routines you do not need
     // Change the registry key under which our settings are stored
     // TODO: You should modify this string to be something appropriate
     // such as the name of your company or organization
     SetRegistryKey(_T("Local AppWizard-Generated Applications"));

     CTestCallDlg dlg;
     m_pMainWnd = &dlg;
     INT_PTR nResponse = dlg.DoModal();
     if (nResponse == IDOK)
     {
          // TODO: Place code here to handle when the dialog is
          //  dismissed with OK
     }
     else if (nResponse == IDCANCEL)
     {
          // TODO: Place code here to handle when the dialog is
          //  dismissed with Cancel
     }

     // Since the dialog has been closed, return FALSE so that we exit the
     //  application, rather than start the application's message pump.
     return FALSE;
}

// TestCallDlg.cpp : implementation file
//
#include "stdafx.h"
#include "TestCall.h"
#include "TestCallDlg.h"
#include "TESTDLL.h"  // I added this line
#ifdef _DEBUG
#define new DEBUG_NEW
#endif

// CAboutDlg dialog used for App About

class CAboutDlg : public CDialog
{
public:
     CAboutDlg();

// Dialog Data
     enum { IDD = IDD_ABOUTBOX };

     protected:
     virtual void DoDataExchange(CDataExchange* pDX);    // DDX/DDV support

// Implementation
protected:
     DECLARE_MESSAGE_MAP()
};

CAboutDlg::CAboutDlg() : CDialog(CAboutDlg::IDD)
{
}

void CAboutDlg::DoDataExchange(CDataExchange* pDX)
{
     CDialog::DoDataExchange(pDX);
}

BEGIN_MESSAGE_MAP(CAboutDlg, CDialog)
END_MESSAGE_MAP()


// CTestCallDlg dialog



CTestCallDlg::CTestCallDlg(CWnd* pParent /*=NULL*/)
     : CDialog(CTestCallDlg::IDD, pParent)
{
     m_hIcon = AfxGetApp()->LoadIcon(IDR_MAINFRAME);
}

void CTestCallDlg::DoDataExchange(CDataExchange* pDX)
{
     CDialog::DoDataExchange(pDX);
}

BEGIN_MESSAGE_MAP(CTestCallDlg, CDialog)
     ON_WM_SYSCOMMAND()
     ON_WM_PAINT()
     ON_WM_QUERYDRAGICON()
     //}}AFX_MSG_MAP
END_MESSAGE_MAP()


// CTestCallDlg message handlers

BOOL CTestCallDlg::OnInitDialog()
{
     CDialog::OnInitDialog();

     // Add "About..." menu item to system menu.

     // IDM_ABOUTBOX must be in the system command range.
     ASSERT((IDM_ABOUTBOX & 0xFFF0) == IDM_ABOUTBOX);
     ASSERT(IDM_ABOUTBOX < 0xF000);

     CMenu* pSysMenu = GetSystemMenu(FALSE);
     if (pSysMenu != NULL)
     {
          CString strAboutMenu;
          strAboutMenu.LoadString(IDS_ABOUTBOX);
          if (!strAboutMenu.IsEmpty())
          {
               pSysMenu->AppendMenu(MF_SEPARATOR);
               pSysMenu->AppendMenu(MF_STRING, IDM_ABOUTBOX, strAboutMenu);
          }
     }

     // Set the icon for this dialog.  The framework does this automatically
     //  when the application's main window is not a dialog
     SetIcon(m_hIcon, TRUE);               // Set big icon
     SetIcon(m_hIcon, FALSE);          // Set small icon

     // TODO: Add extra initialization here
     // Code to test TESTDLL.dll Program
     int n = fnTESTDLL();   /// I added this line and Here is where I am getting the linking errors.*****************

     // Code to test the CTestdll class
     CTESTDLL test;          /// I added this line and Here is where I am getting the linking errors. *****************

     return TRUE;  // return TRUE  unless you set the focus to a control
}

void CTestCallDlg::OnSysCommand(UINT nID, LPARAM lParam)
{
     if ((nID & 0xFFF0) == IDM_ABOUTBOX)
     {
          CAboutDlg dlgAbout;
          dlgAbout.DoModal();
     }
     else
     {
          CDialog::OnSysCommand(nID, lParam);
     }
}

// If you add a minimize button to your dialog, you will need the code below
//  to draw the icon.  For MFC applications using the document/view model,
//  this is automatically done for you by the framework.

void CTestCallDlg::OnPaint()
{
     if (IsIconic())
     {
          CPaintDC dc(this); // device context for painting

          SendMessage(WM_ICONERASEBKGND, reinterpret_cast<WPARAM>(dc.GetSafeHdc()), 0);

          // Center icon in client rectangle
          int cxIcon = GetSystemMetrics(SM_CXICON);
          int cyIcon = GetSystemMetrics(SM_CYICON);
          CRect rect;
          GetClientRect(&rect);
          int x = (rect.Width() - cxIcon + 1) / 2;
          int y = (rect.Height() - cyIcon + 1) / 2;

          // Draw the icon
          dc.DrawIcon(x, y, m_hIcon);
     }
     else
     {
          CDialog::OnPaint();
     }
}

// The system calls this function to obtain the cursor to display while the user drags
//  the minimized window.
HCURSOR CTestCallDlg::OnQueryDragIcon()
{
     return static_cast<HCURSOR>(m_hIcon);
}

0
lcrogers
Asked:
lcrogers
  • 4
1 Solution
 
ikeworkCommented:
hi lcrogers,

what are the errors, please post them here ...

ike
0
 
ikeworkCommented:
CString CTESTDLL::CTESTDLL()
{
     return "Test message.";
}

this does not work, a constructor cannot return anything, add a member-method to that class,
this can return something:

in your libs-header:

class TESTDLL_API CTESTDLL {
public:
     CTESTDLL(void);
     // TODO: add your methods here.

    const char* FuncTest();
};


in your libs-cpp:

const char* CTESTDLL::FuncTest()
{
     return "Test message.";
}


ike
0
 
ikeworkCommented:
and be sure, to reset the constructor, as it was created from the wizard, something like this:

// This is the constructor of a class that has been exported.
// see TESTDLL.h for the class definition
CTESTDLL::CTESTDLL()
{
}


ike
0
 
ikeworkCommented:
did you link your library to the test-project?

go to project-settings/linker and add your .lib - file to the project ...


ike
0

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