Ошибка средств компоновщика lnk2020

I have a project, where I must connect to a library that is C based, and I was not able to get at the functions from C# using the DLLImport. I have to use a project that is C++/CLI based to surface these functions for use. (more to that story but not important).

I studied C++ over 10 years ago, so forgive me if this seems like it is naive.
I purchased a few books on the C++/CLI implementation last year, and have some grasp of what is involved — I only dug into those books for this project. (I have been a programmer for a long time).

I thought I had better start a small project example project to familiarize myself with what will be involved, to make sure I could compile, etc. I started a project using Visual Studio 2008 SP1; Visual C++ > CLR > Class Library. In the project — I want to use both managed and native from the DLL. So the /clr switch is used.

I have used other names in the real code; but this is very, very close. (there are no other files, or functions at this point)

Header:

//myWrapper.h
#pragma once
using namespace System;
namespace myWrapper {
  public ref class myWrappedService {
         myWrappedService();
         bool Connected(String ^user,String ^password,String ^domain);
  }
};

And the implementation has this.

//myWrapper.cpp
//This is the main DLL file
#include "stdafx.h"
#include "myWrapper.h"
using namespace System;
public ref class myWrappedService
   {
      public:
            myWrappedService() {}
            bool Connected(String ^user,String ^password,String ^domain)
            {
               //just a simple result to start - no real functionality
               bool result = false;
               return result;
            }
   };

That is the code — that compiles but gets linker errors.

error LNK2020: unresolved token (06000002)
myWrapper.myWrappedService::Connected

fatal error LNK1120: 1 unresolved external.

This looked dead easy — and I might be thinking to much from a C# approach. I expect this to be something simple — but I am not familiar with what I should be seeing in the CLI approach. (I spent a few hours looking for answers and finally feel I need to post a question where it might get answered).

error LNK2020: unresolved token (06000002) Foo::execute

#pragma once
using namespace System::IO::Ports;
using namespace System;

public ref class Foo
{
protected:
SerialPort^ port;
public:
Foo(SerialPort^ sp);
virtual array<Byte>^ execute();
};

#include "StdAfx.h"#include "Foo.h"
Foo::Foo(SerialPort^ sp)
{
this->port = sp;
}

Решение

Другие решения

Добрый день, Господа!
Пишу приложение Windows Forms Application. Возникла проблема при работе с шрифтами и OpenGL.
При вызове функции ChooseFontA(&cf) появляется ошибка LNK2020.
Прошу помощи!

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#pragma once
 
#include <windows.h>
#include <stdio.h>
#include <math.h>
#include <glgl.h>
#include <glglu.h>
#include <glglut.h>
#include "GLAux.h"
#include <iostream>
#include <fstream>
#include <vcclr.h>
#include <string>
#include <sstream>
#include <vector>
#include <stdarg.h>
#include <malloc.h>
#include <process.h>
#include <commdlg.h>
 
#pragma comment(lib, "opengl32.lib") 
#pragma comment(lib, "glu32.lib")
 
GLvoid BuildFont(GLvoid)           
 
{
    HDC hDC=NULL;
 
    HFONT * font = new HFONT;
 
    LOGFONTA logfont;
 
    CHOOSEFONTA cf;
 
    cf.lStructSize = sizeof(CHOOSEFONT); 
    cf.hwndOwner = (HWND)NULL; 
    cf.hDC = (HDC)NULL; 
    cf.lpLogFont = &logfont; 
    cf.iPointSize = 0; 
    cf.Flags = CF_SCREENFONTS; 
    cf.rgbColors = RGB(0,0,0); 
    cf.lCustData = 0L; 
    cf.lpfnHook = (LPCFHOOKPROC)NULL;
    cf.lpTemplateName = (LPSTR)NULL; 
    cf.hInstance = (HINSTANCE) NULL;
    cf.lpszStyle = (LPSTR)NULL;
    cf.nFontType = SCREEN_FONTTYPE; 
    cf.nSizeMin = 0; 
    cf.nSizeMax = 0;
 
    logfont.lfHeight = -10;
 
    ChooseFontA(&cf); //Наличие этой строки кода вызывает ошибку
}

Добавлено через 21 минуту
Вообще любая работа, касающаяся font, вызывает эту ошибку!
Уже много способов перепробовал, и из MSDN, и из книг. Результат все-равно один и тот же.

Configuration:

VS 2017
ISO C++17
Multi-Threaded DLL project.

I’ve encountered a strange error, I haven’t been able to figure out.   Other than being a Singleton, this is a pretty basic class.

This is one file contained within a .DLL project, which is compiled with /CLR enabled, although this particular class is not a managed class.

(.h)

#pragma once

#include <string>
#include <memory> 

using namespace std;

public class SessionInfo
{
public:
 static std::string UserId;
 static std::string UserName;
 static std::string UserLoginDateTime;
private:
 static SessionInfo& Instance()
 {
  static std::unique_ptr<SessionInfo> _instance(new SessionInfo());
  return *_instance;
 }
private:
 SessionInfo();
 SessionInfo(const SessionInfo &old); // disable copy constructor
 const SessionInfo &operator=(const SessionInfo &old); //disable assignment operator
};

.cpp

#include «SessionInfo.h»
#include <stdio.h>
#include <stdlib.h>
#include <ctime>

SessionInfo::SessionInfo()
{
}

void SessionInfo::setCurrentDateTime()
{
 struct tm newtime;
 __time32_t aclock;
 char buffer[32];
 errno_t errNum;
 _time32(&aclock);   // Get time in seconds.
 _localtime32_s(&newtime, &aclock);   // Convert time to struct tm form.
 errNum = asctime_s(buffer, 32, &newtime);
 if (!errNum)
 {
  //UserLoginDateTime.clear();
  //UserLoginDateTime.append(buffer);
 }

}

If built, as is, it compiles and links without error.   However, if I uncomment ‘UserLoginDateTime.clear()’ and/or ‘UserLoginDateTime.append(buffer)’   I receive the following linker errors:

SessionInfo.obj : error LNK2020: unresolved token (0A000531) «public: static class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > SessionInfo::UserLoginDateTime» (?UserLoginDateTime@SessionInfo@@2V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@A)

SessionInfo.obj : error LNK2001: unresolved external symbol «public: static class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > SessionInfo::UserLoginDateTime» (?UserLoginDateTime@SessionInfo@@2V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@A)