Question

我有一个项目，我正在从VC6迁移到VS2013。在我构建项目的过程中，我遇到了这个错误。

错误LNK2005：“public：virtual __thiscall CMemDC :: ~CMemDC（void）” （?? 1CMemDC @@ UAE @ XZ）已在GameBoard.obj中定义

以下是可能正在创建此问题的文件。

GameBoard.h

#include "DirectSound.h"
#include "MIDI.h"
#include <vector>
class CGameBoard : public CWnd
{
    friend class CTetrisDlg;
    friend class COptionsDlg;

    DECLARE_DYNAMIC(CGameBoard);

// Construction/Destruction
public:
    CGameBoard();
    virtual ~CGameBoard();

.......
};

GameBoard.cpp 文件定义了此析构函数。

#include "stdafx.h"
#include "Tetris.h"
#include "GameBoard.h"
#include "Piece.h"
#include "MemDC.h"
#include "VolumeCtrl.h"

#include <stdlib.h>
#include <time.h>
static CGameBoard * gpGameBoard;

CGameBoard::CGameBoard()
{
    m_pCurPiece = m_pNextPiece = 0;
    m_usLevel = 0;
    m_clrCurPiece = RGB(0,0,0);
    m_bShowGrid = TRUE;
    m_nSquareWidth = 14;
    m_nSquareHeight = 14;
    m_clrBackground = RGB(255, 255, 255);
    m_bExFigures = FALSE;
    m_pMusic = 0;
    m_uTimer = 0;
    m_dwVolume = 100;   // 100% music volume by default

    gpGameBoard = this;
}

CGameBoard::~CGameBoard()
{
    if(m_pCurPiece)
        delete m_pCurPiece;
    if(m_pNextPiece)
        delete m_pNextPiece;

    if( m_pMusic )
        delete m_pMusic;

    gpGameBoard = 0;
}

此析构函数仅在GameBoard.cpp中定义一次，而GameBoard未包含在任何其他cpp或header file中。

MemDC.h

#ifndef _MEMDC_H_
#define _MEMDC_H_

class CMemDC : public CDC {
private:
    CBitmap m_bitmap;       // Offscreen bitmap
    CBitmap* m_oldBitmap;   // bitmap originally found in CMemDC
    CDC* m_pDC;             // Saves CDC passed in constructor
    CRect m_rect;           // Rectangle of drawing area.
    BOOL m_bMemDC;          // TRUE if CDC really is a Memory DC.

public:
    CMemDC(CDC* pDC) : CDC(), m_oldBitmap(NULL), m_pDC(pDC)
    {
        ASSERT(m_pDC != NULL); // If you asserted here, you passed in a NULL CDC.

        m_bMemDC = !pDC->IsPrinting();

        if (m_bMemDC){
            // Create a Memory DC
            CreateCompatibleDC(pDC);
            pDC->GetClipBox(&m_rect);
            m_bitmap.CreateCompatibleBitmap(pDC, m_rect.Width(), m_rect.Height());
            m_oldBitmap = SelectObject(&m_bitmap);
            SetWindowOrg(m_rect.left, m_rect.top);
        } else {
            // Make a copy of the relevent parts of the current DC for printing
            m_bPrinting = pDC->m_bPrinting;
            m_hDC = pDC->m_hDC;
            m_hAttribDC = pDC->m_hAttribDC;
        }
    }

    ~CMemDC()
    {
        if (m_bMemDC) {
            // Copy the offscreen bitmap onto the screen.
            m_pDC->BitBlt(m_rect.left, m_rect.top, m_rect.Width(), m_rect.Height(),
                            this, m_rect.left, m_rect.top, SRCCOPY);
            //Swap back the original bitmap.
            SelectObject(m_oldBitmap);
        } else {
            // All we need to do is replace the DC with an illegal value,
            // this keeps us from accidently deleting the handles associated with
            // the CDC that was passed to the constructor.
            m_hDC = m_hAttribDC = NULL;
        }
    }

    // Allow usage as a pointer
    CMemDC* operator->() {return this;}

    // Allow usage as a pointer
    operator CMemDC*() {return this;}
};

#endif

此问题与定义为here的单一定义规则有关，但我不知道该怎么做。

我做了一些建议here的修改。现在我得到了跟随错误。有什么想法，请吗？

错误LNK1181：无法打开输入文件'Nafxcwd.lib Libcmtd.lib'

Answer 1

您尚未提供完整的代码。但总的来说，似乎你的代码缺少标题保护。这些是必要的，如果没有它们，你最有可能最终出现像你这样的链接器问题。

在Windows上，在所有标题文件的顶部添加此行：

#pragma once

通常，您可以在所有编译器中使用传统的标头防护

#ifndef HEADERNAME_H
#define HEADERNAME_H

//Put content of header file here

#endif

Answer 2

最后，以下设置帮助我解决了这个问题..

Project properties->linker->input->ignore specific default library ..设置为.. nafxcw.lib libcmt.lib
Project properties->c/c++->Code generation->run time library ..设置为.. Multi threaded DLL (/MD)
Project properties->configuration properties->general->Use of MFC ..设置为.. use of MFC in a shared DLL。

除了这些设置之外，我没有更改任何代码（w.r.t.包括警卫等）。

Answer 3

最近我的一些旧代码遇到了同样的问题。我觉得奇怪的是我在代码中定义了一个名为CMemDC的类的错误。我重命名了CMemJBDC类，错误就消失了。

多个析构函数定义无缘无故

3 个答案: