无法创建主窗口？ [英] Cannot create main window?

问题描述

我一直在试图想出这个数小时，我在我的机智的尽头。

在找到一些C ++ MFC教程之后，我试图用C ++编写一个简单的GUI应用程序，但它似乎有问题，在生成主窗口（对话框？）。当我尝试编译代码时，以下消息显示：

GUI_Employee_0501.exe中0x00E7A9DC处的未处理异常：
0xC0000005 ：访问冲突读取位置0xFEFEFF66。

，断点停止在 winmain.cpp > pThread-> m_pMainWnd-> DestroyWindow（）; 。 pThread-> m_pMainWnd 的值为 NULL ，我怀疑是导致此问题的原因。

你指定这里的问题是什么？我有一个示例代码，这与我非常相似，但是工作，所以我真的不知道发生了什么！

  #include< afxwin.h> 
 #includeresource.h
 #include< iostream> 
 using namespace std; 
 
 #pragma注释（链接器/ entry：WinMainCRTStartup / subsystem：console）
 
 CEdit * pFNAME; 
 CEdit * pLNAME; 
 CEdit * pSALARY; 
 CEdit * pDDAY; 
 CEdit * pMMONTH; 
 CEdit * pYYEAR; 
 
 CComboBox * pGENDER; 
 
 CButton * pADD; 
 CButton * pDELETE; 
 CButton * pSAVE; 
 CButton * pLOAD; 
 
 class ENTRY_FORM：public CDialog 
 {
 public：
 ENTRY_FORM（CWnd * pParent = NULL）：CDialog（ENTRY_FORM :: IDD，pParent）{} 
 enum {IDD = dialog_main}; 
 protected：
 virtual void DoDataExchange（CDataExchange * pDX）{CDialog :: DoDataExchange（pDX）; } 
 
 virtual BOOL OnInitDialog（）
 {
 CDialog :: OnInitDialog（）; 
 SetUpInterfacePointers（）; 
 return true; 
} 
 
 void SetUpInterfacePointers（）{...有自己的东西...} 
 
 public：
 afx_msg void add（）{PRESS_ADD （）; } 
 
 void PRESS_ADD（）{...有自己的东西...} 
 
 DECLARE_MESSAGE_MAP（）
}; 
 
类程序：public CWinApp 
 {
 public：
 Program（）{} 
 
 public：
 virtual BOOL InitInstance （）
 {
 CWinApp :: InitInstance（）; 
 cout<< CWinAPP：initInstance< endl; 
 ENTRY_FORM dlg; 
 m_pMainWnd =& dlg; 
 cout<< mpMainWnd< endl; 
 INT_PTR nResponse = dlg.DoModal（）; 
 return FALSE; 
} 
}; 
 
 // 
 BEGIN_MESSAGE_MAP（ENTRY_FORM，CDialog）
 ON_COMMAND（button_add，add）
 END_MESSAGE_MAP（）
 // 
 $ b b编程应用程序; 
   
 
解决方案
 ：
  return FALSE; 
  
到
  return TRUE; 
  
这是因为 CWinApp :: InitInstance 应该在失败的情况下返回FALSE，如果所有初始化都正常，则返回TRUE。如果失败， AfxWinMain 将尝试销毁 m_pMainWnd 指向的窗口，这是不可能的（它导致未定义的行为），因为你分配到 m_pMainWnd 一个局部对象（一旦InitInstance结束就被销毁）。
 
 
 
 / p> 
 
 
 SB Bae  - 要进一步调查并找到根本原因，您需要调试地方，其中m_pMainWnd应在对话结束后设置为NULL。这应该在wincore.cpp中的 CWnd :: OnNcDestroy（）中。有一行 pThread-> m_pMainWnd = NULL; 显然没有在您的应用程序中执行。
 
I've been trying to figure this out for hours now, and I'm at my wit's end. I would surely appreciate it if someone could tell me when I'm doing wrong.

After finding some C++ MFC tutorials, I tried to make a simple GUI application with C++, but it seems to have problem at generating the main window(dialog?). When I'm trying to compile the code, following message shows : 

  
Unhandled exception at 0x00E7A9DC in GUI_Employee_0501.exe:
  0xC0000005: Access violation reading location 0xFEFEFF66.
and the break point stops inside winmain.cpp, at pThread->m_pMainWnd->DestroyWindow();. The value of pThread->m_pMainWnd is NULL, which I suspect as the cause of the problem.

Can you specify what is the problem here? I have a sample code and that is very similar to mine but that works, so I truly have no idea what is happening!
#include <afxwin.h>
#include "resource.h"
#include <iostream>
using namespace std;

#pragma comment(linker, "/entry:WinMainCRTStartup /subsystem:console")

CEdit *pFNAME;
CEdit *pLNAME;
CEdit *pSALARY;
CEdit *pDDAY;
CEdit *pMMONTH;
CEdit *pYYEAR;

CComboBox *pGENDER;

CButton *pADD;
CButton *pDELETE;
CButton *pSAVE;
CButton *pLOAD;

class ENTRY_FORM : public CDialog
{
public:
    ENTRY_FORM(CWnd* pParent = NULL) : CDialog(ENTRY_FORM::IDD, pParent) { }
    enum { IDD = dialog_main };
protected:
    virtual void DoDataExchange(CDataExchange* pDX) { CDialog::DoDataExchange(pDX); }

    virtual BOOL OnInitDialog()
    {
        CDialog::OnInitDialog();
        SetUpInterfacePointers();
        return true;
    }

    void SetUpInterfacePointers(){ ... does its own thing ... }

public:
    afx_msg void add() { PRESS_ADD(); }

    void PRESS_ADD() { ... does its own thing ... }

    DECLARE_MESSAGE_MAP()
};

class Program : public CWinApp
{
public:
    Program(){ }

public:
    virtual BOOL InitInstance()
    {
        CWinApp::InitInstance();
        cout << "CWinAPP:initInstance" << endl;
        ENTRY_FORM dlg;
        m_pMainWnd = &dlg;                  
        cout << "mpMainWnd" << endl;
        INT_PTR nResponse = dlg.DoModal();  
        return FALSE;
    }
};

//
BEGIN_MESSAGE_MAP(ENTRY_FORM, CDialog)
    ON_COMMAND(button_add, add)
END_MESSAGE_MAP()
//

Program theApp;

解决方案
Change in InitInstance():
return FALSE;
to
return TRUE;
This is because CWinApp::InitInstance should return FALSE only in case of failure, and TRUE if all initialization went OK. In case of failure, AfxWinMain will try to destroy window pointed by m_pMainWnd, which is not possible (it causes Undefined Behaviour) because you assign to m_pMainWnd a local object (which is destroyed once InitInstance ends).

[edit]

S.B Bae - to investigate it further and find a root cause, you will need to debug place where m_pMainWnd should be set to NULL once your dialog ends. This should be in CWnd::OnNcDestroy() in wincore.cpp. There is a line pThread->m_pMainWnd = NULL; which apparently is not being executed in your application.

                        
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