标签：c visual-studio-debugging messagebox infinite-loop mutual-recursion
我保留的一些遗留代码卡在无限循环中(因此我自己似乎在一个);但是,我无法弄清楚为什么/如何.
这是应用程序的入口点,它实例化主窗体(frmCentral)：
代码展览A.
public static int Main(string [] args)
{
try
{
AppDomain currentDomain = AppDomain.CurrentDomain;
currentDomain.UnhandledException += new UnhandledExceptionEventHandler(GlobalExceptionHandler);
string name = Assembly.GetExecutingAssembly().GetName().Name;
MessageBox.Show(string.Format("Executing assembly is {0}", name)); // TODO: Remove after testing <= this one is seen
IntPtr mutexHandle = CreateMutex(IntPtr.Zero, true, name);
long error = GetLastError();
MessageBox.Show(string.Format("Last error int was {0}", error.ToString())); // TODO: Remove after testing <= this one is also seen
if (error == ERROR_ALREADY_EXISTS)
{
ReleaseMutex(mutexHandle);
IntPtr hWnd = FindWindow("#NETCF_AGL_BASE_", null);
if ((int) hWnd > 0)
{
SetForegroundWindow(hWnd);
}
return 0;
}
MessageBox.Show("made it into Main method #4"); // TODO: Remove after testing <= this one is seen
ReleaseMutex(mutexHandle);
MessageBox.Show("made it into Main method #5"); // TODO: Remove after testing <= this one is seen
DeviceInfo devIn = DeviceInfo.GetInstance();
MessageBox.Show("made it into Main method #6"); // TODO: Remove after testing <= this one is seen
Wifi.DisableWifi();
MessageBox.Show("made it into Main method #7"); // TODO: Remove after testing <= this one is seen
// Instantiate a new instance of Form1.
frmCentral f1 = new frmCentral();
f1.Height = devIn.GetScreenHeight();
f1.Text = SSCS.GetFormTitle("SSCS HHS", "", "");
MessageBox.Show("made it before Application.Run() in Main method"); // TODO: Remove after testing <= this one is NOT seen
Application.Run(f1);
devIn.Close();
Application.Exit();
return 0;
}
catch(Exception ex)
{
SSCS.ExceptionHandler(ex, "Main");
return 0;
}
} // Main() method
frmCentral的构造函数然后调用一个名为DBConnection.GetInstance()的单例方法(与glorified相反的是什么？)：
CODE EXHIBIT B
public frmCentral()
{
try
{
//
// Required for Windows Form Designer support
//
InitializeComponent();
MessageBox.Show("made it past InitializeComponent() in frmCentral constructor"); // <= this displays
devIn = DeviceInfo.GetInstance();
MessageBox.Show("made it past DeviceInfo.GetInstance() in frmCentral constructor"); // <= this displays
dbconn = DBConnection.GetInstance();
MessageBox.Show("made it past DBConnection.GetInstance() in frmCentral constructor");
WindowState = FormWindowState.Maximized;
UpdateMenuItemSelectable = false;
ResetConnectionFetchForm = false;
AllowNewItems = true;
listboxWork.Focus();
MessageBox.Show("made it through frmCentral constructor"); // <= this one does NOT display
}
catch (Exception ex)
{
SSCS.ExceptionHandler(ex, "frmCentral()");
}
} // frmCentral Constructor
这是“美化”的单一/种类单身方法：
CODE EXHIBIT C
// Singleton pattern, or at least a derivation thereof
public static DBConnection GetInstance()
{
MessageBox.Show("made it into DBConnection.GetInstance()");
try
{
if (instance == null)
{
MessageBox.Show("made it into DBConnection.GetInstance(); instance was null");
instance = new DBConnection();
}
}
catch(Exception ex)
{
SSCS.ExceptionHandler(ex, "DBConnection.GetInstance");
}
return instance;
}
这实例化了DBConnection,因此调用了它的构造函数：
CODE EXHIBIT D
private DBConnection()
{
try
{
// Connection String
string conStr = "Data Source = " + filename;
string cmpStr = conStr + ".tmp";
MessageBox.Show(string.Format("made it into DBConnection constructor. cmpStr == {0}", cmpStr)); // TODO: Comment out or remove
if (File.Exists(filename+".tmp"))
File.Delete(filename+".tmp");
engine = new SqlCeEngine(conStr);
MessageBox.Show(string.Format("SqlCeEngine created. conStr == {0}", conStr)); // TODO: Comment out or remove
if (File.Exists(filename))
{
MessageBox.Show(string.Format("file {0} exists", filename)); // TODO: Comment out or remove
}
else
{
// Create the SQL Server CE database
engine.CreateDatabase();
MessageBox.Show("Made it past call to engine.CreateDatabase()"); // TODO: Comment out or remove
}
engine.Dispose();
objCon = new SqlCeConnection(conStr);
MessageBox.Show("Made it past call to new SqlCeConnection(conStr)"); // TODO: Comment out or remove
objCon.Open();
}
catch(Exception ex)
{
SSCS.ExceptionHandler(ex, "DBConnection.DBConnection");
}
}
我从Code Exhibit A看到了* MessageBox.Show()* s(除非另有说明),然后是Code Exhibit B,然后是Code Exhibit C,然后是Code Exhibit D,然后它在C和D之间来回转换“直到奶牛回家.“
我不明白为什么DBConnection构造函数和DBConnection GetInstance()以递归方式相互调用,但是…我在大海捞针中是否有针,或是隐藏在普通视野中的大象,还是……？ ？
UPDATE
public static void ExceptionHandler(Exception ex, string location)
{
try
{
MessageBox.Show("Exception: " + ex.Message + "\n\nLocation: " + location, GetFormTitle("SSCS: " + ex.GetType().FullName,"",""));
}
catch(Exception exc)
{
MessageBox.Show("Exception Handler generated an exception!\n" + exc.Message + "\n\nCalling Location: " + location, GetFormTitle("SSCS: " + exc.GetType().FullName,"",""));
}
}
更新2
这是更有启发性的晦涩：
public static string GetFormTitle(string formName, string serialNo, string siteNo)
{
string titleBar = formName == "" ? "SSCS HHS" : formName;
if((serialNo == ""))
{
User person = new User();
person.getUserFromTable();
serialNo = person.getSerialNo();
}
if (frmCentral.HashSiteMapping.ContainsKey(siteNo))
{
siteNo = (string) frmCentral.HashSiteMapping[siteNo];
}
if (serialNo != "")
titleBar += " - " + serialNo + (siteNo == "" ? "" : " Site #" + siteNo);
return titleBar;
}
更新3
我添加的未捕获的异常代码：
currentDomain.UnhandledException += new UnhandledExceptionEventHandler(GlobalExceptionHandler);
static void GlobalExceptionHandler(object sender, UnhandledExceptionEventArgs args)
{
Exception e = (Exception)args.ExceptionObject;
MessageBox.Show(string.Format("GlobalExceptionHandler caught {0}; Compact Framework Version == {1}", e.Message, Environment.Version.ToString()));
}
我还没有看到任何证据表明这个处理程序已经达到(无论如何,到目前为止).
更新4
非常有趣 – 在向GetFormTitle添加MessageBox.Show(或两个)之后：
public static string GetFormTitle(string formName, string serialNo, string siteNo)
{
MessageBox.Show(string.Format("GetFormTitle() reached. formName == {0}; serialNo == {1}; siteNo == {2}", formName, serialNo, siteNo)); // TODO: Remove after testing
string titleBar = formName == "" ? "SSCS HHS" : formName;
if((serialNo == ""))
{
User person = new User();
person.getUserFromTable();
serialNo = person.getSerialNo();
}
if (frmCentral.HashSiteMapping.ContainsKey(siteNo))
{
siteNo = (string) frmCentral.HashSiteMapping[siteNo];
}
if (serialNo != "")
titleBar += " - " + serialNo + (siteNo == "" ? "" : " Site #" + siteNo);
MessageBox.Show(string.Format("titleBar val about to be returned. Val is {0}", titleBar)); // TODO: Remove after testing
return titleBar;
}
…这些是我现在看到的MessageBox.Show()的序列：
0) Made it into DBConnection.GetInstance()
1) Made it into DBConnection.GetInstance() instance was null
2) Made it to DBConnection constructor cmpStr == ....
3) Sqlceengine created. conStr == ...
4) File \My Documents\HHSDB.SDF exists
5) Made it past call to new SqlCeConnection(conStr)
6) GetFormTitle() reached. fromName == SSCS:
System.Data.SqlserverCe.SqlCeException; serial No ==; siteNo ==
…接下来是一轮追尾,递归的消息直到我热身启动(我讨厌与Fab 4相矛盾,但与流行的观点相反,幸福绝对不是热情的启动！*)
…所以正好在MessageBox消息显示中,插入了一个异常！全宾夕法尼亚嘻哈(Key Rap)！
* Let's have no attempts at humor revolving around warm booty, now!
这是远程桌面调试的最佳展示,LB2！
解决方法:
这是可能发生的事情(此时是一个理论,直到OP可以确认)：
启动问题的事情……
启动无限循环链的问题可能是objCon.Open();在图表D中.连接到数据库可能存在一些问题,而Open()调用应该抛出异常.这当然会被紧跟在该行之后的本地捕获.
本地catch调用SSCS.ExceptionHandler,它显示在Update 1中.它看起来很温和,但是在它中隐藏了罪魁祸首的帮凶,名称GetFormTitle显示在Update 2中.
事情变得更糟……
GetFormTitle有一段非常有趣的代码：
User person = new User();
person.getUserFromTable();
…最有可能是从数据库中检索用户信息的模型(其他地方).
所以创建了无限循环……
好吧,要从数据库中获取用户,需要一个连接,这很可能导致调用DBConnection.GetInstance(),这将转到objCon.Open();它开始新的循环,因此创建了infinite loop(巧妙地,不使用任何语言的内置循环机制,需要及时注意).
确认：
OP：请把非常简单(意思是没有调用GetFormTitle,请)GetFormTitle中的MessageBoxes,如果上述理论是正确的,你会在执行路径中看到它.
标签：c,visual-studio-debugging,messagebox,infinite-loop,mutual-recursion 来源： https://codeday.me/bug/20190517/1119863.html
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