在某些情况下无法创建派生类的对象 [英] Failed to create object of derived class in some cases

问题描述

// Base Class    
class Base
{
   public:
     void RegisterWithServer();
     // some more functions
   protected:
      Base(std::string aTestName, std::string aServerName);
      ~Base();

   private:    
          std::string mString;
          std::string mServerName;
          yami::agent mYAMIAgent;     
  };


 // Base Class constructor

     Base::Base(string aTargetName, string aServerName):
     mString(aTargetName),
     mServerName(aServerName)
    {
        // my debug statment
         cout <<" we are in Base Class constructor"<< std::endl;
        cout <<" in normal case we get this debug statement  but in case of crash  it doesnt  reach till here I suppose "<< endl;
     }


 // DerivedClass
  class derivedClient: public Base
  {
     public:

      derivedClient(std::string aceptedString);
      virtual ~derivedClient();

     private:
        std::string mServerAddress;
        std::string mServerName;
   };


// constructor
 derivedClient::derivedClient(string aceptedString):
 Base(aceptedString, "ServerTest"),
 mServerAddress(aceptedString),
 mServerName ("ServerTest")
 {
        cout <<" in normal case we get this debug statement  but in case of crash it doesnt  reach till here I suppose "<< endl;

 RegisterWithServer(); // call base class function
};


 // in some other  function in different file

 some function()
{
    .....
   .....
   try
   {
    if( meet certain condition)
    {
         ......
         ......
          cout <<" the code reached till here" << std::endl;
         derivedClient dClient("192.168.2.110");// problem ??

          cout <<"in case of crash below lines are not printed nor any message is printed from both constructors "<< std::endl;

       }
    }

   catch( const yami::yami_logic_error & aYamiException)
   {
    cout << "error: " << aYamiException.what() << endl;
    }

}

b $ b我正在修复现有软件中的错误。

问题 - >在某些时候软件停止响应。
我做了什么 - >我已经跟踪的问题，发现当软件崩溃时，它失败，从对象创建之前从dervived类。

Hi Guys,
I am fixing the bug in the existing software .
Problem -> after some times the software stops responding . What I have done -> I have traced the problem and found that when software crashes it fails before the object creation from dervived class.

派生类调用衍生构造函数和基础构造函数。我添加了调试语句，发现没有打印调试。

The derived class calls dervived constructor and base constructor. I have added debug statement and found nothing is printed on debug.

我想知道为什么代码甚至不会进入派生类和基类？是否有可能私人变量没有正确初始化？

I want to know why the code is not even going into derived class and base class ? is it possible that private variables have not been initialsed properly ?

请对示例代码进行一些评论。

感谢和问候，

Sam

Please throw some comments on sample code.
Thanks and regards,
Sam

推荐答案

我猜想 yami :: agent 的构造函数抛出一个异常， cout没有运行。正如Oli在注释中提到的，在输入类构造函数之前将构造一个类的所有成员变量，因此 yami :: agent :: agent（）将在 Base :: Base（）。

I'm would guess that the constructor for yami::agent throws an exception which is why all the couts are not being run. As Oli mentioned in the comments all member variables of a class will be constructed before the class constructor is entered so yami::agent::agent() will be run before Base::Base() is entered.

编辑：

如果您有类似：

class MyObject
{
     yami::agent m_Agent;    
public:
     MyObject::MyObject() { }
};

那么m_Agent将使用默认构造函数构造，它被声明为 agent const parameters& options = parameters（））; 。正如你所提到的，由于某些原因，yami :: agent :: agent（）抛出一个异常，这可能是由于任何原因，如网络初始化错误，无效的输入参数等....

then m_Agent will get constructed using its default constructor which is declared as agent(const parameters & options = parameters());. As you mention, for some reason yami::agent::agent() throws an exception which could due to any number of reasons such as a network initialization error, invalid input parameters, etc....

如果你想为yami :: agent构造函数指定自定义参数，你可以这样做：

If you want to specify custom parameters to the yami::agent constructor you can do something like:

 yami::parameters& GetDefaultYamiOptions (void)
 {
      static yami::parameters options;

            /* The following are just some example parameters */
      options.set_integer(yami::option_names::connection_retries, 1);
      options.set_integer(yami::option_names::connection_retry_delay_spread, 10);
      options.set_integer(yami::option_names::tcp_nonblocking, true);
      options.set_integer(yami::option_names::file_nonblocking, true);
      options.set_integer(yami::option_names::tcp_connect_timeout, 1000);

      return options;
 }

 class MyObject
 {
      yami::agent m_Agent;    
 public:

     MyObject::MyObject() : m_Agent(GetDefaultYamiOptions())
     {
     }
 };

您需要什么参数可能与我使用的参数不同，问题的原因可能不与不正确的参数相关。它很可能是来自操作系统或甚至硬件的低级网络错误。

What parameters you need may be different than what I use and the cause of the issue may not be even related to incorrect parameters. It could well be a low level networking error from the OS or even hardware.

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