C++ :: Why Are Destructors Called In Reverse
May 15, 2013
"Destructors for a derived class object are called in the reverse order of the constructors for the object. This is a general rule that always applies. Constructors are invoked starting with the base class constructor and then the derived class constructor, whereas the destructor for the derived class is called first when an object is destroyed, followed by the base class destructor."
But why, or is it just because, so programmers know which one and modify their destructor accordingly??
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May 20, 2013
In this code:
#pragma once
#include <iostream>
class CBox // Derived class {
public:
// Constructor
explicit CBox(double lv = 1.0, double wv = 1.0, double hv = 1.0) : m_Length(lv), m_Width(wv), m_Height(hv){}
[Code] .....
Before the program ends, at return 0;
I would expect the CBox destructor to be called 3 times but it is being called 6 times? Why? Also in this code:
#pragma once
#include <iostream>
class CBox // Derived class {
public:
// Constructor
explicit CBox(double lv = 1.0, double wv = 1.0, double hv = 1.0) : m_Length(lv), m_Width(wv), m_Height(hv){}
[Code] .....
Why is the destructor called 3 times? When have you really destroyed a CBox? Doesnt emplace only create it and store it, then thats it?
[URL] .....
For pushback:
void push_back(value_type&& _Val)
{// insert by moving into element at end
if (_Inside(_STD addressof(_Val)))
{// push back an element
size_type _Idx = _STD addressof(_Val) - this->_Myfirst;
[Code] .....
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Mar 5, 2015
I am in a intro C++ class and have an assignment to create a patient appointment scheduling program. I finished my code, but when I run it the destructors in each class are being called a bunch of times and the menu shows up at the bottom of the that, so the whole output looks like a mess. Identifying why the destructors are being called like this?
#include <iostream>
#include <iomanip>
#include <string>
#include <cstdlib>
#include <time.h>
using namespace std;
void ShowMenu ();
[Code] ......
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Aug 29, 2013
I am new to C and trying to reverse a string but the function is not getting called.. the console says :
Enter a stringabhi
bash: line 1: 229 Segmentation fault (core dumped) ./program
Code:
#include<stdio.h>
#include<math.h>
#include<string.h>
char* reverseString(char input[]);
void main()
[Code] ....
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Jan 6, 2014
have a look at the following code :
class Base
{
public:
virtual ~Base()
{
cout << "Calling ~Base()" << endl;
[Code]...
Now this program produces the following result:
Calling ~Derived()
Calling ~Base()
i was reading online and got stuck here. i am unable to understand why 'calling ~Base()' is been printed here? when we reached delete pbase; in int main() it goes to Base class first and finds that its destructor is virtual so it goes to Derive class and finds another destructor and executes it but why does it prints ~Base() in any case?
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Jun 5, 2014
Every time we pass an object to a function, and when the function ends and the object is not necessary anymore the destructor is called. if it's passing by value then a copy of the object is passed. if the object has a pointer inside of it so we implement the copy constructor to create a new pointed-variable so the original pointer will not get deleted.
so far so good. But what about passing an object to a non-member function by reference?
The language says that as soon as the function ends - the object will be deleted , because we passed by ref. that means that after the function ends - the object is not usable anymore! =What does that say? that in c++ you can't pass object by ref. because it will get deleted and un-uasable??
Varifying it with a compiler shows that the object is NOT deleted after the function ends.
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May 4, 2013
I am working on this project where I need a function to be called every second. At this time, I am thinking that I have to create a thread but I am clueless on how it will get called every second.
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Apr 27, 2013
The following are the cases when copy constructor is called.
1)When instantiating one object and initializing it with values from another object.
2)When passing an object by value.
3)When an object is returned from a function by value.
I don't understand #2 How can and object be passed by value? when I think of passing object I think of passing by address or reference. explain
I don't understand #3 how can a function returned object by value I think of again passing by address or reference.
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Apr 8, 2014
Why in this code the destructor is called 2 time? How can i avoid it?
int _tmain(int argc, _TCHAR* argv[]) {
Elenco e1;
std::cout << "Test 2" <<std::endl;
std::cout<<e1.size()<<std::endl;
[Code] ....
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Sep 17, 2013
Whenever my copy constructor is called, my destructor destroys is immediately after.
My copy constructor
CS1CStudent::CS1CStudent(const CS1CStudent& otherCS1CStudent)
{
cout << "
***************************
";
[Code]....
The copy constructor is called twice, once when you pass an object by value, and once when the object is returned from a function by value. But why is the destructor being called twice?
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Jul 12, 2012
I was trying some virtual mechanism then This came to my mind
#include <iostream>
using namespace std;
class A
{
[Code].....
now My concerns is that though the function f() in B was private it gets called by the pointer of class A as it is a virtual function
so is this a violation of access control?
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May 6, 2014
OgreWidget.h
Code:
#ifndef __OGREWIDGET_H__
#define __OGREWIDGET_H__
#include <OGRE/Ogre.h>
#include <QGLWidget>
//#include <QX11Info>
class OgreWidget : public QGLWidget {
//Q_OBJECT;
[Code] ....
The inherited method called createScene is not called.
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Sep 15, 2013
I was wondering that why in the below code, the copy constructor is called 2 times.
Code:
class A {
private:
static int count;
int age;
public:
A()
[code].....
I think that when f(a) is called, since I am passing this as value, no copy constructor should be called. The copy constructor should called when the return object "x" is assigned to:
A b = x;
why copy constructor called 2 times?
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Nov 11, 2013
I would like to know how could I make multiplication of matrix called betrix in this code:
Code:
printf("transposed matrix:
");
int trantrix[size][size]; //transposed matrix
for(i=0;i<size;i++) {
for(j=0;j<size;j++) {
trantrix[i][j] = matrix[j][i];
printf("%d ",trantrix[i][j]);
[Code] ......
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May 17, 2013
When the below is done, does it call the constroctor only, and if yes, constructors do not have return types so how does it work? is there anything behind the scene?
wxAddHandler(new wxPNG_HANDLER);
and
sf::RenderWindow(sf::VideoMode(...),...);
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Dec 6, 2014
I can't get my 'Front End' view model's constructor to be called. If i remove my dependency from the mvvm-light framework and use MSDN mvvm paterns then the constructor is called. What am i doing wrong. It seem like there is a data context binding issue between my XMAL and my view model backing.
ViewModelLocator.cs
using GalaSoft.MvvmLight.Ioc;
using Microsoft.Practices.ServiceLocation;
using Point_Of_Sale.Model;
using System.Collections.Generic;
namespace Point_Of_Sale.ViewModel {
public class ViewModelLocator
[Code] ......
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Jan 29, 2015
Why does the destructor is called just after declaring my object?
// MAIN
int main(void) {
Jucarie j1;
Jucarie j2(j1);
return 0;
}
THE DESTRUCTOR
Jucarie::~Jucarie() {
cout << "Destructor called" << endl;
delete[] material;
material = NULL;
}
I do not have a copy constructor, i just want to use the shallow copy. Why i get Debug Assertion Failed error? If i delete the destructor, all work fine.
I get it, the problem occurs when the material from j1 is deleted right? Because it has already been delete by j2.
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Apr 5, 2014
I am trying to use myfile to create and write user data to a file [URL].
At the moment I only want to save as .txt so that I can open it to see that it wrote to file properly.
The main issue I get is that it says the file is not open when my program gets to the error checking at the very end, a few guides mentioned that if the file was not yet created a file with the specified name would be generated in the same folder as main on the hard drive. I did try creating the file as a notepad .txt file but it still read the error. Here is the snippet concerning the writing of the file:
void WriteToFile() {
if(myfile.is_open()) {
myfile.open("userdata.txt",ios::in);
myfile<<"User name: "<<NameFirst<<" "<<NameLast<<"
[Code] ....
it compiles fine with the rest of the program and everything runs smoothly, it just isn't writing to a file.I have included <string>, <iostream> and <fstream>.
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Nov 19, 2012
#include<iostream>
using namespace std;
class Cents {
public:
int m_nCents;
Cents(int nCents=0):m_nCents(nCents){
cout<<"Calling normal constructor with value:"; m_nCents = nCents;
cout<<m_nCents<<endl;
[code].....
Question is :Why is the overloaded copy constructor that I have written not getting called here?Internally default copy constructor is getting called.Thats why we get value of obj2.m_nCents as 37.
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Aug 27, 2014
I write a DLL MyDLL.dll with Visual C++ 2008, as follows:
(1)MFC static linked
(2)Using multi-thread runtime library.
In the DLL, this is a global data m_Data shared by two export functions, as follows:
ULONGLONG WINAPI MyFun1(LPVOID *lpCallbackFun1) {
...
Write m_Data(using Critical section to protect)
[Code]....
Although MyThread1 and MyThread2 using critical section to protect the shared data m_Data, I will still suspend MyThread1 before accessing the shared data, to prevent any possible conflicts.
The problem is:
(1)When the first invoke of MyFun2, everything is OK, and the return value of MyFun2(that is nResult2) is 1 , which is expected.
(2)When the second, third and fourth invoke of MyFun2, the operations in MyFun2 are executed successfully, but the return value of MyFun2(that is nResult2) is a random value instead of the expected value 1. I try to using Debug to trace into MyFun2, and confirm that the last return statement is just return a value of 1, but the invoker will receive a random value instead of 1 when inspecting nResult2.
(3)After the fourth invoke of MyFun2 and return back to the next statement follow MyFun2, I will always get a "buffer overrun detected" error, whatever the next statement is.
I think this looks like a stack corruption, so try to make some tests:
1.I confirm the /GS (Stack security check) feature in the compiler is ON.
2.If MyFun2 is invoked after MyFun1 in MyThread1 is completed, then everything will be OK.
3.In debug mode, the codeline in MyFun2 that reads the shared data m_Data will not cause any errors or exceptions. Neither will the codeline in MyFun1 that writes the shared Data.
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Oct 26, 2012
Here are the classes:
BaseClass.h
Code:
class BaseClass {
public:
BaseClass();
virtual ~BaseClass();
virtual void printStuff() const;
[Code] ....
When I call printStuff, the DerivedClass's function gets called. Now, if I remove the const part from the DerivedClass's printStuff function, we call the BaseClass's printStuff function.
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Feb 27, 2015
There is already a thread with exactly the same problem I have, but the answer to solve the problem isn't stated at the end. Problem with callback as classmember.
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Oct 28, 2013
My programs complies and runs. However, whenever i try to enter something when prompt to enter the number of accounts i wanted to create my program crashes.
By the way, im using codeblocks.
it says
terminated called after throwing an instance of 'std:: out of range'. what(): basic_string::substr"
Code:
#include <iostream>
#include "clsInterest.h"
#include "clsDate.h"
using namespace std;
[Code] .....
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Mar 14, 2013
Write a program with two functions both called from main(). The first function just prints "Hello". In the second function ask the user to enter a number. Calculate the square root of the number and return the result to main(). In main() print the square root value.
Code:
#include<stdio.h>
#include<math.h>
float fun3 (float );
main()
}
[code]...
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Nov 11, 2014
As I am taking my first steps in C, I study K&R (I guess most of you did the same, right?)
In the introductory chapter about functions (1.7) there is an example showing how to create a function that is then called to calculate powers (b**n). I simplified it to calculate only one given power, 2**5:
Code:
#include <stdio.h>
int power(int m, int n);
main() {
printf("%d", power(2,5));
[Code]....
It will then be called to make the calculation in the above string.
First things first: we already know how to use while(getchar!=EOF) to count characters (K&R chapter 1.5.2) but what if -instead- the input is a specific string? How to "read" it and how to tell my program that the string is finished? And most important: "reading" will be done in the function or in the rest of the body?
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Feb 27, 2013
So on lines 36 - 39 (The commented out functions) is where I'm sure is causing this error because once I don't comment them out pretty much everywhere Flink or Rlink is used or defined I get this error.
#ifndef nodes_Nodes_h
#define nodes_Nodes_h
#include <cstdlib>
[Code]....
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