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  • Copy constructor demo (crashing...)

    - by AKN
    Here is the program... class CopyCon { public: char *name; CopyCon() { name = new char; } CopyCon(const CopyCon &objCopyCon) { name = new char; _tcscpy(name,objCopyCon.name); } ~CopyCon() { if( name != NULL ) { delete name; name = NULL; } } }; int main() { CopyCon objCopyCon1; objCopyCon1.name = "Hai"; CopyCon objCopyCon2(objCopyCon1); objCopyCon1.name = "Hello"; cout<<objCopyCon2.name<<endl; return 0; } Once the code execution completes, when the destructor called, it crashes on 'delete' saying... Debug Error! Program: ... HEAP CORRUPTION DETECTED: after Normal block (#124) at 0x00366990. CRT detected that the application wrote to memory after end of heap buffer. (Press Retry to debug the application) Don't we have to clear the heap memory in destructor. What's wrong with this program? Pls someone help! Copy constructor works perfectly as intended. But still... !?

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  • Creating a new object destroys an older object with different name in C++

    - by Mikael
    First question here! So, I am having some problems with pointers in Visual C++ 2008. I'm writing a program which will control six cameras and do some processing on them so to clean things up I have created a Camera Manager class. This class handles all operations which will be carried out on all the cameras. Below this is a Camera class which interacts with each individual camera driver and does some basic image processing. Now, the idea is that when the manager is initialised it creates two cameras and adds them to a vector so that I can access them later. The catch here is that when I create the second camera (camera2) the first camera's destructor is called for some reason, which then disconnects the camera. Normally I'd assume that the problem is somewhere in the Camera class, but in this case everything works perfectly as long as I don't create the camera2 object. What's gone wrong? CameraManager.h: #include "stdafx.h" #include <vector> #include "Camera.h" class CameraManager{ std::vector<Camera> cameras; public: CameraManager(); ~CameraManager(); void CaptureAll(); void ShowAll(); }; CameraManager.cpp: #include "stdafx.h" #include "CameraManager.h" CameraManager::CameraManager() { printf("Camera Manager: Initializing\n"); [...] Camera *camera1 = new Camera(NodeInfo,1, -44,0,0); cameras.push_back(*camera1); // Adding the following two lines causes camera1's destructor to be called. Why? Camera *camera2 = new Camera(NodeInfo,0, 44,0,0); cameras.push_back(*camera2); printf("Camera Manager: Ready\n"); }

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  • C++ Dynamic Allocation Mismatch: Is this problematic?

    - by acanaday
    I have been assigned to work on some legacy C++ code in MFC. One of the things I am finding all over the place are allocations like the following: struct Point { float x,y,z; }; ... void someFunc( void ) { int numPoints = ...; Point* pArray = (Point*)new BYTE[ numPoints * sizeof(Point) ]; ... //do some stuff with points ... delete [] pArray; } I realize that this code is atrociously wrong on so many levels (C-style cast, using new like malloc, confusing, etc). I also realize that if Point had defined a constructor it would not be called and weird things would happen at delete [] if a destructor had been defined. Question: I am in the process of fixing these occurrences wherever they appear as a matter of course. However, I have never seen anything like this before and it has got me wondering. Does this code have the potential to cause memory leaks/corruption as it stands currently (no constructor/destructor, but with pointer type mismatch) or is it safe as long as the array just contains structs/primitive types?

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  • How do I handle freeing unmanaged structures on application close?

    - by LostKaleb
    I have a C# project in which i use several unmanaged C++ functions. More so, I also have static IntPtr that I use as parameters for those functions. I know that whenever I use them, I should implement IDisposable in that class and use a destructor to invoke the Dispose method, where I free the used IntPtr, as is said in the MSDN page. public void Dispose() { Dispose(true); GC.SuppressFinalize(this); } private void Dispose(bool disposing) { // Check to see if Dispose has already been called. if (!this.disposed) { if (disposing) { component.Dispose(); } CloseHandle(m_InstanceHandle); m_InstanceHandle = IntPtr.Zero; disposed = true; } } [System.Runtime.InteropServices.DllImport("Kernel32")] private extern static Boolean CloseHandle(IntPtr handle); However, when I terminate the application, I'm still left with a hanging process in TaskManager. I believe that it must be related to the used of the MarshalAs instruction in my structures: [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)] public struct SipxAudioCodec { [MarshalAs(UnmanagedType.ByValTStr, SizeConst=32)] public string CodecName; public SipxAudioBandwidth Bandwidth; public int PayloadType; } When I create such a structure should I also be careful to free the space it allocs using a destructor? [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)] public struct SipxAudioCodec { [MarshalAs(UnmanagedType.ByValTStr, SizeConst=32)] public string CodecName; public SipxAudioBandwidth Bandwidth; public int PayloadType; ~SipxAudioCodec() { Marshal.FreeGlobal(something...); } }

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  • How do I handle freeing unmanaged structures in C# on application close?

    - by LostKaleb
    I have a C# project in which i use several unmanaged C++ functions. More so, I also have static IntPtr that I use as parameters for those functions. I know that whenever I use them, I should implement IDisposable in that class and use a destructor to invoke the Dispose method, where I free the used IntPtr, as is said in the MSDN page. public void Dispose() { Dispose(true); GC.SuppressFinalize(this); } private void Dispose(bool disposing) { // Check to see if Dispose has already been called. if (!this.disposed) { if (disposing) { component.Dispose(); } CloseHandle(m_InstanceHandle); m_InstanceHandle = IntPtr.Zero; disposed = true; } } [System.Runtime.InteropServices.DllImport("Kernel32")] private extern static Boolean CloseHandle(IntPtr handle); However, when I terminate the application, I'm still left with a hanging process in TaskManager. I believe that it must be related to the used of the MarshalAs instruction in my structures: [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)] public struct SipxAudioCodec { [MarshalAs(UnmanagedType.ByValTStr, SizeConst=32)] public string CodecName; public SipxAudioBandwidth Bandwidth; public int PayloadType; } When I create such a structure should I also be careful to free the space it allocs using a destructor? [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)] public struct SipxAudioCodec { [MarshalAs(UnmanagedType.ByValTStr, SizeConst=32)] public string CodecName; public SipxAudioBandwidth Bandwidth; public int PayloadType; ~SipxAudioCodec() { Marshal.FreeGlobal(something...); } } Thanks in advance!

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  • Can You Have "Empty" Abstract/Classes?

    - by ShrimpCrackers
    Of course you can, I'm just wondering if it's rational to design in such a way. I'm making a breakout clone and was doing some class design. I wanted to use inheritance, even though I don't have to, to apply what I've learned in C++. I was thinking about class design and came up with something like this: GameObject - base class (consists of data members like x and y offsets, and a vector of SDL_Surface* MovableObject : GameObject - abstract class + derived class of GameObject (one method void move() = 0; ) NonMovableObject : GameObject - empty class...no methods or data members other than constructor and destructor(at least for now?). Later I was planning to derive a class from NonMovableObject, like Tileset : NonMovableObject. I was just wondering if "empty" abstract classes or just empty classes are often used...I notice that the way I'm doing this, I'm just creating the class NonMovableObject just for sake of categorization. I know I'm overthinking things just to make a breakout clone, but my focus is less on the game and more on using inheritance and designing some sort of game framework.

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  • Is there a Design Pattern for preventing dangling references?

    - by iFreilicht
    I was thinking about a design for custom handles. The thought is to prevent clients from copying around large objects. Now a regular handle class would probably suffice for that, but it doesn't solve the "dangling reference problem"; If a client has multiple handles of the same object and deletes the object via one of them, all the others would be invalid, but not know it, so the client could write or read parts of the memory he shouldn't have access to. Is there a design pattern to prevent this from happening? Two ideas: An observer-like pattern where the destructor of an object would notify all handles. "Handle handles" (does such a thing even exist?). All the handles don't really point to the object, but to another handle. When the object gets destroyed, this "master-handle" invalidates itself and therefore all that point to it.

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  • How to setup the c++ rule of three in a virtual base class

    - by Minion91
    I am trying to create a pure virtual base class (or simulated pure virtual) my goal: User can't create instances of BaseClass. Derived classes have to implement default constructor, copy constructor, copy assignment operator and destructor. My attempt: class Base { public: virtual ~Base() {}; /* some pure virtual functions */ private: Base() = default; Base(const Base& base) = default; Base& operator=(const Base& base) = default; } This gives some errors complaining that (for one) the copy constructor is private. But i don't want this mimicked constructor to be called. Can anyone give me the correct construction to do this if this is at all possible?

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  • In C++, is it a reflection of poor software design if objects are deleted manually?

    - by grokus
    With the advent of smart pointers, is it a sign of poor design if I see objects are deleted? I'm seeing some software components in our product that people are still doing this. This practice strikes me as un-idiomatic, but I need to be sure this is the industry consensus. I'm not starting a crusade but it'd be nice to be prepared theory wise. Edit: legit uses of delete, Klaim mentioned the object pool use case. I agree. Bad examples of using delete, I am seeing many new's in constructor or start() and corresponding delete's in the destructor or stop(), why not use scoped_ptr? It makes the code cleaner.

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  • The rule of 5 - to use it or not?

    - by VJovic
    The rule of 3 (the rule of 5 in the new c++ standard) states : If you need to explicitly declare either the destructor, copy constructor or copy assignment operator yourself, you probably need to explicitly declare all three of them. But, on the other hand, the Martin's "Clean Code" advises to remove all empty constructors and destructors (page 293, G12:Clutter) : Of what use is a default constructor with no implementation? All it serves to do is clutter up the code with meaningless artifacts. So, how to handle these two opposite opinions? Should empty constructors/destructors really be implemented?

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  • vector iterator not dereferencable at runtime on a vector<vector<vector<A*>*>*>

    - by marouanebj
    Hi, I have this destructor that create error at runtime "vector iterator not dereferencable". The gridMatrix is a std::vector<std::vector<std::vector<AtomsCell< Atom<T> * > * > * > * > I added the typename and also the typedef but I still have the error. I will move for this idea of vect of vect* of vect* to use boost::multi_array I think, but still I want to understand were this is wrong. /// @brief destructor ~AtomsGrid(void) { // free all the memory for all the pointers inside gridMatrix (all except the Atom<T>* ) //typedef typename ::value_type value_type; typedef std::vector<AtomsCell< Atom<T>* >*> std_vectorOfAtomsCell; typedef std::vector<std_vectorOfAtomsCell*> std_vectorOfVectorOfAtomsCell; std_vectorOfAtomsCell* vectorOfAtomsCell; std_vectorOfVectorOfAtomsCell* vectorOfVecOfAtomsCell; typename std_vectorOfVectorOfAtomsCell::iterator itSecond; typename std_vectorOfVectorOfAtomsCell::reverse_iterator reverseItSecond; typename std::vector<std_vectorOfVectorOfAtomsCell*>::iterator itFirst; //typename std::vector<AtomsCell< Atom<T>* >*>* vectorOfAtomsCell; //typename std::vector<std::vector<AtomsCell< Atom<T>* >*>*>* vectorOfVecOfAtomsCell; //typename std::vector<std::vector<AtomsCell< Atom<T>* >*>*>::iterator itSecond; //typename std::vector<std::vector<AtomsCell< Atom<T>* >*>*>::reverse_iterator reverseItSecond; //typename std::vector<std::vector<std::vector<AtomsCell< Atom<T>* >*>*>*>::iterator itFirst; for (itFirst = gridMatrix.begin(); itFirst != gridMatrix.end(); ++itFirst) { vectorOfVecOfAtomsCell = (*itFirst); while (!vectorOfVecOfAtomsCell->empty()) { reverseItSecond = vectorOfVecOfAtomsCell->rbegin(); itSecond = vectorOfVecOfAtomsCell->rbegin().base(); vectorOfAtomsCell = (*itSecond); // ERROR during run: "vector iterator not dereferencable" // I think the ERROR is because I need some typedef typename or template ???!!! // the error seems here event at itFirst //fr_Myit_Utils::vectorElementDeleter(*vectorOfAtomsCell); //vectorOfVecOfAtomsCell->pop_back(); } } fr_Myit_Utils::vectorElementDeleter(gridMatrix); } If someone want the full code that create the error I'm happy to give it but I do not think we can attach file in the forum. BUT still its is not very big so if you want it I can copy past it here. Thanks

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  • What should I do or don't do to avoid Delphi "push dword" bug.

    - by Maksee
    I found that Delphi 5 generates invalid assembly code in specific cases. I can't understand in what cases in general. The example below produces access violation since a very strange optimization occurs. For a byte in a record or array Delphi generates push dword [...], pop ebx, mov .., bl that works correctly if there are data after this byte (we need at least three to push dword correctly), but fails if the data is inaccessible. I emulated the strict boundaries here with win32 Virtual* functions Specifically the error occurs when the last byte from the block accessed inside FeedBytesToClass procedure. And if I try to change something like using data array instead of object property of remove actionFlag variable, Delphi generates correct assembly instructions. const BlockSize = 4096; type TSomeClass = class private fBytes: PByteArray; public property Bytes: PByteArray read fBytes; constructor Create; destructor Destroy;override; end; constructor TSomeClass.Create; begin inherited Create; GetMem(fBytes, BlockSize); end; destructor TSomeClass.Destroy; begin FreeMem(fBytes); inherited; end; procedure FeedBytesToClass(SrcDataBytes: PByteArray; Count: integer); var j: integer; Ofs: integer; actionFlag: boolean; AClass: TSomeClass; begin AClass:=TSomeClass.Create; try actionFlag:=true; for j:=0 to Count-1 do begin Ofs:=j; if actionFlag then begin AClass.Bytes[Ofs]:=SrcDataBytes[j]; end; end; finally AClass.Free; end; end; procedure TForm31.Button1Click(Sender: TObject); var SrcDataBytes: PByteArray; begin SrcDataBytes:=VirtualAlloc(Nil, BlockSize, MEM_COMMIT, PAGE_READWRITE); try if VirtualLock(SrcDataBytes, BlockSize) then try FeedBytesToClass(SrcDataBytes, BlockSize); finally VirtualUnLock(SrcDataBytes, BlockSize); end; finally VirtualFree(SrcDataBytes, MEM_DECOMMIT, BlockSize); end; end; Initially the error occured when I used access to RGB data of bitmap bits, but the code there is too complex so I narrowed it to this fragment. So the question is what is here so specific that makes Delphi produce push,pop,mov optimization. I need to know this in order to avoid such side effects in general.

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  • Conway's Game of Life - C++ and Qt

    - by Jeff Bridge
    I've done all of the layouts and have most of the code written even. But, I'm stuck in two places. 1) I'm not quite sure how to set up the timer. Am I using it correctly in the gridwindow class? And, am I used the timer functions/signals/slots correctly with the other gridwindow functions. 2) In GridWindow's timerFired() function, I'm having trouble checking/creating the vector-vectors. I wrote out in the comments in that function exactly what I am trying to do. Any help would be much appreciated. main.cpp // Main file for running the grid window application. #include <QApplication> #include "gridwindow.h" //#include "timerwindow.h" #include <stdexcept> #include <string> #include <fstream> #include <sstream> #include <iostream> void Welcome(); // Welcome Function - Prints upon running program; outputs program name, student name/id, class section. void Rules(); // Rules Function: Prints the rules for Conway's Game of Life. using namespace std; // A simple main method to create the window class and then pop it up on the screen. int main(int argc, char *argv[]) { Welcome(); // Calls Welcome function to print student/assignment info. Rules(); // Prints Conway's Game Rules. QApplication app(argc, argv); // Creates the overall windowed application. int rows = 25, cols = 35; //The number of rows & columns in the game grid. GridWindow widget(NULL,rows,cols); // Creates the actual window (for the grid). widget.show(); // Shows the window on the screen. return app.exec(); // Goes into visual loop; starts executing GUI. } // Welcome Function: Prints my name/id, my class number, the assignment, and the program name. void Welcome() { cout << endl; cout << "-------------------------------------------------------------------------------------------------" << endl; cout << "Name/ID - Gabe Audick #7681539807" << endl; cout << "Class/Assignment - CSCI-102 Disccusion 29915: Homework Assignment #4" << endl; cout << "-------------------------------------------------------------------------------------------------" << endl << endl; } // Rules Function: Prints the rules for Conway's Game of Life. void Rules() { cout << "Welcome to Conway's Game of Life." << endl; cout << "Game Rules:" << endl; cout << "\t 1) Any living cell with fewer than two living neighbours dies, as if caused by underpopulation." << endl; cout << "\t 2) Any live cell with more than three live neighbours dies, as if by overcrowding." << endl; cout << "\t 3) Any live cell with two or three live neighbours lives on to the next generation." << endl; cout << "\t 4) Any dead cell with exactly three live neighbours becomes a live cell." << endl << endl; cout << "Enjoy." << endl << endl; } gridcell.h // A header file for a class representing a single cell in a grid of cells. #ifndef GRIDCELL_H_ #define GRIDCELL_H_ #include <QPalette> #include <QColor> #include <QPushButton> #include <Qt> #include <QWidget> #include <QFrame> #include <QHBoxLayout> #include <iostream> // An enum representing the two different states a cell can have. enum CellType { DEAD, // DEAD = Dead Cell. --> Color = White. LIVE // LIVE = Living Cell. ---> Color = White. }; /* Class: GridCell. A class representing a single cell in a grid. Each cell is implemented as a QT QFrame that contains a single QPushButton. The button is sized so that it takes up the entire frame. Each cell also keeps track of what type of cell it is based on the CellType enum. */ class GridCell : public QFrame { Q_OBJECT // Macro allowing us to have signals & slots on this object. private: QPushButton* button; // The button inside the cell that gives its clickability. CellType type; // The type of cell (DEAD or LIVE.) public slots: void handleClick(); // Callback for handling a click on the current cell. void setType(CellType type); // Cell type mutator. Calls the "redrawCell" function. signals: void typeChanged(CellType type); // Signal to notify listeners when the cell type has changed. public: GridCell(QWidget *parent = NULL); // Constructor for creating a cell. Takes parent widget or default parent to NULL. virtual ~GridCell(); // Destructor. void redrawCell(); // Redraws cell: Sets new type/color. CellType getType() const; //Simple getter for the cell type. private: Qt::GlobalColor getColorForCellType(); // Helper method. Returns color that cell should be based from its value. }; #endif gridcell.cpp #include <iostream> #include "gridcell.h" #include "utility.h" using namespace std; // Constructor: Creates a grid cell. GridCell::GridCell(QWidget *parent) : QFrame(parent) { this->type = DEAD; // Default: Cell is DEAD (white). setFrameStyle(QFrame::Box); // Set the frame style. This is what gives each box its black border. this->button = new QPushButton(this); //Creates button that fills entirety of each grid cell. this->button->setSizePolicy(QSizePolicy::Expanding,QSizePolicy::Expanding); // Expands button to fill space. this->button->setMinimumSize(19,19); //width,height // Min height and width of button. QHBoxLayout *layout = new QHBoxLayout(); //Creates a simple layout to hold our button and add the button to it. layout->addWidget(this->button); setLayout(layout); layout->setStretchFactor(this->button,1); // Lets the buttons expand all the way to the edges of the current frame with no space leftover layout->setContentsMargins(0,0,0,0); layout->setSpacing(0); connect(this->button,SIGNAL(clicked()),this,SLOT(handleClick())); // Connects clicked signal with handleClick slot. redrawCell(); // Calls function to redraw (set new type for) the cell. } // Basic destructor. GridCell::~GridCell() { delete this->button; } // Accessor for the cell type. CellType GridCell::getType() const { return(this->type); } // Mutator for the cell type. Also has the side effect of causing the cell to be redrawn on the GUI. void GridCell::setType(CellType type) { this->type = type; redrawCell(); } // Handler slot for button clicks. This method is called whenever the user clicks on this cell in the grid. void GridCell::handleClick() { // When clicked on... if(this->type == DEAD) // If type is DEAD (white), change to LIVE (black). type = LIVE; else type = DEAD; // If type is LIVE (black), change to DEAD (white). setType(type); // Sets new type (color). setType Calls redrawCell() to recolor. } // Method to check cell type and return the color of that type. Qt::GlobalColor GridCell::getColorForCellType() { switch(this->type) { default: case DEAD: return Qt::white; case LIVE: return Qt::black; } } // Helper method. Forces current cell to be redrawn on the GUI. Called whenever the setType method is invoked. void GridCell::redrawCell() { Qt::GlobalColor gc = getColorForCellType(); //Find out what color this cell should be. this->button->setPalette(QPalette(gc,gc)); //Force the button in the cell to be the proper color. this->button->setAutoFillBackground(true); this->button->setFlat(true); //Force QT to NOT draw the borders on the button } gridwindow.h // A header file for a QT window that holds a grid of cells. #ifndef GRIDWINDOW_H_ #define GRIDWINDOW_H_ #include <vector> #include <QWidget> #include <QTimer> #include <QGridLayout> #include <QLabel> #include <QApplication> #include "gridcell.h" /* class GridWindow: This is the class representing the whole window that comes up when this program runs. It contains a header section with a title, a middle section of MxN cells and a bottom section with buttons. */ class GridWindow : public QWidget { Q_OBJECT // Macro to allow this object to have signals & slots. private: std::vector<std::vector<GridCell*> > cells; // A 2D vector containing pointers to all the cells in the grid. QLabel *title; // A pointer to the Title text on the window. QTimer *timer; // Creates timer object. public slots: void handleClear(); // Handler function for clicking the Clear button. void handleStart(); // Handler function for clicking the Start button. void handlePause(); // Handler function for clicking the Pause button. void timerFired(); // Method called whenever timer fires. public: GridWindow(QWidget *parent = NULL,int rows=3,int cols=3); // Constructor. virtual ~GridWindow(); // Destructor. std::vector<std::vector<GridCell*> >& getCells(); // Accessor for the array of grid cells. private: QHBoxLayout* setupHeader(); // Helper function to construct the GUI header. QGridLayout* setupGrid(int rows,int cols); // Helper function to constructor the GUI's grid. QHBoxLayout* setupButtonRow(); // Helper function to setup the row of buttons at the bottom. }; #endif gridwindow.cpp #include <iostream> #include "gridwindow.h" using namespace std; // Constructor for window. It constructs the three portions of the GUI and lays them out vertically. GridWindow::GridWindow(QWidget *parent,int rows,int cols) : QWidget(parent) { QHBoxLayout *header = setupHeader(); // Setup the title at the top. QGridLayout *grid = setupGrid(rows,cols); // Setup the grid of colored cells in the middle. QHBoxLayout *buttonRow = setupButtonRow(); // Setup the row of buttons across the bottom. QVBoxLayout *layout = new QVBoxLayout(); // Puts everything together. layout->addLayout(header); layout->addLayout(grid); layout->addLayout(buttonRow); setLayout(layout); } // Destructor. GridWindow::~GridWindow() { delete title; } // Builds header section of the GUI. QHBoxLayout* GridWindow::setupHeader() { QHBoxLayout *header = new QHBoxLayout(); // Creates horizontal box. header->setAlignment(Qt::AlignHCenter); this->title = new QLabel("CONWAY'S GAME OF LIFE",this); // Creates big, bold, centered label (title): "Conway's Game of Life." this->title->setAlignment(Qt::AlignHCenter); this->title->setFont(QFont("Arial", 32, QFont::Bold)); header->addWidget(this->title); // Adds widget to layout. return header; // Returns header to grid window. } // Builds the grid of cells. This method populates the grid's 2D array of GridCells with MxN cells. QGridLayout* GridWindow::setupGrid(int rows,int cols) { QGridLayout *grid = new QGridLayout(); // Creates grid layout. grid->setHorizontalSpacing(0); // No empty spaces. Cells should be contiguous. grid->setVerticalSpacing(0); grid->setSpacing(0); grid->setAlignment(Qt::AlignHCenter); for(int i=0; i < rows; i++) //Each row is a vector of grid cells. { std::vector<GridCell*> row; // Creates new vector for current row. cells.push_back(row); for(int j=0; j < cols; j++) { GridCell *cell = new GridCell(); // Creates and adds new cell to row. cells.at(i).push_back(cell); grid->addWidget(cell,i,j); // Adds to cell to grid layout. Column expands vertically. grid->setColumnStretch(j,1); } grid->setRowStretch(i,1); // Sets row expansion horizontally. } return grid; // Returns grid. } // Builds footer section of the GUI. QHBoxLayout* GridWindow::setupButtonRow() { QHBoxLayout *buttonRow = new QHBoxLayout(); // Creates horizontal box for buttons. buttonRow->setAlignment(Qt::AlignHCenter); // Clear Button - Clears cell; sets them all to DEAD/white. QPushButton *clearButton = new QPushButton("CLEAR"); clearButton->setFixedSize(100,25); connect(clearButton, SIGNAL(clicked()), this, SLOT(handleClear())); buttonRow->addWidget(clearButton); // Start Button - Starts game when user clicks. Or, resumes game after being paused. QPushButton *startButton = new QPushButton("START/RESUME"); startButton->setFixedSize(100,25); connect(startButton, SIGNAL(clicked()), this, SLOT(handleStart())); buttonRow->addWidget(startButton); // Pause Button - Pauses simulation of game. QPushButton *pauseButton = new QPushButton("PAUSE"); pauseButton->setFixedSize(100,25); connect(pauseButton, SIGNAL(clicked()), this, SLOT(handlePause())); buttonRow->addWidget(pauseButton); // Quit Button - Exits program. QPushButton *quitButton = new QPushButton("EXIT"); quitButton->setFixedSize(100,25); connect(quitButton, SIGNAL(clicked()), qApp, SLOT(quit())); buttonRow->addWidget(quitButton); return buttonRow; // Returns bottom of layout. } /* SLOT method for handling clicks on the "clear" button. Receives "clicked" signals on the "Clear" button and sets all cells to DEAD. */ void GridWindow::handleClear() { for(unsigned int row=0; row < cells.size(); row++) // Loops through current rows' cells. { for(unsigned int col=0; col < cells[row].size(); col++) { GridCell *cell = cells[row][col]; // Grab the current cell & set its value to dead. cell->setType(DEAD); } } } /* SLOT method for handling clicks on the "start" button. Receives "clicked" signals on the "start" button and begins game simulation. */ void GridWindow::handleStart() { this->timer = new QTimer(this); // Creates new timer. connect(this->timer, SIGNAL(timeout()), this, SLOT(timerFired())); // Connect "timerFired" method class to the "timeout" signal fired by the timer. this->timer->start(500); // Timer to fire every 500 milliseconds. } /* SLOT method for handling clicks on the "pause" button. Receives "clicked" signals on the "pause" button and stops the game simulation. */ void GridWindow::handlePause() { this->timer->stop(); // Stops the timer. delete this->timer; // Deletes timer. } // Accessor method - Gets the 2D vector of grid cells. std::vector<std::vector<GridCell*> >& GridWindow::getCells() { return this->cells; } void GridWindow::timerFired() { // I'm not sure how to write this code. // I want to take the original vector-vector, and also make a new, empty vector-vector of the same size. // I would then go through the code below with the original vector, and apply the rules to the new vector-vector. // Finally, I would make the new vector-vecotr the original vector-vector. (That would be one step in the simulation.) cout << cells[1][2]; /* for (unsigned int m = 0; m < original.size(); m++) { for (unsigned int n = 0; n < original.at(m).size(); n++) { unsigned int neighbors = 0; //Begin counting number of neighbors. if (original[m-1][n-1].getType() == LIVE) // If a cell next to [i][j] is LIVE, add one to the neighbor count. neighbors += 1; if (original[m-1][n].getType() == LIVE) neighbors += 1; if (original[m-1][n+1].getType() == LIVE) neighbors += 1; if (original[m][n-1].getType() == LIVE) neighbors += 1; if (original[m][n+1].getType() == LIVE) neighbors += 1; if (original[m+1][n-1].getType() == LIVE) neighbors += 1; if (original[m+1][n].getType() == LIVE) neighbors += 1; if (original[m+1][n+1].getType() == LIVE) neighbors += 1; if (original[m][n].getType() == LIVE && neighbors < 2) // Apply game rules to cells: Create new, updated grid with the roundtwo vector. roundtwo[m][n].setType(LIVE); else if (original[m][n].getType() == LIVE && neighbors > 3) roundtwo[m][n].setType(DEAD); else if (original[m][n].getType() == LIVE && (neighbors == 2 || neighbors == 3)) roundtwo[m][n].setType(LIVE); else if (original[m][n].getType() == DEAD && neighbors == 3) roundtwo[m][n].setType(LIVE); } }*/ }

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  • objective-c default init method for class?

    - by Alex
    Hello, I have two differing methods for initializing my objective-c class. One is the default, and one takes a configuration parameter. Now, I'm pretty green when it comes to objective-c, but I've implemented these methods and I'm wondering if there's a better (more correct/in good style) way to handle initialization than the way I have done it. Meaning, did I write these initialization functions in accordance with standards and good style? It just doesn't feel right to check for the existence of selfPtr and then return based on that. Below are my class header and implementation files. Also, if you spot anything else that is wrong or evil, please let me know. I am a C++/Javascript developer who is learning objective-c as hobby and would appreciate any tips that you could offer. #import <Cocoa/Cocoa.h> // class for raising events and parsing returned directives @interface awesome : NSObject { // silence is golden. Actually properties are golden. Hence this emptiness. } // properties @property (retain) SBJsonParser* parser; @property (retain) NSString* eventDomain; @property (retain) NSString* appid // constructors -(id) init; -(id) initWithAppId:(id) input; // destructor -(void) dealloc; @end #import "awesome.h" #import "JSON.h" @implementation awesome - (id) init { if (self = [super init]) { // if init is called directly, just pass nil to AppId contructor variant id selfPtr = [self initWithAppId:nil]; } if (selfPtr) { return selfPtr; } else { return self; } } - (id) initWithAppId:(id) input { if (self = [super init]) { if (input = nil) { input = [[NSString alloc] initWithString:@"a369x123"]; } [self setAppid:input]; [self setEventDomain:[[NSString alloc] initWithString:@"desktop"]]; } return self; } // property synthesis @synthesize parser; @synthesize appid; @synthesize eventDomain; // destructor - (void) dealloc { self.parser = nil; self.appid = nil; self.eventDomain = nil; [super dealloc]; } @end Thanks!

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  • list of polymorphic objects

    - by LivingThing
    I have a particular scenario below. The code below should print 'say()' function of B and C class and print 'B says..' and 'C says...' but it doesn't .Any ideas.. I am learning polymorphism so also have commented few questions related to it on the lines of code below. class A { public: // A() {} virtual void say() { std::cout << "Said IT ! " << std::endl; } virtual ~A(); //why virtual destructor ? }; void methodCall() // does it matters if the inherited class from A is in this method { class B : public A{ public: // virtual ~B(); //significance of virtual destructor in 'child' class virtual void say () // does the overrided method also has to be have the keyword 'virtual' { cout << "B Sayssss.... " << endl; } }; class C : public A{ public: //virtual ~C(); virtual void say () { cout << "C Says " << endl; } }; list<A> listOfAs; list<A>::iterator it; # 1st scenario B bObj; C cObj; A *aB = &bObj; A *aC = &cObj; # 2nd scenario // A aA; // B *Ba = &aA; // C *Ca = &aA; // I am declaring the objects as in 1st scenario but how about 2nd scenario, is this suppose to work too? listOfAs.insert(it,*aB); listOfAs.insert(it,*aC); for (it=listOfAs.begin(); it!=listOfAs.end(); it++) { cout << *it.say() << endl; } } int main() { methodCall(); retrun 0; }

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  • How do I destruct data associated with an object after the object no longer exists?

    - by Phineas
    I'm creating a class (say, C) that associates data (say, D) with an object (say, O). When O is destructed, O will notify C that it soon will no longer exist :( ... Later, when C feels it is the right time, C will let go of what belonged to O, namely D. If D can be any type of object, what's the best way for C to be able to execute "delete D;"? And what if D is an array of objects? My solution is to have D derive from a base class that C has knowledge of. When the time comes, C calls delete on a pointer to the base class. I've also considered storing void pointers and calling delete, but I found out that's undefined behavior and doesn't call D's destructor. I considered that templates could be a novel solution, but I couldn't work that idea out. Here's what I have so far for C, minus some details: // This class is C in the above description. There may be many instances of C. class Context { public: // D will inherit from this class class Data { public: virtual ~Data() {} }; Context(); ~Context(); // Associates an owner (O) with its data (D) void add(const void* owner, Data* data); // O calls this when he knows its the end (O's destructor). // All instances of C are now aware that O is gone and its time to get rid // of all associated instances of D. static void purge (const void* owner); // This is called periodically in the application. It checks whether // O has called purge, and calls "delete D;" void refresh(); // Side note: sometimes O needs access to D Data *get (const void *owner); private: // Used for mapping owners (O) to data (D) std::map _data; }; // Here's an example of O class Mesh { public: ~Mesh() { Context::purge(this); } void init(Context& c) const { Data* data = new Data; // GL initialization here c.add(this, new Data); } void render(Context& c) const { Data* data = c.get(this); } private: // And here's an example of D struct Data : public Context::Data { ~Data() { glDeleteBuffers(1, &vbo); glDeleteTextures(1, &texture); } GLint vbo; GLint texture; }; }; P.S. If you're familiar with computer graphics and VR, I'm creating a class that separates an object's per-context data (e.g. OpenGL VBO IDs) from its per-application data (e.g. an array of vertices) and frees the per-context data at the appropriate time (when the matching rendering context is current).

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  • Cpp some basic problems

    - by DevAno1
    Hello. My task was as follows : Create class Person with char*name and int age. Implement contructor using dynamic allocation of memory for variables, destructor, function init and friend function show. Then transform this class to header and cpp file and implement in other program. Ok so I've almost finished my Person class, but I get error after destructor. First question is how to write this properly ? #include <iostream> using namespace std; class Person { char* name; int age; public: int * take_age(); Person(){ int size=0; cout << "Give length of char*" << endl; cin >> size; name = new char[size]; age = 0; } ~Person(){ cout << "Destroying resources" << endl; delete *[] name; delete * take_age(); } friend void(Person &p); int * Person::take_age(){ return age; } void init(char* n, int a) { name = n; age = a; } void show(Person &p){ cout << "Name: " << p.name << "," << "age: " << p.age << endl; } }; int main(void) { Person *p = new Person; p->init("Mary", 25); p.show(); system("PAUSE"); return 0; } And now with header/implementation part : - do I need to introduce constructor in header/implementation files ? If yes - how? - my show() function is a friendly function. Should I take it into account somehow ? I already failed to return this task on my exam, but still I'd like to know how to implement it.

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  • Good style for handling constructor failure of critical object

    - by mtlphil
    I'm trying to decide between two ways of instantiating an object & handling any constructor exceptions for an object that is critical to my program, i.e. if construction fails the program can't continue. I have a class SimpleMIDIOut that wraps basic Win32 MIDI functions. It will open a MIDI device in the constructor and close it in the destructor. It will throw an exception inherited from std::exception in the constructor if the MIDI device cannot be opened. Which of the following ways of catching constructor exceptions for this object would be more in line with C++ best practices Method 1 - Stack allocated object, only in scope inside try block #include <iostream> #include "simplemidiout.h" int main() { try { SimpleMIDIOut myOut; //constructor will throw if MIDI device cannot be opened myOut.PlayNote(60,100); //..... //myOut goes out of scope outside this block //so basically the whole program has to be inside //this block. //On the plus side, it's on the stack so //destructor that handles object cleanup //is called automatically, more inline with RAII idiom? } catch(const std::exception& e) { std::cout << e.what() << std::endl; std::cin.ignore(); return 1; } std::cin.ignore(); return 0; } Method 2 - Pointer to object, heap allocated, nicer structured code? #include <iostream> #include "simplemidiout.h" int main() { SimpleMIDIOut *myOut; try { myOut = new SimpleMIDIOut(); } catch(const std::exception& e) { std::cout << e.what() << std::endl; delete myOut; return 1; } myOut->PlayNote(60,100); std::cin.ignore(); delete myOut; return 0; } I like the look of the code in Method 2 better, don't have to jam my whole program into a try block, but Method 1 creates the object on the stack so C++ manages the object's life time, which is more in tune with RAII philosophy isn't it? I'm still a novice at this so any feedback on the above is much appreciated. If there's an even better way to check for/handle constructor failure in a siatuation like this please let me know.

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  • 47 memory leaks. STL pointers.

    - by icelated
    I have a major amount of memory leaks. I know that the Sets have pointers and i cannot change that! I cannot change anything, but clean up the mess i have... I am creating memory with new in just about every function to add information to the sets. I have a Cd/ DVD/book: super classes of ITEM class and a library class.. In the library class i have 2 functions for cleaning up the sets.. Also, the CD, DVD, book destructors are not being called.. here is my potential leaks.. library.h #pragma once #include <ostream> #include <map> #include <set> #include <string> #include "Item.h" using namespace std; typedef set<Item*> ItemSet; typedef map<string,Item*> ItemMap; typedef map<string,ItemSet*> ItemSetMap; class Library { public: // general functions void addKeywordForItem(const Item* const item, const string& keyword); const ItemSet* itemsForKeyword(const string& keyword) const; void printItem(ostream& out, const Item* const item) const; // book-related functions const Item* addBook(const string& title, const string& author, int const nPages); const ItemSet* booksByAuthor(const string& author) const; const ItemSet* books() const; // music-related functions const Item* addMusicCD(const string& title, const string& band, const int nSongs); void addBandMember(const Item* const musicCD, const string& member); const ItemSet* musicByBand(const string& band) const; const ItemSet* musicByMusician(const string& musician) const; const ItemSet* musicCDs() const; // movie-related functions const Item* addMovieDVD(const string& title, const string& director, const int nScenes); void addCastMember(const Item* const movie, const string& member); const ItemSet* moviesByDirector(const string& director) const; const ItemSet* moviesByActor(const string& actor) const; const ItemSet* movies() const; ~Library(); void Purge(ItemSet &set); void Purge(ItemSetMap &map); }; here is some functions for adding info using new in library. Keep in mind i am cutting out alot of code to keep this post short. library.cpp #include "Library.h" #include "book.h" #include "cd.h" #include "dvd.h" #include <iostream> // general functions ItemSet allBooks; ItemSet allCDS; ItemSet allDVDs; ItemSetMap allBooksByAuthor; ItemSetMap allmoviesByDirector; ItemSetMap allmoviesByActor; ItemSetMap allMusicByBand; ItemSetMap allMusicByMusician; const ItemSet* Library::itemsForKeyword(const string& keyword) const { const StringSet* kw; ItemSet* obj = new ItemSet(); return obj; const Item* Library::addBook(const string& title, const string& author, const int nPages) { ItemSet* obj = new ItemSet(); Book* item = new Book(title,author,nPages); allBooks.insert(item); // add to set of all books obj->insert(item); return item; const Item* Library::addMusicCD(const string& title, const string& band, const int nSongs) { ItemSet* obj = new ItemSet(); CD* item = new CD(title,band,nSongs); return item; void Library::addBandMember(const Item* musicCD, const string& member) { ItemSet* obj = new ItemSet(); (((CD*) musicCD)->addBandMember(member)); obj->insert((CD*) musicCD); here is the library destructor..... Library::~Library() { Purge(allBooks); Purge(allCDS); Purge(allDVDs); Purge(allBooksByAuthor); Purge(allmoviesByDirector); Purge(allmoviesByActor); Purge(allMusicByBand); Purge(allMusicByMusician); } void Library::Purge(ItemSet &set) { for (ItemSet::iterator it = set.begin(); it != set.end(); ++it) delete *it; set.clear(); } void Library::Purge(ItemSetMap &map) { for (ItemSetMap::iterator it = map.begin(); it != map.end(); ++it) delete it->second; map.clear(); } so, basically item, cd, dvd class all have a set like this: typedef set<string> StringSet; class CD : public Item StringSet* music; and i am deleting it like: but those superclasses are not being called.. Item destructor is. CD::~CD() { delete music; } Do, i need a copy constructor? and how do i delete those objects i am creating in the library class? and how can i get the cd,dvd, destructor called? would the addbandmember function located in the library.cpp cause me to have a copy constructor? Any real help you can provide me to help me clean up this mess instead of telling me not to use pointers in my sets i would really appreciate. How can i delete the memory i am creating in those functions? I cannot delete them in the function!!

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  • how do i know how many clients are calling my WCF service function

    - by ZhengZhiren
    i am writing a program to test WCF service performance in high concurrency circumstance. On client side, i start many threads to call a WCF service function which returns a long list of data object. On server side, in that function called by my client, i need to know the number of clients calling the function. For doing that, i set a counter variable. In the beginning of the function, i add the counter by 1, but how can i decrease it after the funtion has returned the result? int clientCount=0; public DataObject[] GetData() { Interlocked.Increment(ref clientCount); List<DataObject> result = MockDb.GetData(); return result.ToArray(); Interlocked.Decrement(ref clientCount); //can't run to here... } i have seen a way in c++. Create a new class named counter. In the constructor of the counter class, increase the variable. And decrease it in the destructor. In the function, make a counter object so that its constructor will be called. And after the function returns, its destructor will be called. Like this: class counter { public: counter(){++clientCount; /* not simply like this, need to be atomic*/} ~counter(){--clientCount; /* not simply like this, need to be atomic*/} }; ... myfunction() { counter c; //do something return something; } In c# i think i can do so with the following codes, but not for sure. public class Service1 : IService1 { static int clientCount = 0; private class ClientCounter : IDisposable { public ClientCounter() { Interlocked.Increment(ref clientCount); } public void Dispose() { Interlocked.Decrement(ref clientCount); } } public DataObject[] GetData() { using (ClientCounter counter = new ClientCounter()) { List<DataObject> result = MockDb.GetData(); return result.ToArray(); } } } i write a counter class implement the IDisposable interface. And put my function codes into a using block. But it seems that it doesn't work so good. No matter how many threads i start, the clientCount variable is up to 3. Any advise would be appreciated.

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  • Virtual destructors for interfaces.

    - by wowus
    Do interfaces need a virtual destructor, or is the auto-generated one fine? For example, which of the following two code snippets is best, and why? class Base { public: virtual void foo() = 0; virtual ~Base() {} }; OR... class Base { public: virtual void foo() = 0; };

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  • I want to trace logs using a Macro multi parameter always null. problem c++ windows

    - by sxingfeng
    I am using the following way to cout a function's time: #define TIME_COST(message, ...)\ char szMessageBuffer[2048] = {0};\ va_list ArgList;\ va_start(ArgList, message);\ vsprintf_s(szMessageBuffer, 2048, message, ArgList);\ va_end(ArgList); \ string strMessage(szMessageBuffer);\ CQLogTimer t(strMessage); // CQLogTimer is a self destructor,which will cout life time of its own and print szMessageBuffer. However when I use the macro this : void fun { TIME_COST("hello->%s", filePath); XXXXXX } The message generated always is hello-(null) Can Any one help? Many thanks!

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  • Is there a g++ equivalent to Visual Studio's __declspec(novtable)?

    - by ceretullis
    Is there a g++ equivalent to Visual Studio's __declspec(novtable) argument? Basically, in a pure virtual base class the __declspec(novtable) argument can be used to suppress the creation of a vtable for the base class as well as vtable initialization/deinitialization code in the contstructor/destructor respectively. E.g., class __declspec(novtable) PureVirtualBaseClass { public: PureVirtualBaseClass(){} virtual ~PureVirtualBaseClass() = 0; }; See Paul DiLascia's article for more info. Also see my related question.

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