Question

Just recently I’ve installed the Qt libraries on my computer, and as a complete novice I looked up the Qt 4.7 Getting Started guides online.

Just on the first page they provide the following code:

  1        #include <QtGui>
  2
  3        int main(int argv, char **args)
  4        {
  5            QApplication app(argv, args);
  6
  7            QTextEdit textEdit;
  8            QPushButton quitButton("Quit");
  9
 10            QObject::connect(&quitButton, SIGNAL(clicked()), qApp, SLOT(quit()));
 11
 12            QVBoxLayout layout;
 13            layout.addWidget(&textEdit);
 14            layout.addWidget(&quitButton);
 15
 16            QWidget window;
 17            window.setLayout(&layout);
 18
 19            window.show();
 20
 21            return app.exec();
 22        }

Simple stuff, I would suppose. Upon writing this code in Visual Studio Express 2010, building, and running, most everything works. However, when I try to close the window by means of the “Quit” button or the red-x in the top right of the displayed window (initiating “return app.exec()”), I receive the following:

A dialog box saying,

Unhandled exception at 0x77bc15de in ParticleTracker.exe: 0xC0000005: Access violation reading location 0xdf94b4b4.

And console output saying,

Critical error detected c0000374
Windows has triggered a breakpoint in ParticleTracker.exe.

This may be due to a corruption of the heap, which indicates a bug in ParticleTracker.exe or any of the DLLs it has loaded.

This may also be due to the user pressing F12 while ParticleTracker.exe has focus.

Having entered the debug-mode, I continued through the call stack while repeatedly receiving heap corruption errors.

First-chance exception at 0x77c6e6c3 in ParticleTracker.exe: 0xC0000374: A heap has been corrupted.
Unhandled exception at 0x77bc15de in ParticleTracker.exe: 0xC0000374: A heap has been corrupted.

All of the subsequent exceptions occurred at 0x77bc15de in the executable, with the memory address 0xC0000374 as a corrupted heap.

Honestly, I’m not precisely sure how I could even be getting this issue; I’m not well-versed in C++, but there appears to be nothing wrong with the code.

In the Call-Stack, the process is currently stuck at:
ParticleTracker.exe!main(int argv, char** args) Line 20 + 0x27 bytes
If I enter the disassembly the process is stuck at:

return app.exec();
00FE3831  mov         esi,esp  
00FE3833  call        dword ptr [__imp_QApplication::exec (0FE93D0h)]  
00FE3839  cmp         esi,esp  
00FE383B  call        @ILT+320(__RTC_CheckEsp) (0FE1145h)  
00FE3840  mov         dword ptr [ebp-150h],eax  
00FE3846  mov         byte ptr [ebp-4],5  
00FE384A  mov         esi,esp  
00FE384C  lea         ecx,[ebp-84h]  
00FE3852  call        dword ptr [__imp_QWidget::~QWidget (0FE9404h)]  
00FE3858  cmp         esi,esp  

Any tips? Much appreciated. 🙂

Answer 1

Try this one

#include <QtGui>

int main(int argv, char **args)
{
      QApplication app(argv, args);

      QTextEdit *textEdit = new QTextEdit();
      QPushButton *quitButton = new QPushButton("Quit");

      QObject::connect(quitButton, SIGNAL(clicked()), qApp, SLOT(quit()));

      QVBoxLayout *layout = new QVBoxLayout();
      layout->addWidget(textEdit);
      layout->addWidget(quitButton);

      QWidget *window = new QWidget();
      window->setLayout(layout);

      window->show();

      return app.exec();
  }