My application crashes

I have write a application in which user can add QToolButtoninto the UI dynamic. But there is something wrong seriously with my application.
It often crashes!!
The following is what I get from the DOS output:

H:/QTprojects/testdynamic/debug/testdynamic.exe exited with code 1073807364
in which testdynamic.exe is the application I write.
Do some guys know the reason?
Thanks a lot!

You made a programming mistake? :p

If you show us some code, maybe we can point you to what that mistake is!

Thanks! I agree with you. The following is my code:

Code:

---

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent), ui(new Ui::MainWindowClass)
{
    ui->setupUi(this);
 
}
 
MainWindow::~MainWindow()
{
    delete ui;
}
 
bool MainWindow::on_addExeButton_clicked()
{
    QString filename = QFileDialog::getOpenFileName(this, tr("Choose the application"), tr("."), tr("Excutable(*.exe)"));
    if(filename.isNull())
        return false;
    //user choose an excutive application
    QFileInfo fileInfo(filename);
    QFileIconProvider seekIcon;
    QIcon icon = seekIcon.icon(fileInfo);
    QToolButton *btn = new QToolButton;
    btn->resize( 300, 300);
    btn->setIcon(icon);
//if user click the corresponding button, this app will run the chosen application
    connect(btn, SIGNAL(clicked()), this, SLOT(callExe()));     
    buttons.insert(filename, btn);
    ui->verticalLayout1->addWidget(btn);
    ui->verticalLayout1->addStretch();
}
 
void MainWindow::callExe()
{
    qDebug() << "Ready to execute program";
    QToolButton *sender = static_cast<QToolButton*>(this->sender());
    QString path;
    QMapIterator<QString, QToolButton *> i(buttons);
    while(i.hasNext())
    {
        if(i.peekNext().value() == sender)
        {
            path = i.next().key();
            qDebug() << "Find the path!!\n";
            break;
        }
    }
 
    if(path.isEmpty())
    {
        qDebug() << "******File path is null!!";
        return;
    }
//run the corresponding application
//    QObject *parent = NULL;
//    QString program = "J:\\2\\exeshan\\Debug\\11.ppt";
    QStringList arguments;
    arguments << "-style" << "motif";
    QProcess *myProcess = new QProcess(this);
    myProcess->start(path, arguments);
    connect(myProcess, SIGNAL(error(QProcess::ProcessError)), this, SLOT(badProcess(QProcess::ProcessError)));
    qDebug() << "SLOT successfully!" << endl;
}
 
void MainWindow::badProcess(QProcess::ProcessError error)
{
    qDebug() << "Process error!!" << error;
}

---

in this application, I want to run the other applications through click the buttons in the QMainWindow.

as for me you should use qobject_cast instead of static_cast and then check if QToolButton * sender is NULL or not. Next thing is that you can change the key with value in map - that would make starting app much simpler. Here is my code doing similar thing. Check if it is not crashing or tell me what should I do to crash it :]

Code:

---

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QFileInfo>
#include <QFileIconProvider>
#include <QIcon>
#include <QFileDialog>
#include <QProcess>
 
MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent), ui(new Ui::MainWindow)
{
    ui->setupUi(this);
}
 
MainWindow::~MainWindow()
{
    delete ui;
}
 
void MainWindow::on_actionAdd_application_triggered()
{
	QString filename = QFileDialog::getOpenFileName(this, tr("Choose the application"), qApp->applicationDirPath(), tr("Excutable(*.exe)"));
	if(filename.isNull())
		return;
 
	QFileInfo fileInfo(filename);
	QFileIconProvider seekIcon;
	QIcon icon = seekIcon.icon(fileInfo);
	QToolButton *btn = new QToolButton;
	btn->resize( 300, 300);
	btn->setIcon(icon);
 
	connect(btn, SIGNAL(clicked()), SLOT(slotExecute()));
	m_map.insert(btn, filename);
	ui->verticalLayout_2->addWidget(btn);
}
 
void MainWindow::slotExecute()
{
	QToolButton * btn = qobject_cast<QToolButton *>(sender());
	if (!btn)
		return;
 
	QString filename = m_map.value(btn);
	QProcess::startDetached(filename);
}

---

Thanks!! Uh, I am wondering if it is not suitable to use the C++ static_cast<> or daynamic_cast<>. I am wondering what's the difference between them two and the qobject_cast<>.
Next thing is, I do not think it is necessary in the

Code:

---

void MainWindow::slotExecute()

---

to check if the sender is NULL, because if there is no sender, this SLOT won't be called, right?

Quote:

---

Originally Posted by sophister

Next thing is, I do not think it is necessary in the

Code:

---

void MainWindow::slotExecute()

---

to check if the sender is NULL, because if there is no sender, this SLOT won't be called, right?

---

you can call this slot by yourself somwhere in your code, so this check is needed.
note:

Quote:

---

...Slots are normal C++ functions and can be called normally; their only special feature is that signals can be connected to them.

---

Quote:

---

Originally Posted by sophister

Thanks!! Uh, I am wondering if it is not suitable to use the C++ static_cast<> or daynamic_cast<>. I am wondering what's the difference between them two and the qobject_cast<>.

---

qobject_cast is using meta information for correct casting of Qt's objects.
read this for more info.

Yeah!!
I have found the mistake!!
It hides in the following code:

Code:

---

QMapIterator<QString, QToolButton *> i(buttons);
    while(i.hasNext())
    {
        if(i.peekNext().value() == sender)
        {
            path = i.next().key();
            qDebug() << "Find the path!!\n";
            break;
        }
    }

---

if the first value in the iterator does not equals the sender, the loop will continue forever!! So the solution is to add such code as:

Code:

---

QMapIterator<QString, QToolButton *> i(buttons);
    while(i.hasNext())
    {
  //      qDebug() << "Enter the while loop successfully!";
        if(i.peekNext().value() == sender)
        {
            path = i.next().key();
            qDebug() << "Find the path!!\n";
            break;
        }
        else
        {
            i.next();       // without this, the loop may continue forever!!!!!
        }
    }

---

But I've got another question, following is your code to start another application:

Code:

---

QProcess::startDetached(filename);

---

Are there some different effects between your way and mine? The following is my way to start it:

Code:

---

QStringList arguments;
    arguments << "-style" << "motif";
    QProcess *myProcess = new QProcess(this);
    myProcess->start(path, arguments);

---

Thanks a lot!!

yes, you are right. I forgot that it can be called somewhere by I.
thanks

So I think it will work if I use the ISO C++ dynamic_cast or static_cast.
The doc says the qobject_cast does not require RTTI.
what do you think is not suitable if we use dynamic_cast or static_cast?
By the way, you get up so early!!

Quote:

---

Originally Posted by sophister

So I think it will work if I use the ISO C++ dynamic_cast or static_cast.
The doc says the qobject_cast does not require RTTI.
what do you think is not suitable if we use dynamic_cast or static_cast?

---

for objects which inherit from QObject it's better to use qobject_cast.

Quote:

---

Originally Posted by sophister

By the way, you get up so early!!

---

my local time is 09:09 am :)

Thanks.
I thought your local time is six o'clock.
uh, my local time is 2 : 15 p.m.:)

Quote:

---

Originally Posted by sophister

But I've got another question, following is your code to start another application:

Code:

---

QProcess::startDetached(filename);

---

---

in this case a process will start as

Quote:

---

Unix: The started process will run in its own session and act like a daemon.

Windows: Arguments that contain spaces are wrapped in quotes. The started process will run as a regular standalone process.

---

in this case

Quote:

---

Originally Posted by sophister

Are there some different effects between your way and mine? The following is my way to start it:

Code:

---

QStringList arguments;
    arguments << "-style" << "motif";
    QProcess *myProcess = new QProcess(this);
    myProcess->start(path, arguments);

---

Thanks a lot!!

---

you don't lose communication with a process, i.e. you can handle signals readyReadStandardError, readyReadStandardOutput etc.
so, if you don't need to process signals then you can use only static methods for starting processes.

Oh, I see.
thank you, very very much!!