分段错误错误（信号名称：SIGSEGV）的原因是什么，如何找到/修复它？

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QString>
#include \"ui_mainwindow.h\"
#include \"foamdata.h\"
#include \"domaingeneration.h\"


namespace Ui {
    class MainWindow;
}


class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();
    int getXDim() const { return ui->xDim->value(); } // THIS is where it points to!!
    int getYDim() const { return ui->yDim->value(); }


private slots:
    void on_findDir_clicked();

    void on_create_clicked();

    void on_generateDomain_clicked();

private:
    Ui::MainWindow *ui;
    DomainGeneration dg;    //declaring second window as a member of main window
};

#endif // MAINWINDOW_H

#include \"domaingeneration.h\"
#include \"ui_domaingeneration.h\"
#include <QCheckBox>
#include \"mainwindow.h\"

DomainGeneration::DomainGeneration(QWidget *parent) :
    QDialog(parent),
    ui(new Ui::DomainGeneration)
{
    ui->setupUi(this);

    // Generating checkboxes for domain generation
    MainWindow* main;
    int x_dim = main->getXDim();
    int y_dim = main->getYDim();
    QVector<QCheckBox*> checkBoxVector;
    for(int i = 0; i < x_dim; ++i){
        for(int j = 0; j < y_dim; ++j){
            checkBoxVector.append(new QCheckBox(this));
            checkBoxVector.last()->setGeometry(i * 20, j * 20, 20, 20);
        }
    }
}


DomainGeneration::~DomainGeneration()
{
    delete ui;
}

#include \"mainwindow.h\"
#include \"ui_mainwindow.h\"
#include \"functions.h\"
#include \"main.cpp\"
#include <QtGui/QApplication>
#include <QFileDialog>
#include <fstream>
#include \"foamdata.h\"
#include \"domaingeneration.h\"


MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
}

MainWindow::~MainWindow()
{
    delete ui;
}




// This is the function that handles the directory search when the \'browse\' button is pressed
void MainWindow::on_findDir_clicked()
{
    QString path;   //declaring the path to the base directory

    path = QFileDialog::getExistingDirectory(   //gathering the directory from QFileDialog class
        this, tr(\"Choose the project directory\"),
        \"/home\",
        QFileDialog::ShowDirsOnly
        | QFileDialog::DontResolveSymlinks );

    ui->baseDir->setText( path );   //setting the retrieved path into the line edit box
}



// This function makes the project by creating a new directory with name \'project_name\'
// in the base directory, and collects the OpenFOAM version number and simulation type
void MainWindow::on_create_clicked()
{

    QString project_name, foam_version, full_dir, slash, base_dir;
    base_dir = ui->baseDir->text();
    project_name = ui->projectName->text();     //getting the text from the \'projectName\' field
    foam_version = ui->version->currentText();  //getting the selection from the \'version\' drop-down box

    project_info.save_version(foam_version);        //saving data in a global project variable
    project_info.save_projName(project_name);
    project_info.save_simType(ui->simType->currentText());

    //first checking if the fields have input in them:
    QString blank = \"\";
    QString no_text0 = \"Please enter project name\";
    if( project_name==no_text0 || (project_name==blank) ) {
        ui->projectName->setText( no_text0 );
        return;
    }


    QString no_text1 = \"Please enter a valid directory\";
    if( base_dir==no_text1 || base_dir==blank || !QDir( base_dir ).exists() ) {
        ui->baseDir->setText( no_text1 );
        return;
    }


    slash = \"/\";        // needed to separate folders in the directory (can\'t use a literal)
    full_dir = base_dir.append(slash.append(project_name));
    project_info.save_directory(full_dir);

    if( !QDir(full_dir).exists() )  //check if directory already exists
        QDir().mkdir(full_dir);     //creating directory

    QString blockmesh_filename, suffix;
    suffix = \"_blockMeshDict\";
    slash = \"/\";    //must re-define
    blockmesh_filename = full_dir.append( slash.append( project_name.append(suffix) ) );
    std::ofstream create_file( blockmesh_filename.toStdString().c_str() );  //creating empty blockmesh file

}


void MainWindow::on_generateDomain_clicked()    //opening the new window for domain generation
{
    dg.show();
}