分段故障错误(信号名称:SIGSEGV）的原因是什么，以及如何查找/修复它

我一直在开发Qt Creator应用程序，最近遇到了一个运行时错误，我不知道如何查找和修复。程序启动后意外完成，当我运行调试时，它会给我错误：

劣等因为接收到来自操作系统

信号名称：SIGSEGV

信号含义：分段故障

现在我知道这个错误是由试图访问无效内存位置引起的，但我完全不知道我是怎么触发它的。调试器似乎指向了一行特定的代码：

#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

该功能用于：

#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;
}

这是主窗口源代码：

#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();
}

有人能帮我找出到底发生了什么事吗？