Signal name: SIGSEGV error - c++

Question

I Keep getting this error when i try and build this app. Help?
The inferior stopped because it received a signal from the operating system.
Signal name: SIGSEGV
Signal meaning: Segmentation fault
Here is the code for the mainwindow.cpp file
It says the error is on line 122 which is the
copyAct->setEnabled(false);
this is about half way down.
#include "mainwindow.h"
#include <QtGui>
MainWindow::MainWindow(QWidget *parent)
{
textEdit = new QPlainTextEdit;
setCentralWidget(textEdit);
createActions();
createMenus();
createToolBars();
createStatusBar();
readSettings();
connect(textEdit->document(), SIGNAL(contentsChanged()),this, SLOT(documentWasModified()));
setCurrentFile("");
setUnifiedTitleAndToolBarOnMac(true);
}
void MainWindow::closeEvent(QCloseEvent *event)
{
if(maybeSave()){
writeSettings();
event->accept();
}
else{
event->ignore();
}
}
void MainWindow::newFile()
{
if(maybeSave()){
textEdit->clear();
setCurrentFile("");
}
}
void MainWindow::open()
{
if(maybeSave()){
QString fileName = QFileDialog::getOpenFileName(this);
if(!fileName.isEmpty())
loadFile(fileName);
}
}
bool MainWindow::save()
{
if(curFile.isEmpty()){
return saveAs();
}
else{
return saveFile(curFile);
}
}
bool MainWindow::saveAs()
{
QString fileName = QFileDialog::getSaveFileName(this);
if(fileName.isEmpty())
return false;
return saveFile(fileName);
}
void MainWindow::about()
{
QMessageBox::about(this, tr("About Application"),
tr("Whatever you want it to say here!"));
}
void MainWindow::documentWasModified()
{
setWindowModified(textEdit->document()->isModified());
}
void MainWindow::createActions()
{
newAct = new QAction(tr("&New"), this);
newAct->setShortcuts(QKeySequence::New);
newAct->setStatusTip(tr("Create a new file"));
connect(newAct, SIGNAL(triggered()), this, SLOT(newFile()));
openAct = new QAction(tr("&Open..."), this);
openAct->setShortcuts(QKeySequence::Open);
openAct->setStatusTip(tr("Open an existing file"));
connect(openAct, SIGNAL(triggered()), this, SLOT(open()));
saveAct = new QAction(tr("&Save"), this);
saveAct->setShortcuts(QKeySequence::Save);
saveAct->setStatusTip(tr("Save an open file"));
connect(saveAct, SIGNAL(triggered()), this, SLOT(save()));
saveAsAct = new QAction(tr("&Save As"), this);
saveAsAct->setShortcuts(QKeySequence::SaveAs);
saveAsAct->setStatusTip(tr("Save a new file"));
connect(openAct, SIGNAL(triggered()), this, SLOT(saveAs()));
exitAct = new QAction(tr("&Exit"), this);
exitAct->setShortcuts(QKeySequence::Close);
exitAct->setStatusTip(tr("Exit the application"));
connect(exitAct, SIGNAL(triggered()), this, SLOT(close()));
cutAct = new QAction(tr("&Cut"), this);
cutAct->setShortcuts(QKeySequence::Cut);
cutAct->setStatusTip(tr("Cut the selected text"));
pasteAct = new QAction(tr("&Paste"), this);
pasteAct->setShortcuts(QKeySequence::Paste);
pasteAct->setStatusTip(tr("Paste selected text"));
connect(pasteAct, SIGNAL(triggered()), this, SLOT(setEnabled(bool)));
aboutAct = new QAction(tr("&About"), this);
aboutAct->setShortcuts(QKeySequence::UnknownKey);
aboutAct->setStatusTip(tr("About the application"));
connect(aboutAct, SIGNAL(triggered()), this, SLOT(show()));
cutAct->setEnabled(false);
copyAct->setEnabled(false);
connect(textEdit, SIGNAL(copyAvailable(bool)), cutAct, SLOT(setEnabled(bool)));
connect(textEdit, SIGNAL(copyAvailable(bool)), copyAct, SLOT(setEnabled(bool)));
}
void MainWindow::createMenus()
{
fileMenu = menuBar()->addMenu(tr("&File"));
fileMenu->addAction(newAct);
fileMenu->addAction(openAct);
fileMenu->addAction(saveAct);
fileMenu->addAction(saveAsAct);
fileMenu->addSeparator();
fileMenu->addAction(exitAct);
editMenu = menuBar()->addMenu(tr("&Edit"));
editMenu->addAction(cutAct);
editMenu->addAction(copyAct);
editMenu->addAction(pasteAct);
menuBar()->addSeparator();
helpMenu = menuBar()->addMenu(tr("&Help"));
helpMenu->addAction(aboutAct);
}
void MainWindow::createToolBars()
{
fileToolBar = addToolBar(tr("File"));
fileToolBar->addAction(newAct);
fileToolBar->addAction(openAct);
fileToolBar->addAction(saveAct);
editToolBar = addToolBar(tr("Edit"));
editToolBar->addAction(cutAct);
editToolBar->addAction(copyAct);
editToolBar->addAction(pasteAct);
}
void MainWindow::createStatusBar()
{
statusBar()->showMessage(tr("Ready"));
}
void MainWindow::readSettings()
{
QSettings settings("Zach Starnes", "Zach's Text Editor");
QPoint pos = settings.value("pos", QPoint(200, 200)).toPoint();
QSize size = settings.value("size", QSize(400, 400)).toSize();
resize(size);
move(pos);
}
void MainWindow::writeSettings()
{
QSettings settings("Zach Starnes", "Zach's Text Editor");
settings.setValue("pos", pos());
settings.setValue("size", size());
}
bool MainWindow::maybeSave()
{
if (textEdit->document()->isModified()) {
QMessageBox::StandardButton ret;
ret = QMessageBox::warning(this, tr("Application"),
tr("The document has been modified.\n"
"Do you want to save your changes?"),
QMessageBox::Save | QMessageBox::Discard | QMessageBox::Cancel);
if (ret == QMessageBox::Save)
return save();
else if (ret == QMessageBox::Cancel)
return false;
}
return true;
}
void MainWindow::loadFile(const QString &fileName)
{
QFile file(fileName);
if (!file.open(QFile::ReadOnly | QFile::Text)) {
QMessageBox::warning(this, tr("Application"),
tr("Cannot read file %1:\n%2.")
.arg(fileName)
.arg(file.errorString()));
return;
}
QTextStream in(&file);
#ifndef QT_NO_CURSOR
QApplication::setOverrideCursor(Qt::WaitCursor);
#endif
textEdit->setPlainText(in.readAll());
#ifndef QT_NO_CURSOR
QApplication::restoreOverrideCursor();
#endif
setCurrentFile(fileName);
statusBar()->showMessage(tr("File loaded"), 2000);
}
bool MainWindow::saveFile(const QString &fileName)
{
QFile file(fileName);
if (!file.open(QFile::WriteOnly | QFile::Text)) {
QMessageBox::warning(this, tr("Application"),
tr("Cannot write file %1:\n%2.")
.arg(fileName)
.arg(file.errorString()));
return false;
}
QTextStream out(&file);
#ifndef QT_NO_CURSOR
QApplication::setOverrideCursor(Qt::WaitCursor);
#endif
out << textEdit->toPlainText();
#ifndef QT_NO_CURSOR
QApplication::restoreOverrideCursor();
#endif
setCurrentFile(fileName);
statusBar()->showMessage(tr("File saved"), 2000);
return true;
}
void MainWindow::setCurrentFile(const QString &fileName)
{
curFile = fileName;
textEdit->document()->setModified(false);
setWindowModified(false);
QString shownName = curFile;
if (curFile.isEmpty())
shownName = "untitled.txt";
setWindowFilePath(shownName);
}
QString MainWindow::strippedName(const QString &fullFileName)
{
return QFileInfo(fullFileName).fileName();
}

Answer 1

Looks like for every other action you have (which I assume are member data pointers), you've allocated some memory for:
aboutAct = new QAction(tr("&About"), this);
copyAct seems to be the only action you haven't allocated anything for, and therefore you are dereferencing an invalid pointer.
copyAct->setEnabled(false); // segfault :(
You are missing something like this, I assume:
copyAct = new QAction(tr("&Copy"), this);
I hope this isn't your entire cpp file either, as I don't see a destructor nor any delete's to match all those new commands.