Qt5.12.12 with msvc 2017 x64.
I create a QThreadStorage object at the beginning of my app, when I close my app, it crashs. After debug, I find it is caused by double free of the data in QThreadStorage. Here is my code. Am I use it wrong?
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
QThreadStorage<QString> data;
data.setLocalData("TEst");
QMainWindow window;
window.show();
return a.exec();
}
And here is error information and trace stack.
Error information
trace stack
Related
Got an error running the following problem:
#include <QMessageBox>
#include <QApplication>
int main() {
QApplication app();
QMessageBox msgBox(QMessageBox::Critical,
QObject::tr("text1"),
QObject::tr("text2"),
QMessageBox::Ok);
msgBox.exec();
return 0;
}
The error is:
The program breaks at QMessageBox msgBox(...);
The call stack is:
EDIT: Even after i have added QApplication instance in XTerm window named qtcreator_process_stub i see the following:
QWidget: Must construct QApplication before a QWidget
The line
QApplication app();
doesn't create a QApplication object - it actually declares a function taking no arguments and returning a QApplication! This is sometimes known as the "most vexing parse".
To actually construct the application object, you need to provide the program's arguments:
QApplication app(argc, argv);
The full program is then
#include <QMessageBox>
#include <QApplication>
int main(int argc, char **argv) {
QApplication app(argc, argv);
QMessageBox msgBox(QMessageBox::Critical,
QObject::tr("text1"),
QObject::tr("text2"),
QMessageBox::Ok);
msgBox.exec();
return 0;
}
Is it possible to restart a qt application after its crashing? Just like those windows service which will restart on its own. If so, how could I do it? I have tried code like this:
#define RESTART_CODE 1000
int main(int argc, char *argv[])
{
int return_from_event_loop_code;
QPointer<QApplication> app;
QPointer<MainWindow> main_window;
do
{
if(app) delete app;
if(main_window) delete main_window;
app = new QApplication(argc, argv);
main_window = new MainWindow(app);
return_from_event_loop_code = app->exec();
}
while(return_from_event_loop_code==RESTART_CODE)
return return_from_event_loop_code;
}
But it is not working...
What should I do now?
create another qt application that runs your application.
#include <QApplication>
#include "QProcess"
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
QProcess aProcess;
QString exe = "Your process name with exact path";
QByteArray myOut;
while(1)
{
aProcess.start(exe);
//aProcess.waitForStarted();
//myOut = aProcess.readAllStandardOutput();
//printf("%s",myOut.constData());
aProcess.waitForFinished(-1);
//QString output(aProcess.readAllStandardOutput());
myOut = aProcess.readAllStandardOutput();
printf("%s",myOut.constData());
}
return a.exec();
}
this program will restart your app when it crashed or closed
You can use my open source library:
https://marketplace.qt.io/products/main-loop-wdt-for-qt-qml
It is a watchdog timer for the main loop and only works if the main loop freezes (double mutex lock, infinite loop, etc.), but it would not work in an application crash.
I'm trying to use libtorrent in my Qt5 application but keep getting segfaults
with messages like malloc(): memory corruption. After hours of debbuging I come up with this small piece of code which triggers this problem:
int main(int argc, char *argv[])
{
QGuiApplication app(argc, argv);
std::string filename = "fedora.torrent";
libtorrent::error_code ec;
libtorrent::add_torrent_params parameters;
std::cerr << "111\n";
parameters.ti = new libtorrent::torrent_info(filename, ec);;
std::cerr << "222\n";
return app.exec()
}
In this case constructor of torrent_info produce segfault. But if I move libtorrent related code before creation of QGuiApplication like this:
int main(int argc, char *argv[])
{
std::string filename = "fedora.torrent";
libtorrent::error_code ec;
libtorrent::add_torrent_params parameters;
std::cerr << "111\n";
parameters.ti = new libtorrent::torrent_info(filename, ec);;
std::cerr << "222\n";
QGuiApplication app(argc, argv);
return app.exec()
}
then it works just fine. Also this problem exist only in 32-bit build, in 64-bit build both variants work the same.
This is most likely caused by building libtorrent with one set of TORRENT_* defines and linking against it with a different set. Some of those defines affect layouts of some structs used in the public API and when differing between the calling application and the library introduce ABI incompatibility issues.
The program name is GoToCell in the form I created a label and two push buttons and I wrote the code in main.cpp as follows:
#include <QtGui/QApplication>
#include<QDialog>
#include "ui_GoToCell.h"
#include "GoToCell.h"
int main(int argc, char *argv[]) {
QApplication a(argc, argv);
Ui::GoToCell ui;
QDialog *dialog=new QDialog;
ui.setupUi(dialog);
dialog->show();
return a.exec();
}
While running it I'm getting the following errors:
GoToCell is not a member of ui
What should I do?
I think you have misspelled object name in objectName property in the GoToCell.ui form.
Change it to GoToCell. It will then execute.
Can one place an arbitrary program (firefox, openoffice, etc...) in a QX11EmbedContainer? The fllowing seems, to work
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
QX11EmbedContainer container;
container.show();
QProcess * process = new QProcess(&container);
QString executable("xterm");
QStringList arguments;
arguments << "-into";
arguments << QString::number(container.winId());
process->start(executable, arguments);
int status = app.exec();
process->close();
return status;
}
but the next snippet launches a new window, not what I want
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
QX11EmbedContainer container;
container.show();
QProcess * process = new QProcess(&container);
QString executable("konsole");
process->start(executable);
int status = app.exec();
process->close();
return status;
}
The first example work because xterm is able to reparent its top level widget (an X11 window). You tell it to do so with the argument -into <WinId>.
I don't know if Konsole can do that, i don't use it and the man page doesn't seem to talk about this.
But that doesn't mean it is not doable, the X Window system is very flexible and anyone can reparent another window (that's how windows managers add decorations to windows).
Take a look at man 3 XReparentWindow ;-)