QStateMachine is not emitting started() signal in release mode-CodePudding

I am using QStateMachine framework for a device controller class. It works fine in debug mode. But, in the release mode QStateMachine::started() signal is not being emitted. A simple widget project for the problem (form is empty) is below.

Qt Version 5.14.1
Compiler : MSVC 2017, MinGW (both are 64-bit and results are same)

Test.pro

QT  = core gui widgets 
CONFIG  = c  11
DEFINES  = QT_DEPRECATED_WARNINGS
SOURCES  = main.cpp mainwindow.cpp
HEADERS  = mainwindow.h
FORMS  = mainwindow.ui

main.cpp

#include "mainwindow.h"

#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();
    return a.exec();
}

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QStateMachine>

QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
    Q_OBJECT
public slots:
    void stateMachineStarted();

public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();

private:
    Ui::MainWindow *ui;
    QStateMachine *stateMachine;
};
#endif // MAINWINDOW_H

mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"

#include <QDebug>

void MainWindow::stateMachineStarted()
{
    qDebug() << "MainWindow::stateMachineStarted()";
}

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    qDebug() << "MainWindow::MainWindow()";
    ui->setupUi(this);
    stateMachine = new QStateMachine;

    QState *closed = new QState;
    QState *setup = new QState;
    QState *opened = new QState;
    QState *closing = new QState;

    stateMachine->addState(closed);
    stateMachine->addState(setup);
    stateMachine->addState(opened);
    stateMachine->addState(closing);

    Q_ASSERT(connect(stateMachine, &QStateMachine::started, this, &MainWindow::stateMachineStarted));

    stateMachine->setInitialState(closed);
    stateMachine->start();
}

MainWindow::~MainWindow()
{
    qDebug() << "MainWindow::~MainWindow()";
    delete ui;
}

Application output in debug mode (I closed the form after few seconds.)

12:39:09: Starting C:\bin\build-Test-Desktop_Qt_5_14_2_MSVC2017_64bit-Debug\debug\Test.exe ...
MainWindow::MainWindow()
MainWindow::stateMachineStarted()
MainWindow::~MainWindow()
12:39:11: C:\bin\build-Test-Desktop_Qt_5_14_2_MSVC2017_64bit-Debug\debug\Test.exe exited with code 0

Application output in release mode (I closed the form after few seconds.)

12:27:51: Starting C:\bin\build-Test-Desktop_Qt_5_14_2_MSVC2017_64bit-Release\release\Test.exe ...
MainWindow::MainWindow()
MainWindow::~MainWindow()
12:27:53: C:\bin\build-Test-Desktop_Qt_5_14_2_MSVC2017_64bit-Release\release\Test.exe exited with code 0

CodePudding user response：

In release mode, it is likely that the connection is not made because you wrapped it inside a Q_ASSERT macro.

See Q_ASSERT release build semantics for more informations.