CODEWITHSUNDEEP
c++qtclion
Михаил Беляков
Михаил Беляков

Reputation: 11

How can I fix memory problem connected to Heap?

I have met a problem while using Qt. When I try to start the below program it exits with code: -1073741819 (0xC0000005)

#include <iostream>
#include <QApplication>
#include <QWidget>
#include <QVBoxLayout>
#include <QSlider>
#include <QPixmap>
#include <QPainter>
#include <QPaintEvent>

class ColorfulCircle : public QWidget
{
Q_OBJECT

public:
    ColorfulCircle(QWidget *parent) {
        setParent(parent);
        mGreenCircle = QPixmap("GreenCircle.png");
        mYellowCircle = QPixmap("YellowCircle.png");
        mRedCircle = QPixmap("RedCircle.png");

        if (mGreenCircle.isNull() || mYellowCircle.isNull() || mRedCircle.isNull()) {
            std::cerr << "Failed to load circle images!" << std::endl;
            return;
        }

        mCurrentCircle = mGreenCircle;
        setFixedSize(100, 100);
    }

    QSize minimumSizeHint() const override {
        return QSize(100, 100);
    }

protected:
    void paintEvent(QPaintEvent *e) override {
        QPainter p(this);
        p.drawPixmap(e->rect(), mCurrentCircle);
    }

public slots:
    void setGreen() {
        mCurrentCircle = mGreenCircle;
        update();
    }

    void setYellow() {
        mCurrentCircle = mYellowCircle;
        update();
    }

    void setRed() {
        mCurrentCircle = mRedCircle;
        update();
    }

private:
    QPixmap mCurrentCircle;
    QPixmap mGreenCircle;
    QPixmap mYellowCircle;
    QPixmap mRedCircle;
};

int main(int argc, char **argv) {
    QApplication app(argc, argv);

    QWidget window;
    window.setWindowTitle("Colorful Circle");
    window.setFixedSize(200, 250);

    QVBoxLayout *layout = new QVBoxLayout(&window);

    ColorfulCircle circle(nullptr);
    layout->addWidget(&circle, 0, Qt::AlignCenter);

    QSlider slider(Qt::Horizontal);
    slider.setRange(0, 100);
    layout->addWidget(&slider);

    QObject::connect(&slider, &QSlider::valueChanged, [&circle](int newValue) {
        if (newValue < 33) {
            circle.setGreen();
        } else if (newValue < 66) {
            circle.setYellow();
        } else {
            circle.setRed();
        }
    });

    window.show();

    return app.exec();
}

#include <main.moc>

I tried to do something, checked via debugger but I'm not so good at this. Some tries gave me another exit code: -1073740940 (0xC0000374). But I think that there is the same problem in both cases

Upvotes: 1

Views: 76

Answers (1)

3CxEZiVlQ
3CxEZiVlQ

Reputation: 38863

layout->addWidget() takes ownership of a pointed object. Passing addresses of auto/stack variables to there is an error: when the app exits, it comes to call delete &circle; delete &slider;.

The correct code should be like this:

    ColorfulCircle* circle = new ColorfulCircle(nullptr);
    layout->addWidget(circle, 0, Qt::AlignCenter);

    QSlider* slider = new QSlider(Qt::Horizontal);
    slider->setRange(0, 100);
    layout->addWidget(slider);

Upvotes: 4

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