HELP) Initialization issue with QList<QList<QLineSeries*>> m_seriess_2d

Joonsoo

Hello

I'm using Qt Chart to float multiple pieces of data on a single chart

Press the current button to reset the chart and update the data again

The program will continue to be terminated in the process of clearing m_serious_2d, a two-dimensional array

I tried gpt and several documents, but I couldn't solve them
If you know the answer, please let me know

private:
	Ui::performance_page m_ui;

	QList<QChart*> m_chart;
	QList<QChartView*> m_chartview;
	QList<QList<QLineSeries*>> m_seriess_2d;
	QList<QDateTimeAxis*> m_axis_x_list;
	QList<QValueAxis*> m_axis_y_list;

void performance_page::clear()
{
	cout << "performance_page::clear" << endl;

	m_selected = -1;
	
	for (int i = 0; i < m_chartview.size(); i++)
	{
		if (m_chartview[i])
		{
			m_chartview[i]->deleteLater();
			m_chartview[i] = nullptr;
		}
		if (m_chart[i])
		{
			delete m_chart[i];
			m_chart[i] = nullptr;
			m_axis_x_list[i] = nullptr;
			m_axis_y_list[i] = nullptr;
		}

	}
	
	m_chartview.clear();
	m_chart.clear();
	m_axis_x_list.clear();
	m_axis_y_list.clear();
	
	for (int i = 0; i < m_seriess_2d.size(); i++)
	{
		for (int j = 0; j < m_seriess_2d[i].size(); j++)
		{
			if (nullptr != m_seriess_2d[i][j])
			{
				m_seriess_2d[i][j] = nullptr;
			}
		}
		m_seriess_2d[i].clear();
	}
	//m_seriess_2d.clear(); - Program boom!!

JonB

@Joonsoo said in HELP) Initialization issue with QList<QList<QLineSeries*>> m_seriess_2d:

//m_seriess_2d.clear(); - Program boom!!

"Program boom!!" is not a proper description/diagnosis of an issue. Run it inside a debugger and look at the stack trace if it "crashes" for a clue as to where/why.

The error might not directly be caused by clearing a series. It might show up there as a result of something else. You might e.g. try commenting out the series deletion to see whether it still happens. One thought I have is that you have done delete m_chart[i] on a QChart which is presumably the chart in use by m_chartview[i]. Is that safe, the QChartView now references a QChart which has been deleted? Remember that the QChartView takes ownership of the QChart. Similarly I am not sure you need to clear your multiple QLineSeries, when they were added to the QChart it took ownership of them.

Joonsoo

@JonB

Well, I've tried several initialization methods that other GPTs tell me, but I kept getting errors while trying to make m_serious_2d size zero

m_seriess_2d.resize(0);
m_seriess_2d.clear();

If you do this, you'll get an error
I don't know why

I've tried to operate it without using it anywhere else, but I can't solve it!

What am I missing?

Christian Ehrlicher

Please provide a minimal, compilable example to reproduce the crash. Minimize your code until it no longer crashes.

Joonsoo

@Christian-Ehrlicher ```

for (int i = 0; i < m_list.size(); i++)
{
	int m_seriess_size =  m_seriess_2d.size();

	if (i < m_seriess_size)
	{
	}
	else
	{
		m_seriess_2d.push_back(QList<QLineSeries*>());
	}

	m_seriess_2d[i].resize(4);

	for (int j = 0; j < 4; j++)
	{
		QLineSeries* series = new QLineSeries();
		series->setName(QString::fromLocal8Bit(m_list[i]->getProcName().c_str()));
		m_chart[j]->addSeries(series);
		m_seriess_2d[i][j] = series;
	}
}

for (int i = 0; i < m_list.size(); i++)
{
	for (int j = 0; j < 4; j++)
	{
		m_seriess_2d[i][j] = nullptr;
	}
	m_seriess_2d[i].clear();
}
m_seriess_2d.clear();

Even if you try to initialize it after creating it, m_serious_2d.clear(); an error occurs in this part as shown in the picture above

In this situation, m_serious_2d is not even added to the chart

What's the problem?

jsulm

@Joonsoo This is not a minimal compilable example. And you also did not provide stack trace after the crash.

Joonsoo

@jsulm

Well, I don't know how to minimize it
If you look at the current code

After the creation of m_serious_2d is completed, initialize it
There's an error

Are you saying that there should be no problem with this part?

Doesn't m_serious_2d own ownership?

Does Chart have ownership in Chartview?

jsulm

@Joonsoo @Christian-Ehrlicher asked you to provide a minimal compilable example, not a piece of code.
m_serious_2d contains lists of pointers, so it does not own QLineSeries.
It could help if you would provide the stack trace after the crash...

Joonsoo

@jsulm

https://forum.qt.io/topic/145364/forum-guidelines-code-of-conduct

Aha, I understand..

Sorry I'm not good at it, so I don't think I can split it to the point where it can be compiled..

Christian Ehrlicher

It's for sure a double free - please provide a minimal, compilable example to reproduce the issue