QSettings crashes immediately

Saviz

I have a class called "Preferences". I try to use this class to save and read from an INI file to manage the settings of my application. In this class I have a "QSettings" object that I create on the heap (I need it to stay alive because I use it later on in my class). I use it to get some information from an INI file.

Preferences.h:

class Perferences : public QObject
{
    Q_OBJECT

public:
    explicit Perferences(

            QObject *parent = nullptr
            );

public:
    ~Perferences(

            );

private:
    QSettings* settings;

private:
    void method_Initialize(

            );
    void method_LoadValues(

            );
};

Preferences.cpp:

#include "preferences.h"

Perferences::Perferences(QObject *parent) : QObject{parent}
{
    method_Initialize();
}

Perferences::~Perferences()
{

}

void Perferences::method_Initialize()
{
    QSettings* settings = new QSettings(

                QApplication::applicationDirPath() + "/preferences/preferences.ini",
                QSettings::Format::IniFormat,
                this
                );

    if(!settings->contains("PATH_INPUT_VIDEOLOCATION"))
    {
        settings->setValue(

                    "PATH_INPUT_VIDEOLOCATION",
                    "NoValue"
                    );

        settings->sync();
    }

    // Until this line everything is fine. The file and the key-value is created.
    // The crash occurs in the following method:
    method_LoadValues();
}

void Perferences::method_LoadValues()
{
    try
    {
        QVariant output = settings->value(
                    
                    "PATH_INPUT_VIDEOLOCATION",
                    QStandardPaths::writableLocation(QStandardPaths::MoviesLocation)
                    );
        
        if(!output.isValid())
        {
            qDebug() << "Not valid. Something went wrong.";
        }
    }

    catch (const std::exception& e)
    {
        qWarning() << e.what();
    }
}

The issue is, as soon as I attempt to get the value from settings (using the method settings->value()) my application immediately crashes.

I event checked the INI file:

[General]
PATH_INPUT_VIDEOLOCATION=NoValue

Any help is highly appreciated.

Cobra91151

@Saviz

Hello!

From the first look at your code, you create QSettings* settings; twice. The first one is the class member variable and the second it is the local pointer variable.

Code:

private:
    QSettings* settings;


void Perferences::method_Initialize()
{
    QSettings* settings = new QSettings(

I think, this could lead to crash. I recommend you use the class member variable and remove the local pointer variable from method_Initialize.

Code:

private:
    QSettings* settings;

void Perferences::method_Initialize()
{
    settings = new QSettings(

JonB

@Saviz
Your QSettings* settings local variable in method_Initialize() shadows member variable Perferences::settings, which remains uninitialized?

Your compiler warning level should have allowed a warning to be shown?

SGaist

Hi,

Beside the good points made by my fellows, you don't need to keep a QSettings member variable, especially the way you use it. You can simply allocate it in you methods and use it as shown in the documentation.

Saviz

@JonB You are correct. However, the funny thing is it actually doesn't give a warning for some reason. I don't know how I managed to miss this! I guess it has been a long day :)

Saviz

@SGaist That is a very good point. I will change it.