uninitialized switchcase error

[saber]

this is my function.

void coreaction::batteryCheck()
{
    if (sm.getShowBattery()) {
        UPower *u = new UPower(this);
        
        Battery *b;
        foreach (Battery *bat, *u->batteries()) {
            b = u->batteries()->value(bat->path());
        }
        ui->batteryProg->setValue(b->percentage());

        switch( b->state() ) {
            case Battery::FullyCharged:
                ui->batteryStatus->setText( tr( "Full" ) );
                break;
            case Battery::Discharging:
                ui->batteryStatus->setText( tr( "Discharging" ) );
                break;
            case Battery::Charging:
                ui->batteryStatus->setText( tr( "Charging" ) );
                break;
            default:
                ui->batteryStatus->setText( tr( "No Battery" ) );
                break;
        }
        ui->batteryframe->setVisible(true);
    } else {
        ui->batteryframe->setVisible(false);
    }
}

battery.h

#ifndef BATTERY_H
#define BATTERY_H

#include <QObject>


class QDBusInterface;

class Battery : public QObject {

    Q_OBJECT

    Q_ENUMS(State)
    Q_PROPERTY(QString sysfsPath READ sysfsPath STORED false)
    Q_PROPERTY(QString model READ model STORED false)
    Q_PROPERTY(QString vendor READ vendor STORED false)
    Q_PROPERTY(QString technology READ technology STORED false)
    Q_PROPERTY(QString path READ path STORED false)
    Q_PROPERTY(bool powerSupply READ powerSupply STORED false)
    Q_PROPERTY(bool hasHistory READ hasHistory STORED false)
    Q_PROPERTY(bool hasStatistics READ hasStatistics STORED false)
    Q_PROPERTY(bool isPresent READ isPresent STORED false)
    Q_PROPERTY(bool isRechargeable READ isRechargeable STORED false)
    Q_PROPERTY(double energy READ energy STORED false)
    Q_PROPERTY(double energyEmpty READ energyEmpty STORED false)
    Q_PROPERTY(double energyFull READ energyFull STORED false)
    Q_PROPERTY(double energyFullDesign READ energyFullDesign STORED false)
    Q_PROPERTY(double energyRate READ energyRate STORED false)
    Q_PROPERTY(double voltage READ voltage STORED false)
    Q_PROPERTY(double percentage READ percentage STORED false)
    Q_PROPERTY(double capacity READ capacity STORED false)
    Q_PROPERTY(State state READ state STORED false)
    Q_PROPERTY(int lowLevel READ lowLevel)
    Q_PROPERTY(double toFull READ toFull STORED false)
    Q_PROPERTY(double toEmpty READ toFull STORED false)

public:
    Battery(const QString & path, QObject *parent = 0);
    ~Battery();

    /* Enums */
    enum State {FullyCharged, Charging, Discharging};

    /* Properties */
    QString sysfsPath() const;
    QString model() const;
    QString vendor() const;
    QString technology() const;
    const QString & path() const;

    bool powerSupply() const;
    bool hasHistory() const;
    bool hasStatistics() const;
    bool isPresent() const;
    bool isRechargeable() const;
    bool isValid() const;

    double energy() const;
    double energyEmpty() const;
    double energyFull() const;
    double energyFullDesign() const;
    double energyRate() const;
    double voltage() const;
    double percentage() const;
    double capacity() const;
    double toFull() const;
    double toEmpty() const;
    int lowLevel() const;
    void setLowLevel(int value);

    Battery::State state() const;

private:
    void createInterface();

    QDBusInterface      *m_interface;
    QString             m_path;
    bool                m_hasAlreadyBeenLow;
    bool                m_hasAlreadyBeenFull;
    int                 m_lowLevel;
    bool                m_valid;

public Q_SLOTS:
    void refresh();

private Q_SLOTS:
    void update();

Q_SIGNALS:
    void changed();
    void low();
    void full();
};

this is battery.cpp

#include "battery.h"

#include <QtDBus/QDBusConnection>
#include <QtDBus/QDBusInterface>
#include <QSettings>


Battery::Battery(const QString &path, QObject *parent)
    : QObject(parent), m_interface(0),
      m_path(path), m_hasAlreadyBeenLow(false),
      m_hasAlreadyBeenFull(false), m_valid(false)  {

    createInterface();
}

Battery::~Battery() {

}

void Battery::createInterface() {
    if(m_interface==0 || !m_interface->isValid()) {
        m_interface = new QDBusInterface("org.freedesktop.UPower", m_path,
                                         "org.freedesktop.UPower.Device", QDBusConnection::systemBus(), this);
        connect(m_interface, SIGNAL(Changed()), this, SIGNAL(changed()));
        if(!m_interface->isValid()) {
            delete m_interface;
            m_interface = 0;
            m_valid = false;
            return;
        }
    }

    m_valid = true;
}

void Battery::refresh() {
    m_interface->call("Refresh");
}

void Battery::update() {
    int level = percentage();

    if(level<lowLevel()) {
        if(!m_hasAlreadyBeenLow) {
            m_hasAlreadyBeenLow = true;
            emit low();
        }
    } else {
        m_hasAlreadyBeenLow = false;
    }

    if(state() == FullyCharged) {
        if(!m_hasAlreadyBeenFull) {
            m_hasAlreadyBeenFull = true;
            emit full();
        }
    } else {
        m_hasAlreadyBeenFull = false;
    }
}

bool Battery::isValid() const {
    return m_interface->property("Type").toInt() == 2 && m_valid;
}

int Battery::lowLevel() const {
    QSettings settings;
    settings.beginGroup("Batteries_Low_Level");
        int lvl = settings.value(m_path, 20).toInt();
    settings.endGroup();
    return lvl;
}

void Battery::setLowLevel(int value) {
    QSettings settings;
    settings.beginGroup("Batteries_Low_Level");
        settings.setValue(m_path, value);
    settings.endGroup();
}

QString Battery::sysfsPath() const {
    return m_interface->property("NativePath").toString();
}

QString Battery::model() const {
    return m_interface->property("Model").toString();
}

QString Battery::vendor() const {
    return m_interface->property("Vendor").toString();
}

QString Battery::technology() const {
    return m_interface->property("Technology").toString();
}

const QString & Battery::path() const {
    return m_path;
}

bool Battery::powerSupply() const {
    return m_interface->property("PowerSupply").toBool();
}

bool Battery::hasHistory() const {
    return m_interface->property("HasHistory").toBool();
}

bool Battery::hasStatistics() const {
    return m_interface->property("HasStatistics").toBool();
}

bool Battery::isPresent() const {
    return m_interface->property("IsPresent").toBool();
}

bool Battery::isRechargeable() const {
    return m_interface->property("IsRechargeable").toBool();
}

double Battery::energy() const {
    return m_interface->property("Energy").toDouble();
}

double Battery::energyEmpty() const {
    return m_interface->property("EnergyEmpty").toDouble();
}

double Battery::energyFull() const {
    return m_interface->property("EnergyFull").toDouble();
}

double Battery::energyFullDesign() const {
    return m_interface->property("EnergyFullDesign").toDouble();
}

double Battery::energyRate() const {
    return m_interface->property("EnergyRate").toDouble();
}

double Battery::voltage() const {
    return m_interface->property("Voltage").toDouble();
}

double Battery::percentage() const {
    return m_interface->property("Percentage").toDouble();
}

double Battery::capacity() const {
    return m_interface->property("Capacity").toDouble();
}

double Battery::toEmpty() const {
    return m_interface->property("TimeToEmpty").toDouble();
}

double Battery::toFull() const {
    return m_interface->property("TimeToFull").toDouble();
}

Battery::State Battery::state() const {
    uint state = m_interface->property("State").toUInt();
    switch( state ) {
        case (uint) 0:
            return FullyCharged;
            break;

        case (uint) 1:
            return Charging;
            break;

        case (uint) 2:
            return Discharging;
            break;

        default:
            return FullyCharged;
            break;
    }
}

problem is when i compile i got this error

g++ -c -pipe -O2 -march=armv7-a -mfloat-abi=hard -mfpu=vfpv3-d16 -O2 -pipe -fstack-protector-strong -fno-plt -std=gnu++11 -Wall -W -D_REENTRANT -fPIC -DQT_DEPRECATED_WARNINGS -DQT_NO_DEBUG -DQT_PRINTSUPPORT_LIB -DQT_MULTIMEDIAWIDGETS_LIB -DQT_CHARTS_LIB -DQT_WIDGETS_LIB -DQT_MULTIMEDIA_LIB -DQT_GUI_LIB -DQT_DBUS_LIB -DQT_NETWORK_LIB -DQT_CONCURRENT_LIB -DQT_CORE_LIB -I. -isystem /usr/include/qt -isystem /usr/include/qt/QtPrintSupport -isystem /usr/include/qt/QtMultimediaWidgets -isystem /usr/include/qt/QtCharts -isystem /usr/include/qt/QtWidgets -isystem /usr/include/qt/QtMultimedia -isystem /usr/include/qt/QtGui -isystem /usr/include/qt/QtDBus -isystem /usr/include/qt/QtNetwork -isystem /usr/include/qt/QtConcurrent -isystem /usr/include/qt/QtCore -I. -isystem /usr/include/libdrm -I. -I/usr/lib/qt/mkspecs/linux-g++ -o mimeutils.o corefm/mimeutils.cpp
make: *** [Makefile:2028: corebox.o] Error 1
make: *** Waiting for unfinished jobs....
coreaction/coreaction.cpp: In member function 'void coreaction::batteryCheck()':
coreaction/coreaction.cpp:114:25: warning: 'b' may be used uninitialized in this function [-Wmaybe-uninitialized]
         switch( b->state() ) {
                 ~~~~~~~~^~
==> ERROR: A failure occurred in build().
    Aborting...

what i missing??

[jsulm]

@saber Take a look at this code:

Battery *b;
foreach (Battery *bat, *u->batteries()) {
    b = u->batteries()->value(bat->path());
}

If u->batteries() returns an empty list b will be a dangling pointer and your app will crash. That's what compiler is telling you.
To be honest I don't understand this code: why do you iterate in a loop over the whole list but only keep the last value in b? It would be way faster to directly access the last element.

[saber]

@jsulm

please can u show the right way to do this .
please .
it is done by my friend and he is not in touch .
i need the fix badly.

[jsulm]

@saber This is really not difficult:

Battery *b = nullptr;
foreach (Battery *bat, *u->batteries()) {
    b = u->batteries()->value(bat->path());
}
if (!b)
    return;

[saber]

@jsulm
thanks for the solution .

can i invite u to join my project ? i know it is not the way to do that. but my app needs many fix that i can't ask all of them in forum.

my app is for linux.please check it out CoreBox
thanks.