Getting SIGSEGV on "finished" signal from QNetwowkAccessManager

SGaist

Hi and welcome to devnet,

connect(mpNetManager, SIGNAL(finished(QNetworkReply*)), this, SLOT(downloadFinished()));

You are missing the parameter of downloadFinished

Fernando

You're right, sorry.

Corrected .cpp source (still the same problem):

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

MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent), ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    initializeNetwork();
    testDownload();
}


MainWindow::~MainWindow()
{
    delete ui;
    mpNetManager->deleteLater();
}


void MainWindow::initializeNetwork()
{
    mpNetManager = new QNetworkAccessManager;
}


void MainWindow::testDownload()
{
    if (mpNetManager)
    {
        QNetworkRequest netRequest;
        QUrl downloadURL(TEST_URL);
        netRequest.setUrl(downloadURL);
        connect(mpNetManager, SIGNAL(finished(QNetworkReply * )), this, SLOT(downloadFinished(QNetworkReply * )));
        mpNetManager->get(netRequest);
    }
}


void MainWindow::downloadFinished (QNetworkReply* pNetReply)
{
    if (pNetReply)
    {
        if(pNetReply->error())
        {
                qDebug() << "ERROR!";
                qDebug() << pNetReply->errorString();
        }
        else
        {
            QString    qsDownloadPath = "downloaded.txt";
            QFile *pOutFile = new QFile(qsDownloadPath);
            if(pOutFile->open(QFile::WriteOnly))
            {
                pOutFile->write(pNetReply->readAll());
                pOutFile->flush();
                pOutFile->close();
            }
            delete pOutFile;
                qDebug() << "Download finished";
                qDebug() << "Content written to";
                qDebug() << qsDownloadPath;
        }
        pNetReply->deleteLater();
    }
}

[edit: Added missing coding tags SGaist]

SGaist

What do you get if you run your application through a debugger ?

Fernando

As I stated, when i launch the debugger, as soon as the "finished" signal fires I get the message

"The inferior stopped because it received a signal from the operating system
Signal name: SIGSEGV
Signal meaning: Segmentation Fault"

This is from C:\Windows\SysWOW64\ntdll.dll, instruction "rtlmovmemory"

This only happens while debugging: the program runs fine in Release.

SGaist

Can you check with a tool like Dependency Walker the libraries you are currently linking to ?

Fernando

Sure:

LIBGCC_S_DW2-1.DLL
QT5CORED.DLL
QT5NETWORKD.DLL
QT5WIDGETSD.DLL
API-MS-WIN-APPMODEL-RUNTIME-L1-1-0.DLL
API-MS-WIN-CORE-WINRT-ERROR-L1-1-0.DLL
API-MS-WIN-CORE-WINRT-L1-1-0.DLL
API-MS-WIN-CORE-WINRT-ROBUFFER-L1-1-0.DLL
API-MS-WIN-CORE-WINRT-STRING-L1-1-0.DLL
API-MS-WIN-SHCORE-SCALING-L1-1-1.DLL
DCOMP.DLL
IESHIMS.DLL

SGaist

That part looks good

Then let's get step by step. Does it also fail if you comment out the network stuff ?

Fernando

It debugs nicely without

mpNetManager->get(netRequest);

And it runs nicely (even with mpNetManager->get(netRequest)) when not debugging (even if the build was in debug mode).
To me, it's a bug in the debugger :-) , at least under Windows7-64.

SGaist

Using Qt's MinGW package ?

Fernando

Sorry, I was out of town.

Yes, using Qt's MinGW package (I don't have and don't like Visual Studio :-) ).

SGaist

So you have MinGW 4.9 ?

Fernando

Yes, MinGW 4.9.1.
Do you think I should file a bug report?