Question about Qcombo box < crash issue

bask185

I have more combo boxes, it was just an example of how I put things in them

ambershark

@bask185 You need to build and run the debug version in order to get the stack trace with detailed information. If you do this and then post that information we can tell you where your crash is.

Based on the release stack trace you are crashing in QString. We don't know where yet but if you repost the debug build stack trace we will. It should tell us line and file.

bask185

ASSERT failure in QList<T>::operator[]: "index out of range", file ../../../Qt5.7.0/5.7/gcc_64/include/QtCore/qlist.h, line 545

index out of range issue it seems, I verified that z is always within the range (0-2)

1   __GI_raise                                                                                                                 raise.c       54  0x7ffff5b81428 
2   __GI_abort                                                                                                                 abort.c       89  0x7ffff5b8302a 
3   QMessageLogger::fatal(const char *, ...) const                                                                                               0x7ffff653ff4e 
4   qt_assert_x(const char *, const char *, const char *, int)                                                                                   0x7ffff653b821 
5   QList<QString>::operator[]                           // << this the one                                                        qlist.h       545 0x427f8d       
6   Setup::on_serialPortBox_activated                                                                                          setup.cpp     115 0x424c04       
7   Setup::qt_static_metacall                                                                                                  moc_setup.cpp 116 0x4297aa       
8   Setup::qt_metacall                                                                                                         moc_setup.cpp 183 0x4299ee       
9   QMetaObject::activate(QObject *, int, int, void * *)                                                                                         0x7ffff6746700 
10  QComboBox::activated(QString const&)                                                                                                         0x7ffff77d4c65 
11  ??                                                                                                                                           0x7ffff77d6126 
12  ??                                                                                                                                           0x7ffff77d88e9 
13  ??                                                                                                                                           0x7ffff77de91d 
14  QMetaObject::activate(QObject *, int, int, void * *)                                                                                         0x7ffff6746056 
15  ??                                                                                                                                           0x7ffff77d528b 
16  QCoreApplicationPrivate::sendThroughObjectEventFilters(QObject *, QEvent *)                                                                  0x7ffff671e853 
17  QApplicationPrivate::notify_helper(QObject *, QEvent *)                                                                                      0x7ffff76dc505 
18  QApplication::notify(QObject *, QEvent *)                                                                                                    0x7ffff76e3808 
19  QCoreApplication::notifyInternal2(QObject *, QEvent *)                                                                                       0x7ffff671eae0 
20  QApplicationPrivate::sendMouseEvent(QWidget *, QMouseEvent *, QWidget *, QWidget *, QWidget * *, QPointer<QWidget>&, bool)                   0x7ffff76e27bf 
... <More>

VRonin

problem looks to be in: ui->descriptionLabel->setText(list[z]); almost surely because list is empty as I never saw you setting the user role to a QStringList anywhere in your code

bask185

@VRonin that is probably because I cannot find the words 'user' or 'role' anywhere on the doc.qt page and I don't understand how I can succesfully use a QStringClass for my purpose.

@all Nobody knows how I can display the description of my serial port???

VRonin

@bask185 said in Question about Qcombo box < crash issue:

I cannot find the words 'user' or 'role' anywhere on the doc.qt page

😕 http://doc.qt.io/qt-5/qcombobox.html#insertItem

Nobody knows how I can display the description of my serial port???

we do and we tried to explain you how. you have to save it in the data of the combobox

bask185

@VRonin I was looking on the QStringList page ...

I was doing that in an other function

for (QSerialPortInfo &info : infos) {
        QStringList list;

        list << info.portName();
        ui->serialPortBox->addItem(list.first(), list);
    }

So I was stuffing port names in the combo box, but not the description because that is not what I want. The descriptions are to be printed under the combobox in a text label.

So that function made me thinking, I made a new private QStringList variable called 'list2' and in the same function in which I fill the combobox I also fill 'list2' with dem descriptions

for (QSerialPortInfo &info : infos) {
        QStringList list;

        list << info.portName();
        list2 << info.description(); // < new line
        ui->serialPortBox->addItem(list.first(), list);
    }

so now I only had to do.

void Setup::on_serialPortBox_activated(const QString &arg1)
{
    z = ui->serialPortBox->currentIndex();

    ui->descriptionLabel->setText(list2[z]);
}

And voila:
USB 2.0

VRonin

not how I would have done it but good enough for rock and roll

P.S.
I'd have done:

for (const QSerialPortInfo &info : infos) 
        ui->serialPortBox->addItem(info.portName(), info.description());

and then, in the constructor, added:
connect(ui->serialPortBox,static_cast<void(QComboBox::*)(int)>(&QComboBox::currentIndexChanged),[this](){ui->descriptionLabel->setText(ui->serialPortBox->currentData().toString();});

no need for QStringLists

bask185

dat looks rather.. exremely complicated compared to what I did O.o vague C++ syntax sometimes. Besides I really must avoid the use of pointers whenever possible, pointers are not good for my mental health -_-*

VRonin

ambershark

@bask185 said in Question about Qcombo box < crash issue:

Besides I really must avoid the use of pointers whenever possible, pointers are not good for my mental health

Lol, you may want to consider something other than C++. ;) I felt that way when I was first learning, but if you continue to feel that way, you really need a language that does it for you. Java, C#, python, tons of options. Python will even let you use Qt. :)

bask185

I was having a perfectly fine working application in processing. I shook dat code right out of my sleeve. Easy OO programming, no difficult vague words such as 'public' or 'private', no pointers, some easy global variables which I can use in every class I make. Truly processing is by far the easiest program ever :D

And do you know what it takes to export an application to Linux? Ctrl shift E, check Linux, press Export applications and BAM it works! Java ftw! But.... app was too heavy for my rpi... freakin java -_-". Now it takes me more than a week to crosscompile for the rpi. I had to install ubuntu on my Pc to find out I had only one 1GB space left so I had to delete my windows OS.... I do kinda regret I did not learn python and Tkinter first...

But the things I learn.. priceless

ambershark

@bask185 Yea java is just so slow and heavy. That's why I could never get into it.

I use an ide (CLion) that is written in java and it is so slow compared to the other one I use that is written in C++ (slickedit). I like CLion's features, but the java engine is just so slow. It's almost unusable on large projects, meanwhile slickedit has no speed issues.

Another anecdote.. I spun up an AWS micro server the other day to run upsource from jetbrains. It needed > 2GB in RAM just to start the application because of the java and cassandra dependency. If I wrote a similar application to upsource in something faster like C++ it would take maybe 50mb to start, not >2gb, lol. I killed the AWS server as I didn't want to pay for the bigger server just to mess around with upsource and installed it locally on a server in my office.

Morale of the story, java is great for easy, it does everything for you, programming, but it is awful when it comes to actually using the software that is produced, lol.