QList<const QBluetoothDeviceInfo* declaration / definiton problem

[Anonymous_Banned275]

What am I missing in my code ?
( copied from text editor , hence NO code formatting )

Declaration

 QList<const QBluetoothDeviceInfo* > RemoteDeviceInfo;

This works

  RemoteDeviceInfo.append(&info);  adds info  corrrectly

            // verify
            text = "!!!!!!!!!   DEBUG verify RemoteDeviceInfo \n";
            text += " name \n";
            text += RemoteDeviceInfo.at(0)->name();  OK 
            qDebug() << text;
            m_ui->plainTextEdit_8->appendPlainText(text);
            // m_ui->plainTextEdit_3->appendPlainText(text

          for(auto &device:RemoteDeviceInfo)
            {
                text = " BUILD  range loop test ";
                m_ui->plainTextEdit_8->appendPlainText(text);

                text = " device name ";
                text += device->name();        OK 
                m_ui->plainTextEdit_8->appendPlainText(text);
            }

when I attempt to verify RemoteDeviceInfo contents using another method

it fails

   if(!RemoteDeviceInfo.isEmpty())      this passes 
                        {
                            for (auto &device:RemoteDeviceInfo)
                            {
                                text = " For loop test ";
                                qDebug() << text;
                                text = " device address \n";
                                text += device->address().toString();  apparently fails here 
                                qDebug() << text;
                                m_ui->plainTextEdit_8->appendPlainText(text);
                                text = " device name  \n";
                                text += device->name(); // >address().toString()
                                qDebug() << text;
                                m_ui->plainTextEdit_8->appendPlainText(text);


                            }
                        }
                    }

Using debug I do not detect anything in RemoteDeviceInfo

---

Fixed that formatting for you[@J-Hilk]

[Axel Spoerl]

@AnneRanch
If you want free advice here, please take the time and effort to format your code nicely.
You can safely assume that container classes work correctly. So probably your “other method” queries it at a point where it is still empty or empty again. Since you don’t show the code where you populate the list, it’s hard to say why it is empty when you expect the opposite.

[Anonymous_Banned275]

@Axel-Spoerl OK, I did say I copied
the text from text editor

( copied from text editor , hence NO code formatting )

• which should be understood that it could not be formatted to your liking using forum software.

If it bothers you to give free advise because I did not formatted the code correctly

• my advise to you is - do not reply at all .

Your opinion is non productive , it does not help me to solve the problem.

Even if code is not formatted to your liking you should be able to determine that the issue is NOT in "filling the variable ".
I specifically included code which I said works as expected and code which verifies the contents of the variable.
Apparently you either did not bother to read it or have no understanding of the code .
If you not get the code - why don't you ask for explanation ?
Let's get back to resolving the issue and stop bickering about formalities.
Cheers

PS The forum editor replaces dash with dot it knows Morse code....

[Axel Spoerl]

@AnneRanch
Thanks for your advice not to reply, and for the hint that my opinion is non productive. Also thanks for the encouragement to crawl my way through unformatted code. I wish you a perfect solution to the issue. Keep smiling!

[Anonymous_Banned275]

@Axel-Spoerl Many thanks for the reply. I do appreciate it. Here is my view and some missing explanation from original post .
The container is filed , copied from another variable, when the class is constructed and the code posted works as expected.
The other method , in same class . is run AFTER GUI " button" is clicked - hence manually and well after the class is constructed. Its current , starting task , is just to certify the contents of the container.
That is what is failing.
I just do not understand why the same code of test verifying range loop works in one function / method and fails in another.
Obviously I am missing something and I do not know what.
The container if defined as a variable in the "public" area of the class , perhaps the definition is wrong. I just do not know.
Thanks for taking your time to discuss this issue.

[Axel Spoerl]

@AnneRanch
Please don't take it offensive: Nobody, including me, will have fun reading code, if it is not formatted.
I haven't read it and I won't read it the way it is posted.
It's possible to format it, it just takes a bit patience and time.
Start the code block with 3 times ` and end it the same way.
Don't stop, before the code looks nice in the preview window on your right.
Please also post the entire code, not just fragments.
If you want anybody here to dig into an issue: That's your ticket.

For the records: If you feel like insulting me (again) for claiming formatted code: Swallow it from now on.

[Anonymous_Banned275]

@Axel-Spoerl OK, here is my unbiased opinion . I have described the problem and I firmly believe it is not a coding issue.
There is something wrong with the way the container is defined or used. However , it it helps to find a solution I can re post reformatted code.
Please keep in mind it is a code under construction,

    Q_OBJECT

public:
    // add May 14
    void on_applyButton_10_clicked();
    //making a list May 13
    QList<const QBluetoothDeviceInfo* > RemoteDeviceInfo;

This copies data from info into RemoteDeviceInfo and works as expected

{
            text = "\n TASK addDevice ";
            qDebug()<< text;
            m_ui->plainTextEdit->appendPlainText(text);
            m_ui->plainTextEdit_3->appendPlainText(text);
            text = " device address ";
            text += info.address().toString();
            qDebug()<< text;
            m_ui->plainTextEdit->appendPlainText(text);
            m_ui->plainTextEdit_3->appendPlainText(text);

            text = " device name ";
            text += info.name();
            text += "\n";

            qDebug()<< text;
            m_ui->plainTextEdit->appendPlainText(text);
            m_ui->plainTextEdit_3->appendPlainText(text);

            text = " TASK pair device name ";
            text += info.name();
            text += "\n";
            qDebug()<< text;
            m_ui->plainTextEdit->appendPlainText(text);
            //return;

            // QBluetoothLocalDevice::Pairing
            int pairingStatus = localDevice->pairingStatus(info.address());
            text = " TASK pairingStatus ";
            text += info.name();
            text += QString::number(pairingStatus);
            qDebug()<< text;
            m_ui->plainTextEdit->appendPlainText(text);


            //QList devicesList info
            RemoteDeviceInfo = new QBluetoothHostInfo();
            //TestClass* test_1 = new TestClass(&a);
            //test_list.append(test_1);

            RemoteDeviceInfo.append(&info);

            // verify
            text = "!!!!!!!!!   DEBUG verify RemoteDeviceInfo \n";
            text += " name \n";
            text += RemoteDeviceInfo.at(0)->name();
            qDebug() << text;
            m_ui->plainTextEdit_8->appendPlainText(text);
            // m_ui->plainTextEdit_3->appendPlainText(text);

            for(auto &device:RemoteDeviceInfo)
            {
                text = " BUILD  range loop test ";
                m_ui->plainTextEdit_8->appendPlainText(text);

                text = " device name ";
                text += device->name();
                m_ui->plainTextEdit_8->appendPlainText(text);
            }












            //return;

            text = " TASK pairingStatus ";
            text += info.name();
            text += QString::number(pairingStatus);  // this is usibg last localDevice->pairingStatus(info.address());
            if (pairingStatus == QBluetoothLocalDevice::Paired || pairingStatus == QBluetoothLocalDevice::AuthorizedPaired )
            {
                text += " PAIRED ";
                //item->setForeground(QColor(Qt::green));
            }
            else
            {
                text += " NOT PAIRED ";

                //item->setForeground(QColor(Qt::black));

            }

            //return;

            qDebug()<< text;
            m_ui->plainTextEdit->appendPlainText(text);


            // request pairing

            if( pairingStatus == 0 )
            {
                text = " TASK request pairing ";
                text += info.name();
                qDebug()<< text;
                m_ui->plainTextEdit->appendPlainText(text);

                localDevice->requestPairing(info.address(),QBluetoothLocalDevice::Pairing());


                text = " TASK continue ";
                qDebug()<< text;
                m_ui->plainTextEdit->appendPlainText(text);

            }









#ifdef BYPASS


            QString label = QString("%1 %2").arg(info.address().toString()).arg(info.name());
            //    QList<QListWidgetItem *> items = ui->list->findItems(label, Qt::MatchExactly);
            if (items.empty()) {
                QListWidgetItem *item = new QListWidgetItem(label);
                QBluetoothLocalDevice::Pairing pairingStatus = localDevice->pairingStatus(info.address());
                if (pairingStatus == QBluetoothLocalDevice::Paired || pairingStatus == QBluetoothLocalDevice::AuthorizedPaired )
                    item->setForeground(QColor(Qt::green));
                else
                    item->setForeground(QColor(Qt::black));

                //       ui->list->addItem(item);
#endif
            }

This s code attempts to verify the contents of RemoteDeviceInfo and fails to  do so.


                    void SettingsDialog::on_applyButton_11_clicked()
                    {
                        text = "Test range loop \n";
                        text += Q_FUNC_INFO;
                        qDebug()<< text;
                        m_ui->plainTextEdit_8->appendPlainText(text);
                        if(!RemoteDeviceInfo.isEmpty())
                        {
                            for (auto &device:RemoteDeviceInfo)
                            {
                                text = " For loop test ";
                                qDebug() << text;
                                text = " device address \n";
                                text += device->address().toString();
                                qDebug() << text;
                                m_ui->plainTextEdit_8->appendPlainText(text);
                                text = " device name  \n";
                                text += device->name(); // >address().toString()
                                qDebug() << text;
                                m_ui->plainTextEdit_8->appendPlainText(text);


                            }
                        }
                    }

I will be more than happy to provide additional information to help solve this if requested

I have added class variable TEST and set it when RemoteDeviceInfo is build. I have also added debug text to the function verifying the content of RemoteDeviceInfo and it can be seen in attached run output as set to 1.

qt.bluetooth.bluez: Device discovery aborted due to unexpected adapter changes from another process.
"Test range loop \nvoid SettingsDialog::on_applyButton_11_clicked() !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! TEST !!!!!!!!!!!!1"
" For loop test "
11:04:07: /mnt/RAID_124/PROJECTS_May14_BASE_/mdi/MDI crashed.

[Christian Ehrlicher]

@AnneRanch said in QList<const QBluetoothDeviceInfo* declaration / definiton problem:

        RemoteDeviceInfo = new QBluetoothHostInfo();

        RemoteDeviceInfo.append(&info);

This does not even compile and even if it would - storing an adress to a local variable will result in a crash afterwards.

[Axel Spoerl]

Adding to @Christian-Ehrlicher:

RemoteDeviceInfo = new QBluetoothHostInfo();

assigns pointer to a heap allocated BluetoothHostInfo to a member variable, defined as a QList<const QBluetoothDeviceInfo* >. Whatever has been in the list up to then, will be discarded. If the code gets compiled somehow (on my machine, it doesn't), the list now contains one single, default-constructed element.

RemoteDeviceInfo.append(&info);

This appends the pointer to a (probably) stack allocated QBluetoothHostInfo object. Now the list will contain two pointers. One to the new default-constructed element, and another one pointing to the object that has been passed to the function as an argument. As soon as the argument-passed object goes out of scope, the list contains a pointer to a stale object.

Next time the function is called, the list is initialized with another new default-constructed object. The previous one will leak.

I hope that brings you closer to the problem.

[JonB]

@Axel-Spoerl said in QList<const QBluetoothDeviceInfo* declaration / definiton problem:

If the code gets compiled somehow (on my machine, it doesn't),

It won't compile as shown and as @Christian-Ehrlicher said. The member variable is

QList<const QBluetoothDeviceInfo* > RemoteDeviceInfo;

You can't go RemoteDeviceInfo = new anything 'coz it's not a pointer :)

I suspect whatever the real code there the RemoteDeviceInfo.append(&info); statement is storing pointers to local variable in the list, later on in other function they point to undefined.

[Anonymous_Banned275]

@Axel-Spoerl I am very sorry , but the code I posted DOES HAVE AN ERROR and it won't compile.
I accidentally just posted the version which does not have the offending code of code commented out.
As a said my code works AKA it does compile , but fails to retrieve the contents of the container.

[Anonymous_Banned275]

@JonB said in QList<const QBluetoothDeviceInfo* declaration / definiton problem:

RemoteDeviceInfo.append(&info); statement is storing pointers to local variable in the list

...and that looks as the core of the problem , but why ?

It is declared as class "common" variable....

[JonB]

@AnneRanch
WHAT "is declared as class "common" variable...."?

If you mean the RemoteDeviceInfo, yes, but that is not the problem here.

The problem is your statement RemoteDeviceInfo.append(&info);. Where is that info actually declared? The code you have posted won't compile that line for the info, not just the new earlier.

Should we guess the line

//QList devicesList info

is not actually commented out? There is no other declaration for info you show. In that case it would explain the bad behaviour. But we don't know because you won't paste whatever code you use which actually compiles! We accept you have code which does compile so you get your result, but until you show that actual code it's guesswork.

You show a block

            //QList devicesList info
            RemoteDeviceInfo = new QBluetoothHostInfo();
            //TestClass* test_1 = new TestClass(&a);
            //test_list.append(test_1);

            RemoteDeviceInfo.append(&info);

What does that really look like, copied & pasted, when it compiles and gives you the bad behaviour? Does it actually read:

            QList devicesList info;
            //RemoteDeviceInfo = new QBluetoothHostInfo();
            //TestClass* test_1 = new TestClass(&a);
            //test_list.append(test_1);

            RemoteDeviceInfo.append(&info);

[Anonymous_Banned275]

@JonB ok , AS I said I have accidentally posted wrong copy of the code.
With that removed it compiles and when I add to the new container the data shows up in the verifying loop ( as I said before ),
there is nothing wrong with info and its addition to the new container.

PS IN MY OPINION here is a shinning example that code posting is not of that great help - I have repeatedly state what runs and what does not and you started compiling code which did not need to be compiled to find the problem - simple reading thru should have been sufficient to find the problem.
But Alex insisted , so you got to find for yourself (!) what rums and what does not, and to prove what ?
...It fails in the subsequent usage....for still unknown reason.
However, I am still confident that together we can find the problem...

[Axel Spoerl]

But Alex insisted

Here is what I insisted on:

Please also post the entire code, not just fragments.

The post contains fragments, and obviously the wrong ones.

IN MY OPINION here is a shinning example that code posting is not of that great help

In my opinion here is a shining example that posting wrong and incomplete code is not helpful.

[JonB]

@AnneRanch said in QList<const QBluetoothDeviceInfo* declaration / definiton problem:

PS IN MY OPINION here is a shinning example that code posting is not of that great help - I have repeatedly state what runs and what does not and you started compiling code which did not need to be compiled to find the problem - simple reading thru should have been sufficient to find the problem.

Nope. We need the code. If you want to know what's wrong in it. We have suggested the most likely cause. The RemoteDeviceInfo.append(&info) is wrong, and that's the answer to your original

Using debug I do not detect anything in RemoteDeviceInfo

[Anonymous_Banned275]

@Axel-Spoerl NO , YOU GOT COMPLETE WORKing CODE - after the wrong line is removed.

Can we get back to the problem and quit bickering , it is getting tiresome.

[Axel Spoerl]

@AnneRanch said in QList<const QBluetoothDeviceInfo* declaration / definiton problem:

NO , YOU GOT COMPLETE WORKing CODE - after the wrong line is removed.

Untrue. The code posted is not complete. As an example, the class definition starts with Q_OBJECT => Large parts of the declarations are missing in the first fragment.

The second fragment misses the function name, let alone that I don't see where this unnamed function is called and where info is declared, as @JonB asked.

@AnneRanch said in QList<const QBluetoothDeviceInfo* declaration / definiton problem:

Can we get back to the problem

Good idea. Please let's start with what was asked in the beginning: Please post your entire code.

and quit bickering

You don't have to quit bickering all at once. It's totally fine if you fade it out gradually. Or have I misunderstood, and intention was to insult me? Forgiven with a smile! Just have a look at the code of conduct when it suits you.

it is getting tiresome.

Kind of agree.

[Anonymous_Banned275]

@Axel-Spoerl said in QList<const QBluetoothDeviceInfo* declaration / definiton problem:

The second fragment misses the function name, let alone that I don't see where this unnamed function is called and where info is declared, as @JonB asked.

What is " second fragment " ?
The code contains two functions /methods....

Please be more specific and make use of the requested (!) code and highlight where is " the missing function" problem.

Since the add of info works and is verified in the code - as I repeatedly stated - the source of info is material.
JonB is a nice guy , but this time on wrong track...

Please quit stalling with silly requests for more code - if the code is missing a function it would not compile , duh...

[Axel Spoerl]

@AnneRanch
To summarize:
@Christian Ehrlicher and @JonB, both truly nice guys, have already told you what the problem is: A pointer to a (probably) stack allocated object info is added to the list RemoteDeviceInfo. When it goes out of scope, the pointer points to a deleted object and things go banana from there. That's the most likely scenario based on the code fragments we see.

In the next post, your call out @JonB, apparently in disagreement with the current findings.

Very interestingly you twist things around, blaming us for not finding whatever you would accept as being the problem:

simple reading thru should have been sufficient to find the problem.

In essence that means:

• you know you have a problem
• you don't know what it is
• you are certain that it's not, what @Christian-Ehrlicher and @JonB (very capable experts) say it is - even though they point at something obviously wrong
• on the other hand you claim (and blame), that the code fragments posted must be sufficient for others to figure out your problem

Question: Have you read and understood what we believe could be (part of) the problem?

Three behaviors make it rather hard to dive deeper

• consistently ignoring requests to post your entire code (for clarity: entire means all, everything, the whole)
• such requests being called "silly", "bickering" (thanks by the way, it has made me laugh out loud)
• no feedback on the findings pointed out earlier (like e.g. "Ok, thanks, I will test a different approach and let you know")

"Simple reading thru should have been sufficient to find the problem" => I have just done as you said.
My count is:

• 3 refusals to co-operate
• 2 insults
• 1 thank you
• 1 apology (none for the insults, though)
• 0 please

My finding: Communicating with you isn't fun. IMHO, communication is your problem.

Good bye, @AnneRanch