Segmentation fault qComboBox

[Cucus]

Hi

When I try to clean my combo box to add new values (may not be the same number of elements) I have a segmentation fault. It always happens on the second time where the comboBox is modified. Here's the code:

void MenuPrincipal::updateComboBox(std::vector<std::vector<float> > solutions)
{
    QString solution;
    QList<QString> finalText;
    solution = " ";
 
    ui->comboBox->clear();  //segmentation fault
 
//adding objects...
    for(int i=0;i<solutions.size();i++)
    {
        solution = "";
        solution.append("(");
        solution.append(QString::number(i+1));
        solution.append(")");
        solution.append(" -> ");
        for(int j=0;j<6;j++)
        {
            solution.append(QString::number((double)solutions[i][j],'f',2));
            if(j<solutions[i].size()-1)solution.append(" , ");
        }
        finalText.push_back(solution);
    }
 
    QStringList longerList = (finalText);
    this->ui->comboBox->addItems(longerList);
}

void MenuPrincipal::updateComboBox(std::vector<std::vector<float> > solutions)
{
    QString solution;
    QList<QString> finalText;
    solution = " ";
  
    ui->comboBox->clear();  //segmentation fault

//adding objects...
    for(int i=0;i<solutions.size();i++)
    {
        solution = "";
        solution.append("(");
        solution.append(QString::number(i+1));
        solution.append(")");
        solution.append(" -> ");
        for(int j=0;j<6;j++)
        {
            solution.append(QString::number((double)solutions[i][j],'f',2));
            if(j<solutions[i].size()-1)solution.append(" , ");
        }
        finalText.push_back(solution);
    }

    QStringList longerList = (finalText);
    this->ui->comboBox->addItems(longerList);
}

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[stampede]

Are you sure clear() causes crash ? Can you post backtrace ?
I see another problem in this code - you have to check if solutions[i] have enough elements before trying to access it, try this way:

const int count = solutions[i].count();
for(int j=0;j<6;j++){
    if( j < count ){
        solution.append(QString::number((double)solutions[i][j],'f',2));
        if(j<count-1) solution.append(" , ");
    }

const int count = solutions[i].count();
for(int j=0;j<6;j++){
    if( j < count ){
        solution.append(QString::number((double)solutions[i][j],'f',2));
        if(j<count-1) solution.append(" , ");
    }

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[Cucus]

You can see here how I check where's the error:

First step
first update.jpg
Second step
second step.jpg

I control the number of elements of solution in another function.

[stampede]

Have you tried to run with debugger ? It will show you where it crashed exactly (you can clearly see if its inside QComboBox class).

[robert.cerne]

Hi,

I have had the same problem. Every time my application would modify the QComboBox object there was a high probability that a segmentation fault would occur. I have solved the problem by disabling the QComboBox. Example code is the following:

comboBoxComponent->setDisabled(true);
comboBoxComponent->clear();
comboBoxComponent->setDisabled(false);

comboBoxComponent->setDisabled(true);
comboBoxComponent->clear();
comboBoxComponent->setDisabled(false);

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