I’m doing pagination and need to store ready-made models for some pages. Create threads to fill models for pages. If I debug the program, get a segfault sometimes when finish executing the fillModel lambda, sometimes when creating QSqlQuery in getQuery.

#include <QCoreApplication>
#include <thread>
#include <vector>
#include <mutex>
#include <condition_variable>
#include <QDebug>
#include <QSqlQueryModel>
#include <QSqlQuery>


struct Thread 
{
    std::thread thread;
    QSqlQueryModel model = QSqlQueryModel();
    std::mutex done_mtx;
    std::condition_variable done_cv;
    bool done = false;
};

std::vector<Thread> pages_threads(3); // There is contains prepared models

QSqlQuery getQuery(int page_index)
{
    static std::atomic<int> id = 1;
    QString connect_name = QString::number(++id);
    QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE", connect_name);
    db.setDatabaseName("path_to_db");
    db.open();
    if(!db.isOpen() || !db.isValid())
        qDebug() << "DB not open";
    QString query = "SELECT * FROM USER LIMIT 20 OFFSET " + QString::number( (page_index-1) * 20);
    QSqlQuery sqlQ(query, db);
    return sqlQ;
}

void fillThread(int i)
{
    auto fillModel = [](int page_index, int thread_idx)
    {// When this lambda finish get a seg fault
        pages_threads[thread_idx].model.setQuery( getQuery(page_index) );
        std::lock_guard<std::mutex> lk( pages_threads[thread_idx].done_mtx);
        pages_threads[thread_idx].done = true;
        pages_threads[thread_idx].done_cv.notify_one();
    };
    switch (i) {
    case 0:
        pages_threads[0].done = false;
        pages_threads[0].thread = std::thread( fillModel, 0, 0);
        pages_threads[0].thread.detach();
        break;
    case 1:
        pages_threads[1].done = false;
        pages_threads[1].thread = std::thread( fillModel, 1, 1);
        pages_threads[1].thread.detach();
        break;
    case 2:
        pages_threads[0].done = false;
        pages_threads[1].done = false;
        pages_threads[2].done = false;

        pages_threads[0].thread = std::thread( fillModel, 0, 0);
        pages_threads[1].thread = std::thread( fillModel, 1, 1);
        pages_threads[2].thread = std::thread( fillModel, 2, 2);

        pages_threads[0].thread.detach();
        pages_threads[2].thread.detach();
        pages_threads[1].thread.join();
        break;
    default:
        break;
    }
}

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    fillThread(2);
    return a.exec();
}

code which trigger seg fault

stack

I use QT 6.6.1 version, GDB 11.2, Windows 10, SQLite