Summary of general debugging methods for Qt5 programs

1. Use qDebug to print key information and view it in the program output window, such as:

void QtAppDebug::on_pushButton_clicked() 
{
    
    
    qDebug() << "---QtAppDebug---" << endl; 
}

2. Use QMessageBox to display key information, and view through the window during program operation, such as:

void QtAppDebug::on_pushButton_clicked()
{
    
    
    QMessageBox::information(this,"Test","---QtAppDebug---");
}

3. Annotate the suspicious code, gradually narrow the scope according to the order of module functions, and accurately locate the bug code, such as:

void QtAppDebug::on_pushButton_clicked() 
{
    
    
#if 0
    QMessageBox::information(this,"Test","---QtAppDebug---");
#endif
}

4. qtcreator uses F10, F11, F5 for single-step debugging to view key data information during program operation;

5. Print debugging information to the log file for analysis, use examples , a more comprehensive system log framework can learn Log4Qt;

6. When debugging the complex interface display, you can set the color of the control to clearly view the size and boundary of the control, as follows:

void QtAppDebug::on_pushButton_clicked()
{
    
    
    ui->pushButton->setStyleSheet("background-color:red");
}

7. Add exception capture code, generate dump file when crash, analyze and locate according to dump file, as follows:

//异常捕获函数
long ApplicationCrashHandler(EXCEPTION_POINTERS *pException){
    
    
    {
    
    
        // 在程序exe的上级目录中创建dmp文件夹
        QDir *dmp = new QDir;
        bool exist = dmp->exists("../dmp/");
        if(exist == false)
            dmp->mkdir("../dmp/");
    }
    QDateTime current_date_time = QDateTime::currentDateTime();
    QString current_date = current_date_time.toString("yyyy_MM_dd_hh_mm_ss");
    QString time =  current_date + ".dmp";
    EXCEPTION_RECORD *record = pException->ExceptionRecord;
    QString errCode(QString::number(record->ExceptionCode, 16));
    QString errAddr(QString::number((uint)record->ExceptionAddress, 16));
    QString errFlag(QString::number(record->ExceptionFlags, 16));
    QString errPara(QString::number(record->NumberParameters, 16));
    qDebug()<<"errCode: "<<errCode;
    qDebug()<<"errAddr: "<<errAddr;
    qDebug()<<"errFlag: "<<errFlag;
    qDebug()<<"errPara: "<<errPara;
    HANDLE hDumpFile = CreateFile((LPCSTR)QString("../dmp/" + time).utf16(),
                                  GENERIC_WRITE, 0, NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);
    if(hDumpFile != INVALID_HANDLE_VALUE) {
    
    
        MINIDUMP_EXCEPTION_INFORMATION dumpInfo;
        dumpInfo.ExceptionPointers = pException;
        dumpInfo.ThreadId = GetCurrentThreadId();
        dumpInfo.ClientPointers = TRUE;
        MiniDumpWriteDump(GetCurrentProcess(), GetCurrentProcessId(),hDumpFile, MiniDumpNormal, &dumpInfo, NULL, NULL);
        CloseHandle(hDumpFile);
    }
    else{
    
    
        qDebug()<<"hDumpFile == null";
    }
    return EXCEPTION_EXECUTE_HANDLER;
}```
//注冊异常捕获函数
SetUnhandledExceptionFilter((LPTOP_LEVEL_EXCEPTION_FILTER)ApplicationCrashHandler);