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  4. Logging messages: qlogging.h

Logging messages: qlogging.h

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  • SGaistS Offline
    SGaistS Offline
    SGaist
    Lifetime Qt Champion
    wrote on last edited by
    #2

    Hi,

    Do you have a custom message handler ?

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    Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

    sitesvS 1 Reply Last reply
    0
    • SGaistS SGaist

      Hi,

      Do you have a custom message handler ?

      sitesvS Offline
      sitesvS Offline
      sitesv
      wrote on last edited by
      #3

      @SGaist I don’t know.

      void messageHandler(QtMsgType type, const QMessageLogContext &context, const QString &msg);
      ...
      void main(...)
      {
      qInstallMessageHandler(messageHandler);
      }
      
      1 Reply Last reply
      0
      • SGaistS Offline
        SGaistS Offline
        SGaist
        Lifetime Qt Champion
        wrote on last edited by
        #4

        Well, installing a custom message handler usually means to you are using a custom message handler.

        You have to handle the threading aspect in your custom handler.

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        Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

        sitesvS 2 Replies Last reply
        1
        • SGaistS SGaist

          Well, installing a custom message handler usually means to you are using a custom message handler.

          You have to handle the threading aspect in your custom handler.

          sitesvS Offline
          sitesvS Offline
          sitesv
          wrote on last edited by
          #5

          @SGaist , so, This messageHandler handles various types of log messages. So, I think this is a custom messages handler. Tomorrow I will post a code of handler.

          SGaistS 1 Reply Last reply
          0
          • SGaistS SGaist

            Well, installing a custom message handler usually means to you are using a custom message handler.

            You have to handle the threading aspect in your custom handler.

            sitesvS Offline
            sitesvS Offline
            sitesv
            wrote on last edited by sitesv
            #6

            @SGaist said in Logging messages: qlogging.h:

            You have to handle the threading aspect in your custom handler

            What do you mean?

            1 Reply Last reply
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            • sitesvS sitesv

              @SGaist , so, This messageHandler handles various types of log messages. So, I think this is a custom messages handler. Tomorrow I will post a code of handler.

              SGaistS Offline
              SGaistS Offline
              SGaist
              Lifetime Qt Champion
              wrote on last edited by
              #7

              @sitesv said in Logging messages: qlogging.h:

              @SGaist , so, This messageHandler handles various types of log messages. So, I think this is a custom messages handler. Tomorrow I will post a code of handler.

              Calling qInstallMessageHandler implies that you are using a custom message handler.

              @sitesv said in Logging messages: qlogging.h:

              @SGaist said in Logging messages: qlogging.h:

              You have to handle the threading aspect in your custom handler

              What do you mean?

              That you have to use proper threading primitives to protect the resources you access in your handler.

              Interested in AI ? www.idiap.ch
              Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

              sitesvS 1 Reply Last reply
              1
              • SGaistS SGaist

                @sitesv said in Logging messages: qlogging.h:

                @SGaist , so, This messageHandler handles various types of log messages. So, I think this is a custom messages handler. Tomorrow I will post a code of handler.

                Calling qInstallMessageHandler implies that you are using a custom message handler.

                @sitesv said in Logging messages: qlogging.h:

                @SGaist said in Logging messages: qlogging.h:

                You have to handle the threading aspect in your custom handler

                What do you mean?

                That you have to use proper threading primitives to protect the resources you access in your handler.

                sitesvS Offline
                sitesvS Offline
                sitesv
                wrote on last edited by
                #8

                @SGaist there is a handler code:

                // Handler
                void messageHandler(QtMsgType type, const QMessageLogContext &context, const QString &msg)
                {
                    // Creating writing-stream
                    QTextStream out(m_logFile.data());
                    // Adding data/time
                    out << QDateTime::currentDateTime().toString("yyyy-MM-dd hh:mm:ss.zzz ");
                    // Detecting message type
                    switch (type){
                        case QtInfoMsg:     out << "INF "; break;
                        case QtDebugMsg:    out << "DBG "; break;
                        case QtWarningMsg:  out << "WRN "; break;
                        case QtCriticalMsg: out << "CRT "; break;
                        case QtFatalMsg:    out << "FTL "; break;
                    }
                    // Adding message type and message
                    out << context.category << ": " << msg << endl;
                    out.flush();
                }
                

                There are no external resources... Only message as handler parameter.

                Christian EhrlicherC 1 Reply Last reply
                0
                • sitesvS sitesv

                  @SGaist there is a handler code:

                  // Handler
                  void messageHandler(QtMsgType type, const QMessageLogContext &context, const QString &msg)
                  {
                      // Creating writing-stream
                      QTextStream out(m_logFile.data());
                      // Adding data/time
                      out << QDateTime::currentDateTime().toString("yyyy-MM-dd hh:mm:ss.zzz ");
                      // Detecting message type
                      switch (type){
                          case QtInfoMsg:     out << "INF "; break;
                          case QtDebugMsg:    out << "DBG "; break;
                          case QtWarningMsg:  out << "WRN "; break;
                          case QtCriticalMsg: out << "CRT "; break;
                          case QtFatalMsg:    out << "FTL "; break;
                      }
                      // Adding message type and message
                      out << context.category << ": " << msg << endl;
                      out.flush();
                  }
                  

                  There are no external resources... Only message as handler parameter.

                  Christian EhrlicherC Online
                  Christian EhrlicherC Online
                  Christian Ehrlicher
                  Lifetime Qt Champion
                  wrote on last edited by
                  #9

                  @sitesv Please read the answer from @SGaist :

                  That you have to use proper threading primitives to protect the resources you access in your handler.

                  So make sure your message handle can not be called from two threads simultaneously with e.g. a mutex.

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                  1 Reply Last reply
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                  • JonBJ Offline
                    JonBJ Offline
                    JonB
                    wrote on last edited by
                    #10

                    @Christian-Ehrlicher , @SGaist
                    I have a quick question here: does Qt have any restriction on which threads can execute a QFile::method(), compared to the thread where the QFile m_logFile was created? Like, I know you can only do QSql... operations in the thread which created the database connection, does that apply to QFile, or are you free to write to that from any thread??

                    1 Reply Last reply
                    0
                    • Christian EhrlicherC Online
                      Christian EhrlicherC Online
                      Christian Ehrlicher
                      Lifetime Qt Champion
                      wrote on last edited by
                      #11

                      No, as long as you add a proper mutex.

                      Qt Online Installer direct download: https://download.qt.io/official_releases/online_installers/
                      Visit the Qt Academy at https://academy.qt.io/catalog

                      1 Reply Last reply
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