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QMQTT undefined reference to ...

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

    Hi,

    Might be a silly question but are you linking your application against that module ?

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

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    • A Offline
      A Offline
      Alex-Krieg
      wrote on last edited by
      #3

      How do you mean that?
      This is the first time I want to use an external library.
      It may well be that I did not do that. How should I do that?

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      • SGaistS Offline
        SGaistS Offline
        SGaist
        Lifetime Qt Champion
        wrote on last edited by
        #4

        Link against the library generate by that project: LIBS += -lqmqtt .

        Just in case, if you'd like to remain with Qt's own framework, it now provides the QtMqtt module that you can use as any other Qt modules.

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

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        • A Offline
          A Offline
          Alex-Krieg
          wrote on last edited by
          #5

          that with LIBS + = does not work.
          I understand the context not synonymous if you just -qmqtt angiel, how knows QT what needs to be done with it? Is this a path or a file or is it something?

          Do you mean with QtMqtt what is described here? http://blog.qt.io/blog/2017/08/14/introducing-qtmqtt-protocol/
          If so, I would be very happy, because I thought that it is not yet public.

          By the way, are you Swiss? =)
          I'm swiss.

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          • SGaistS Offline
            SGaistS Offline
            SGaist
            Lifetime Qt Champion
            wrote on last edited by
            #6

            Qt doesn't, the LIBS variable is where you give options to give to the linker.

            Did you build and install that project ? If so where did you install it ? You might need to give an additional path for the linker to find the library.

            I already gave you the link to the official repository in my previous answer.

            Yes I am.

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

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            • A Offline
              A Offline
              Alex-Krieg
              wrote on last edited by Alex-Krieg
              #7

              Yes I have build the library.
              Location is where I have my QT projects.
              From there with the CMD I have processed the following commands:
              qmake
              make
              make install
              Where are the libraries of QT installed?
              I downloaded the library from your link and ran the same commands but there were errors.

              0_1511049553967_40e6b86f-eb31-4bd9-9c46-ddb6bad05b9b-grafik.png

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              • A Offline
                A Offline
                Alex-Krieg
                wrote on last edited by
                #8

                @SGaist
                How do I have to proceed to install the library from your link?
                I have already downloaded the zip.
                Where do I have to unzip it and how do I build it?
                I work under Windows 8.1 and compile with MinGW.

                aha_1980A 1 Reply Last reply
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                • A Alex-Krieg

                  @SGaist
                  How do I have to proceed to install the library from your link?
                  I have already downloaded the zip.
                  Where do I have to unzip it and how do I build it?
                  I work under Windows 8.1 and compile with MinGW.

                  aha_1980A Offline
                  aha_1980A Offline
                  aha_1980
                  Lifetime Qt Champion
                  wrote on last edited by
                  #9

                  @Alex-Krieg said in QMQTT undefined reference to ...:

                  @SGaist
                  How do I have to proceed to install the library from your link?

                  If you mean QtMqtt, it does not matter where you install it. make install will copy headers, .lib and .dll to the correct position in your Qt tree.

                  Afterwards you can add QT += mqtt (I guess) in your pro file and all should be fine automatically.

                  For the other library however (if you want to use it), you need to specify the link path too:

                  LIBS += -L/path/to/lib -llibname-without-extension

                  Qt has to stay free or it will die.

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                  • A Offline
                    A Offline
                    Alex-Krieg
                    wrote on last edited by
                    #10

                    @aha_1980
                    Thank you for this info but in my last Picture you can se, that I had an error during the "make" I realy downt know why. In my .pro is the "QT += qmqtt" but it says "Project ERROR: Unknown module(s) in QT: mqtt"

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                    • SGaistS Offline
                      SGaistS Offline
                      SGaist
                      Lifetime Qt Champion
                      wrote on last edited by
                      #11

                      Do I read the error correctly: -std-c++1z ? That should be -std=c++1z

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

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                      • A Offline
                        A Offline
                        Alex-Krieg
                        wrote on last edited by
                        #12

                        @SGaist its "-std=c++1z"
                        What can you say about this?
                        I really do not understand that anymore

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                        • SGaistS Offline
                          SGaistS Offline
                          SGaist
                          Lifetime Qt Champion
                          wrote on last edited by
                          #13

                          That enables C++17 support, did you trigger it somewhere ?

                          Otherwise, why not build it trough Qt Creator ? That will ensure that the build environment matches the Qt version you want to use directly.

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

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                          • A Offline
                            A Offline
                            Alex-Krieg
                            wrote on last edited by
                            #14

                            Ok mit Qt-Creater hat es funktioniert.
                            Die Dlls und so wurden erzeugt.
                            Jetzt habe ich im Projekt auf diese Verzeichnisse verwiesen aber da kommt immer der Error: "Project ERROR: Unknown module(s) in QT: mqtt"
                            Habe ich was falsch gemacht?

                            0_1511131268078_02f50105-e8cb-4c02-9047-a767676374df-grafik.png

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                            • aha_1980A Offline
                              aha_1980A Offline
                              aha_1980
                              Lifetime Qt Champion
                              wrote on last edited by
                              #15

                              @Alex-Krieg: Did you run make install after buildin QtMqtt? You can add it as build step after make in the Projects settings un Creator.

                              Qt has to stay free or it will die.

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                              • A Offline
                                A Offline
                                Alex-Krieg
                                wrote on last edited by
                                #16

                                @aha_1980 rly? you are the best.
                                after the make install it worked. Thank you very much. I'm very happy about that now.
                                Thanks a lot. =)

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