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qDebug Initial setup Messed up?

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  • P Offline
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    PascalJedi
    wrote on 22 Feb 2016, 19:44 last edited by
    #1

    Just starting with QT, but something seems very off on my setup and wondering if others had a similar issue (Nothing showing up in google).

    Created a new test project; added "core" to the .pro file, wrote some code, but can't get past the first qDebug print. I moved the print all the way to the start of the application, but alas I always get a qDebug() SIGSEGV

    Thoughts on how I screwed this up?

    #include "mainwindow.h"
    #include <QApplication>
    #include <QDebug>

    int main(int argc, char *argv[])
    {
    qDebug() << "Hi"; // << This creates a SIGSEGV

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    • M Offline
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      mrjj
      Lifetime Qt Champion
      wrote on 22 Feb 2016, 20:18 last edited by mrjj
      #2

      Hi and welcome
      Can u mention Qt version and platform ?

      P 1 Reply Last reply 22 Feb 2016, 20:56
      0
      • S Offline
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        SGaist
        Lifetime Qt Champion
        wrote on 22 Feb 2016, 20:27 last edited by
        #3

        Hi and welcome to devnet,

        In order to initialize Qt's subsystems you should first create a Q*Application. Depending on your application it will be a QtCoreApplication, QGuiApplication or a QApplication.

        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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        • S Offline
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          SGaist
          Lifetime Qt Champion
          wrote on 22 Feb 2016, 20:40 last edited by
          #4

          I missed one point: qDebug should work without any Q*Application created.

          Do you have any static QWidget object ?

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

          P 1 Reply Last reply 22 Feb 2016, 21:02
          0
          • M mrjj
            22 Feb 2016, 20:18

            Hi and welcome
            Can u mention Qt version and platform ?

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            PascalJedi
            wrote on 22 Feb 2016, 20:56 last edited by
            #5

            @mrjj

            I am running stock Ubuntu 15.10


            Qt Creator 3.6.0
            Based on Qt 5.5.1 (GCC 4.9.1 20140922 (Red Hat 4.9.1-10), 64 bit)

            Built on Dec 15 2015 01:01:12

            From revision b52c2f91f5

            Enterprise Features: Enabled
            Licensee: ****

            Copyright 2008-2015 The Qt Company Ltd. All rights reserved.

            The program is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.

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            • S SGaist
              22 Feb 2016, 20:40

              I missed one point: qDebug should work without any Q*Application created.

              Do you have any static QWidget object ?

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              PascalJedi
              wrote on 22 Feb 2016, 21:02 last edited by
              #6

              @SGaist

              Hi, and thank you both for taking the time to reply.

              I basically went File->New->QT Widgets Application

              I then went and did the button tutorial with a button and a label. Pressed button, worked fine. Then went and added a debug print inside that caller and it seg faulted. Scratched my head, google searched, moved the qDebug to the first line in main.

              I fully admit, this may be something super simple, but just don't know what setting I am missing.

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              • S Offline
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                SGaist
                Lifetime Qt Champion
                wrote on 22 Feb 2016, 21:20 last edited by
                #7

                Since you're not doing anything special, I don't see any reason for such a segmentation fault to occur.

                Can you run your application through the debugger ? That could provide some more information about what is happening.

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

                P 1 Reply Last reply 22 Feb 2016, 21:27
                0
                • S SGaist
                  22 Feb 2016, 21:20

                  Since you're not doing anything special, I don't see any reason for such a segmentation fault to occur.

                  Can you run your application through the debugger ? That could provide some more information about what is happening.

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                  PascalJedi
                  wrote on 22 Feb 2016, 21:27 last edited by
                  #8

                  @SGaist

                  Nothing special. I just did a command line application and qDebug works; I then went back and created a test another test widget application and it works there too.

                  I just deleted that first project and am starting to test out and play with the environment.

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                  • S Offline
                    S Offline
                    SGaist
                    Lifetime Qt Champion
                    wrote on 22 Feb 2016, 21:31 last edited by
                    #9

                    Looks like you had a gremlin in that project ;)

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

                    P 1 Reply Last reply 22 Feb 2016, 21:34
                    1
                    • S SGaist
                      22 Feb 2016, 21:31

                      Looks like you had a gremlin in that project ;)

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                      PascalJedi
                      wrote on 22 Feb 2016, 21:34 last edited by
                      #10

                      @SGaist If there is one thing that is for sure; I can destroy any project while doing a "hello world" tutorial! Thanks for the eSupport.

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                      3/10

                      22 Feb 2016, 20:27

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