C++ Gurus

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  Solved Qt on CentOS 7 not working
  • Dino

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  Dear jsulm,

  In the end, it was indeed a mess with 32-bit and 64-bit libraries.

  To fix my problems I have to uninstall all version of Qt on my machine and all OpenGL libraries. Then I have installed the latest version of Qt and the mesa-libGL-devel-11.2.2-2.20160614.el7.x86_64.rpm package.

  Again thank you for your help.

  Kind Regards,

  Dino

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  This topic is deleted!
  • feniks_fire

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  Solved Exception Handling - throw without type not allowed
  • Alan B

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  Many thanks for the replies. That clears it up.

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  Unsolved Logical constness
  • Eeli K

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  Throwing in one more thing to consider. Pointers:

  class ClassA{ public: void nonConstMethod() { qDebug("running nonConstMethod");} }; class ClassB1{ ClassA a; public: void nonConstMethod(){ a.nonConstMethod(); // ok } void constMethod() const{ a.nonConstMethod(); // fail not const in const method } };

  Nothing strange so far but check what happens if we move a from stack to heap:

  class ClassB2{ ClassA* a; ClassB2() :a(new ClassA()){} ~ClassB2() {delete a;} void nonConstMethod(){ a->nonConstMethod(); // ok } void constMethod() const{ a->nonConstMethod(); // ok } };

  What's going on?! it's simple if you think about it: inside ClassB2::constMethod, a behaves like a ClassA* const not like a const ClassA* so calling non-const methods is allowed

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  Unsolved why when i want copy (with memcpy)struct array to char array , character array is null??
  • stackprogramer

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  @stackprogramer Instead of hacking around with low level stuff you should take a look at http://doc.qt.io/qt-5/qdatastream.html

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  Solved Templates question
  • Kofr

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  the problem was with constantness

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  Solved New class
  • Arthux

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  Thank a lot !

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  Solved "&/*parent*/" as argument?
  • pdsc_dy

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  @pdsc_dy I moved your question to "C++ Gurus" forum as it is not related to Qt but to C++.
  References (this & thing) are one of the C++ concepts, so you should learn C++.

• 

  Unsolved vsprintf can not work on mac OS
  vsprintf mac os • • shangke

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  What does the debugger say ?
  It can crash in many ways.

  Maybe you could use a large static buffer:
  char dest[1000];
  and use vsnprintf, vswprintf instead.

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  Solved pimpl move semantic error management
  • VRonin

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  @VRonin
  obviously I missed that link and you already did your homework ;-)

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  Unsolved How to split a string in C++?
  • kyleflores

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  char str[] ="- This, a sample string.";
  char * pch;
  printf ("Splitting string "%s" into tokens:\n",str);
  pch = strtok (str," ,.-");
  while (pch != NULL)
  {
  printf ("%s\n",pch);
  pch = strtok (NULL, " ,.-");
  }

• 

  Solved its just a quiz... (for me at least)
  • Stanislav Silnicki

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  wow! its beautiful! )

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  Solved error in print value of const *char in data in Qt?
  memcpy const char qdebug array • • stackprogramer

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  @VRonin
  i before write my code to this method 369 book:

  void WeatherBalloon::sendDatagram() { QByteArray datagram; QDataStream out(&datagram, QIODevice::WriteOnly); out.setVersion(QDataStream::Qt_4_3); out << QDateTime::currentDateTime() << temperature() << humidity() << altitude(); udpSocket.writeDatagram(datagram, QHostAddress::LocalHost, 5824); }

  But we want to connect UDP processing data to GUI app, it can not read QDataStream Method and it Crashs. The app is written in C#,So we should try a method that work with VisualStudio.
  Agian Than kyou for attention
  best regards stackprogramer

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  Unsolved X11: Opening QWidget in a separate XScreen
  • ElSampsa

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  @ElSampsa said in X11: Opening QWidget in a separate XScreen:

  Trying to configure multiple xscreens for the nouveau graphics driver is such a pain these days..

  But you can use graphics driver instead of nouveau... :)

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  Solved qt app into rt-preempt
  • gfxx

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  @Konstantin-Tokarev yes you are in right ...

  regards
  giorgio

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  This topic is deleted!
  • kshegunov

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  Solved Libvlc function libvlc_new_callbacks
  • aurquiel

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  @_PIB You should ask C++ questions here: https://forum.qt.io/category/34/c-gurus
  It would be more natural to ask VLC related questions in a VLC forum/mailing list.

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  Solved Virtual inheritance polymorphic call resolution
  • kshegunov

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  Okay. Thanks!

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  Solved Calling methods for all non-null objects in a pointer list
  • Asperamanca

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  Wrapper for AnyOf:

  template <class IteratorT, class MethodT, class... Args> static bool anyOf(const IteratorT& iterFrom, const IteratorT& iterTo, MethodT method, Args... args) { for(auto iter=iterFrom;iter != iterTo;++iter) { if ((*iter) == nullptr) { continue; } if (method(*iter,args...)) { return true; } } return false; } template <class ContainerT, class MethodT, class... Args> static bool anyOf(const ContainerT& container, MethodT method, Args... args) { return anyOf(container.constBegin(), container.constEnd(), method, args...); }

  Further idea: Use type traits to make the methods work for containers with objects as well (e.g. QLIst<QRect>)

• 

  Unsolved reading csv file to form modbus request packet
  • musclemania05

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  Hi,

  Please don't post the same question on multiple sub-forum. One is enough.

  Duplicate

  Closing this one.

• 

  Solved how to use the elements that is not belong in your class
  • victor wang

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  @victor-wang Yes, you just add "const QString &cannum" to your constructor in DIDOThread as I shown.

• 

  Unsolved Send and receive in TCP/IP
  • isan

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  @SGaist Hi, I'm use orange pi board and QT not compile on it

• 

  Unsolved Cin doesn't work in console but works correctly with terminal in OSX. (QT 5.8)
  • itzalak2

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  Like @jsulm wrote, it won't appear if you run it from a normal terminal.

• 

  Solved Trying to implement a callback function of libvlc problem with the types variables to pass
  • aurquiel

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  @aurquiel Again - read the error message.
  Return types are different: int != long

• 

  Solved How can i pass data between Qwidgets forms?
  • Eduardo12l

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  @Eduardo12l
  since you have overloaded constructor, you don't need to give L a default value.
  if you want, you can use

  Dialog3( QWidget *parent = 0, const QList<int> &L = QList<int>() )

  QList<int>() will construct a QList<int> instance with empty value.

  for what @SGaist says, you can modify the constructor this way

  Dialog3( const QList<int> &L = QList<int>(), QWidget *parent = 0 )

  as I have said, you don't need to set a default value for L, so

  Dialog3( const QList<int> &L, QWidget *parent = 0 )

  is enough

• 

  Solved Pre-incrementation -> strange thing
  • feniks_fire

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  Thanks, for reply.
  I don't expect that this can be UB, even in my dreams :|.

  Anyway topic solved.

• 

  Unsolved Make ID card reader in C++/Qt5?
  • yumyumyum

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  Put your program in debug mode and go step by step inside Beidsdk_GetObjectValue to see what line triggers the ui, once you find out, step into that line and repeat the process until you pinpoint the final WINAPI (or any other core API) call

  P.S.

  goto finalize;

  😱

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  Unsolved Error in function argument libusb, works in codeblock but no in class at Qt
  • aurquiel

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  Hi,

  Because you are trying to pass a member variable as a callback. You can't, your callback should be a free function.

• 

  Unsolved How to pass a 2D array without memory issue ?
  • TremblayGIS

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  @TremblayGIS said in How to pass a 2D array without memory issue ?:

  i'm gone a try that

  Try what? my point was that you code does not need to be changed but that the error was coming from somewhere else, like nbPixel ,nLignes or nColonnes

• 

  Unsolved Make virtual camera in C++/Qt5?
  • yumyumyum

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  What is that ?

• 

  Unsolved Capture image using OPENCV in c++ (Qt creator 5.7)
  • Faisal_Ali

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  Hi,

  Reading and writing images and video right from the OpenCV documentation.

• 

  Unsolved Transition qt4.6 to qt5.7 with Erorr token
  • liondavid

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  I mean don't use #include <QtGui> or #include <QtWidgets>. Include what you are using: #include <QWidget>, #include <QImage> etc.

  By the way, QtGui has not been renamed QtWidgets, the widget related classes have been moved to the QtWidgets module hence your errors.

• 

  Solved ifstream not working in Qt 5.8 with clang on Mac
  • Amir_P

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  @Amir_P Oh I see why you had flushing issues, you didn't use endl in your streams.

  endl not only adds a newline \n but it also flushes. You should be able to add << endl and have it flush for you at some point.

  Edit: oops @Wieland said exactly this.. I should have read his whole post instead of skimming it.. ;)

• 

  Unsolved How to use const keywords with pointers?
  • kyleflores

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  Hi, I think you should come and take a look at https://www.youtube.com/watch?v=Y1KOuFYtTF4&index=4&list=WL, it's very useful for using const keyword in C++.

• 

  Unsolved New QCoreApplication crash in non Qt environment
  • Damien

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• 

  Unsolved How to know the average without disclosing the salaries?
  • kyleflores

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  See http://crypto.stackexchange.com/questions/40396/showing-the-decrypted-sum-of-encrypted-values

• 

  Solved Compiling Qt 5.7 applications without Xcode
  • FamilyHistorian

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  @FamilyHistorian said in Compiling Qt 5.7 applications without Xcode:

  @ambershark
  First, Linux Rocks!, Mac follows.
  Windoze ..
  .
  .
  .
  You are correct. the build process needs xcrun, apparently to compile a simple test program before configuring my application so I do need Xcode.
  Thanks for your help :)
  Paul

  Lol agreed on the linux part. Been running Linux since about 2000 with a brief break from 2006-2008 for OSX. And while I love OSX I got real sick of my computers costing more than cars every year, so I've been back on linux since. :)

  Good to know it does indeed require Xcode. I kind of figured that but it was worth a test. I use that permissions thing on my release builds all the time to make sure my distribution package is working and running independently of the Qt installed on my system. So I just permission out my Qt directory and run my app, if it tries to load something that isn't contained in my dist then it fails with permission probs. ;)

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  Error including Qt5 Network in CMakeLists.txt?
  • marmoc

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  @Konstantin-Tokarev has a point, if you are using QHostAddress in your library target, you forgot to link against Qt5::network

  I was meaning that if you configured your project once and after that you added the dependency to the network module, you would likely need to do a full reconfigure of your project.

• 

  How to check a number is perfect square or not using addition operation?
  • kyleflores

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  LMGTFY: http://stackoverflow.com/questions/12862637/perfect-square-or-not

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  Clang vs GCC
  • Kofr

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  I'm using Microsoft's compiler for Windows, GCC for Linux.

  And I find that GCC is definitely the slower one of the two. Why? Have no idea.