Error Undefined Reference To Vtable Q Object
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Error Undefined Reference To Vtable For Qt
Learn more about hiring developers or posting ads with us Stack Overflow Questions Jobs Documentation qobject undefined reference to vtable for Tags Users Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 4.7 million programmers, just like q_object undefined reference to vtable you, helping each other. Join them; it only takes a minute: Sign up Q_OBJECT throwing 'undefined reference to vtable' error [duplicate] up vote 40 down vote favorite 15 This question already has an answer here: Qt Linker
Undefined Reference To Vtable For Constructor
Error: “undefined reference to vtable” 8 answers I'm using Qt Creator 2.0.1 with Qt 4.7.0 (32 bit) on Windows 7 Ultimate 32 bit. Consider the following code, which is a minimum to produce the error: class T : public QObject, public QGraphicsItem { Q_OBJECT public: T() {} QRectF boundingRect() const {return QRectF();} void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget) {} }; int main() { T t; return 0; } The above code fragment causes
Undefined Reference To Vtable For Class
the following linker errors: In function `T': undefined reference to `vtable for T' undefined reference to `vtable for T' In function `~T': undefined reference to `vtable for T' undefined reference to `vtable for T' If I comment out the line that contains Q_OBJECT, it compiles fine. I need signal and slots with QGraphicsItem so I need Q_OBJECT. What is wrong with the code? Thanks. c++ qt linker-error vtable share|improve this question asked Jan 23 '11 at 14:24 Donotalo 7,147145993 marked as duplicate by djf, Rubens, Phil Hannent, tjameson, John Doyle Jul 13 '13 at 19:03 This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question. add a comment| 5 Answers 5 active oldest votes up vote 71 down vote accepted It is because the unit generated by MOC isn't included in the linking process. Or maybe it isn't generated at all. The first thing I'd do is to put the class declaration in a separate header file, perhaps the build system isn't scanning implementation files. Another possibility is that the class in question once didn't belong to Qt meta object system (that is, it had no Q_OBJECT or maybe didn't inherit from QObject at all), so qmake needs to be run again in order to create the necessary r
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Undefined Reference To Vtable For Mainwindow'
more about Stack Overflow the company Business Learn more about hiring developers or posting ads with us undefined reference to vtable for boost Stack Overflow Questions Jobs Documentation Tags Users Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 4.7 million programmers, just like you, http://stackoverflow.com/questions/4774291/q-object-throwing-undefined-reference-to-vtable-error helping each other. Join them; it only takes a minute: Sign up Undefined reference to vtable… Q_OBJECT macro [duplicate] up vote -1 down vote favorite This question already has an answer here: Qt Linker Error: “undefined reference to vtable” 8 answers When I uncomment the Q_OBJECT macro that I need for signal-slot I get a undefined reference http://stackoverflow.com/questions/7904684/undefined-reference-to-vtable-q-object-macro to vtable for MyApp error, but without the macro it compiles perfectly but I can't use signals and slots without it. I think I may be doing something stupid wrong, but please try helping because I realy can't find the problem. O and I know my code is untidy and am working on it. myapp.h: #ifndef MYAPP_H #define MYAPP_H #include
I could not shake off the following error recently, when writing a class Browser http://www.theirishpenguin.com/2007/07/01/qobject-qmake-and-sadness-undefined-reference-to-vtable.html which inherited from QObject. Apparently, the answer is that sometimes you http://josipovic.be/wordpress/blog/2010/08/11/%E2%80%9Cundefined-reference-to-vtable%E2%80%9D-for-qobject-derived-classes-in-the-implementation-cpp-file/ simply have to delete your Makefiles and regenerate them using QMake (KDevelop automatically creates Makefiles from me if none are found), in order to get over this error. /path/to/frogface/trunk/src/browser.cpp:38: undefined reference to `vtable for Browser' browser.o: In function `Browser': /path/to/frogface/trunk/src/browser.cpp:34: undefined undefined reference reference to `vtable for Browser' /path/to/frogface/trunk/src/browser.cpp:34: undefined reference to `vtable for Browser' collect2: ld returned 1 exit status gmake[1]: *** [../bin/frogface] Error 1 gmake: *** [sub-src-make_default] Error 2 *** Exited with status: 2 *** Thanks to the patient folks on the QT mailing for the help! Funnily enough as I write this, someone’s undefined reference to just posted the following checklist on the #qt irc channel, which is good advice Make sure the Q_OBJECT macro is present in the definition of all QObject-derived classes Make sure you define your QObject-derived classes in your header files ONLY Make sure all of your header files are listed in your .profile in the HEADERS=list Run qmake every time you add Q_OBJECT to one of your classes or modify your .pro file The last one is particularly important as I’ve made an art form out of forgetting it :)
Comments Please enable JavaScript to view the comments powered by Disqus. comments powered by Disqus INFO subscribe via RSS SOCIAL theirishpenguin theirishpenguin ABOUT Ruby/JS dev. One eye on design. Occasionally stops writing code and starts writing words when the Internet is down. Thoughts and opinions expressed here are my own. If you're interested in Ruby in Ireland, be sure to check out RubyIreland.com.to vtable” seems to be a common problem with Qt's meta-object system in combination with GCC. The main cause due to GCC is described here: http://gcc.gnu.org/faq.html#vtables But with QObject it gets a bit more complex. When you use the macro Q_OBJECT, you define some virtual methods which might trigger the above GCC error under certain circumstances. So make sure your use of the Q_OBJECT macro fulfills the following requirements: Make sure the Q_OBJECT macro is present in the definition of all QObject-derived classes Make sure you define your QObject-derived classes in your header files ONLY Make sure all of your header files are listed in your .pro file in the HEADERS-list Run qmake every time you add Q_OBJECT to one of your classes or modify your .pro file (Source: http://www.theirishpenguin.com/2007/07/01/qobject-qmake-and-sadness-undefined-reference-to-vtable/) Not fulfilling point 2: You get the “undefined reference to vtable” error if you put your QObject-derived class in the implementation file because moc will not “add” the implementation of the virtual functions to the cpp file. Apparently you can enforce this by adding “#include cpp_file_name.moc” to your “cpp_file_name.cpp” file. Moc will detect this and will generate a “cpp_file_name.moc” file. Comments (0) No Comments » No comments yet. RSS feed for comments on this post. TrackBack URL Leave a comment Name (required) Mail (will not be published) (required) Website Pages:About Referral OneDrive Referral OneDrive Referral (Zorica) Categories: Gaming Philosophy Corruption Programming batch C++ Oracle php Postgres PowerShell Qt Uncategorized Search: Archives: August 2014 August 2013 July 2013 June 2013 April 2013 July 2012 July 2011 November 2010 August 2010 June 2010 May 2010 March 2010 Meta: Log in RSS Comments RSS Valid XHTML XFN WP Powered by Wo