C++ - Undefined reference to `vtable

Question

I was wondering why I was getting this error: undefined reference to `vtable for BaseRenderer'

I tried searching around but cannot seem to figure this out. I've tried getting rid of the virtual function, removing the constructor, etc.

My BaseRenderer.h

class BaseRenderer : public Renderer
{
 Q_OBJECT

    public:
        BaseRenderer();
        BaseRenderer(QWidget *parent);
        void paintGL();

        virtual ~BaseRenderer();

 public slots:
  void loadDialog();

 signals:

    protected:
        Mesh loadMesh(string fileName);

    private:

        OBJParser objParser;
        Mesh baseTerrain;

};

My BaseRenderer.cpp

BaseRenderer::BaseRenderer()              <------ Error leads me here
{
}

BaseRenderer::BaseRenderer(QWidget *parent) : Renderer(parent)
{

}

BaseRenderer::~BaseRenderer()
{
    //dtor
}

How would I go about getting rid of this issue? I also hear it may be the compiler...? Thanks for the help :)

@John - it's a Qt macro, which means this source file has to be run through a separate Qt tool (`moc.exe`) for a bunch of code to be generated for Qt-specific behaviors like slots and signals. — wkl, Dec 01 '10 at 06:01
@birryree: Ah. I have no familiarity with Qt whatsoever, so I'll bow out of this one — John Dibling, Dec 01 '10 at 06:02
Or, if you use qmake, it generates the moc commands in your makefile for you. — paxdiablo, Dec 01 '10 at 06:02
Check that your header is listed in the HEADERS section in the .pro file. — Frank Osterfeld, Dec 01 '10 at 06:33

score 9 · Accepted Answer · answered Dec 01 '10 at 06:44

9

Since Q_OBJECT is in the parent class, Renderer, you don't have to also include it BaseRenderer. Just get rid of Q_OBJECT and it should work :)

answered Dec 01 '10 at 06:44

Pellanor

205
1
3

It works for me. can you elaborate more why removing Q_OBJECT solve this? I subclass thing from QWidget – swdev Sep 06 '13 at 09:21
If you add slots in a subclass, this doesn't work. See e.g. https://github.com/telegramdesktop/tdesktop/issues/5723#issuecomment-466628042 – Eugene Gr. Philippov Feb 23 '19 at 08:27
Also, some docs (search the web on this) suggest that `Q_OBJECT` should always be present in `QObject` direct or indirect subclasses. – Eugene Gr. Philippov Feb 23 '19 at 10:41

score 2 · Answer 2 · answered Dec 01 '10 at 06:33

2

See 'What does it mean that the "virtual table" is an unresolved external?' in the C++ FAQ Lite.

answered Dec 01 '10 at 06:33

Karl Knechtel

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score 1 · Answer 3 · answered Dec 01 '10 at 06:00

1

I think this highly unhelpful message is really complaining about you not providing definitions for the other functions in your BaseRenderer class, as your baseRenderer.cpp file seems to only have the constructor and destructors.

answered Dec 01 '10 at 06:00

wkl

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score 1 · Answer 4 · answered Dec 01 '10 at 06:35

1

Make sure you implement all declared methods, especially the slot. Then check that your header is listed in the HEADERS section in the .pro file and then run qmake.

answered Dec 01 '10 at 06:35

Frank Osterfeld

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score 1 · Answer 5 · edited May 23 '17 at 10:29

1

I would guess it's the same issue I had when asking this question: Why won't this compile (link) with the Q_OBJECT macro in place?

Try rerunning qmake like paxdiablo and Tobias suggest.

edited May 23 '17 at 10:29

Community

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answered Dec 01 '10 at 06:55

teukkam

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C++ - Undefined reference to `vtable

5 Answers5

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