Comments on: QObject, QMake and Sadness – ‘Undefined reference to vtable’

By: moorecm

moorecm — Mon, 07 Mar 2011 22:13:49 +0000

Finally someone who knows what their talking about. Those steps are awesome. Thank you!

By: “Undefined reference to vtable” for QObject-derived classes in the implementation (.cpp) file. « Davor Josipovic

Tue, 25 Jan 2011 03:57:33 +0000

[...] (Source: http://www.theirishpenguin.com/2007/07/01/qobject-qmake-and-sadness-undefined-reference-to-vtable/) [...]

By: g

Sat, 25 Dec 2010 21:08:13 +0000

Thanks!!! Save me a lot of time.. Happens from time to time with QT creator

By: Ppdlive

Ppdlive — Sun, 12 Dec 2010 20:26:08 +0000

I speak about HEADERS and SOURCES variables which includes src files, if someone not get it.

By: Ppdlive

Ppdlive — Sun, 12 Dec 2010 20:20:56 +0000

For read QT surfer, i get supplementary information. Order in pro file is play important role. For get it, i loose 3 fucken hours, looking on ‘undefined reference to `vtable blablalba… ‘ . I hope that will be helpful for someone, who will have the same situation.

peace!

By: Pieter

Pieter — Thu, 18 Nov 2010 12:48:10 +0000

Thanks, good advice!

By: Rick

Rick — Sun, 07 Nov 2010 07:09:16 +0000

An important note for those who still have banging their heads on the wall with this error:

—
Do NOT, I repeat, DO *NOT* ADD THE Q_OBJECT MACRO to classes that don’t (yet) use signals and slots, even if they derive from QObject! (This can happen if your project is in the early stages of development, where you don’t define the signals and slots for a class, but you plan to add them later).
—

Some files produced the “no relevant classes found, no code generated”, and when the vtable was not found (because no signals-and-slots code was generated), I got the link error.

After removing the Q_OBJECT macro from said classes, everything ran fine – even if they were QObject descendants. But the tricky thing was when I had included the definition for MORE THAN ONE class in a header file, and running moc DID produce some code, but not for ALL classes! (Also I didn’t use the standard qmake because I was developing the project in Code::Blocks IDE, and had to run moc for every file separately, so it was a quite particular case).

After removing the Q_OBJECT macro from the offending “incomplete” classes (without signals/slots), compilation proceeded correctly.

If you add this warning to your 4-checklist, all the frustrated qt programmers will thank you

By: Naji

Naji — Tue, 19 Oct 2010 18:46:03 +0000

Really… Three years after your posting and it is still helping…. Thanks for your posting!

By: RCL

RCL — Fri, 14 May 2010 01:45:01 +0000

Thanks! Every time I run into this issue (it happened a few times) your “checklist” comes to help…

By: donglongchao

donglongchao — Mon, 02 Nov 2009 09:38:21 +0000

Edit the .pro file: Just add a space into it and then delete the space.That is OK.
Oh…………That is really crazy.Nokia should fix this fuc* bug ASAP.