CODEWITHSUNDEEP
c++qtqwt
mike
mike

Reputation: 1322

Unresolved external symbol: QMetaObject const QwtPlotMagnifier::staticMetaObject

I have a library that uses QwtPlotMagnifier, amongst other Qwt classes. I decided to subclass QwtPlotMagnifier so that I can emit a signal when the plot is rescaled. The library (mylib.lib) compiles, but the application using it is now complaining about an unresolved external related to the moc output of QwtPlotMagnifier.

I am linking qwt statically; so the requirement to have the preprocessor directive QWT_DLL in the lowest level library doesn't apply here.

Here's the error (the subclass is called PlotMagnifier):

mylib.lib(moc_PlotMagnifier.obj) : error LNK2001: unresolved external symbol "public: static struct QMetaObject const QwtPlotMagnifier::staticMetaObject" (?staticMetaObject@QwtPlotMagnifier@@2UQMetaObject@@B)

Nothing special about the subclass declaration:

#pragma once

#include "qwt_plot_magnifier.h"
/**
subclass of QwtPlotMagnifier to provide a signal when zooming is complete
*/
class PlotMagnifier : public QwtPlotMagnifier
{
    Q_OBJECT
public:
  explicit PlotMagnifier(QWidget *w);
  virtual ~PlotMagnifier();
signals:
  void rescaled();
protected:
  virtual void rescale(double factor);  
};

I'm on visual studio 2013 fwiw. My application still includes qwtd.lib as it always has. This has got to be a stupid mistake on my part.. kickstart my brain please, someone!

Upvotes: 3

Views: 2312

Answers (2)

mohabouje
mohabouje

Reputation: 4050

Add this line to .pro file to give the compiler a hint for an external symbol:

DEFINES += QWT_DLL

In the file qwt_global.h have the macro. Without this macro, the compiler will think this is an internal symbol.

Upvotes: 2

Dmitriy
Dmitriy

Reputation: 548

Check, if you have all needed includes in you Visual Studio project.

C/C++ / Additional Include Directories
Here should be a path to <qwt_dir\include> be

Linker / General / Additional Library Directories
Here should be a path to <qwt_dir\lib> be

Linker / Input
Should include qwtd.lib (for debug configuration) and qwt.lib (for release)

Also, check that you have those entries in Release and Debug configurations, it is easy to configure only Debug, while working on Release configuration.

Also, check that you have moc_* file (something like moc_plotmagnifier.cpp) for your PlotMagnifier under Generated Files in your project view, sometimes Qt addin fails to add them.

Upvotes: 0

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