QwtPlot derived class

[Marco Trapanese]

Hello,

I want to create a class based upon QwtPlot. I declare it as usual:

#include <Qwt/qwt_plot.h>
 
class myplot : public QwtPlot{
    Q_OBJECT
 
public:
    explicit myplot(QWidget *parent = 0);
 
signals:
 
public slots:
 
};

#include <Qwt/qwt_plot.h>

class myplot : public QwtPlot{
    Q_OBJECT

public:
    explicit myplot(QWidget *parent = 0);
    
signals:
    
public slots:
    
};

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But I get the error:

"During startup program exited with code 0xc0000005".

I know it's an access violation error. But I don't know why it happens only if I create a class derived from QwtPlot. In my application there are several Qwt items and all works fine.

What I should do to find (and fix) the issue?
Thanks in advance
Marco

ps. I get the same behavior if I include the incrementalplot for example

[FelixB]

you could debug and search the code that is responsible for thisaccess violation.

[desantossierra]

could you copy your *.cpp?
no errors for me in the declaration

[Uwe]

This is usually a problem of your build/runtime environment and has nothing to do with the code.

Uwe

[Marco Trapanese]

you could debug and search the code that is responsible for thisaccess violation.

I wrote: "During startup [...]". That means no code is executed (better, no code visible through debug).

could you copy your *.cpp?
no errors for me in the declaration

No code in the cpp file, but the empty implementation of the constructor:

myplot::myplot(QWidget *parent): QwtPlot(parent) { }

myplot::myplot(QWidget *parent): QwtPlot(parent) { }

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I've just found I need to remove the Q_OBJECT macro. Without it runs.

Does anyone know why?

This is usually a problem of your build/runtime environment and has nothing to do with the code.

Maybe. But why removing the Q_OBJECT macro it works? It seems code related.

[Uwe]

Usually because your build environment doesn't handle moc and the generated cpp files properly.

Uwe

[Marco Trapanese]

Usually because your build environment doesn't handle moc and the generated cpp files properly.

Anyway, this happens only with Qwt. I have several classes that uses Q_OBJECT without problem.
How to handle moc and cpp files properly?

[Uwe]

So that moc is called, whenever the header changes, and the generated cpp file gets compiled and linked.

Uwe

[Marco Trapanese]

Isn't this the default behavior? In fact, all classes I write but the Qwt-derived ones work.

[Uwe]

Isn't this the default behavior?

It depends on your IDE - f.e. MSVC has never heard of something like moc.

Uwe

[Marco Trapanese]

QtCreator 2.4.0