Heap corruption in QwtPolarGrid::updateScaleDiv

[kreyszig]

This post is aimed at Uwe, I hope this may sound familiar or flag up something I have set up incorrectly:

I have an issue (Invalid address specified to RtlFreeHeap) that only seems to show up in release builds (on windows). I am seeing very repeatable heap corruption whenever I enable more than a single axis in my subclass of QwtPolarPlot.

edit: in fact this is an issue whenever I use even a single axis which is not AxisAzimuth

e.g. here is my constructor for my subclass. As you can see below it is a slightly modified version of one of the polardemo example, removing some of the setup. I have my own member interval classes instead of having them declared outside the class as in the example, but otherwise it is pretty similar.

The last readable code I have in my stack trace is axis.scaleDraw->setScaleDiv( sd ); in qwt_polar_grid.cpp.

Does this ring a bell at all regarding double frees or mismatch between delete and free, for example? Obviously I am not adding curves until after I initialise the plot, unlike the example this was taken from, but if I turn on the axes after adding the curve I still have the same problem.

Any thoughts would be very well received - this gets through Dr Memory (-light) OK on debug and release. I am using qwtpolar 1.1.1, qt 4.7.1 and Qwt 6.1.0. Qt and Qwt are both shared libraries; I have tried qwtpolar as both shared and static library and get the same error.

class PolarPlot: public QwtPolarPlot
{
    Q_OBJECT
 
public:
    PolarPlot( QString name, QWidget * = NULL );
    void add_curve(QString name, PolarCurve * curve);
    //void update_curve(QString name, double * r, double *t);
    virtual void replot();
private:
 
    QwtPolarGrid *d_grid;    
    QwtInterval _radialInterval;
    QwtInterval _azimuthInterval;
 
};
 
PolarPlot::PolarPlot( QString name, QWidget *parent ):
    QwtPolarPlot( QwtText( name ), parent )
{    
    setAutoReplot( false );
 
    setPlotBackground( QColor("#ffffb3"));
 
    _radialInterval.setMinValue(0);
    _radialInterval.setMaxValue(360.0);
    _azimuthInterval.setMinValue(0);
    _azimuthInterval.setMaxValue(360.0);
 
    setScale( QwtPolar::ScaleRadius,
        _azimuthInterval.minValue(), _azimuthInterval.maxValue(),
        _azimuthInterval.width());
 
    setScaleMaxMinor( QwtPolar::Azimuth, 2 );
    setScale( QwtPolar::ScaleRadius,
        _radialInterval.minValue(), _radialInterval.maxValue() );
 
    // grids, axes
 
    d_grid = new QwtPolarGrid();
    d_grid->setPen( QPen(Qt::darkGray) );
    for ( int scaleId = 0; scaleId < QwtPolar::ScaleCount; scaleId++ )
    {
        d_grid->showGrid( scaleId );
        d_grid->showMinorGrid( scaleId );
 
        QPen minorPen( Qt::gray );
        d_grid->setMinorGridPen( scaleId, minorPen );
    }
    d_grid->setAxisPen( QwtPolar::AxisAzimuth, QPen( Qt::black ) );
    d_grid->setAxisPen( QwtPolar::AxisTop, QPen( Qt::red ) );
    d_grid->setAxisPen( QwtPolar::AxisRight, QPen( Qt::black ) );
    d_grid->setAxisPen( QwtPolar::AxisLeft, QPen( Qt::black ) );
    d_grid->setAxisPen( QwtPolar::AxisBottom, QPen( Qt::black ) );
 
 
    d_grid->showAxis( QwtPolar::AxisAzimuth, true);
    d_grid->showAxis( QwtPolar::AxisTop, true);                   // <-unless this and all non azimuth axes are false, I get heap corruption
    d_grid->showAxis( QwtPolar::AxisRight, false);
    d_grid->showAxis( QwtPolar::AxisLeft, false );        
    d_grid->showAxis( QwtPolar::AxisBottom, false );
 
    d_grid->showGrid( QwtPolar::Azimuth, true);
    d_grid->showGrid( QwtPolar::Radius, true );
    d_grid->attach( this );
 
    // curves
 
    /*for ( int curveId = 0; curveId < PlotSettings::NumCurves; curveId++ )
    {
        d_curve[curveId] = createCurve( curveId );
        d_curve[curveId]->attach( this );
    }*/
 
    // markers
    /*QwtPolarMarker *marker = new QwtPolarMarker();
    marker->setPosition( QwtPointPolar( 57.3, 4.72 ) );
    marker->setSymbol( new QwtSymbol( QwtSymbol::Ellipse,
        QBrush( Qt::white ), QPen( Qt::green ), QSize( 9, 9 ) ) );
    marker->setLabelAlignment( Qt::AlignHCenter | Qt::AlignTop );
 
    QwtText text( "Marker" );
    text.setColor( Qt::black );
    QColor bg( Qt::white );
    bg.setAlpha( 200 );
    text.setBackgroundBrush( QBrush( bg ) );
 
    marker->setLabel( text );
    marker->attach( this );
 
    QwtLegend *legend = new QwtLegend;
    insertLegend( legend,  QwtPolarPlot::BottomLegend );*/
}

class PolarPlot: public QwtPolarPlot
{
    Q_OBJECT

public:
    PolarPlot( QString name, QWidget * = NULL );
    void add_curve(QString name, PolarCurve * curve);
    //void update_curve(QString name, double * r, double *t);
    virtual void replot();
private:
    
    QwtPolarGrid *d_grid;    
    QwtInterval _radialInterval;
    QwtInterval _azimuthInterval;

};

PolarPlot::PolarPlot( QString name, QWidget *parent ):
    QwtPolarPlot( QwtText( name ), parent )
{    
    setAutoReplot( false );

    setPlotBackground( QColor("#ffffb3"));

    _radialInterval.setMinValue(0);
    _radialInterval.setMaxValue(360.0);
    _azimuthInterval.setMinValue(0);
    _azimuthInterval.setMaxValue(360.0);

    setScale( QwtPolar::ScaleRadius,
        _azimuthInterval.minValue(), _azimuthInterval.maxValue(),
        _azimuthInterval.width());

    setScaleMaxMinor( QwtPolar::Azimuth, 2 );
    setScale( QwtPolar::ScaleRadius,
        _radialInterval.minValue(), _radialInterval.maxValue() );

    // grids, axes

    d_grid = new QwtPolarGrid();
    d_grid->setPen( QPen(Qt::darkGray) );
    for ( int scaleId = 0; scaleId < QwtPolar::ScaleCount; scaleId++ )
    {
        d_grid->showGrid( scaleId );
        d_grid->showMinorGrid( scaleId );

        QPen minorPen( Qt::gray );
        d_grid->setMinorGridPen( scaleId, minorPen );
    }
    d_grid->setAxisPen( QwtPolar::AxisAzimuth, QPen( Qt::black ) );
    d_grid->setAxisPen( QwtPolar::AxisTop, QPen( Qt::red ) );
    d_grid->setAxisPen( QwtPolar::AxisRight, QPen( Qt::black ) );
    d_grid->setAxisPen( QwtPolar::AxisLeft, QPen( Qt::black ) );
    d_grid->setAxisPen( QwtPolar::AxisBottom, QPen( Qt::black ) );
    

    d_grid->showAxis( QwtPolar::AxisAzimuth, true);
    d_grid->showAxis( QwtPolar::AxisTop, true);                   // <-unless this and all non azimuth axes are false, I get heap corruption
    d_grid->showAxis( QwtPolar::AxisRight, false);
    d_grid->showAxis( QwtPolar::AxisLeft, false );        
    d_grid->showAxis( QwtPolar::AxisBottom, false );

    d_grid->showGrid( QwtPolar::Azimuth, true);
    d_grid->showGrid( QwtPolar::Radius, true );
    d_grid->attach( this );

    // curves

    /*for ( int curveId = 0; curveId < PlotSettings::NumCurves; curveId++ )
    {
        d_curve[curveId] = createCurve( curveId );
        d_curve[curveId]->attach( this );
    }*/

    // markers
    /*QwtPolarMarker *marker = new QwtPolarMarker();
    marker->setPosition( QwtPointPolar( 57.3, 4.72 ) );
    marker->setSymbol( new QwtSymbol( QwtSymbol::Ellipse,
        QBrush( Qt::white ), QPen( Qt::green ), QSize( 9, 9 ) ) );
    marker->setLabelAlignment( Qt::AlignHCenter | Qt::AlignTop );

    QwtText text( "Marker" );
    text.setColor( Qt::black );
    QColor bg( Qt::white );
    bg.setAlpha( 200 );
    text.setBackgroundBrush( QBrush( bg ) );

    marker->setLabel( text );
    marker->attach( this );

    QwtLegend *legend = new QwtLegend;
    insertLegend( legend,  QwtPolarPlot::BottomLegend );*/
}

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Added after 42 minutes:

In addition, I also see the same problem if I build the polardemo example myself in visual studio. I am doing this by hand, i.e. adding the source and headers to a new project and setting up as per my other qt projects. I have checked with a dependency walker that the dlls I am using are consistent with what I expect, i.e. the dlls built on this machine from source.

[kreyszig]

Nevermind. I had rebuilt qwt while trying to sort this out and hadn't moved the new qwt.dll into my path. With this in place it is fine.