I work on a project that is using C++ code in a PIC32 microcontroller. C++ classes are used to structure the pages and widgets used on display.

All pages extends the base class Page. All pages contains widgets. All widgets extends the base class Widget. Both of the base classes have some virtual functions.

Here is an heavily simplified example of the code just to show the global structure :

class PageHome : public Page
{
    public:
        //...

        virtual void paint(void);
        virtual void repaint(void);
    
    private:
        //...
}

class PageHome : public Page
{
    public:
        //...
    
        void paint(void);
        void repaint(void);

    private:
        WidgetLabel *m_lblTest1;
        WidgetLabel *m_lblTest2;

}

class PageConfiguration : public Page
{
    public:
        //...
    
        void paint(void);
        void repaint(void);

    private:
        WidgetLabel *m_lblTest1;
        WidgetLabel *m_lblTest2;

}

void main()
{
    Page *pPageHome = new PageHome();
    Page *pPageConfiguration = new PageConfiguration();
    
    //...
}

Now, what I observe is a big difference in program size after compilation when using widgets or not in pages.

Second page not using WidgetLabel :

Program Used: 245,332 (0x3BE54) Free: 16,812 (0x41AC)

Second page not using only one WidgetLabel :

Program Used: 250,532 (0x3D2A4) Free: 11,612 (0x2D5C)

Second page not using two WidgetLabel :

Program Used: 250,628 (0x3D304) Free: 11,516 (0x2CFC)

Each time I use a widget for the first time in one page (already used in other pages), the first instance consume a lot of memory, arround 5KB of program memory. Other instances consume less. Maybe I’m wrong, but I was expecting this 5KB memory usage only for the first instance for the complete program, not per page. So, is it normal? Could it be because of a bad structure design?

The code is compiled for PIC32 using MicroChip xc32 v2.50. Tested with other more recent versions without significant differences (not counting bytes but the memory behavior).