ARM Compiner c++ error (class, virtual, override)

Fortunately what you claim you would like to happen does not actually happen as it would make a lot of code that has already been written not work (as well as create what could only be described as "undefined behavior".

This not a compiler bug.

One way to look at this is that construction happens from base class to the derived class(es). How can the base class call ANYTHING in a derived class if the derived class has not been constructed yet? That is what you are asking to happen and this is not something that would make sense.

Also on Destruction, you could have an issue that a base class tries to call a function in a derived class AFTER the destructor has been called.

Thanks for answer.

If compiler was written like this, when have it your way. But this way is violate an a foundation of object-oriented implementation.

For methods which shouldn't be overridden present a simple class methods
The main purpose of virtual methods is posibility of it overriding.

For hiding simple methods in child class in modern implementation of c++ present new operator. In this case classes works like this time. The parent class has one method and it calls when it calls from parent class, and child has second method with same name and it calls when it calls from child class. It not an overriding.

I understand if this way was used because a lot of code use this way, but it this case should to be a tutorial aabout limitation or peculiarity of c++ in ARM Compiler v5

P.S.
The example with constructor was used because it have smaller code. Method calling the same in case of it callint after construction and not initialised class it's not a reason to calling method this way, because overridding get a possibility to call an overrided method on a begin of new method if it nessesary and at the begin of construction of child class all for parent and child parts is allocated in memory an it filled initial values of calsss fileds.

Yes. The code in example executed the same way as in my program.

Maybe I explain not correct.

I think that reason of overriding virtual methods is to call a new emplementation of method even if it calls from parent class method.

Maybe I'm not right.

My aim was to make a basic class and functional in it and override some methods in child with adding functionality.

I think that reason of overriding virtual methods is to call a new emplementation of method even if it calls from parent class method.

Your thinking is correct. You just cannot call overridden virtual methods from a constructor / destructor. ( even using this->constructor(); )

My aim was to make a basic class and functional in it and override some methods in child with adding functionality.

Sure again. You once again cannot do that with constructors.

If you actually think about it, you should be able to convince yourself that it cannot work in all cases. (especially ones that require child class initialization)

I think that reason of overriding virtual methods is to call a new emplementation of method even if it calls from parent class method.

Your thinking is correct. You just cannot call overridden virtual methods from a constructor / destructor. ( even using this->constructor(); )

Of cause correct. May be its not correct from side of standard c++11
I show one example on c# one of most robust oop language. May be its not correct to compare with c++, but its show an essence of the idea.

class Parent
    {
        public Parent()
        {
            vMethod();
            sMethod();
        }
        public virtual void vMethod()
        {
            Debug.WriteLine("vParent");
        }

        public void sMethod()
        {
            Debug.WriteLine("sParent");
        }
    }

    class Child : Parent
    {
        public Child()
        {
            vMethod();
            sMethod();
        }
        public override void vMethod()
        {
            Debug.WriteLine("vChild");
        }

        public new void sMethod()
        {
            Debug.WriteLine("sChild");
        }
    }
...
static void Main(string[] args)
        {
            Child c = new Child();
...

The result of program working:
vChild
sParent
vChild
sChild

So as we can see, when start constructor of Child class its call Parrent constructor, which calls vMethod() and sMethod(). vMethod() is overriden, so it print "vChild", sMethod is simple class method, so it print "sParent". After Parent constructor calls child constructor code. It again calls vMethod() and sMethod(). vMethod() is overriden, so it again print "vChild". sMethod is declarated as new, so when it calls from Child class, calls new version of sMethod. So it print "sChild".

In this case operators "override" and "virtual" has the meaning. Now its like a "new" operator.

Now in ARM compiler "virtual" operator it like "new" operator in example above, but from the poiny of oop "override" is redefinition of method address in previous position of vertual method table.

When some years ago read how it works, I read that for virtual methods plased table in memory with methods addresses. When you override method in child class in child class table on plase of method putted new address and the old address putten at new plase at the end of virtual method table. So you have a posibility to call old method from parent (for example above

public override void vMethod()
{
    base.vMethod();
    Debug.WriteLine("vChild");
}

)

My aim was to make a basic class and functional in it and override some methods in child with adding functionality.

Sure again. You once again cannot do that with constructors.

If you actually think about it, you should be able to convince yourself that it cannot work in all cases. (especially ones that require child class initialization)

I gust show a code which I try to use an I think you understand an idea. Maybe its more difficult then need for this task, but its beautiful in my opinion

template <class T>
class Driver
{
        private:
                static SemaphoreHandle_t busy_smphr;
        public:
                ~Driver<T> ();
                static T* Open(TickType_t xTicksToWait);
                virtual void Close();
};

template <class T>
SemaphoreHandle_t Driver<T>::busy_smphr = xSemaphoreCreateMutex();

template <class T>
Driver<T>::~Driver<T> ()
{
        Close();
};

template <class T>
T* Driver<T>::Open(TickType_t xTicksToWait)
{
        if (xSemaphoreTake(Driver<T>::busy_smphr, xTicksToWait)==pdTRUE)
           return new T();
        else
           return NULL;
};

template <class T>
void Driver<T>::Close()
{
    xSemaphoreGive(T::busy_smphr);
};

Ans the child class
NewDevice.h

class NewDevice: public Driver<NewDevice>
{
  public:
        static NewDevice* Open(TickType_t xTicksToWait);
        static void Init(void);
        void Method();
        virtual void Close();
};

NewDevice.cpp

NewDevice* NewDevice::Open(TickType_t xTicksToWait)
{
        NewDevice* husart = Driver<NewDevice>::Open(xTicksToWait);
        if (husart!=NULL){
                ...
        }
        return husart;
}

void NewDevice::Close() {
        Driver<NewDevice>::Close();
}

void NewDevice::Method() {
        ...
}

And using in code

NewDevice::Init();
NewDevice* drv = NewDevice::Open(10);
if (drv!=NULL)
   drv->Method();
delete drv;

On deleting object calls destructor from parent, which should to call new overriden Close(), which should to call previous Close(). But its doesn't work. I found a slution, but its not so beautiful.

Thanks for your answers.

Calling virtual method from a constructor/destructor is a fundamental C++ programming mistake !

Hank you. I agree with you.

If call virtual method not from constructor all works correct.