QMap value type with virtual destructor

[Vikram.Saralaya]

Hello,

I solved a problem that troubled me for a while and now I am interested in getting more insight into what has been happening here..

I have a custom data type that I want to store as a value in QMap.

QMap<uint, CustomType>

QMap<uint, CustomType>

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My CustomType looks like:

class CustomType
{
public:
    CustomType() { m_objectRef = nullptr; m_slotName = nullptr; }
    CustomType(QObject* obj, const char* slotName) { m_objectRef = obj; m_slotName = slotName; }
    virtual ~CustomType() {}
 
    // Accessors
    QObject*                GetObjectName() { return m_objectRef; }
    const char*             GetSlotName()   { return m_slotName; }
 
private:
    QObject*                m_objectRef;
    const char*             m_slotName;
};

class CustomType
{
public:
    CustomType() { m_objectRef = nullptr; m_slotName = nullptr; }
    CustomType(QObject* obj, const char* slotName) { m_objectRef = obj; m_slotName = slotName; }
    virtual ~CustomType() {}

    // Accessors
    QObject*                GetObjectName() { return m_objectRef; }
    const char*             GetSlotName()   { return m_slotName; }

private:
    QObject*                m_objectRef;
    const char*             m_slotName;
};

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I get a compilation error saying:

undefined reference to `_imp___ZTV10CustomType'

undefined reference to `_imp___ZTV10CustomType'

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Solution:
Remove virtual keyword from the destructor.

My question:
Why can't I have a virtual destructor here?

Thank you!

Regards
Vikram

[stampede]

Do not store or pass polymorphic types by value, pass by reference, pointer or most preferably wrap your objects in smart pointers. Passing polymorphic objects by value can cause slicing.
Unrelated, but using constructor initializer lists instead of assigning in constructor body is a good habit.

[prasad_N]

Solution:
Remove virtual keyword from the destructor.

My question:
Why can't I have a virtual destructor here?

I tried your code actually it is getting complied with and without virtual.

[Vikram.Saralaya]

I tried your code actually it is getting complied with and without virtual.

I can confirm that I can easily reproduce that problem on my mingw-32bit compiler. Strange.. well I will stop worrying about it for now. Thanks for trying