How do you fix undefined reference to Vtable?

How do you fix undefined reference to Vtable?

How to fix the error?

1. Look at your class definition.
2. Find the definition for that function.
3. Check your link command.
4. Repeat steps 2 and 3 for each virtual function, then for each non-virtual function, until the error is resolved.

What is a Vtable C++?

For every class that contains virtual functions, the compiler constructs a virtual table, a.k.a vtable. The vtable contains an entry for each virtual function accessible by the class and stores a pointer to its definition. Only the most specific function definition callable by the class is stored in the vtable.

Is the default destructor virtual?

Trivial destructor The destructor is not virtual (that is, the base class destructor is not virtual) All direct base classes have trivial destructors. All non-static data members of class type (or array of class type) have trivial destructors.

What does undefined symbol mean in C++?

It means you haven’t written a function, or you haven’t created a variable, or you haven’t linked against the library or object code that contains the missing function or variable.

How do I run Makefiles?

Also you can just type make if your file name is makefile/Makefile . Suppose you have two files named makefile and Makefile in the same directory then makefile is executed if make alone is given. You can even pass arguments to makefile.

What is a virtual function in C++?

A C++ virtual function is a member function in the base class that you redefine in a derived class. It is declared using the virtual keyword. It is used to tell the compiler to perform dynamic linkage or late binding on the function.

What does virtual void mean in C++?

For example, class Base { virtual void func(); } When a Base Class has a virtual member function, any class that inherits from the Base Class can redefine the function with exactly the same prototype i.e. only functionality can be redefined, not the interface of the function.

What is vTable and VPTR in C++?

# Vtable is created by compiler at compile time. # VPTR is a hidden pointer created by compiler implicitly. # If base class pointer pointing to a function which is not available in base class then it will generate error over there. # Vtable gets created for each class which has virtual functions.

What is vTable and vPointer?

vTable is a kind of function pointer array that contains the addresses all virtual functions of this class. Compiler builds this vTable at compile time. vPointer: Now for every object of a class that has a vTable associated with it, contains a vPointer in first 4 bytes. This vPointer points to the vTable of that class.

Is implicitly deleted?

A implicitly-declared copy assignment operator for class T is defined as deleted if any of the following is true: T has a user-declared move constructor; T has a user-declared move assignment operator. Otherwise, it is defined as defaulted.

Is destructor called automatically in C++?

A destructor is a member function that is invoked automatically when the object goes out of scope or is explicitly destroyed by a call to delete . A destructor has the same name as the class, preceded by a tilde ( ~ ).

Why does my vtable become an undefined reference?

If this selection process fails to pick any translation units, then the vtable becomes an undefined reference. Hence the error, whose message is admittedly not particularly clear.

Does derived have undefined reference to vtable for iBase?

However as Derived overrides methods from IBase, it has vtable attached to it that will reference IBase. When linker says “undefined reference to vtable for IBase” it basically means that Derived has vtable reference to IBase but it can’t find any compiled object code of IBase to look up to.

What is a vtable in C++?

🙂 For those sticking around: A vtable is basically the most common implementation of polymorphism in C++. When vtables are used, every polymorphic class has a vtable somewhere in the program; you can think of it as a (hidden) static data member of the class.

Why is vftable not included in the object file?

That means GCC will only include vftable in the object file for the translation unit where the definition of the first non-pure, and non-inline virtual member function is present. If there is no such definition, vftable will not be included for the class.