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why do I need virtual table?
What is a vtable in C++?
So far I know that vtable is a virtual table which has an array of pointers to virtual functions. Is there an article I can read with an example of a practical implementation? (Any walk through will be appreciated.)
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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.
In computer programming, a virtual method table (VMT), virtual function table, virtual call table, dispatch table, vtable, or vftable is a mechanism used in a programming language to support dynamic dispatch (or run-time method binding).
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.
It has no type. It's an implementation detail unspecified by the standard; it is not part of the language. Note that C++ doesn't say that there has to be a virtual table or a virtual "pointer" at all (though this is the most common implementation of RTTI in C++ toolchains). Also, your analysis is wrong.
V-tables (or virtual tables) are how most C++ implementations do polymorphism. For each concrete implementation of a class, there is a table of function pointers to all the virtual methods. A pointer to this table (called the virtual table) exists as a data member in all the objects. When one calls a virtual method, we lookup the object's v-table and call the appropriate derived class method.
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