How does Vptable and VPTR work?
The compiler places the addresses of the virtual functions for that particular class in the VTABLE. In each class with virtual functions, it secretly places a pointer, called the vpointer (abbreviated as VPTR), which points to the VTABLE for that object.
What is the purpose of a vtable?
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).
How does a vtable work?
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.
What is the full form of VPTR?
Explanation: vptr is abbreviated for a virtual pointer which is used to point virtual tables of a class.
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.
How virtual keyword works in the backend concept of vTable and _vptr?
Working of virtual functions(concept of VTABLE and VPTR) If object of that class is created then a virtual pointer(VPTR) is inserted as a data member of the class to point to VTABLE of that class. For each new object created, a new virtual pointer is inserted as a data member of that class.
What is vtable and vPointer?
When was vtable created?
The vtable is created at compile time. When a new object is created during run time, the hidden vtable pointer is set to point to the vtable.
Does every class have vtable?
As a non-standard rule of thumb (vtables are not dictated by the standard) which applies to virtually all compilers: Only classes with virtual member functions and/or a virtual destructor have a vtable. Other classes not.
How many VPTR does a class have?
So what you are asking for entirely depends on the compiler you are using. GCC will in theory most likely create two vtables (one for B and one for D ) and three vptrs (one for each of the object instances d1 , d2 , d3 ).
Why is VPTR not static?
The runtime class of the object is a property of the object itself. In effect, vptr represents the runtime class, and therefore can’t be static .
What is vtable and vPointer and how C++ does run time binding using them?
What is vtable & vPointer and How C++ do run time binding using them: vTable: Every class that has one or more virtual member functions in it has a vTable associated with it. vTable is a kind of function pointer array that contains the addresses all virtual functions of this class.