virtual-functions

Can virtual functions like X::f() in the following code struct X { constexpr virtual int f() const { return 0; } }; be constexpr ? Kerrek SB This answer is no longer correct as of C++20. No. From [dcl.constexpr]/3 (7.1.5, "The constexpr specifier"): The definition of a constexpr function shall satisfy the following requirements: — it shall not be virtual Up through C++17, virtual functions could not be declared constexpr . The general reason being that, in constexpr code, everything happen can at compile time. So there really isn't much point to having a function which takes a reference to a

at my working place (php only) we have a base class for database abstraction. When you want to add a new database table to the base layer, you have to create a subclass of this base class and override some methods to define individual behaviour for using this table. The normal behaviour should stay the same. Now I have seen many new programmers at our company, who just override the method for the default behaviour. Some are so "nice" to put in all the default behaviour and just add there individual stuff where they like it, others kill themself trying to use the baseclass and their inheritor.

I am new to C++. Could anybody tell me the difference between method overriding and virtual function concepts in c++. The functionality of virtual functions can be over-ridden in its derived classes. Redefining a function in a derived class is called function overriding. why do we actually have virtual functions? pyon ABSTRACT In this paper, we discuss virtual functions in C++. Part zero explains how virtual functions are declared and overridden. Part one attempts (and perhaps fails) to explain how virtual functions are implemented. Part two is a sample program that uses the example classes

This is not about "When VTABLE is created?" . Rather, when the VPTR should be initialized? Is it at the beginning/end of the constructor or before/after the constructor? A::A () : i(0), j(0) -->> here ? { -->> here ? //... -->> here ? } The machinery for virtual calls (usually a v-table, but doesn't need to be) is set up during the ctor-initializer , after construction of base subobjects and before construction of members. Section [class.base.init] decrees: Member functions (including virtual member functions, 10.3) can be called for an object under construction. Similarly, an object under

I was under the impression that whenever you do one of these: Add a new public virtual method virtual void aMethod(); Add a new public non-virtual method void aMethod(); Implement a public pure-virtual method from an interface virtual void aMethod override; Was actually breaking binary compatibility, meaning that if a project had build on a previous version of the DLL, it would not be able to load it now that there is new methods available. From what I have tested using Visual Studio 2012, none of these break anything. Dependency Walker reports no error and my test application was calling the