vtable

Consider a program that has a class Foo containing a function Foo::fn declared like this: virtual void fn(); and a subclass of Foo called Bar . Will declaring Bar::fn like this: virtual void fn() override final; cause calls to fn in Bar or subclasses of Bar to be any more efficient, or will it just keep subclasses of Bar from overriding fn ? If calls are made more efficient using final , what is the simplest, most efficient method to define Bar::fn such that its functionality is exactly that of Foo::fn ? If fn is defined as final in Bar , the compiler can dispatch calls to fn through a pointer

I have a small doubt in Virtual Table, whenever compiler encounters the virtual functions in a class, it creates Vtable and places virtual functions address over there. It happens similarly for other class which inherits. Does it create a new pointer in each class which points to each Vtable? If not how does it access the Virtual function when the new instance of derived class is created and assigned to Base PTR? Each time you create a class that contains virtual functions, or you derive from a class that contains virtual functions, the compiler creates a unique VTABLE for that class. If you

Note: This question is purely about asm.js not about C++ nor any other programming language. As the title already says: How should a function pointer be implemented in a efficient way? I couldn't find anything on the web, so I figured asking it here. Edit: I would like to implement virtual functions in the compiler I'm working on. In C++ I would do something like this to generate a vtable : #include <iostream> class Base { public: virtual void doSomething() = 0; }; class Derived : public Base { public: void doSomething() { std::cout << "I'm doing something..." << std::endl; } }; int main() {

I am trying to write an Http proxy that basically works like indianwebproxy So i fired up qtcreator and but one of my classes is failing to compile with the infamous error : undefined reference to vtable for HttpProxyThreadBrowser . I can't figure out why its doing this. I read through similar questions on Stackoverflow and apparently the problem is with undefined virtual methods that are not pure But i have not declared any virtual functions. Here is my class class HttpProxyThreadBrowser : public QThread { public: HttpProxyThreadBrowser(QTcpSocket outgoingSocket,QTcpSocket browserSocket

I am debugging a defect and have narrowed it down to the vtable pointer for an object being 0xdddddddd . This answer indicates that Win32 debug builds will generally set dead memory, or memory which has been deleted, to this special value. Note that the pointer itself looks valid, it's just the vtable pointer that is 0xdddddddd . Here's a snippet of code: std::list<IMyObject*>::const_iterator it; for (it = myObjects.begin(); it != myObjects.end(); ++it) { IMyObject* pMyObject = *it; if (pMyObject == 0) continue; pMyObject->someMethod(); // Access violation } If I break at the line of the

n3797 says: § 7.1.6.4/14: A function declared with a return type that uses a placeholder type shall not be virtual (10.3). Therefore the following program is ill-formed: struct s { virtual auto foo() { } }; All I can find for the rationale is this vague one-liner from n3638 : virtual It would be possible to allow return type deduction for virtual functions, but that would complicate both override checking and vtable layout, so it seems preferable to prohibit this. Can anyone provide further rationale or give a good (code) example that agrees with the above quote? The rationale that you