vtable

问题 C++ has multiple inheritance. The implementation of multiple inheritance at the assembly level can be quite complicated, but there are good descriptions online on how this is normally done (vtables, pointer fixups, thunks, etc). Java doesn't have multiple implementation inheritance, but it does have multiple interface inheritance, so I don't think a straight forward implementation with a single vtable per class can implement that. How does java implement interfaces internally? I realize that

问题 Nearly the final step but still some strange erros.... bash-3.2$ make g++ -Wall -c -g Myworld.cc g++ -Wall -g solvePlanningProblem.o Position.o AStarNode.o PRM.o PRMNode.o World.o SingleCircleWorld.o Myworld.o RECTANGLE.o CIRCLE.o -o solvePlanningProblem Undefined symbols: "vtable for Obstacle", referenced from: Obstacle::Obstacle()in Myworld.o "typeinfo for Obstacle", referenced from: typeinfo for RECTANGLEin RECTANGLE.o typeinfo for CIRCLEin CIRCLE.o ld: symbol(s) not found collect2: ld

问题 Does every class have virtual function table in C++? I know virtual table is for polymorphism. Class with virtual functions must have v-table. But how about class has no virtual function? Or how about class has no base class? 回答1: The language specification of C++ does not define what a "vtable" is, or which classes need one. A particular implementation of C++ in a compiler often uses a vtable to implement virtual methods. If a class has no virtual methods (and no superclasses with virtual

问题 I think I might be confusing myself. I know class with virtual functions in C++ has a vtable (one vtable per class type), so the vtable of Base class will have one element &Base::print() , while the vtable of Child class will have one element &Child::print() . When I declare my two class objects, base and child , base 's vtable_ptr will pointer to Base class's vtable, while child 's vtable_ptr will point to Child class's vtable. After I assign the address of base and child to an array of Base

问题 This question already has answers here : Hoisting the dynamic type out of a loop (a.k.a. doing Java the C++ way) (4 answers) Closed 6 years ago . Suppose I have the following code void f(PolymorphicType *p) { for (int i = 0; i < 1000; ++i) { p->virtualMethod(something); } } Will the compiler's generated code dereference p 's vtable entry for virtualMethod 1 or 1000 times? I am using Microsoft's compiler. edit here is the generated assembly for the real-world case I'm looking at. line-

问题 My question has changed from the other one I have posted. I started out with multiple files and decided to put it all in one main.cpp file for now just to get it working. main.cpp: #include <iostream> using namespace std; class arrayListType { public: bool isEmpty() ; bool isFull() ; int listSize() ; int maxListSize() ; void print() ; bool isItemAtEqual(int location, int item) ; virtual void insertAt(int location, int insertItem) = 0; virtual void insertEnd(int insertItem) = 0; void removeAt

问题 Regarding this post: For implementations that use vtable, the answer is: Yes, usually. You might think that vtable isn't required for abstract classes because the derived class will have its own vtable, but it is needed during construction: While the base class is being constructed, it sets the vtable pointer to its own vtable. Later when the derived class constructor is entered, it will use its own vtable instead. I'm assuming the answer is correct, but I don't quite get it. Why is the

问题 I struggle with a memory violation error in my C++ code, and it makes me crazy. I have to use some existing classes and they work fine almost everywhere else. I am trying to make a copy of a custom Array object, than modify inner values later. But there is something wrong with that copy operation... The symptoms are the following: Segmentation fault after the copy, but not immediately Warning: can't find linker symbol for virtual table for 'MyClass<T>' value MyClass<T> has nothing to do with

问题 I get this error /.../mainwindow.o:-1: In function `MainWindow::MainWindow(QWidget*)': /.../mainwindow.cpp:-1: Chyba:undefined reference to `vtable for Msnger' and i dont understand why. Only problems i found causing this message are declaration without definition and i dont see any of theese in my code. here is class Msnger msnger.h: #include <QObject> class Msnger : public QObject { Q_OBJECT public: Msnger() {}; ~Msnger() {}; void sendOn(); signals: void ton() {}; }; msnger.cpp: #include

问题 I'm defining a class 'function' and two others classes 'polynomial' and 'affine' that inherit from 'function'. class function { public: function(){}; virtual function* clone()const=0; virtual float operator()(float x)const=0; //gives the image of a number by the function virtual function* derivative()const=0; virtual float inverse(float y)const=0; virtual ~function(){} }; class polynomial : public function { protected: int degree; private: float *coefficient; public: polynomial(int d);