problem about virtual-method-Collection of common programming errors

• 
  Chris
  java jvm methods virtual-method
  Consider this simple Java class:class MyClass {public void bar(MyClass c) {c.foo();} }I want to discuss what happens on the line c.foo().Original, Misleading QuestionNote: Not all of this actually happens with each individual invokevirtual opcode. Hint: If you want to understand Java method invocation, don’t read just the documentation for invokevirtual!At the bytecode level, the meat of c.foo() will be the invokevirtual opcode, and, according to the documentation for invokevirtual, more or less
• 
  threed
  c# virtual-method
  Is it possible to determine if a virtual method has been overridden:class ABase {public void DoSomething(object p){p.Process();if( /* DoSomethingExtra is implemented */ )DoSomethingExtra(p);}public virtual void DoSomethingExtra(object p) { }}class ADerived {public override void DoSomethingExtra(object p){p.ProcessMore();} }I realize that this example seems stupid (e.g. why don’t you just call DoSomethingExtra() since it doesn’t do anything). I assure you I have a legitimate case for this. Any
• 
  Dani
  java performance comparable virtual-method
  I profiled my code and found out that my class, which implements Comparable<T>, spends 8x more cpu time in compareTo(Object)than in compareTo(T)I assume that the slowdown is because of virtual table lookup for this method.Is there a way to force static invocation of the function? (like in non virtual C++ methods)I still want to use the Comparable<T> interface since I use TreeSet with this object and I’d like not to rewrite this code.EDIT: No, I didn’t implement the compareTo(Object)
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  Kara
  c++ shared-memory virtual-method
  I have a class whose objects are used in shared memory. Therefore, I must be sure that they do not have virtual methods (which crash the program when called via vtable).I would like to guard against anybody accidentally adding a virtual method in violation of this requirement. Ideally, the compiler would refuse to even compile the class if it contains virtual methods.Solutions do not necessarily need to be standards compliant, it is sufficient if they work on Apple’s gcc-4.2 or MSVC.How can I ac
• 
  LinuxPenseur
  c++ constructor overriding virtual-method
  Suppose I have two C++ classes:class A { public:A() { fn(); }virtual void fn() { _n = 1; }int getn() { return _n; }protected:int _n; };class B : public A { public:B() : A() {}virtual void fn() { _n = 2; } };If I write the following code:main() {B b;int n = b.getn(); }One might expect that n is set to 2.It turns out that n is set to 1. Why?
• 
  Kara
  c++ templates inheritance virtual-method
  Possible Duplicate:Why do I get “unresolved external symbol” errors when using templates? I have a little bit complicated set of classes. Class _A which has child parametrized class A which has two children A1 and A2. Class B. Contains pointer on object of class _A as member. Has two child classes B1 and B2 which correspond to classes A1 and A2 each. B1 constructs _A as A1. B2 as A2 respectivelly. And finally class Y which has child BY defined inside of class B. Now how it is present in files.
• 
  Kara
  c++ debugging visual-studio-2005 virtual-method
  A colleague of mine had a problem with some C++ code today. He was debugging the weird behaviour of an object’s virtual method. Whenever the method executed ( under debug, Visual Studio 2005 ), everything went wrong, and the debugger wouldn’t step in that method, but in the object’s destructor! Also, the virtual table of the object, only listed it’s destructor, no other methods.I haven’t seen this behaviour before, and a runtime error was printed, saying something about the ESP register. I wish
• 
  Kara
  c++ destructor unresolved-external virtual-method
  Consider the following:In X.h:class X {X();virtual ~X(); };X.cpp:#include “X.h”X::X() {}Try to build this (I’m using a .dll target to avoid an error on the missing main, and I’m using Visual Studio 2010):Error 1 error LNK2001: unresolved external symbol “private: virtual __thiscall X::~X(void)” (??1X@@EAE@XZ)Small modifications result in a successful build, however:X.h:class X {inline X(); // Now inlined, and everything buildsvirtual ~X(); };orX.h:class X {X();~X(); // No longer virtual, and
• 
  iammilind
  c++ linker-error language-lawyer virtual-method
  struct A {virtual void foo(); // unused and unimplementedvirtual void bar () {} };int main () {A obj; // okobj.bar(); // <– added this editionA* pm = (A*)malloc(sizeof(A)); // okA* pn = new A; // linker error }For objects on stack it works fine. But for allocation on heap with new (not malloc), it gives linker error:undefined reference to `vtable for A’
• 
  PiotrNycz
  c++ constructor g++ standards virtual-method
  I know that within constructor of Base class – when calling virtual method – the Base method is called, not derived – see Calling virtual functions inside constructors.My question is related to this topic. I’ve just wondered what happens if I call virtual method in Derived class constructor – but before constructing Base part. I mean calling virtual method to evaluate Base class constructor argument, See code:class Base { public:Base(const char* name) : name(name) {cout << “Base():” <&l
• 
  Roddy
  c++ debugging destructor virtual-method
  I was debugging an odd problem where an objects VMT suddenly seemed to point to the base object’s methods.class Base { virtual void foo() {} }class Derived: public Base { void foo() {} }Derived * d = new Derived;… much complex fettling …d->foo(); // Help! called Base::foo()!!!It turned that a bug in the ‘complex’ code was effectively doing delete d;. I won’t go into details except to say that boost::noncopyable is your friend, and never under ANY circumstances roll your own smart pointer
• 
  Jonathan Leffler
  c++ virtual-method
  Possible Duplicate:Undefined symbols “vtable for …” and “typeinfo for…”?C++ Undefined Reference to vtable and inheritance I’ve a problem with a little project required from my university. It’s a simple project of a chess game.I’ve the obscure error undefined reference to `vtable for XXX when I define an inherited class from an abstract one… This is the codePieces.hclass Pieces { public:Pieces(char color) : pieceColor(color) {}virtual ~Pieces() {}virtual c
• 
  Max
  c++ inheritance undefined virtual-method
  I’m having a bit of trouble using virtual functions in C++, and I might be misusing them in a constructor. The problem is that when linking a component lib (written by me) into my final executable, a virtual function is marked as undefined, even though I have written an implementation for it, and linked it.I have the following class:template<class BufferType, class ConnectionType, class HandlerType> class UdpConnection { public: UdpConnection(size_t dispatchCount) : service(),listener(serv

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