Technical facts

Operating system(s) or programming environment(s)

Lubuntu 15.04 (vivid)

IDE(s):

Qt Creator 3.1.1

Project type:

Console application

C++ standard:

C++98

Compiler(s):

G++ 4.9.2

Libraries used:

STL: GNU ISO C++ Library, version 4.9.2

Qt project file: ./CppDynamic_castExample1/CppDynamic_castExample1.pro


include(../../ConsoleApplication.pri) #Or use the code below

# QT += core

# QT += gui

# greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

# CONFIG   += console

# CONFIG   -= app_bundle

# TEMPLATE = app

# CONFIG(release, debug|release) {

#   DEFINES += NDEBUG NTRACE_BILDERBIKKEL

# }

# QMAKE_CXXFLAGS += -std=c++11 -Wall -Wextra -Weffc++

# unix {

#   QMAKE_CXXFLAGS += -Werror

# }



SOURCES += main.cpp

./CppDynamic_castExample1/main.cpp


#include <cassert>



struct Base

{

  virtual ~Base() {}

};



struct Derived : public Base { };



int main()

{

  //Base initialized with derived, can be downcasted to derived

  {

    Base * const p1 = new Derived;

    Derived * const p2 = dynamic_cast<Derived*>(p1);

    assert(p1);

    assert(p2);

    assert(p1 == p2);

    delete p1;

    //delete p2; //Do not re-delete!

  }

  //Base initialized with base, cannot be downcasted to derived

  {

    Base * const p1 = new Base;

    Derived * const p2 = dynamic_cast<Derived*>(p1);

    assert( p1);

    assert(!p2);

    assert(p1 != p2);

    delete p1;

  }

  //Const base initialized with derived, can be downcasted to const derived

  {

    Base * const p1 = new Derived;

    const Derived * const p2 = dynamic_cast<const Derived*>(p1);

    assert(p1);

    assert(p2);

    assert(p1 == p2);

    delete p1;

    //delete p2; //Do not re-delete!

  }

  //Const base initialized with base, cannot be downcasted to const derived

  {

    const Base * const p1 = new Base;

    const Derived * const p2 = dynamic_cast<const Derived*>(p1);

    assert( p1);

    assert(!p2);

    assert(p1 != p2);

    delete p1;

  }

  //Const base initialized with derived, cannot be down- and const-casted to non-const derived

  {

    const Base * const p1 = new Derived;

    //Removing const: will and should not compile

    //Derived * const p2 = dynamic_cast<Derived*>(p1));

    assert(p1);

    delete p1;

  }

  //Base initialized with derived, can be downcasted to const derived with adding constness

  {

    const Base * const p1 = new Derived;

    //Adding const: will and should compile

    const Derived * const p2 = dynamic_cast<const Derived*>(p1);

    assert(p1);

    assert(p2);

    assert(p1 == p2);

    delete p1;

    //delete p2; //Do not re-delete!

  }

}

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(C++) Dynamic_castExample1

Technical facts

Qt project file: ./CppDynamic_castExample1/CppDynamic_castExample1.pro

./CppDynamic_castExample1/main.cpp