C / C++ / MFC

yeti11 wrote:

I have been thinking about; if i have pointer stored inside vector, at the end it
is stored as address to something and the address is the same size in any case. So
if i cast it, there should be no changes, but i still got a core dump (it works for
instance in 20 cases, but then one crashes).

yeti11 wrote:

i dont want to loose general usage of library and coupling it with like 15 classes
that have nothing to do with it and... well it would be a mess.

yeti11 wrote:

i want to understand what i am doing wrong and why

yeti11 wrote:

What is wrong with casting vector holding pointers?

yeti11 wrote:

Can you please tell me why? Pointer is a pointer however you turn it... sure if it is object i
understand the reason, but the question is what is the problem if i use it as pointer? Or rather
the question is understanding...

#include <iostream>
 
class CClass1
{
public:
	CClass1() : m_Data(0) {}
	int m_Data;
};
 
class CClass2
{
public:
	CClass2() : m_pData("Hello") {}
	const char* m_pData;
};
 
void main()
{
	using namespace std;
 
	CClass2 c2;
	CClass1 *pOne = reinterpret_cast<CClass1*>(&c2);
	cout << pOne->m_Data << endl;
}

#include <iostream>
#include <vector>
 
class CBase
{
public:
	virtual void Print() { std::cout << "CBase" << std::endl; }
};
 
class CDerived : public CBase
{
public:
	virtual void Print() { std::cout << "CDerived" << std::endl; }
};
 
int main(int argc, char* argv[])
{
	typedef std::vector<CBase*> BVec_t;
	typedef std::vector<CDerived*> DVec_t;
 
	DVec_t dvec;
	dvec.push_back(new CDerived);
	BVec_t &bvec = *reinterpret_cast<BVec_t*>(&dvec); // Don't do this at home...
 
	CBase *pBase = bvec.front();
	pBase->Print();
	delete pBase;
 	
	return 0;
}

yeti11 wrote:

but it did help me to abandon the idea that something is
wrong with cast

class A
{
public:
	A() {}
	virtual ~A() { std::cout << "destroying class A" << std::endl; }
	virtual print() const { std::cout << "class A" << std::endl; }
};
class B : public A
{
public:
	B() {}
	virtual ~B() { std::cout << "destroying class B" << std::endl; }
	virtual print() const { std::cout << "class B" << std::endl; }
};

int main(/*int argc, char* argv[]*/)
{
	std::vector<A*> a_vec;
	int i;
	for( i=0; i<3; ++i )
		a_vec.push_back(new B);

	for( i=0; i<3; ++i )
		a_vec[i]->print();

	for( i=0; i<3; ++i )
		delete a_vec[i];

	return 0;
}