C / C++ / MFC

Base Class.
Child Class.

CBaseClass * pBase = new CBaseClass();
CChildClass * pChild = (CChildClass *) pBase;

class CBaseClass
{
public:
	virtual void Function() // this is virtual function
	{
		cout<<"\nBase Class.";
	}
};
 
class CChildClass : CBaseClass
{
public:
	void Function() // overriden virtual function
	{
		cout<<"\nChild Class.";
	}
};

CChildClass* pChild = (CChildClass*)pBase;

Derived * d = new Derived;
Base* b = d;

class Base;
class A : public Base;
class B : public Base;
Base* b = new B;
A* p = (A*)b; // huge mistake because b points to a B instance so the code that uses p can crash anytime if you are not lucky!!!!

CBaseClass* p = new CChildClass; // the compiler automatically upcasts the CChildClass* to CBaseClass*
p->Function();                   // calls the Function of CChildClass because we created a CChildClass instance above!

Cast Derived to Base - OK
Cast Base to Derived - Bad

#include <cstdlib>
#include <iostream>
#include <windows.h>
 
using namespace std;
 
typedef bool  (*cbtype)  (char *what, int, int, char *str);
 
bool SomeCallback( char *c1 , int i1 , int i2, char *c2)
{
     printf("%s\r\n" , c1);
     printf("%d\r\n" , i1);
     printf("%d\r\n" , i2);
     printf("%s\r\n" , c2);
     return true;
}
 
void ArcExtract ()
{  
	
	HINSTANCE GetProcDLL = LoadLibrary("unarc.dll");
	if(GetProcDLL==NULL)
        {
		//handle error
	}
 
	typedef int (__cdecl * CallingFun)(cbtype, ...);
 
    	CallingFun FreeArcExtract;
    FreeArcExtract =(CallingFun) GetProcAddress(HMODULE (GetProcDLL), "FreeArcExtract");
	if(FreeArcExtract==NULL)
	{
		//handle error
	}
	FreeArcExtract((cbtype)SomeCallback,
"l", "--", "d:\\test.arc", "", "", "", "", "", "", "");
    FreeLibrary(GetProcDLL);
}
 
int main(int argc, char *argv[])
{
    ArcExtract ();
    //system("pause");

    return EXIT_SUCCESS;
}

#include <cstdlib>
#include <iostream>
#include <windows.h>

using namespace std;

typedef int __stdcall cbtype (char *what, int int1, int int2, char *str);

int  __stdcall somecallback (char *what, int int1, int int2, char *str)
{
   cout << what << endl;
   cout << int1 << endl;
   cout << int2 << endl;
   cout << str << endl;
}

void ArcExtract ()
{  
	
	HINSTANCE GetProcDLL = LoadLibrary("unarc.dll");
    FARPROC GetProcessID = GetProcAddress(HMODULE(GetProcDLL), "FreeArcExtract");
    
	typedef int (__stdcall * CallingFun)(cbtype, ...);

    CallingFun FreeArcExtract;
    FreeArcExtract = CallingFun(GetProcessID);
 
	FreeArcExtract(somecallback,"l", "--", "d:\\test.arc", "", "", "", "", "", "", "");

    FreeLibrary(GetProcDLL);
}

int main(int argc, char *argv[])
{
    ArcExtract ();
    system("pause");

    return EXIT_SUCCESS;
}