#include <stdlib.h
#include <string.h
#include <stdio.h
#include <assert.h

#define zeroclass(PTR,TYPE)                                                         \
{                                                                                   \
    int Error_Different_Types[ sizeof(*(PTR)) == sizeof(TYPE) ]={0};                \
    struct zeroclass_bigger_ : public TYPE { virtual zeroclass_muchbigger(){} };    \
    if( sizeof(zeroclass_bigger_)  sizeof(TYPE) ) memset( (PTR), 0, sizeof(TYPE) );\
    else            memset( (((void**)(PTR))+1), 0, sizeof(TYPE)-sizeof(void*) );   \
}                                                                                        

struct pepe
{
    int Count;

    pepe::pepe( void )
    {
        zeroclass( this, pepe );
    }

    void Alive( void )
    {
        printf( "(Normal)I am alive[%d]!!!\n", Count);
    }

};

struct pepe2
{
    int Count;

    pepe2::pepe2( void )
    {
        zeroclass( this, pepe2 );
    }

    virtual void Alive( void )
    {
        printf( "(Virtual)I am alive[%d]!!!\n", Count);
    }
};

void main( void )
{
    pepe  P1;
    pepe2 P2;

    P1.Alive();
    P2.Alive();

    // Also can be use like this
    zeroclass( &P1, pepe  );
    zeroclass( &P2, pepe2 );

    P1.Alive();
    P2.Alive();
}