Initializing a class using malloc ()

Question

How should a C ++ class be used when its memory is reserved from C malloc?

I use the C library (lua), and I need to open the C ++ class for it, in this case, so that the garbage collects these reserved spaces, lua makes a memory reservation.

Below is a simpler scenario:

#include <string>

class Clase{
private:
    std::string valor;
public:
    Clase(){}
    Clase(const std::string & valor) : valor(valor){}
    const std::string & get() const { return this->valor; }
    void set(const std::string & valor){ this->valor = valor;}
    ~Clase(){}
};

typedef struct
{
    Clase cls;
}Estructura;

int main(int argc, char ** argv)
{
    Estructura * est = (Estructura *) malloc(sizeof(Estructura));

    est->cls.set("Hola");   // First attempt

    Clase myCls;   // Second attempt
    est->cls = myCls;

    return 0;
}

I understand and verified that with malloc the class constructor is not called; which was expected, and therefore the copy (assign) statement cannot be called with an invalid instance (string inside the class). I suspect that the second attempt failed at the same point when copying a string inside an instance of the class.

So:

• Is it possible to correctly initialize an instance of a class in which memory is reserved by malloc?
• What other reservations exist ?, vtables?
• malloc ? ( , Clase , ? [ , ))

Clase Estructura, , ?

, , lua ?, __gc - ?

Answer 1

malloc new, . :

void *memory = malloc(sizeof(Estructura));

Estructura *est = new(memory)Estructura;

, - :

est->~Estructura();

, , vtables, , . , , free. delete , .