In deep copy

I need to do an in deep copy of a struct but I cant have distinct pointers for both my variables... here's some of the code:

Code:

---

TypeEl copieCarte(TypeEl e1, int *err)
{
        TypeEl e2;               
       
        e2 = initTypeEl(compareCarte,
                copieCarte,
                getValueCarte,
                setValueCarte,
                detruireCarte,
                err);

        e2.el = (Carte *)malloc(sizeof(Carte));

        if( e1.copie != copieCarte )  *err = NI;
        else if( e2.el == NULL )  *err = NEM;
        else
        {
                *err = OK;

                e2.el = e1.el;
        }
       
        return e2;
}

---

The structs referring to that code:

typedef enum {CHAR, INT, UNSIGNED, LONG, FLOAT, DOUBLE, LDOUBLE, STRING, OTHER} Types;

typedef struct sTypeEl TypeEl;

struct sTypeEl

{
void *el;

int (*compare)(TypeEl, TypeEl, int * err);
struct sTypeEl (*copie)(TypeEl, int *err);
Types (*getValue)(TypeEl, void *e, int *err);
Types (*setValue)(TypeEl *,void *e, int *err);
struct sTypeEl (*detruire)(TypeEl, int *err);

};

typedef struct
{
Kind kind;
Value value;
}Carte;


Any help/thoughts would be apreciated
thx

Quote:

---

Originally Posted by Belzebuts

Code:

---

TypeEl copieCarte(TypeEl e1, int *err)
{
        TypeEl e2;               
       
        e2 = initTypeEl(compareCarte,
                copieCarte,
                getValueCarte,
                setValueCarte,
                detruireCarte,
                err);

        e2.el = (Carte *)malloc(sizeof(Carte));

        if( e1.copie != copieCarte )  *err = NI;
        else if( e2.el == NULL )  *err = NEM;
        else
        {
                *err = OK;

                e2.el = e1.el;  /* pointer copy */
        }
       
        return e2;    /* structure return */
}

---

---

A thought --

In the highlighted code, you're replacing the poiinter to the Carte that you just allocated with the pointer contained in the original (e1) instance, thus defeating your deep copy *and* creating a memory leak (the newly allocated Carte is lost).

You're probably looking to do a structure copy, which can be expressed, in your case, as

Code:

---

*e2.el = *e1.el;  /* structure copy */

---

assuming that your compiler supports structure copies. If it does not, you can always use

Code:

---

memcpy(e2.el, e1.el, sizeof(Carte));

---

I recommend that you always put a comment in the code someplace that points out that you're doing structure passing, copy, and return. Believe it or not, not all compilers support these features. Also, many experienced C programmers avoid these operations (especially structure passing and structure return) because they can be quite inefficient.