Thread: dereferencing a void *

i use a void pointer to point either one of two distinct class types.

say:

class x{...}
class y{...}

and

void *p;
x object1;
y object2;

p = (x *)&object1;


etc....
and somehow when i need to reach to one of object1's fields:
i want to use p to reach the object but
i receive

"attempt to dereference a generic pointer" error?
is there anybody who has faced this error before?
thanks in advance

yeah that was pretty much the same solution that i have tried
but it didn't work
you might be right about not using void * in C++

but does anyone has an advice to use what when i need to point two distict types via only one pointer.

(i'm implemeting a b+ tree and i need to point to internal nodes and leaf nodes with a unique type of pointer)

that's what i'm doing actually,
it's probably a property of C++ but i couldn't fix
let me be more informative:

class Int_Node{
public:
//internal node
vector<int> keys;
vector<void *> pointers;
};

class Leaf_Node{
public:
//leaf node
vector<int> records;
Int_Node *parent_node;
};

Leaf_Node bk2;
//......bk2 leaf has an internal node as the parent node
//then i want to reach the sibling leaf node

cout << ((Leaf_Node *)(bk2.parent_node->pointers[1]))->records[0];

//and this line of code gives the error
//i hope this code clearifies the problem

I can think of several solutions to your problem. What you are trying to do would be the first thing I would so as it is the easiest.

Example

Code:

int *i = new int;
char j[4] = "hi!!";

i = (int *)j; //casting a char array into an int pointer

//or for an object

struct a {
    int i;
};

struct b {
    char j[4];
    b() {
         std::memcpy(j, "hi!!", 4);
    }
};

a A;
b *B = (b *)&A;

((a *)b)->i = 6;

Get it? You may also want to make an abstract base class.

Quoting master5001
>int *i = new int;

Remember to delete...

delete i;

>char j[4] = "hi!!";

Needs to be five elements long for the terminating null

char* j = "hi!!";
char j[] = "hi!!";
char j[5] = "hi!!";

Thanks for clarifying that PolyOOP, That syntax can be used like a char array, but attempted modifications will have undefined results (most likely a seg fault).