C++: why a self pointer of a struct automatically changes to void*

Question

struct ptr{
    int node;
    ptr *next;
    ptr(){}
    ptr(int _node, ptr *_next){ node=_node; next=_next; }
};
struct list_t{
    ptr *sht;
    int size;
    void push(int node){
        size++;
        sht=new ptr(node,sht);
    }
}shthead[100001], comp[200001], tree[200001];

The struct ptr is used as a linked list. But when I debug the code in gdb, I found that the ptr*'s were all converted to void*.
GDB output:

(gdb) pt ptr
type = struct ptr {
    int node;
    void *next;
  public:
    ptr(void);
    ptr(int, void *);
}

However, I can still see the data of the struct if I covert them back to ptr* in gdb.
What's the reason for this please?

I'm using Arch Linux, GNOME, g++ 4.5.0, gdb 7.1. Without any compilation flags but a -g.
This GDB was configured as "i686-pc-linux-gnu"

Answer 1

Works fine for me on OS X.

(gdb) pt ptr
type = class ptr {
  public:
    int node;
    ptr *next;

    ptr(void);
    ptr(int, ptr *);
}

gdb version:

Shadow:code dkrauss$ gdb -v
GNU gdb 6.3.50-20050815 (Apple version gdb-1346) (Fri Sep 18 20:40:51 UTC 2009)
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This GDB was configured as "x86_64-apple-darwin".