C++ inherited classes

[Werner LEMBERG]

This is a question about gdb 4.18 and g++ 2.95.2.

Consider the following small input file:

  class node
  {
    int node_value;
  };

  class xxx_node : public node
  {
    int xxx_node_value;
  };


  int
  main(void)
  {
    node *n;
    xxx_node xxx;

    n = &xxx;
  }

I compiled the program with `g++ -Wall -g -O0 -o zz zz.cc'.  Running
`gdb zz' yields

  (gdb) tb main
  Breakpoint 1 at 0x80483e6: file zz.cc, line 18.
  (gdb) r
  Starting program: /usr/local/home/ft/a/zz 
  main () at zz.cc:18
  18        n = &xxx;
  (gdb) set args
  (gdb) n
  19      }
  (gdb) p n
  $1 = (node *) 0xbffff7b0
  (gdb) p *n
  $2 = {node_value = 1074869784}
  (gdb) p *(xxx_node *)n
  $3 = {<node> = {node_value = 1074869784}, xxx_node_value = 0}
  (gdb) set print object on
  (gdb) p n
  $4 = (node * ?) 0xbffff7b0
  (gdb) p *n
  $5 = {node_value = 1074869784}
  (gdb) p *(xxx_node *)n
  $6 = (node ?) {node_value = 1074869784}
  (gdb)

Now my question: Why do I get (node * ?) in $4 and not (xxx_node *)?
And $6 looks like a real bug to me... Am I doing something
fundamentally wrong or am I missing something?  Or is my gdb/g++
version too old?


    Werner