[python][rfc] Attempt to print the base class if a there is no Python pretty-printer for a derived class.

[Phil Muldoon]

Pedro Alves wrote:
> On Friday 27 March 2009 17:50:39, Tom Tromey wrote:
>   
>> Pedro> Does this do sensible things if class Y has some
>> Pedro> fields that mask the Base class's ones, when you only have a
>> Pedro> pretty printer for Base?
>>
>> Yeah... it pretty-prints Base, then goes on to print the subclass
>> fields as usual (perhaps pretty-printing them as well).
>>     
>
> Okay, I was concerned if the pretty printer for Base would
> access Y::x instead of Base::x
It is a printer for Base, but that does not mean it will print out the 
Base values. Take this example:

class Base : public std::tr1::unordered_map<int, char *>
{
public:
  std::tr1::unordered_map<int, char *> map;

  Base ()
  {
    map[1]="Base";
  }
};

class Derived : public Base
{
public:
  std::tr1::unordered_map<int, char *> map;

  Derived ()
  {
    map[1]="Derived";
  }
};

If you instantiate Derived and print it with the patch, you will get:

(pg-gdb) python import gdb.libstdcxx.v6.printers
(pg-gdb) p derived
$2 = {
  <Base> = std::tr1::unordered_map with 0 elements,
  members of Derived:
  map = std::tr1::unordered_map with 1 elements = {
    [1] = 0x403952 "Derived"
  }
}


Regards

Phil
Phil