[Bug debug/59161] GDB pretty printers: iterator->reference not printed

["redi at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59161

--- Comment #6 from Jonathan Wakely <redi at gcc dot gnu.org> ---
That seems quite arbitrary and inconsistent. In other contexts if I return a
gdb.Value it gets stringified as expected, e.g the
StdListPrinter._iterator.__next__ method does:

    return ('[%d]' % count, val)

where val is a gdb.Value, but gdb automatically converts that to a string via
something like: "%s = %s" % ('[%d]' % count, val) and so the gdb.Value is
converted properly.

But when a gdb.Value is returned directly the simplified form is used.

Returning gdb.Value directly is a documented part of the API:

https://sourceware.org/gdb/onlinedocs/gdb/Pretty-Printing-API.html

> Otherwise, if this method returns an instance of gdb.Value, then gdb prints this value.

And I can't see what possible use it is to print { ref = } for this object,
ever.

Paul's change is intended to suppress the address in his example at
https://sourceware.org/ml/gdb/2009-11/msg00105.html but by the reasoning above
he should have made his pretty-printer do:

    return str(self.val['whybother']['contents'])

Also, in his case he was getting the address *and* the string contents, but in
this reference example we *only* print the address, not the value. Suppressing
the address in that case seems undesirable.