Fix some _GLIBCXX_DEBUG pretty printer errors

[François Dumont]

On 06/03/2018 22:21, Jonathan Wakely wrote:
>
>> @@ -575,10 +586,12 @@ class StdDebugIteratorPrinter:
>>      # and return the wrapped iterator value.
>>      def to_string (self):
>>          base_type = gdb.lookup_type('__gnu_debug::_Safe_iterator_base')
>> +        itype = self.val.type.template_argument(0)
>>          safe_seq = self.val.cast(base_type)['_M_sequence']
>> -        if not safe_seq or self.val['_M_version'] != safe_seq['_M_version']:
>> +        if not safe_seq:
>> +            return str(self.val.cast(itype))
> So what's the effect of this change when we get a value-initialized
> debug iterator? It prints the wrapped (value-initialized) non-debug
> iterator instead?
>
Yes, for instance this test in smiple11.cc:


 Â  std::deque<int>::iterator deqiter0;
// { dg-final { note-test deqiter0 {non-dereferenceable iterator for 
std::deque} } }

 Â Â Â  Was failing when running 'make check-debug 
RUNTESTFLAGS=prettyprinters.exp' because it was displaying 'invalid 
iterator' rather than non-dereferenceable. Now it is succeeded.

François