On Wed, Oct 13, 2010 at 3:16 PM, Steinar Bang <sb_at_dod.no> wrote:
>>>>>> "Hyrum K. Wright" <hyrum_wright_at_mail.utexas.edu>:
>> At this point, it's my turn to get confused. I'm speaking
>> specifically of cases where we return STL classes. Brane's earlier
>> suggestion to create an implicit bool conversion works fine for our
>> custom classes. The problem I'm trying to solve is "how does one
>> return the equivalent of '(const char *) NULL' in an std::string?"
>> It's a this point that pointers start coming into play, because a NULL
>> std::string * is quite feasible, whereas a NULL std::string isn't.
> Ah, ok. That was at a different part of the thread... which I avoided
> responding to because I have any good answers at hand. :-)
> Do you need the distrinction between an empty string and a NULL?
> If not then I would return an empty string for a NULL on the C side.
Yes, so that's a no-go.
> There's also the consideration that some std::string implementations are
> deep copying (the gcc version uses refcounting (or at least used to do
> so), but the VC++ one used to use deep copying. I'm not sure if that
> still is the case).
> Then maybe what you want to return is const std::string& (which leaves
> you with the headache of managing the life cycle of the std::string, so
> maybe not... though... you have the context of the wrapper class and
> could cache them lazily there. That would increase the footprint of the
> wrapper, though).
I don't want the caller to have to depend upon the lifetime of the
source object, hence the desire to return something by value or a
newly allocated pointer.
Additionally, it still wouldn't work, since references have to point
to some object, hence there is no such thing as a "null reference".
(This entire conversation is reminding my why I *hate* C++. To bad
there isn't too much of an alternative here... :/)
Received on 2010-10-13 23:47:55 CEST