Maxim Yegorushkin wrote:
> [...]
>
> Why not just:
>
> if(level2 const* l2 = dynamic_cast<level2 const*>(&b))
> {
> // no need comparing typeinfo's
> }
>
> ?
I want to cast to a level 1 class which is a parent of several level 2
classes. Otherwise you are right - I could cast to the actual type directly.
The real code looks more like this:
if (typeid(b) == typeid(level2a) || typeid(b) == typeid(level2b) ||
typeid(b) == typeid(level2c))
{
const level1 *l1 = dynamic_cast<const level1*>(&b);
}
Class level1 is the parent of all the level2 classes. I have to check for
several types but don't need to write the same code then at least for all
the level2 classes.
>> It looks like a problem with g++. The code I was talking about is in
>> a shared library. When I link the executable statically dynamic_cast
>> works. When I use however the shared library dynamic_cast returns 0.
>> Same code but different behavior due to linking.
>>
>> There is a section "dynamic_cast, throw, typeid don't work with
>> shared libraries" at http://gcc.gnu.org/faq.html#dso.
>
> I wonder how you reached such a conclusion. Where on that page do they
> say it does not work?
The title is pretty clear I think: "dynamic_cast,throw, typeid don't work
with shared libraries". :-) They are talking about template instantiations,
vague linkage, not an exhaustive list, namesspaces etc. This all doesn't
sound like adding a linker switch fixes all your problems. This sounds like
be ready for all kind of problems.
Anyway if I can downcast to the actual type and then back to its parent with
the following code (no compilation error, no runtime error) why should a
dynamic_cast to the parent l1 not work?
if (typeid(b) == typeid(level2))
{
const level2 *l2 = dynamic_cast<const level2*>(&b);
const level1 *l1 = l2;
}
Boris
_______________________________________________
help-gplusplus mailing list
help-gplusplus@gnu.org
http://lists.gnu.org/mailman/listinfo/help-gplusplus
