On Thu, Apr 11, 2024 at 2:03 PM Frederick Virchanza Gotham via
Std-Proposals <std-proposals_at_[hidden]> wrote:

>
> Step 1 of implementing it is to be able to see all of the base classes
> of the Derived type at runtime having only its type_info. So I propose
> adding a new method called 'bases' to std::type_info. At first I
> thought this new method should return a pointer to a null-terminated
> array of pointers to type_info's, as follows:
>
> std::type_info const *const *type_info::bases(void) const noexcept;
>
> But Microsoft's array of type_info's isn't laid out the same way as
> Itanium's. So we need a special iterator to compensate for this,
> "class type_info_iterator", and so the method 'bases' returns a pair
> of iterators [first,last) to the type_info's of all the base classes.
> I've written it into my paper with implementations for Microsoft and
> Itanium:
>
> http://www.virjacode.com/papers/extend_type_info.htm
>
> And also implemented it on GodBolt:
>
> https://godbolt.org/z/fbTvbTK11
>

I think there is another option which might be simpler. A
`dynamic_upcast()` function where all the source type information is passed
at runtime would make implementing `any_upcast()` trivial. It's prototype
could be:

```
template<typename T> T* dynamic_upcast(void *ptr, const type_info& type);
```

My guess is that the implementation of such a function could reuse big
parts of the implementation of the preexisting dynamic_cast.

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