Re: [boost] Re: dangerous_cast<>

From: Gabriel Dos Reis (gdr_at_[hidden])
Date: 2002-12-04 15:41:16

"David B. Held" <dheld_at_[hidden]> writes:

| "Gabriel Dos Reis" <gdr_at_[hidden]> wrote in message
| news:m38yz5pp08.fsf_at_uniton.integrable-solutions.net...
| > [...]
| > What do mean exactly by a "valid Foo*"?
| 
| Hmm...I think 5.2.10/7 is more relevant.  I guess it depends on what
| "unspecified" means.  I assumed that it meant that you have a Foo*,
| but it might not point to an actual Foo.

OK, now, let's recall the original construct 

    template <class T>
    struct holder
    {
       union {
          aligned_POD<T>::type aligner;
          char storage[sizeof(T)];
       };
    };

the Standard makes no guarantee that you do the conversion

   char* -> void* -> T*

on &h.storage[0] and have a usuable T*.

-- Gaby