Gabriel Dos Reis <[EMAIL PROTECTED]> writes:
> David Abrahams <[EMAIL PROTECTED]> writes:
>
> | Gabriel Dos Reis <[EMAIL PROTECTED]> writes:
> |
> | > "David B. Held" <[EMAIL PROTECTED]> writes:
> | >
> | > | Does this have any merit whatsoever?
> | > |
> | > | template <typename T, typename U>
> | > | T* dangerous_cast(U* p)
> | > | {
> | > | return static_cast<T*>(static_cast<void*>(p));
> | > | }
> | >
> | > Is it any different from reinterpret_cast<T*>(p) ?
> |
> | It might be, depending on your compiler. The behavior of
> | reinterpret_cast<T*> is implementation-defined.
>
> The mapping used by reinterpret_cast<> is implementation defined,
> thus an implementation is required to document it.
>
> 1) Do you have any corresponding guarantee for converting a void* to
> T* when the source is *not* a T* nor the address obtained from a T?
>
> 2) Isn't the mapping U* -> void* -> T* at best
> implementation-defined if not undefined behaviour?
template <class T>
struct holder
{
union {
aligned_POD<T>::type aligner;
char storage[sizeof(T)];
};
};
holder<Foo> h;
new (h.storage) Foo;
...
T* u = dangerous_cast<T*>(h.storage); // can't do this with reinterpret_cast
HTH,
--
David Abrahams
[EMAIL PROTECTED] * http://www.boost-consulting.com
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