"Eric Woodruff" <[EMAIL PROTECTED]> writes:
> "David B. Held" <[EMAIL PROTECTED]> wrote in message
> aslftb$cr2$[EMAIL PROTECTED]">news:aslftb$cr2$[EMAIL PROTECTED]...
>> "Eric Woodruff" <[EMAIL PROTECTED]> wrote in message
>> aslbsn$nt3$[EMAIL PROTECTED]">news:aslbsn$nt3$[EMAIL PROTECTED]...
>> > [snip]
>> >
>> > > holder<Foo> h;
>> > > new (h.storage) Foo;
>> >
>> > What is the meaning of that syntax?
>>
>> This is placement new syntax. It means construct a Foo at the address
>> h.storage, without allocating any memory.
>>
>
> So the type really is of Foo, which has to mean that casting h.storage back
> to a Foo* using reinterpret_cast is covered by the standard.
No, the standard only guarantees that you can do a round-trip
cast. The pointer didn't start out as a Foo*. The fact that it has the
same address as a Foo* doesn't mean anything. Just for example,
something like the following is a perverse but legal reinterpret_cast
implementation:
if is_pointer<source_type> and is_pointer<dest_type>
return (dest_type)(
(unisgned)src
^ sizeof(remove_pointer<source_type>::type)
^ sizeof(remove_pointer<dest_type>::type));
...
--
David Abrahams
[EMAIL PROTECTED] * http://www.boost-consulting.com
Boost support, enhancements, training, and commercial distribution
_______________________________________________
Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
