Joel de Guzman [EMAIL PROTECTED] wrote in message
news:[EMAIL PROTECTED]
David B. Held wrote:
Fernando Cacciola [EMAIL PROTECTED] wrote in message
news:[EMAIL PROTECTED]
[...]
I think I like this enhanced version.
'max_size_type_that_fit_in_padding'
must better be one of the intergral types
to make easy and safe to use, so I guess that
there might ocurr that some bits
are wasted anyway.
Why couldn't it be a char[]?
char[] makes sense. Add a tag_size constant int and we're
in business :-)
The reason why I discarded an array (or my problem with it, maybe)
is that it is difficult to get/set it because of
its semantics (array are not first class objects).
Furthermore, suppose there is no padding in a particular
implementation, how is the user supposed to allocate
the tag?
Of course, he can allocate it in its own structure, but he'll
need some awkward metaprogramming in such a case because
the tag will be either in the aligned_storage or somewhere
else.
I think that an usable solution, which might not exploit the
padding 100%, but which will be quite easy to use is this:
templateclass T, class tag_t
struct aligned_storage
{
void const* address() const ;
void* address();
// If tag_t fits in the padding, it is allocated there,
// else it is allocated separately (but in here)
tag_t const tag() const ;
tag_t tag();
}
Fernando Cacciola
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