Subject: Re: [boost] How to get the size of an C-array?
From: Andrey Semashev (andrey.semashev_at_[hidden])
Date: 2009-10-15 13:50:59
Mathias Gaunard wrote:
> vicente.botet wrote:
>
>> Can someone in this list explain why the standard don't allows to
>> recover the number of elements allocated by new[]? What is the deep
>> reason?
>
> I suppose the reason is to not introduce a distinction between types
> with destructors and types without.
>
> If this was to be provided, a meta-function to tell whether a type has a
> trivial destructor or not would be needed as well.
Why? From the underlying allocator point of view there's not much
difference in allocating memory for PODs and non-PODs.
My guess is that this is not possible in order to allow trivial
implementation of new/delete allocators in terms of malloc/free. The
latter don't allow to acquire the size of allocated buffer, so in order
to provide this ability for new/delete it would have to add its own
header to store the size, which would lead to more extensive memory
consumption. It's a pity that malloc/free allocator don't allow buffer
size acquisition, especially since the size is most likely stored somehow.