Re: std::make_shared creating a single block?
 

Am 21.11.2012 23:59, schrieb Andy Champ:
> I came across this reference:
>
> <http://en.cppreference.com/w/cpp/memory/shared_ptr/make_shared>
>
> "This function allocates memory for the T object and for the
> shared_ptr's control block with a single memory allocation. In contrast,
> the declaration std::shared_ptr<T> p(new T(Args...)) performs two memory
> allocations, which may incur unnecessary overhead."

As Luca said, it's encounraged, not required.

> The Microsoft compilers allocate two blocks for this, one for the
> control block and one for the object.

Are you really sure? If I remember correctly, Stephan T. Lavavej -- one
of Microsoft's C++ standard library devlopers -- explained how this
one-allocation trick works in one of his pubpicly available lecture
videos [1]. So, I'm surprized to read that you think Microsoft
implements make_shared to use two memory allocations.

Cheers!
SG

[1]
<http://channel9.msdn.com/shows/Going+Deep/C9-Lectures-Stephan-T-Lavavej-Standard-Template-Library-STL-3-of-n/>