Re: What are the differences between std::shared_ptr and boost::shared_ptr?
On 19 Sep., 11:31, Juha Nieminen wrote:
SG wrote:
Just to make sure: You are aware of the fact that it's possible to
implement std::make_shared so that make_shared<vector<int>> allocates
the reference counter and the vector in one go, right?
Yes, I'm completely aware of that. However, if you can allocate the
reference count (plus the other needed data by shared_ptr) in the same
memory block as the actual object being managed, the exact same thing
can be done with an array (instead of a single object). You just allocate
a memory block for the reference count plus what is needed for the array.
There's really not much difference.
So, what's your point? Should C++0x or C++1x offer something like
this?
So, unless you come up with a "juha::make_shared_array" template which
crams reference counter and array into the same memory block (so only
one allocation is needed), there is no improvement in terms of number
of allocations. As of now, Boost doesn't offer this kind of function
template.
Well, if the argument is "it's not possible to have reference-counted
arrays which use one single allocation with current implementations of
the C++ standard library or Boost",
I'm only saying I'm not aware of any such "shared_array"
implementation which works with only one allocation and that I don't
consider something like this to be a valuable addition to the standard
library. It would replicate much of std::vector<>'s interface without
being resizable just to save one allocation.
then you may be correct. That doesn't
mean it's impossible to do, of course.
I'm not saying that it's impossible. I'm just questioning its
usefulness given the possible alternatives.
Cheers!
SG