Design Behavior of auto_ptr, unique_ptr and shared_ptr for arrays

Question

while understanding about auto_ptr, unique_ptr and shared_ptr I came to know that auto_ptr destructor uses delete, not delete[] where as unique_ptr does handle it properly.

auto_ptr<char> aptr(new char[100]);
unique_ptr<char []> uptr(new char[100]);

Anyhow auto_ptr is deprecated in c++11.And I know unique_ptr has much more functionality than auto_ptr. I have two questions related to this behavior

a) Why while designing behavior for auto_ptr by c++ standard library team has not considered it's disadvantages for arrays.

b) Also even though shared_ptr introduced in c++11 why it's implementation doesn't support deleting of array?

possible duplicate of Why isn't there a std::shared_ptr<T[]> specialisation? — Niko
– Niko, Commented May 11, 2013 at 13:31
You shouldn't be dealing with plain arrays in the first place. you can use a smart pointer to a std::array or a std::vector or a container of your choice. — stefan
– stefan, Commented May 11, 2013 at 13:36

Mike Seymour · Accepted Answer · 2013-05-11 13:40:47Z

5

Why while designing behavior for auto_ptr by c++ standard library team has not considered it's disadvantages for arrays.

I can't comment on why auto_ptr wasn't very well designed; I can only observe that it wasn't, which is why it's now deprecated. It's not really worth worrying about; just pretend it never existed.

Also even though shared_ptr introduced in c++11 why it's implementation doesn't support deleting of array?

It supports arbitrary deleters, so you can do that; just slightly less conveniently than with unique_ptr:

std::shared_ptr<int> p(new int[42], std::default_delete<int[]>());

answered May 11, 2013 at 13:40

Mike Seymour

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Scott Jones · Accepted Answer · 2013-05-11 13:36:25Z

2

Here is a good read on the tortured history of auto_ptr: http://www.aristeia.com/BookErrata/auto_ptr-update.html. The truth is, until rvalue references were invented, there was little hope of designing a bullet proof smart pointer with exception safety for standard containers.

answered May 11, 2013 at 13:36

Scott Jones

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