Re: auto_ptr to char[]

From:

"Alf P. Steinbach" <alfps@start.no>

Newsgroups:

comp.lang.c++

Date:

Sun, 10 Feb 2008 18:39:10 +0100

Message-ID:

<13qudi6litlmc04@corp.supernews.com>

* Howard Hinnant:

In article <1202608309.31136.9.camel@maihem>,
Tristan Wibberley <maihem-nn1@maihem.org> wrote:

On Sat, 2008-02-09 at 19:36 -0500, Howard Hinnant wrote:

Fwiw, the current C++0X working paper
(http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2521.pdf) has
wording that will allow:

std::unique_ptr<char[]> my_data(new char[size]);
memcpy(my_data.get(), data, size);

will this work as expected in c++0x:

template<typename T>
std::unique_ptr<T> make_unique_ptr(T&& initval)
{
return std::unique_ptr<T> initval;
}

...
auto my_data = make_unique_ptr(new char[size]);
...

No. The problem is that new char[size] returns a char*, not a char[].

No, char[] would also lose crucial type information.

The problem is loss of associated type information.

A solution would have to provide a mechanism to pick up the otherwise
lost type information.

That could also solve the problem of detecting literals.

What was the proposed solution for detecting literals?

Therefore in make_unique_ptr T is deduced as char*. After that you'll
need unique_ptr<typename remove_pointer<T>::type> instead of
unique_ptr<T> to make things work (except for the array business).

If not, I wonder how many decades till they fix the whole auto_ptr
concept enough for the name of a class of that style to even appear in a
program without serious risk of totally invisible U/B.

We're open to suggestions and participation.

Cheers,

- Alf

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