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Section: 20.3.1.3.2 [unique.ptr.single.ctor] Status: Resolved Submitter: Howard Hinnant Opened: 2009-04-25 Last modified: 2016-01-28
Priority: Not Prioritized
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Discussion:
Message c++std-lib-23182 led to a discussion in which several people expressed interest in being able to convert an auto_ptr to a unique_ptr without the need to call release. Below is wording to accomplish this.
[ Batavia (2009-05): ]
Pete believes it not a good idea to separate parts of a class's definition. Therefore, if we do this, it should be part of unique-ptr's specification.
Alisdair believes the lvalue overload may be not necessary.
Marc believes it is more than just sugar, as it does ease the transition to unique-ptr.
We agree with the resolution as presented. Move to Tentatively Ready.
[ 2009-07 Frankfurt ]
Moved from Tentatively Ready to Open only because the wording needs to be tweaked for concepts removal.
[ 2009-08-01 Howard deconceptifies wording: ]
I also moved the change from 99 [depr.auto.ptr] to 20.3.1.3 [unique.ptr.single] per the Editor's request in Batavia (as long as I was making changes anyway). Set back to Review.
[ 2009-10 Santa Cruz: ]
Move to Ready.
[ 2010-03-14 Howard adds: ]
We moved N3073 to the formal motions page in Pittsburgh which should obsolete this issue. I've moved this issue to NAD Editorial, solved by N3073.
Rationale:
Solved by N3073.
Proposed resolution:
Add to 20.3.1.3 [unique.ptr.single]:
template <class T, class D>
class unique_ptr
{
public:
template <class U>
unique_ptr(auto_ptr<U>& u);
template <class U>
unique_ptr(auto_ptr<U>&& u);
};
Add to 20.3.1.3.2 [unique.ptr.single.ctor]:
template <class U> unique_ptr(auto_ptr<U>& u); template <class U> unique_ptr(auto_ptr<U>&& u);Effects: Constructs a unique_ptr with u.release().
Postconditions: get() == the value u.get() had before the construciton, modulo any required offset adjustments resulting from the cast from U* to T*. u.get() == nullptr.
Throws: nothing.
Remarks: U* shall be implicitly convertible to T* and D shall be the same type as default_delete<T>, else these constructors shall not participate in overload resolution.