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2083. const-qualification on weak_ptr::owner_before

Section: 20.3.2.3 [util.smartptr.weak], 20.3.2.3.6 [util.smartptr.weak.obs] Status: C++14 Submitter: Ai Azuma Opened: 2011-09-06 Last modified: 2016-01-28

Priority: Not Prioritized

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Discussion:

Is there any reason why weak_ptr::owner_before member function templates are not const-qualified?

Daniel Krügler:

I don't think so. To the contrary, without these to be const member function templates, the semantics of the specializations owner_less<weak_ptr<T>> and owner_less<shared_ptr<T>> described in 20.3.2.4 [util.smartptr.ownerless] is unclear.

It is amusing to note that this miss has remain undetected from the accepted paper n2637 on. For the suggested wording changes see below.

[2012, Kona]

Move to Ready.

[2012, Portland: applied to WP]

Proposed resolution:

This wording is relative to the FDIS.

1. Change the class template weak_ptr synopsis in 20.3.2.3 [util.smartptr.weak] as indicated:

   namespace std {
     template<class T> class weak_ptr {
     public:
       typedef T element_type;
       […]
       template<class U> bool owner_before(shared_ptr<U> const& b) const;
       template<class U> bool owner_before(weak_ptr<U> const& b) const;
     };
     […]
   }
   

2. Change the prototypes in 20.3.2.3.6 [util.smartptr.weak.obs] before p6 as indicated:

   template<class U> bool owner_before(shared_ptr<U> const& b) const;
   template<class U> bool owner_before(weak_ptr<U> const& b) const;