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4557. Remove constexpr from owner_less and owner_before

Section: 20.3.2.2.6 [util.smartptr.shared.obs], 20.3.2.3.6 [util.smartptr.weak.obs], 20.3.2.4 [util.smartptr.ownerless] Status: Immediate Submitter: Tim Song Opened: 2026-03-25 Last modified: 2026-03-25

Priority: Not Prioritized

View all other issues in [util.smartptr.shared.obs].

View all issues with Immediate status.

Discussion:

Addresses US 75-138

LEWG decided to remove constexpr from owner_before and owner_less.

[Croydon 2026-03-25; move to Immediate.]

Proposed resolution:

This wording is relative to N5032.

1. Modify 20.3.2.2.1 [util.smartptr.shared.general], class template shared_ptr synopsis, as indicated:

   namespace std {
     template<class T> class shared_ptr {
     public:
       […]
       template<class U>
         constexpr bool owner_before(const shared_ptr<U>& b) const noexcept;
       template<class U>
         constexpr bool owner_before(const weak_ptr<U>& b) const noexcept;
       size_t owner_hash() const noexcept;
       template<class U>
         constexpr bool owner_equal(const shared_ptr<U>& b) const noexcept;
       template<class U>
         constexpr bool owner_equal(const weak_ptr<U>& b) const noexcept;
     };
   
     […]
   }
   

2. Modify 20.3.2.2.6 [util.smartptr.shared.obs] as indicated:

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

   -19- […]

3. Modify 20.3.2.3.1 [util.smartptr.weak.general], class template weak_ptr synopsis, as indicated:

   namespace std {
     template<class T> class weak_ptr {
     public:
       […]
       template<class U>
         constexpr bool owner_before(const shared_ptr<U>& b) const noexcept;
       template<class U>
         constexpr bool owner_before(const weak_ptr<U>& b) const noexcept;
       size_t owner_hash() const noexcept;
       template<class U>
         constexpr bool owner_equal(const shared_ptr<U>& b) const noexcept;
       template<class U>
         constexpr bool owner_equal(const weak_ptr<U>& b) const noexcept;
     };
   
     […]
   }
   

4. Modify 20.3.2.3.6 [util.smartptr.weak.obs] as indicated:

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

   -4- […]

5. Modify 20.3.2.4 [util.smartptr.ownerless], class template owner_less synopsis, as indicated:

   namespace std {
     template<class T = void> struct owner_less;
   
     template<class T> struct owner_less<shared_ptr<T>> {
       constexpr bool operator()(const shared_ptr<T>&, const shared_ptr<T>&) const noexcept;
       constexpr bool operator()(const shared_ptr<T>&, const weak_ptr<T>&) const noexcept;
       constexpr bool operator()(const weak_ptr<T>&, const shared_ptr<T>&) const noexcept;
     };
   
     template<class T> struct owner_less<weak_ptr<T>> {
       constexpr bool operator()(const weak_ptr<T>&, const weak_ptr<T>&) const noexcept;
       constexpr bool operator()(const shared_ptr<T>&, const weak_ptr<T>&) const noexcept;
       constexpr bool operator()(const weak_ptr<T>&, const shared_ptr<T>&) const noexcept;
     };
   
     template<> struct owner_less<void> {
       template<class T, class U>
         constexpr bool operator()(const shared_ptr<T>&, const shared_ptr<U>&) const noexcept;
       template<class T, class U>
         constexpr bool operator()(const shared_ptr<T>&, const weak_ptr<U>&) const noexcept;
       template<class T, class U>
         constexpr bool operator()(const weak_ptr<T>&, const shared_ptr<U>&) const noexcept;
       template<class T, class U>
         constexpr bool operator()(const weak_ptr<T>&, const weak_ptr<U>&) const noexcept;
   
       using is_transparent = unspecified;
     };
   }