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3364. Initialize data members of ranges and their iterators

Section: 25.7.11.2 [range.take.while.view], 25.7.12.2 [range.drop.view], 25.7.13.2 [range.drop.while.view], 25.7.23.3 [range.elements.iterator] Status: C++20 Submitter: Johel Ernesto Guerrero Peña Opened: 2020-01-07 Last modified: 2021-02-25

Priority: 0

View all other issues in [range.take.while.view].

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Discussion:

Before P1035 was accepted, no data member in [ranges] whose type could potentially be an aggregate or fundamental type was left without initializer. P1035 left some such data members without initializer, so it is possible to have them have indeterminate values. We propose restoring consistency.

[2020-01-14 Status set to Tentatively Ready after five positive votes on the reflector.]

Proposed resolution:

This wording is relative to N4842.

1. Modify 25.7.11.2 [range.take.while.view] as follows:

   class take_while_view : public view_interface<take_while_view<V, Pred>> {
     template<bool> class sentinel;                      // exposition only
   
     V base_ = V();                                      // exposition only
     semiregular-box<Pred> pred_;                        // exposition only
   
   public:
   

2. Modify 25.7.12.2 [range.drop.view] as follows:

   private:
     V base_ = V();                                     // exposition only
     range_difference_t<V> count_ = 0;                  // exposition only
   };
   

3. Modify 25.7.13.2 [range.drop.while.view] as follows:

   private:
     V base_ = V();                                     // exposition only
     semiregular-box<Pred> pred_;                       // exposition only
   };
   

4. Modify 25.7.23.3 [range.elements.iterator] as follows:

   class elements_view<V, N>::iterator {                // exposition only
     using base-t = conditional_t<Const, const V, V>;
     friend iterator<!Const>;
   
     iterator_t<base-t> current_ = iterator_t<base-t>();
   public: