Issue 2210: Missing allocator-extended constructor for allocator-aware containers

Title: Missing allocator-extended constructor for allocator-aware containers
Status: c++14
Section: [sequences] [associative] [unord]
Submitter: Jonathan Wakely

Created on 2012-11-01.00:00:00 last changed 130 months ago

Messages

Date: 2013-04-18.22:58:13

Proposed resolution:

This wording is relative to N3485.

Edit the synopsis in [deque.overview]/2:

namespace std {
  template <class T, class Allocator = allocator<T> >
  class deque {
  public:
    […]
    explicit deque(const Allocator& = Allocator());
    explicit deque(size_type n, const Allocator& = Allocator());
    […]
  };
}

Edit [deque.cons]/2:
```
explicit deque(size_type n, const Allocator& = Allocator());
```
-3- Effects: Constructs a deque with n default-inserted elements using the specified allocator.

Edit the synopsis in [forwardlist.overview]/3:

namespace std {
  template <class T, class Allocator = allocator<T> >
  class forward_list {
  public:
    […]
    explicit forward_list(const Allocator& = Allocator());
    explicit forward_list(size_type n, const Allocator& = Allocator());
    […]
  };
}

Edit [forwardlist.cons]/3:
```
explicit forward_list(size_type n, const Allocator& = Allocator());
```
-3- Effects: Constructs a forward_list object with n default-inserted elements using the specified allocator.

Edit the synopsis in [list.overview]/2:

namespace std {
  template <class T, class Allocator = allocator<T> >
  class list {
  public:
    […]
    explicit list(const Allocator& = Allocator());
    explicit list(size_type n, const Allocator& = Allocator());
    […]
  };
}

Edit [list.cons]/3:
```
explicit list(size_type n, const Allocator& = Allocator());
```
-3- Effects: Constructs a list with n default-inserted elements using the specified allocator.

Edit the synopsis in [vector.overview]/2:

namespace std {
  template <class T, class Allocator = allocator<T> >
  class vector {
  public:
    […]
    explicit vector(const Allocator& = Allocator());
    explicit vector(size_type n, const Allocator& = Allocator());
    […]
  };
}

Edit [vector.cons]/3:
```
explicit vector(size_type n, const Allocator& = Allocator());
```
-3- Effects: Constructs a vector with n default-inserted elements using the specified allocator.

Edit the synopsis in [vector.bool]/1:

namespace std {
  template <class Allocator> class vector<bool, Allocator> {
  class vector {
  public:
    […]
    explicit vector(const Allocator& = Allocator());
    explicit vector(size_type n, const Allocator& = Allocator());
    explicit vector(size_type n, const bool& value = bool(),
                    const Allocator& = Allocator());
    […]
  };
}

Add to the synopsis in [map.overview] p2:

namespace std {
  template <class Key, class T, class Compare = less<Key>,
    class Allocator = allocator<pair<const Key, T> > > {
  class map {
  public:
    […]
    map(initializer_list<value_type>,
      const Compare& = Compare(),
      const Allocator& = Allocator());
    template <class InputIterator>
    map(InputIterator first, InputIterator last, const Allocator& a)
      : map(first, last, Compare(), a) { }
    map(initializer_list<value_type> il, const Allocator& a)
      : map(il, Compare(), a) { }
    ~map();
    […]
  };
}

Add to the synopsis in [multimap.overview] p2:

namespace std {
  template <class Key, class T, class Compare = less<Key>,
    class Allocator = allocator<pair<const Key, T> > > {
  class multimap {
  public:
    […]
    multimap(initializer_list<value_type>,
      const Compare& = Compare(),
      const Allocator& = Allocator());
    template <class InputIterator>
    multimap(InputIterator first, InputIterator last, const Allocator& a)
      : multimap(first, last, Compare(), a) { }
    multimap(initializer_list<value_type> il, const Allocator& a)
      : multimap(il, Compare(), a) { }
    ~multimap();
    […]
  };
}

Add to the synopsis in [set.overview] p2:

namespace std {
  template <class Key, class Compare = less<Key>,
    class Allocator = allocator<Key> > {
  class set {
  public:
    […]
    set(initializer_list<value_type>,
      const Compare& = Compare(),
      const Allocator& = Allocator());
    template <class InputIterator>
    set(InputIterator first, InputIterator last, const Allocator& a)
      : set(first, last, Compare(), a) { }
    set(initializer_list<value_type> il, const Allocator& a)
      : set(il, Compare(), a) { }
    ~set();
    […]
  };
}

Add to the synopsis in [multiset.overview] p2:

namespace std {
  template <class Key, class Compare = less<Key>,
    class Allocator = allocator<Key> > {
  class multiset {
  public:
    […]
    multiset(initializer_list<value_type>,
      const Compare& = Compare(),
      const Allocator& = Allocator());
    template <class InputIterator>
    multiset(InputIterator first, InputIterator last, const Allocator& a)
      : multiset(first, last, Compare(), a) { }
    multiset(initializer_list<value_type> il, const Allocator& a)
      : multiset(il, Compare(), a) { }
    ~multiset();
    […]
  };
}

Add to the synopsis in [unord.map.overview] p3:

namespace std {
  template <class Key, class T,
    class Hash = hash<Key>,
    class Pred = std::equal_to<Key>,
    class Allocator = std::allocator<std::pair<const Key, T> > > {
  class unordered_map {
  public:
    […]
    unordered_map(initializer_list<value_type>,
      size_type = see below,
      const hasher& hf = hasher(),
      const key_equal& eql = key_equal(),
      const allocator_type& a = allocator_type());
    unordered_map(size_type n, const allocator_type& a)
      : unordered_map(n, hasher(), key_equal(), a) { }
    unordered_map(size_type n, const hasher& hf, const allocator_type& a)
      : unordered_map(n, hf, key_equal(), a) { }
    template <class InputIterator>
      unordered_map(InputIterator f, InputIterator l, size_type n, const allocator_type& a)
      : unordered_map(f, l, n, hasher(), key_equal(), a) { }
    template <class InputIterator>
      unordered_map(InputIterator f, InputIterator l, size_type n, const hasher& hf, 
	    const allocator_type& a)
      : unordered_map(f, l, n, hf, key_equal(), a) { }
    unordered_map(initializer_list<value_type> il, size_type n, const allocator_type& a)
      : unordered_map(il, n, hasher(), key_equal(), a) { }
    unordered_map(initializer_list<value_type> il, size_type n, const hasher& hf, 
	  const allocator_type& a)
      : unordered_map(il, n, hf, key_equal(), a) { }
    ~unordered_map();
    […]
  };
}

Add to the synopsis in [unord.multimap.overview] p3:

namespace std {
  template <class Key, class T,
    class Hash = hash<Key>,
    class Pred = std::equal_to<Key>,
    class Allocator = std::allocator<std::pair<const Key, T> > > {
  class unordered_multimap {
  public:
    […]
    unordered_multimap(initializer_list<value_type>,
      size_type = see below,
      const hasher& hf = hasher(),
      const key_equal& eql = key_equal(),
      const allocator_type& a = allocator_type());
    unordered_multimap(size_type n, const allocator_type& a)
      : unordered_multimap(n, hasher(), key_equal(), a) { }
    unordered_multimap(size_type n, const hasher& hf, const allocator_type& a)
      : unordered_multimap(n, hf, key_equal(), a) { }
    template <class InputIterator>
      unordered_multimap(InputIterator f, InputIterator l, size_type n, const allocator_type& a)
      : unordered_multimap(f, l, n, hasher(), key_equal(), a) { }
    template <class InputIterator>
      unordered_multimap(InputIterator f, InputIterator l, size_type n, const hasher& hf, 
	    const allocator_type& a)
      : unordered_multimap(f, l, n, hf, key_equal(), a) { }
    unordered_multimap(initializer_list<value_type> il, size_type n, const allocator_type& a)
      : unordered_multimap(il, n, hasher(), key_equal(), a) { }
    unordered_multimap(initializer_list<value_type> il, size_type n, const hasher& hf, 
	  const allocator_type& a)
      : unordered_multimap(il, n, hf, key_equal(), a) { }
    ~unordered_multimap();
    […]
  };
}

Add to the synopsis in [unord.set.overview] p3:

namespace std {
  template <class Key,
    class Hash = hash<Key>,
    class Pred = std::equal_to<Key>,
    class Allocator = std::allocator<Key> > {
  class unordered_set {
  public:
    […]
    unordered_set(initializer_list<value_type>,
      size_type = see below,
      const hasher& hf = hasher(),
      const key_equal& eql = key_equal(),
      const allocator_type& a = allocator_type());
    unordered_set(size_type n, const allocator_type& a)
      : unordered_set(n, hasher(), key_equal(), a) { }
    unordered_set(size_type n, const hasher& hf, const allocator_type& a)
      : unordered_set(n, hf, key_equal(), a) { }
    template <class InputIterator>
      unordered_set(InputIterator f, InputIterator l, size_type n, const allocator_type& a)
      : unordered_set(f, l, n, hasher(), key_equal(), a) { }
    template <class InputIterator>
      unordered_set(InputIterator f, InputIterator l, size_type n, const hasher& hf, 
	    const allocator_type& a)
      : unordered_set(f, l, n, hf, key_equal(), a) { }
    unordered_set(initializer_list<value_type> il, size_type n, const allocator_type& a)
      : unordered_set(il, n, hasher(), key_equal(), a) { }
    unordered_set(initializer_list<value_type> il, size_type n, const hasher& hf, 
	  const allocator_type& a)
      : unordered_set(il, n, hf, key_equal(), a) { }
    ~unordered_set();
    […]
  };
}

Add to the synopsis in [unord.multiset.overview] p3:

namespace std {
  template <class Key,
    class Hash = hash<Key>,
    class Pred = std::equal_to<Key>,
    class Allocator = std::allocator<Key> > {
  class unordered_multiset {
  public:
    […]
    unordered_multiset(initializer_list<value_type>,
      size_type = see below,
      const hasher& hf = hasher(),
      const key_equal& eql = key_equal(),
      const allocator_type& a = allocator_type());
    unordered_multiset(size_type n, const allocator_type& a)
      : unordered_multiset(n, hasher(), key_equal(), a) { }
    unordered_multiset(size_type n, const hasher& hf, const allocator_type& a)
      : unordered_multiset(n, hf, key_equal(), a) { }
    template <class InputIterator>
      unordered_multiset(InputIterator f, InputIterator l, size_type n, const allocator_type& a)
      : unordered_multiset(f, l, n, hasher(), key_equal(), a) { }
    template <class InputIterator>
      unordered_multiset(InputIterator f, InputIterator l, size_type n, const hasher& hf, 
	    const allocator_type& a)
      : unordered_multiset(f, l, n, hf, key_equal(), a) { }
    unordered_multiset(initializer_list<value_type> il, size_type n, const allocator_type& a)
      : unordered_multiset(il, n, hasher(), key_equal(), a) { }
    unordered_multiset(initializer_list<value_type> il, size_type n, const hasher& hf, 
	  const allocator_type& a)
      : unordered_multiset(il, n, hf, key_equal(), a) { }
    ~unordered_multiset();
    […]
  };
}

msg6425 (view)

Date: 2013-04-15.00:00:00

[ 2013-04-18, Bristol ]

msg6233 (view)

Date: 2013-03-15.00:00:00

[ 2013-03-15 Issues Teleconference ]

Moved to Review.

Jonathan: There are lots of places where this is missing.

Howard: We should ping Pablo, this might be a deliberate design decision.

msg6232 (view)

Date: 2012-12-17.21:46:53

The forward_list(size_type) constructor has no allocator-extended equivalent, preventing the following code from compiling:

#include <forward_list>
#include <vector>
#include <scoped_allocator>

using namespace std;

int main()
{
  using list = forward_list<int>;
  vector<list, scoped_allocator_adaptor<list::allocator_type>> v;
  v.emplace_back(1u);
}

The very same problem exists for all allocator-aware sequence containers.

In addition it exists for associative containers. For example, it's possible to construct std::set<int>{0, 1, 2} but not std::set<int>{{0, 1, 2}, alloc}, and possible to construct std::set<int>{begin, end} but not std::set<int>{begin, end, alloc}.

This makes the following program fail when SCOPED is defined:

#include <set>
#include <vector>
#include <scoped_allocator>

#if SCOPED
using A = std::scoped_allocator_adaptor<std::allocator<int>>;
#else
using A = std::allocator<int>;
#endif

int main()
{
  int values[] = {0, 1, 2};
  std::vector<std::set<int>, A> v;
  v.emplace_back(std::begin(values), std::end(values));
}

History
Date	User	Action	Args
2014-02-20 13:20:35	admin	set	status: wp -> c++14
2013-04-25 19:07:07	admin	set	status: voting -> wp
2013-04-19 21:44:50	admin	set	status: ready -> voting
2013-04-18 22:58:13	admin	set	messages: + msg6462
2013-04-18 22:58:13	admin	set	status: review -> ready
2013-03-18 14:33:00	admin	set	messages: + msg6425
2013-03-18 13:02:36	admin	set	status: new -> review
2012-11-01 22:07:51	admin	set	messages: + msg6233
2012-11-01 00:00:00	admin	create