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2081.Allocator requirements should includeCopyConstructible

Section: 16.4.4.6[allocator.requirements]Status:C++14Submitter: Jonathan WakelyOpened: 2011-08-30Last modified: 2016-01-28

Priority:Not Prioritized

View otheractive issues in [allocator.requirements].

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Discussion:

As discussed in c++std-lib-31054 and c++std-lib-31059, theAllocatorrequirements implicitly requireCopyConstructible becausea.select_on_container_copy_construction() andcontainer.get_allocator() both return a copy by value, but therequirement is not stated explicitly anywhere.

In order to clarify that allocators cannot have 'explicit' copyconstructors, the requirements should includeCopyConstructible.

[2012, Kona]

Move to Ready.

[2012, Portland: applied to WP]

Proposed resolution:

This wording is relative to the FDIS.

1. Change Table 28 — Allocator requirements in 16.4.4.6[allocator.requirements]:

   Table 28 — Allocator requirements

   Expression	Return type	Assertion/note pre-/post-condition	Default
   X a1(a); X a1 = a;		Shall not exit via an exception. post:a1 == a
   …
   X a1(move(a)); X a1 = move(a);		Shall not exit via an exception. post:a1 equals the prior value ofa.

2. Change 16.4.4.6[allocator.requirements] paragraph 4:

   An allocator typeX shall satisfy the requirements ofCopyConstructible (16.4.4.2[utility.arg.requirements]). TheX::pointer,X::const_pointer,X::void_pointer, andX::const_void_pointer types shall satisfy the requirements ofNullablePointer (16.4.4.4[nullablepointer.requirements]). No constructor, comparison operator, copy operation, move operation, or swap operation on these types shall exit via an exception.X::pointer andX::const_pointer shall also satisfy the requirements for a random access iterator (24.3[iterator.requirements]).