Issue 866: Qualification of placement new-expressions (original) (raw)

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866. Qualification of placement new-expressions

Section: 26.11 [specialized.algorithms], 20.3.2.2.7 [util.smartptr.shared.create] Status: C++11 Submitter: Alberto Ganesh Barbati Opened: 2008-07-14 Last modified: 2016-01-28

Priority: Not Prioritized

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Discussion:

LWG issue 402(i) replaced "new" with "::new" in the placement new-expression in 20.2.10.2 [allocator.members]. I believe the rationale given in 402(i) applies also to the following other contexts:

• in 26.11 [specialized.algorithms], all four algorithms unitialized_copy,unitialized_copy_n, unitialized_fill and unitialized_fill_n use the unqualified placement new-expression in some variation of the form:

  new (static_cast<void*>(&*result)) typename iterator_traits::value_type(*first);

• in 20.3.2.2.7 [util.smartptr.shared.create] there is a reference to the unqualified placement new-expression:

  new (pv) T(std::forward(args)...),

I suggest to add qualification in all those places. As far as I know, these are all the remaining places in the whole library that explicitly use a placement new-expression. Should other uses come out, they should be qualified as well.

As an aside, a qualified placement new-expression does not need additional requirements to be compiled in a constrained context. By adding qualification, the HasPlacementNew concept introduced recently inN2677 (Foundational Concepts)would no longer be needed by library and should therefore be removed.

[ San Francisco: ]

Detlef: If we move this to Ready, it's likely that we'll forget about the side comment about the HasPlacementNew concept.

[ post San Francisco: ]

Daniel: HasPlacementNew has been removed fromN2774 (Foundational Concepts).

Proposed resolution:

Replace "new" with "::new" in:

• 26.11.5 [uninitialized.copy], paragraphs 1 and 3
• 26.11.7 [uninitialized.fill] paragraph 1
• [uninitialized.fill.n] paragraph 1
• 20.3.2.2.7 [util.smartptr.shared.create] once in paragraph 1 and twice in paragraph 2.