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Section: 18.104.22.168 [allocator.members] Status: CD1 Submitter: Martin Sebor Opened: 2006-05-17 Last modified: 2019-01-01
Priority: Not Prioritized
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The description of the allocator member function
allocate() requires that the hint argument be
either 0 or a value previously returned from
Footnote 227 further suggests that containers may pass the address of
an adjacent element as this argument.
I believe that either the footnote is wrong or the normative
requirement that the argument be a value previously returned from a
allocate() is wrong. The latter is supported by
the resolution to issue 20-004 proposed in c++std-lib-3736 by Nathan
Myers. In addition, the hint is an ordinary void* and not the
pointer type returned by
the two types potentially being incompatible and the requirement
impossible to satisfy.
See also c++std-lib-14323 for some more context on where this came up (again).
Remove the requirement in 22.214.171.124, p4 that the hint be a value
previously returned from
allocate(). Specifically, change
the paragraph as follows:
Requires: hint either 0 or previously obtained from member
allocate and not yet passed to member
The value hint may be used by an implementation to help improve performance
[Footnote: 223)In a container member function, the address of an adjacent element is often a good choice to pass for this argument.