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Section: 23.2.2.5 [container.alloc.reqmts] Status: New Submitter: Alisdair Meredith Opened: 2023-08-14 Last modified: 2025-10-16
Priority: 4
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Discussion:
Trying to interpret the specification for allocator-aware containers, 23.2.2.5 [container.alloc.reqmts].
P1 establishes thatstd::array is not an allocator-aware container, but all other containers in
the standard are.
P2 then adds vocabulary, with ruling that if a container type X is not allocator-aware then
the specification is as-if the allocator were std::allocator<T>. I cannot find a specification
for allocator-aware, and do not believe we should treat this as a recursive definition, as
the only standard container that would be affected would be std::array, which absolutely
does not want to apply all the terms in this subclause.
It looks like we might mean types that do not have everything specified by the first
sentence, such as an allocator_type member. Perhaps we want to say a container
type X is allocator-aware using allocator A if […], and then that basic_string and
containers that are not otherwise allocator aware are are treated as-if they were
allocator-aware using std::allocator<typename X::value_type> (where value_type
is already guaranteed to exist by the container requirements, 23.2.2.2 [container.reqmts] p1).
[2025-10-16; Reflector poll]
Set priority to 4 after reflector poll.
"NAD. 'If X is not allocator-aware' is equivalent to 'if X is not an allocate-aware container type'. Note that 23.2.2.5 [container.alloc.reqmts]/2 is not defining the requirements on an allocator-aware container; it's defining the related Cpp17Meow requirements. The allocator-aware container requirements are defined in paragraphs 3 and later, so this isn't a recursive definition."
Proposed resolution: