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### 3437. `__cpp_lib_polymorphic_allocator` is in the wrong header

Section: 17.3.2 [version.syn] Status: WP Submitter: Jonathan Wakely Opened: 2020-04-29 Last modified: 2020-11-09

Priority: 0

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Discussion:

17.3.2 [version.syn] says that `__cpp_lib_polymorphic_allocator` is also defined in `<memory>`, but `std::polymorphic_allocator` is defined in `<memory_resource>`. This seems like an error in P1902R1. The macro should be in the same header as the feature it relates to.

[2020-05-09; Reflector prioritization]

Set status to Tentatively Ready after six votes in favour during reflector discussions.

[2020-11-09 Approved In November virtual meeting. Status changed: Tentatively Ready → WP.]

Proposed resolution:

This wording is relative to N4861.

1. Modify 17.3.2 [version.syn] as indicated:

   >     […]
   >     #define __cpp_lib_parallel_algorithm    201603L // also in <algorithm>, <numeric>
   >     #define __cpp_lib_polymorphic_allocator 201902L // also in <memorymemory_resource>
   >     #define __cpp_lib_quoted_string_io      201304L // also in <iomanip>
   >     […]