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### 3274. Missing feature test macro for `<span>`

Section: 17.3.1 [support.limits.general] Status: C++20 Submitter: Jonathan Wakely Opened: 2019-09-05 Last modified: 2021-02-25

Priority: 0

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Discussion:

There is no feature test macro for `std::span`.

For the purposes of SD-6, I think we want two values: `201803L` for the original addition of `<span>` by P0122R7 (Jacksonville, 2018) and then `201902L` for the API changes from P1024R3 (Kona, 2019). The C++ working draft only needs the newer value.

[2019-09-24 Issue Prioritization]

Status to Tentatively Ready and priority to 0 after eight positive votes on the reflector.

Proposed resolution:

This wording is relative to N4830.

1. Modify the Table 36 "Standard library feature-test macros" [tab:support.ft] in 17.3.1 [support.limits.general] as indicated:

   > Table 36: Standard library feature-test macros [tab:support.ft]
   > Macro name | Value | Header(s)
   > --- | --- | ---
   > `[…]`
   > `__cpp_lib_span` | `201902L` | `<span>`
   > `[…]`