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### 3659. Consider `ATOMIC_FLAG_INIT` undeprecation

Section: D.26.5 [depr.atomics.flag] Status: SG1 Submitter: Aaron Ballman Opened: 2022-01-18 Last modified: 2022-01-22

Priority: 3

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Discussion:

P0883R2 deprecated `ATOMTIC_VAR_INIT` and `ATOMIC_FLAG_INIT` largely based on rationale from WG14. However, WG14 only deprecated `ATOMIC_VAR_INIT` because we were told by implementers that `ATOMIC_FLAG_INIT` is still necessary for some platforms (platforms for which "clear" is actually not all zero bits, which I guess exist).

I'd like to explore whether WG21 should undeprecate `ATOMIC_FLAG_INIT` as there was no motivation that I could find in the paper on the topic or in the discussion at P0883R0 [Jacksonville 2018].

One possible approach would be to undeprecate it from `<stdatomic.h>` only (C++ can still use the constructors from `<atomic>` and shared code can use the macros from `<stdatomic.h>`).

[2022-01-30; Reflector poll]

Set priority to 3 after reflector poll. Send to SG1.

Proposed resolution: