LWG-3417: Deprecate volatile atomic inc/dec and wait/notify operations

[Shengxin Pei (TPPPP72)]

Resolves LWG 3417 (Missing volatile atomic deprecations) adding deprecation checks to volatile atomic increment/decrement operators as well as wait/notify operations when is_always_lock_free is false.

Close #6312

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[Shengxin Pei (TPPPP72)]

@microsoft-github-policy-service agree

[Copilot]

Pull request overview

Implements LWG 3417 by completing conditional deprecation checks for volatile atomic operations.

Changes:

• Adds checks for volatile increment/decrement and wait/notify operations.
• Adds and registers coverage across supported language modes.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
stl/inc/atomic	Adds conditional deprecation checks.
tests/std/tests/P1831R1_deprecated_volatile_atomic/test.cpp	Exercises affected operations.
tests/std/tests/P1831R1_deprecated_volatile_atomic/env.lst	Configures the test matrix.
tests/std/test.lst	Registers the test.

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[A. Jiang (frederick-vs-ja)]

I strongly doubt whether this test file makes any sense. At least, it certainly isn't verifying deprecation at this moment.

IIUC, MSVC STL hasn't been verifying deprecation messages in its test suite.

[Alex Guteniev (AlexGuteniev)]

It tests deprecation silencing, i.e. that these functions can be made back available as for now.

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated no new comments.

Suppressed comments (1)

tests/std/tests/P1831R1_deprecated_volatile_atomic/test.cpp:31

• These calls only use atomic<int> (and below, atomic<int*>), both of which are always lock-free in this implementation. Therefore _Deprecate_non_lock_free_volatile<_Ty, false> is never selected, so the test does not exercise the newly added wait/notify deprecation path or its suppression. Please also instantiate these operations with a guaranteed non-lock-free trivially copyable type.

    volatile atomic<int> ai{0};
    ai.notify_one();
    ai.notify_all();
    ai.wait(1);