std::atomic_flag::wait(3)

🦋 std::atomic_flag::wait(3) 🦋

okay so bestie, welcome to the C++ Standard Libary manual page for std::atomic_flag::wait — yes, the manual name is folded right in here, and the group chat is open. 💅✨

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🌸 NAME 🌸

std::atomic_flag::wait - std::atomic_flag::wait

literally the name is the same thing twice, and that's iconic. periodt. 👑

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✨ Synopsis ✨

void wait( bool old, std::memory_order order =
                         std::memory_order::seq_cst ) const
(1) (since C++20)
noexcept;
void wait( bool old, std::memory_order order =
                         std::memory_order::seq_cst ) const
(2) (since C++20)
volatile noexcept;

bestie, these are atomic waiting operations 😭 and the vibe is: it behaves as if it repeatedly does this little loop:

• Compare this->test(order) with that of old.
  • If those are equal, then blocks until *this is notified by notify_one() or notify_all(), or the thread is unblocked spuriously.
  • Otherwise, returns.

no cap: these functions are guaranteed to return only if value has changed, even if the underlying implementation unblocks spuriously. 🫶

🚨 okay bestie, important: if order is one of std::memory_order::release and std::memory_order::acq_rel, the behavior is undefined. not cute, not safe, undefined. 💀

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🎀 Parameters 🎀

• old — the value to check the atomic_flag's object no longer contains.
• order — memory order constraints to enforce.

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💖 Return value 💖

(none) — literally none, bestie. 🙈

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🧚 Notes 🧚

this form of change-detection is often more efficient than simple polling or pure spinlocks. ✨

due to the ABA problem, transient changes from old to another value and back to old might be missed, and not unblock. 😭 that's the tea.

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🍓 Example 🍓

so the Example section is literally incomplete bestie:

This section is incomplete Reason: no example

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🔥 See also 🔥

• notify_one — notifies at least one thread waiting on the atomic object. (C++20) (public member function)
• notify_all — notifies all threads blocked waiting on the atomic object. (C++20) (public member function)
• atomic_flag_notify_one — notifies a thread blocked in atomic_flag_wait. (C++20) (function)
• atomic_flag_notify_all — notifies all threads blocked in atomic_flag_wait. (C++20) (function)

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👑 Category 👑

• Todo no example — category tag: * Todo no example. slay, but also 😭.

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mwah 💋 — this page came from http://cppreference.com, version/date 2024.06.10, and it's std::atomic_flag::wait(3). that's the footer tea, periodt. 🫶🌈