std::condit...variable_any(3)

💖 NAME 💖

std::condition_variable_any — the icon, the moment, the class. This is the std::condit...variable_any(3) page from the C++ Standard Library manual, and bestie, it’s giving synchronization with range 💅✨

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🦋 Synopsis 🦋

Defined in header <condition_variable>
class condition_variable_any;           (since C++11)

Okay so picture this: the condition_variable_any class is a generalization of std::condition_variable. Whereas std::condition_variable works only on std::unique_lock<std::mutex>, condition_variable_any can operate on any lock that meets the BasicLockable requirements. The way that’s lowkey a glow-up for custom lock types? Obsessed.

See std::condition_variable for the description of the semantics of condition variables — same condition-variable energy, just a more flexible lock situation ✨

The class std::condition_variable_any is a StandardLayoutType. It is not CopyConstructible, MoveConstructible, CopyAssignable, or MoveAssignable. No cap, it is not out here being copied or moved around.

vibe check: if the lock is std::unique_lock<std::mutex>, std::condition_variable may provide better performance. So don’t be fake about it — pick the one that fits your lock 💅

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🎀 Member functions 🎀

• constructor — constructs the object (public member function)
• destructor — destructs the object (public member function)
• operator= — not copy-assignable, [deleted] (public member function)

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🔔 Notification 🔔

• notify_one — notifies one waiting thread (public member function)
• notify_all — notifies all waiting threads (public member function)

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🌸 Waiting 🌸

• wait — blocks the current thread until the condition variable is awakened (public member function)
• wait_for — blocks the current thread until the condition variable is awakened or after the specified timeout duration (public member function)
• wait_until — blocks the current thread until the condition variable is awakened or until specified time point has been reached (public member function)

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🧚 Notes 🧚

std::condition_variable_any can be used with std::shared_lock in order to wait on a std::shared_mutex in shared ownership mode. Shared ownership mode and condition-variable waiting? It’s giving collaborative main character energy 🫶

A possible use for std::condition_variable_any with custom Lockable types is to provide convenient interruptible waits: the custom lock operation would both lock the associated mutex as expected, and also perform the necessary setup to notify this condition variable when the interrupting signal is received.^[1] iykyk — that’s the custom-lock interruptible-wait trick, and it ate.

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👑 See also 👑

• condition_variable — provides a condition variable associated with a std::unique_lock (C++11) (class)

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🌈 External links 🌈

1. ↑ Anthony Williams (2012, 1st ed./ 2019, 2nd ed.), “C++ Concurrency in Action”, 9.2.4 “Interrupting a wait on std::condition_variable_any”.

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Source/version/date tea ☕: http://cppreference.com, 2024.06.10, page std::condit...variable_any(3) — mwah, go forth and synchronize, bestie 💋✨