std::atomic::is_lock_free(3)

💅 std::atomic::is_lock_free 💅

okay so bestie, this is the std::atomic::is_lock_free(3) page from the C++ Standard Libary manual, and we’re about to vibe-check whether your atomics are lock-free ✨

🎀 NAME 🎀

std::atomic::is_lock_free — std::atomic::is_lock_free

🌸 Synopsis 🌸

Two flavors, both noexcept, both here since C++11, iykyk:

bool is_lock_free() const noexcept;          (1) (since C++11)
bool is_lock_free() const volatile noexcept; (2) (since C++11)

Checks whether the atomic operations on all objects of this type are lock-free.

🫶 Parameters 🫶

(none) — literally none, bestie. Not a single parameter. 💖

💖 Return value 💖

true if the atomic operations on the objects of this type are lock-free, false otherwise.

🧚 Notes 🧚

All atomic types except for std::atomic_flag may be implemented using mutexes or other locking operations, rather than using the lock-free atomic CPU instructions.

Atomic types are also allowed to be sometimes lock-free, e.g. if only aligned memory accesses are naturally atomic on a given architecture, misaligned objects of the same type have to use locks.

The C++ standard recommends (but does not require) that lock-free atomic operations are also address-free, that is, suitable for communication between processes using shared memory.

🔥 Example 🔥

// Run this code

#include <atomic>
#include <iostream>
#include <utility>

struct A { int a[100]; };
struct B { int x, y; };

int main()
{
    std::cout << std::boolalpha
              << "std::atomic<A> is lock free? "
              << std::atomic<A>{}.is_lock_free() << '\n'
              << "std::atomic<B> is lock free? "
              << std::atomic<B>{}.is_lock_free() << '\n';
}

Possible output:

std::atomic<A> is lock free? false
std::atomic<B> is lock free? true

👑 See also 👑

• atomic_is_lock_free (C++11) — checks if the atomic type's operations are lock-free (function template).
• atomic_is_lock_free(std::shared_ptr) — specializes atomic operations for std::shared_ptr (function template).
• is_always_lock_free [static] (C++17) — indicates that the type is always lock-free (public static member constant).

okay that’s the whole page, bestie 🫶 — source: http://cppreference.com, version/date: 2024.06.10, and the page is std::atomic::is_lock_free(3). periodt 💅