What are the memory_order flags in std::atomic?

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**memory_order** — controls the ordering guarantees of atomic operations. ```cpp std::atomic x{0}, y{0}; std::atomic z{0}; // relaxed — no ordering guarantees x.store(1, std::memory_order_relaxed); // release — previous writes visible to acquire x.store(1, std::memory_order_release); // acquire — sees writes before release if (y.load(std::memory_order_acquire) == 1) { // x.store(1) is guaranteed visible } // acq_rel — both acquire and release y.fetch_add(1, std::memory_order_acq_rel); // seq_cst — total order (default, strongest) z.store(1, std::memory_order_seq_cst); ``` **Orderings (weakest to strongest):** - relaxed — no synchronization. - consume — data dependency ordering (deprecated). - acquire — prevents reads/writes from moving before. - release — prevents reads/writes from moving after. - acq_rel — both. - seq_cst — total order. **Rule:** Use seq_cst unless you have a specific reason and proof of correctness.

C++: What are the memory_order flags in std::atomic?