Lesson 40: Atomic Operations (std::atomic)

Atomic Operations (std::atomic)\n\nstd::atomic provides lock‑free primitives for safe concurrent access to simple data types. They guarantee atomic read‑modify‑write operations and avoid the overhead of mutexes for fine‑grained synchronization.\n\n---\n\n## Example: Atomic counter increment\ncpp\n#include <atomic>\n#include <thread>\n\nstd::atomic<int> atomicCounter{0};\n\nvoid inc(int n) {\n for (int i = 0; i < n; ++i) {\n atomicCounter.fetch_add(1, std::memory_order_relaxed);\n }\n}\n\nint main() {\n std::thread t1(inc, 1000);\n std::thread t2(inc, 1000);\n t1.join();\n t2.join();\n std::cout << \"Atomic counter: \" << atomicCounter.load() << '\\n';\n return 0;\n}\n\n\n## Compare‑exchange example\ncpp\nstd::atomic<int> flag{0};\nint expected = 0;\nif (flag.compare_exchange_strong(expected, 1)) {\n // We successfully set flag from 0 to 1\n std::cout << \"Acquired flag\\n\";\n}\n\n\n> Tip: Use std::atomic_flag for a simple spin‑lock, but be wary of busy‑waiting.\n\n---\n\n<Alert type="warning">Atomic operations are only safe for trivially copyable types. For complex structures, protect them with mutexes or design lock‑free data structures.