Atomic Operations
C11 stdatomic.h provides types (atomic_int, _Atomic) and operations (atomic_load, atomic_store, atomic_fetch_add, atomic_compare_exchange_strong) that are guaranteed indivisible. Memory orderings: memory_order_relaxed (no ordering), memory_order_acquire/release (synchronize-with relationship), memory_order_seq_cst (default, strongest, safest). Lock-free programming is hard — prefer mutexes unless profiling proves they’re the bottleneck. Atomics are the building blocks of lock-free data structures.