c / expert
Snippet
Atomic Compare-and-Swap (CAS) with stdatomic.h
Uses C11's stdatomic.h to perform a lock-free update. atomic_compare_exchange_weak checks if the current value matches 'expected'; if so, it updates it to 'desired'. If not, it updates 'expected' with the actual current value, allowing for a retry loop.
snippet.c
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#include <stdatomic.h>#include <stdbool.h>void safe_update(atomic_int *val) {int expected = atomic_load(val);int desired;do {desired = expected + 1;} while (!atomic_compare_exchange_weak(val, &expected, desired));}
Breakdown
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atomic_int *val
Declaration of an atomic integer type ensuring thread-safe access.
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atomic_compare_exchange_weak
Atomically compares the object with expected and replaces it with desired if equal.