ATOMIC_*_LOCK_FREE

 

C

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Concurrency support (C11)

Technical Specifications

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Concurrency support library

Threads thrd_create thrd_equal thrd_current    thrd_sleep thrd_yield thrd_exit thrd_detach thrd_join thrd_successthrd_timedoutthrd_busythrd_nomemthrd_error    Atomic operations atomic_init ATOMIC_VAR_INIT (until C23) ATOMIC_***_LOCK_FREE atomic_is_lock_free atomic_store atomic_load atomic_exchange atomic_compare_exchange atomic_fetch_add atomic_fetch_sub atomic_fetch_or atomic_fetch_xor atomic_fetch_and

Atomic flags atomic_flag ATOMIC_FLAG_INIT atomic_flag_test_and_set atomic_flag_clear Memory ordering memory_order kill_dependency atomic_thread_fence atomic_signal_fence Mutual exclusion mtx_init mtx_lock mtx_timedlock mtx_trylock call_once mtx_unlock mtx_destroy mtx_plainmtx_recursivemtx_timed Condition variables cnd_init cnd_signal cnd_broadcast cnd_wait cnd_timedwait cnd_destroy Thread-local storage thread_local TSS_DTOR_ITERATIONS    tss_create tss_get tss_set tss_delete

 

Defined in header <stdatomic.h>
#define ATOMIC_BOOL_LOCK_FREE     /* implementation-defined */ #define ATOMIC_CHAR_LOCK_FREE     /* implementation-defined */ #define ATOMIC_CHAR16_T_LOCK_FREE /* implementation-defined */ #define ATOMIC_CHAR32_T_LOCK_FREE /* implementation-defined */ #define ATOMIC_WCHAR_T_LOCK_FREE  /* implementation-defined */ #define ATOMIC_SHORT_LOCK_FREE    /* implementation-defined */ #define ATOMIC_INT_LOCK_FREE      /* implementation-defined */ #define ATOMIC_LONG_LOCK_FREE     /* implementation-defined */ #define ATOMIC_LLONG_LOCK_FREE    /* implementation-defined */ #define ATOMIC_POINTER_LOCK_FREE  /* implementation-defined */		(since C11)
#define ATOMIC_CHAR8_T_LOCK_FREE  /* implementation-defined */		(since C23)

Expands to preprocessor constant expressions that evaluate to either 0, 1, or 2 which indicate the lock-free property of the corresponding atomic types (both signed and unsigned).

Value	Explanation
0	The atomic type is never lock-free
1	The atomic type is sometimes lock-free
2	The atomic type is always lock-free

References

• C17 standard (ISO/IEC 9899:2018):

• 7.17.1/3 atomic lock-free macros (p: 200)

• C11 standard (ISO/IEC 9899:2011):

• 7.17.1/3 atomic lock-free macros (p: 273)