Standard library header <stdatomic.h> (C11)

This header provides atomic operations, in particular, it's a part of the concurrency support library.

Atomic operations

Operations on atomic types
ATOMIC_BOOL_LOCK_FREEATOMIC_CHAR_LOCK_FREEATOMIC_CHAR8_T_LOCK_FREEATOMIC_CHAR16_T_LOCK_FREEATOMIC_CHAR32_T_LOCK_FREEATOMIC_WCHAR_T_LOCK_FREEATOMIC_SHORT_LOCK_FREEATOMIC_INT_LOCK_FREEATOMIC_LONG_LOCK_FREEATOMIC_LLONG_LOCK_FREEATOMIC_POINTER_LOCK_FREE (C11)(C11)(C23)(C11)(C11)(C11)(C11)(C11)(C11)(C11)(C11)	indicates that the given atomic type is lock-free (macro constant)
atomic_is_lock_free (C11)	indicates whether the atomic object is lock-free (function)
atomic_storeatomic_store_explicit (C11)	stores a value in an atomic object (function)
atomic_loadatomic_load_explicit (C11)	reads a value from an atomic object (function)
atomic_exchangeatomic_exchange_explicit (C11)	swaps a value with the value of an atomic object (function)
atomic_compare_exchange_strongatomic_compare_exchange_strong_explicitatomic_compare_exchange_weakatomic_compare_exchange_weak_explicit (C11)	swaps a value with an atomic object if the old value is what is expected, otherwise reads the old value (function)
atomic_fetch_addatomic_fetch_add_explicit (C11)	atomic addition (function)
atomic_fetch_subatomic_fetch_sub_explicit (C11)	atomic subtraction (function)
atomic_fetch_oratomic_fetch_or_explicit (C11)	atomic bitwise OR (function)
atomic_fetch_xoratomic_fetch_xor_explicit (C11)	atomic bitwise exclusive OR (function)
atomic_fetch_andatomic_fetch_and_explicit (C11)	atomic bitwise AND (function)
Flag type and operations
atomic_flag (C11)	lock-free atomic boolean flag (struct)
atomic_flag_test_and_setatomic_flag_test_and_set_explicit (C11)	sets an atomic_flag to true and returns the old value (function)
atomic_flag_clearatomic_flag_clear_explicit (C11)	sets an atomic_flag to false (function)
Initialization
atomic_init (C11)	initializes an existing atomic object (function)
ATOMIC_VAR_INIT (C11)(deprecated in C17)(removed in C23)	initializes a new atomic object (function macro)
ATOMIC_FLAG_INIT (C11)	initializes a new atomic_flag (macro constant)
Memory synchronization ordering
memory_order (C11)	defines memory ordering constraints (enum)
kill_dependency (C11)	breaks a dependency chain for memory_order_consume (function macro)
atomic_thread_fence (C11)	generic memory order-dependent fence synchronization primitive (function)
atomic_signal_fence (C11)	fence between a thread and a signal handler executed in the same thread (function)

Convenience type aliases
Typedef name	Full type name
atomic_bool (C11)	_Atomic_Bool
atomic_char (C11)	_Atomicchar
atomic_schar (C11)	_Atomicsignedchar
atomic_uchar (C11)	_Atomicunsignedchar
atomic_short (C11)	_Atomicshort
atomic_ushort (C11)	_Atomicunsignedshort
atomic_int (C11)	_Atomicint
atomic_uint (C11)	_Atomicunsignedint
atomic_long (C11)	_Atomiclong
atomic_ulong (C11)	_Atomicunsignedlong
atomic_llong (C11)	_Atomiclonglong
atomic_ullong (C11)	_Atomicunsignedlonglong
atomic_char8_t (C23)	_Atomicchar8_t
atomic_char16_t (C11)	_Atomicchar16_t
atomic_char32_t (C11)	_Atomicchar32_t
atomic_wchar_t (C11)	_Atomicwchar_t
atomic_int_least8_t (C11)	_Atomicint_least8_t
atomic_uint_least8_t (C11)	_Atomicuint_least8_t
atomic_int_least16_t (C11)	_Atomicint_least16_t
atomic_uint_least16_t (C11)	_Atomicuint_least16_t
atomic_int_least32_t (C11)	_Atomicint_least32_t
atomic_uint_least32_t (C11)	_Atomicuint_least32_t
atomic_int_least64_t (C11)	_Atomicint_least64_t
atomic_uint_least64_t (C11)	_Atomicuint_least64_t
atomic_int_fast8_t (C11)	_Atomicint_fast8_t
atomic_uint_fast8_t (C11)	_Atomicuint_fast8_t
atomic_int_fast16_t (C11)	_Atomicint_fast16_t
atomic_uint_fast16_t (C11)	_Atomicuint_fast16_t
atomic_int_fast32_t (C11)	_Atomicint_fast32_t
atomic_uint_fast32_t (C11)	_Atomicuint_fast32_t
atomic_int_fast64_t (C11)	_Atomicint_fast64_t
atomic_uint_fast64_t (C11)	_Atomicuint_fast64_t
atomic_intptr_t (C11)	_Atomicintptr_t
atomic_uintptr_t (C11)	_Atomicuintptr_t
atomic_size_t (C11)	_Atomicsize_t
atomic_ptrdiff_t (C11)	_Atomicptrdiff_t
atomic_intmax_t (C11)	_Atomicintmax_t
atomic_uintmax_t (C11)	_Atomicuintmax_t

Synopsis

#define __STDC_VERSION_STDATOMIC_H__ 202311L

void atomic_init(volatile A* obj, /*C*/ value);
/*type*/ kill_dependency(/*type*/ y);
void atomic_thread_fence(memory_order order);
void atomic_signal_fence(memory_order order);
bool atomic_is_lock_free(const volatile A* obj);
void atomic_store(volatile A* object, /*C*/ desired);
void atomic_store_explicit(volatile A* object, /*C*/ desired, memory_order order);
/*C*/ atomic_load(const volatile A* object);
/*C*/ atomic_load_explicit(const volatile A* object, memory_order order);
/*C*/ atomic_exchange(volatile A* object, /*C*/ desired);
/*C*/ atomic_exchange_explicit(volatile A* object, /*C*/ desired, memory_order order);
bool atomic_compare_exchange_strong(volatile A* object, /*C*/* expected, /*C*/ desired);
bool atomic_compare_exchange_strong_explicit(volatile A* object, /*C*/* expected,
/*C*/ desired, memory_order success, memory_order failure);
bool atomic_compare_exchange_weak(volatile A* object, /*C*/* expected, /*C*/ desired);
bool atomic_compare_exchange_weak_explicit(volatile A* object, /*C*/* expected,
/*C*/ desired, memory_order success, memory_order failure);
/*C*/ /*atomic_fetch_key*/(volatile A* object, M operand);
/*C*/ /*atomic_fetch_key_explicit*/(volatile A* object, M operand, memory_order order);
bool atomic_flag_test_and_set(volatile atomic_flag* object);
bool atomic_flag_test_and_set_explicit(volatile atomic_flag* object,
                                       memory_order order);
void atomic_flag_clear(volatile atomic_flag* object);
void atomic_flag_clear_explicit(volatile atomic_flag* object,
                                memory_order order);