Table of Contents

C++ Library – <atomic>

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Introduction

These are types that encapsulate a value whose access is guaranteed to not cause data races and can be used to synchronize memory accesses among different threads and he atomic library provides components for fine-grained atomic operations allowing for lockless concurrent programming. Each atomic operation is indivisible with regards to any other atomic operation that involves the same object.

Atomic type

Sr.No.	Member types & Definition
1	atomic Atomic class template and specializations for bool, integral, and pointer types

C-style atomic types

The following are atomic types and also defined in this header.

contained type	atomic type	description
`bool`	`atomic_bool`
`char`	`atomic_char`	atomics for fundamental integral types. These are either typedefs of the corresponding full specialization of the `atomic` class template or a base class of such specialization.
`signed char`	`atomic_schar`
`unsigned char`	`atomic_uchar`
`short`	`atomic_short`
`unsigned short`	`atomic_ushort`
`int`	`atomic_int`
`unsigned int`	`atomic_uint`
`long`	`atomic_long`
`unsigned long`	`atomic_ulong`
`long long`	`atomic_llong`
`unsigned long long`	`atomic_ullong`
`wchar_t`	`atomic_wchar_t`
`char16_t`	`atomic_char16_t`
`char32_t`	`atomic_char32_t`
`intmax_t`	`atomic_intmax_t`	atomics for width-based integrals (those defined in `<cinttypes>`). Each of these is either an alias of one of the above atomics for fundamental integral types or of a full specialization of the `atomic` class template with an extended integral type. Where N is one in 8, 16, 32, 64, or any other type width supported by the library.
`uintmax_t`	`atomic_uintmax_t`
`int_least`N`_t`	`atomic_int_least`N`_t`
`uint_least`N`_t`	`atomic_uint_least`N`_t`
`int_fast`N`_t`	`atomic_int_fast`N`_t`
`uint_fast`N`_t`	`atomic_uint_fast`N`_t`
`intptr_t`	`atomic_intptr_t`
`uintptr_t`	`atomic_uintptr_t`
`size_t`	`atomic_size_t`
`ptrdiff_t`	`atomic_ptrdiff_t`

Operations on atomic types

Sr.No.	Operations & Definition
1	atomic_is_lock_free It is used to checks if the atomic type”s operations are lock-free
2	atomic_store & atomic_store_explicit It automically replaces the value of the atomic object with a non-atomic argument
3	atomic_load & atomic_load_explicit It atomically obtains the value stored in an atomic object
4	atomic_exchange & atomic_exchange_explicit It atomically replaces the value of the atomic object with non-atomic argument and returns the old value of the atomic
5	atomic_compare_exchange_weak & atomic_compare_exchange_weak_explicit & atomic_compare_exchange_strong & atomic_compare_exchange_strong_explicit It atomically compares the value of the atomic object with non-atomic argument and performs atomic exchange if equal or atomic load if not
6	atomic_fetch_add & atomic_fetch_add_explicit It adds a non-atomic value to an atomic object and obtains the previous value of the atomic
7	atomic_fetch_sub & atomic_fetch_sub_explicit It subtracts a non-atomic value from an atomic object and obtains the previous value of the atomic
8	atomic_fetch_and & atomic_fetch_and_explicit It replaces the atomic object with the result of logical AND with a non-atomic argument and obtains the previous value of the atomic
9	atomic_fetch_or & atomic_fetch_or_explicit It replaces the atomic object with the result of logical OR with a non-atomic argument and obtains the previous value of the atomic
10	atomic_fetch_xor & atomic_fetch_xor_explicit It replaces the atomic object with the result of logical XOR with a non-atomic argument and obtains the previous value of the atomic

Flag type and operations

Sr.No.	Flag type & Definition
1	atomic_flag The lock-free boolean atomic type
2	atomic_flag_test_and_set & atomic_flag_test_and_set_explicit It atomically sets the flag to true and returns its previous value
3	atomic_flag_clear & atomic_flag_clear_explicit It atomically sets the value of the flag to false

Sr.No.

Flag type & Definition

atomic_flag

The lock-free boolean atomic type

atomic_flag_test_and_set & atomic_flag_test_and_set_explicit

It atomically sets the flag to true and returns its previous value

atomic_flag_clear & atomic_flag_clear_explicit

It atomically sets the value of the flag to false

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