std::atomic<T>:: fetch_sub
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| Member functions | ||||
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(C++20)
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(C++20)
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(C++20)
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| Constants | ||||
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(C++17)
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| Specialized member functions | ||||
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Specialized for integral,
floating-point (C++20) and pointer types |
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atomic::fetch_sub
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Specialized for integral and
pointer types only |
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(C++26)
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(C++26)
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| Specialized for integral types only | ||||
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member only of
atomic<
Integral
>
specializations
and
atomic<
Floating
>
specializations
(since C++20)
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T fetch_sub
(
T arg,
std::
memory_order
order
=
std:: memory_order_seq_cst ) noexcept ; |
(1) | (since C++11) |
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T fetch_sub
(
T arg,
std::
memory_order
order
=
std:: memory_order_seq_cst ) volatile noexcept ; |
(2) | (since C++11) |
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member only of
atomic<T*>
partial specialization
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T
*
fetch_sub
(
std::
ptrdiff_t
arg,
std::
memory_order
order
=
|
(3) | (since C++11) |
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T
*
fetch_sub
(
std::
ptrdiff_t
arg,
std::
memory_order
order
=
|
(4) | (since C++11) |
Atomically replaces the current value with the result of arithmetic subtraction of the value and arg . That is, it performs atomic post-decrement. The operation is read-modify-write operation. Memory is affected according to the value of order .
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For floating-point types, the floating-point environment in effect may be different from the calling thread's floating-point environment. The operation need not be conform to the corresponding std::numeric_limits traits but is encouraged to do so. If the result is not a representable value for its type, the result is unspecified but the operation otherwise has no undefined behavior. |
(since C++20) |
T
is not a complete object type, the program is ill-formed.
|
It is deprecated if std:: atomic < T > :: is_always_lock_free is false and overload (2) or (4) participates in overload resolution. |
(since C++20) |
Parameters
| arg | - | the other argument of arithmetic subtraction |
| order | - | memory order constraints to enforce |
Return value
The value immediately preceding the effects of this function in the modification order of * this .
Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| P0558R1 | C++11 | arithmetic permitted on pointers to (possibly cv-qualified) void or function | made ill-formed |
See also
|
(C++11)
(C++11)
|
subtracts a non-atomic value from an atomic object and obtains the previous value of the atomic
(function template) |
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increments or decrements the atomic value by one
(public member function) |