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Difference between revisions of "cpp/atomic/atomic init"

From cppreference.com
< cpp‎ | atomic
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{{cpp/title|atomic_init}}
 
{{cpp/title|atomic_init}}
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{{cpp/atomic/navbar}}
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{{cpp/thread/navbar}}
 
{{dcl begin}}
 
{{dcl begin}}
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{{dcl header | atomic}}
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{{dcl header|atomic}}
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{{dcl | since=c++11 | deprecated=c++20 |
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{{dcl|num=1|since=c++11|deprecated=c++20|
 
template< class T >
 
template< class T >
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void atomic_init( std::atomic<T>* obj,
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void atomic_init
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                  typename std::atomic<T>::value_type desired ) noexcept;
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    ( std::atomic<T>* obj,
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      typename std::atomic<T>::value_type desired ) noexcept;
 
}}
 
}}
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{{dcl | since=c++11 | deprecated=c++20 |
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{{dcl|num=2|since=c++11|deprecated=c++20|
 
template< class T >
 
template< class T >
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void atomic_init( volatile std::atomic<T>* obj,
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void atomic_init
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                  typename std::atomic<T>::value_type desired ) noexcept;
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    ( volatile std::atomic<T>* obj,
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      typename std::atomic<T>::value_type desired ) noexcept;
 
}}
 
}}
 
{{dcl end}}
 
{{dcl end}}
  
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Initializes the default-constructed atomic object {{tt|obj}} with the value {{tt|desired}}. The function is not atomic: concurrent access from another thread, even through an atomic operation, is a data race.  
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Initializes the default-constructed atomic object {{c|obj}} with the value {{c|desired}}. The function is not atomic: concurrent access from another thread, even through an atomic operation, is a data race.  
  
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If {{tt|obj}} was not default-constructed, the behavior is undefined.
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If {{c|obj}} was not default-constructed, or this function is called twice on the same {{c|obj}}, the behavior is undefined.
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−
If this function is called twice on the same {{tt|obj}}, the behavior is undefined.
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===Parameters===
 
===Parameters===
 
{{par begin}}
 
{{par begin}}
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{{par | obj | pointer to an atomic object to initialize}}
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{{par|obj|pointer to an atomic object to initialize}}
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{{par | desired | the value to initialize atomic object with}}
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{{par|desired|the value to initialize atomic object with}}
 
{{par end}}
 
{{par end}}
  
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===Example===
 
===Example===
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{{example
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{{example}}
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|
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| code=
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| output=
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}}
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===Defect reports===
 
===Defect reports===
 
{{dr list begin}}
 
{{dr list begin}}
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{{dr list item|std=C++11|paper=P0558R1|before=exact type match required because {{tt|T}} is deduced from multiple arguments|after={{tt|T}} is deduced from the {{tt|atomic}} argument only}}
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{{dr list item|std=C++11|paper=P0558R1|before=exact type match was required because<br>{{tt|T}} was deduced from multiple arguments|after={{tt|T}} is only deduced<br>from {{c|obj}}}}
 
{{dr list end}}
 
{{dr list end}}
  
 
===See also===
 
===See also===
 
{{dsc begin}}
 
{{dsc begin}}
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{{dsc inc | cpp/atomic/dsc ATOMIC_VAR_INIT}}
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{{dsc inc|cpp/atomic/dsc ATOMIC_VAR_INIT}}
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{{dsc inc | cpp/atomic/atomic/dsc constructor}}
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{{dsc inc|cpp/atomic/atomic/dsc constructor}}
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{{dsc see c | c/atomic/atomic_init}}
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{{dsc see c|c/atomic/atomic_init}}
 
{{dsc end}}
 
{{dsc end}}
  
 
{{langlinks|de|es|fr|it|ja|pt|ru|zh}}
 
{{langlinks|de|es|fr|it|ja|pt|ru|zh}}

Latest revision as of 22:45, 20 September 2023

 
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Defined in header <atomic>
template< class T >

void atomic_init
    ( std::atomic<T>* obj,

      typename std::atomic<T>::value_type desired ) noexcept;
 (1) (since C++11)
(deprecated in C++20)
template< class T >

void atomic_init
    ( volatile std::atomic<T>* obj,

      typename std::atomic<T>::value_type desired ) noexcept;
 (2) (since C++11)
(deprecated in C++20)

Initializes the default-constructed atomic object obj with the value desired. The function is not atomic: concurrent access from another thread, even through an atomic operation, is a data race.

If obj was not default-constructed, or this function is called twice on the same obj, the behavior is undefined.

Contents

[edit] Parameters

obj - pointer to an atomic object to initialize
desired - the value to initialize atomic object with

[edit] Return value

(none)

[edit] Notes

This function is provided for compatibility with C. If the compatibility is not required, std::atomic may be initialized through their non-default constructors.

[edit] Example

This section is incomplete
Reason: no example

[edit] 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 exact type match was required because
T was deduced from multiple arguments 		T is only deduced
from obj

[edit] See also

(C++11)(deprecated in C++20)
 constant initialization of an atomic variable of static storage duration
(function macro) [edit]
constructs an atomic object
(public member function of std::atomic<T>) [edit]
C documentation for atomic_init
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