Difference between revisions of "cpp/thread/once flag"
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An object of type {{tt|std::once_flag}} that is passed to multiple calls to {{lc|std::call_once}} allows those calls to coordinate with each other such that only one of the calls will actually run to completion. | An object of type {{tt|std::once_flag}} that is passed to multiple calls to {{lc|std::call_once}} allows those calls to coordinate with each other such that only one of the calls will actually run to completion. | ||
| − | {{tt|std::once_flag}} is | + | {{tt|std::once_flag}} is neither copyable nor movable. |
===Member functions=== | ===Member functions=== | ||
{{member | {{small|std::once_flag::}}once_flag | | {{member | {{small|std::once_flag::}}once_flag | | ||
{{ddcl | | {{ddcl | | ||
| − | once_flag(); | + | constexpr once_flag() noexcept; |
}} | }} | ||
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(none) | (none) | ||
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{{dsc begin}} | {{dsc begin}} | ||
{{dsc inc | cpp/thread/dsc call_once}} | {{dsc inc | cpp/thread/dsc call_once}} | ||
| + | {{dsc see c | c/thread/call_once | once_flag}} | ||
{{dsc end}} | {{dsc end}} | ||
| − | + | {{langlinks|de|es|fr|it|ja|pt|ru|zh}} | |
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Latest revision as of 06:55, 16 October 2021
| Defined in header <mutex>
|
||
| class once_flag; |
(since C++11) | |
The class std::once_flag is a helper structure for std::call_once.
An object of type std::once_flag that is passed to multiple calls to std::call_once allows those calls to coordinate with each other such that only one of the calls will actually run to completion.
std::once_flag is neither copyable nor movable.
Contents |
[edit] Member functions
std::once_flag::once_flag
| constexpr once_flag() noexcept; |
||
Constructs an once_flag object. The internal state is set to indicate that no function has been called yet.
Parameters
(none)
[edit] See also
| (C++11) |
invokes a function only once even if called from multiple threads (function template) |
| C documentation for once_flag
| |
