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std:: once_flag

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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

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)


See also

(C++11)
invokes a function only once even if called from multiple threads
(function template)
C documentation for once_flag