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.

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

call_once (C++11)

invokes a function only once even if called from multiple threads (function template)