NAME

std::once_flag - std::once_flag

Synopsis

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