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.
constexpr once_flag(); |
Constructs an once_flag object. The internal state is set to indicate that no function has been called yet.
(none).
noexcept specification: noexcept|
(C++11) | invokes a function only once even if called from multiple threads (function template) |
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