| Defined in header |
std::once_flag is a helper structure for
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() noexcept;
once_flag object. The internal state is set to indicate that no function has been called yet.
| invokes a function only once even if called from multiple threads
| C documentation for
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