std::once_flag (3) - Linux Manuals

std::once_flag: std::once_flag


std::once_flag - std::once_flag


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


constexpr once_flag() noexcept;

Constructs an once_flag object. The internal state is set to indicate that no function has been called yet.



See also

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