once_flag Structure
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Represents a struct that is used with the template function call_once to ensure that initialization code is called only once, even in the presence of multiple threads of execution.
Syntax
struct once_flag { constexpr once_flag() noexcept; once_flag(const once_flag&); once_flag& operator=(const once_flag&); };
Remarks
The once_flag``struct has only a default constructor.
Objects of type once_flag can be created, but they cannot be copied.
Requirements
Header: mutex
Namespace: std