Why Can\'t I Pass Non-Const References to `std::async`?

Passing Non-Const References to std::async

In std::async, passing a non-const reference as an argument results in an error. This is a deliberate design choice.

Rationale

Determining whether a function object accepts its arguments by reference is not always feasible. Thus, std::async must either copy all arguments or accept them by reference. Copying arguments ensures safety as they cannot become dangling or cause race conditions.

Exception: std::ref

To allow non-const reference parameters, std::ref can be used. This is an explicit opt-in to potentially dangerous reference semantics, requiring careful handling of dangling references and race conditions.

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