stdfuture

Stdfuture is not an official standard name, but it is commonly used in documentation and code to refer to the C++ standard library type std::future. std::future<T> represents the result of an asynchronous operation that will become available at some point in the future. It can hold either a value of type T or an exception that was thrown during the asynchronous task.

A std::future<T> is typically produced by calling std::async, by creating a std::promise<T> and obtaining its associated future, or by wrapping a callable in a std::packaged_task. Once created, a future provides synchronization with the corresponding asynchronous operation. The result is retrieved by calling get(), which may block until the result is ready and will rethrow any exception stored by the task. The future can also be queried with valid() and made to wait with wait(), wait_for(), or wait_until().

std::future<T> is movable but not copyable. After get() is called, the future becomes invalid for further use. For scenarios where multiple consumers are needed, the future can be converted to a std::shared_future<T> via the share() method, allowing multiple observers to access the result.

Limitations include the lack of built-in continuations in the standard library (as of most recent standards), meaning callbacks must be implemented manually or via libraries. Futures also do not support cancellation of the asynchronous operation; cancellation must be managed by the task itself or by higher-level abstractions. Nonetheless, std::future provides a fundamental mechanism for non-blocking, asynchronous result retrieval in modern C++.