std::future_errc(3)

💖 std::future_errc 💖

okay so bestie, this is the std::future_errc(3) page from the C++ Standard Libary manual — yes, the header spells it like that, and we’re not fixing it, we’re just vibing 🫶. It’s giving “tiny enum, big error-code energy,” and I’m obsessed.

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🌸 NAME 🌸

std::future_errc — std::future_errc (the name is literally the name, bestie 💅).

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✨ Synopsis ✨

Defined in header <future>

enum class future_errc {

    broken_promise             = /* implementation-defined */,
    future_already_retrieved   = /* implementation-defined */,
(since C++11)
    promise_already_satisfied  = /* implementation-defined */,
    no_state                   = /* implementation-defined */

};

The scoped enumeration std::future_errc defines the error codes reported by std::future and related classes in std::future_error exception objects. Only four error codes are required, although the implementation may define additional error codes. Because the appropriate specialization of std::is_error_code_enum is provided, values of type std::future_errc are implicitly convertible to std::error_code.

All error codes are distinct and non-zero. No cap, every single one is doing its own thing and none of them are zero — zero is not invited to this party 💀.

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🎀 Member constants 🎀

• broken_promise — the asynchronous task abandoned its shared state.
• future_already_retrieved — the contents of shared state were already accessed through std::future.
• promise_already_satisfied — attempt to store a value in the shared state twice.
• no_state — attempt to access std::promise or std::future without an associated shared state.

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💅 Non-member functions 💅

• make_error_code(std::future_errc) — constructs a future error code; (C++11); function.
• make_error_condition(std::future_errc) — constructs a future error_condition; (C++11); function.

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🌈 Helper classes 🌈

• is_error_code_enum<std::future_errc> — extends the type trait std::is_error_code_enum to identify future error codes; (C++11); class template.

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🍓 Example 🍓

This section is incomplete

Reason: no example

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💀 Defect reports 💀

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

• DR LWG 2056 — Applied to: C++11. Behavior as published: broken_promise was specified to be zero which is conventionally used to mean "no error". Correct behavior: specified to be non-zero.

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🦋 See also 🦋

• error_code — holds a platform-dependent error code; (C++11); class.
• error_condition — holds a portable error code; (C++11); class.

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⭐ Category ⭐

• Todo no example

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source/version/date check: this one’s from http://cppreference.com, version 2024.06.10, and it’s the std::future_errc(3) page — bye bestie, go handle your error codes 💅✨