Defined in header <future> | ||
|---|---|---|
enum class future_errc {
broken_promise = /* implementation-defined */,
future_already_retrieved = /* implementation-defined */,
promise_already_satisfied = /* implementation-defined */,
no_state = /* implementation-defined */
};
| (since C++11) |
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.
| Constant | Explanation |
|---|---|
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 |
|
(C++11) | constructs a future error code (function) |
|
(C++11) | constructs a future error_condition (function) |
|
(C++11) | extends the type trait std::is_error_code_enum to identify future error codes (class template) |
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| LWG 2056 | C++11 | broken_promise was specified to be zero which is conventionally used to mean "no error" | specified to be non-zero |
|
(C++11) | holds a platform-dependent error code (class) |
|
(C++11) | holds a portable error code (class) |
© cppreference.com
Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.
https://en.cppreference.com/w/cpp/thread/future_errc