std:: future_errc

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.

Member constants

Name	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

Non-member functions

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

Helper classes

is_error_code_enum <std::future_errc> (C++11)

extends the type trait std::is_error_code_enum to identify future error codes (class template)

Example

This section is incomplete Reason: no example

Defect reports

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

See also

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