std::launch - cppreference.com (original) (raw)
| | | | | ------------------------------------------------------------------------------------------------------------------------------------------- | | ------------- | | enum class launch : /* unspecified */ { async = /* unspecified */, deferred = /* unspecified */, /* implementation-defined */ }; | | (since C++11) |
std::launch is a BitmaskType. It specifies the launch policy for a task executed by the std::async function.
[edit] Constants
The following constants denoting individual bits are defined by the standard library:
| Enumerator | Meaning |
|---|---|
| async | the task is executed on a different thread, potentially by creating and launching it first |
| deferred | the task is executed on the calling thread the first time its result is requested (lazy evaluation) |
In addition, implementations are allowed to:
- define additional bits and bitmasks to specify restrictions on task interactions applicable to a subset of launch policies, and
- enable those additional bitmasks for the first (default) overload of std::async.
[edit] 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 2102 | C++11 | std::launch was an implementation-defined type | it is not implementation-defined |
[edit] See also
| | runs a function asynchronously (potentially in a new thread) and returns a std::future that will hold the result (function template) [edit] | | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |