std::launch
Defined in header <future> | ||
|---|---|---|
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.
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.
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 |
See also
|
(C++11) | runs a function asynchronously (potentially in a new thread) and returns a std::future that will hold the result (function template) |
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https://en.cppreference.com/cpp/thread/launch
