std:: launch
|
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
Defined in header
<future>
|
||
|
enum
class
launch
:
/* unspecified */
{
async
=
/* unspecified */
,
|
(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:
| Name | Explanation |
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) |