std::experimental::packaged_task<R(Args...)>::packaged_task (library fundamentals TS)
From cppreference.com
< cpp | experimental | lib extensions | packaged task
| packaged_task() noexcept; |
(1) | (library fundamentals TS) |
| template <class F> explicit packaged_task( F&& f ); |
(2) | (library fundamentals TS) |
| template <class F, class Allocator> explicit packaged_task( std::allocator_arg_t, const Allocator& alloc, F&& f ); |
(3) | (library fundamentals TS) |
| packaged_task( const packaged_task& ) = delete; |
(4) | (library fundamentals TS) |
| packaged_task( packaged_task&& rhs ) noexcept; |
(5) | (library fundamentals TS) |
Constructs a new std::experimental::packaged_task object.
1) Constructs a
std::experimental::packaged_task object with no task and no shared state.2) Constructs a
std::experimental::packaged_task object with a shared state and a copy of the task, initialized with std::forward<F>(f). This constructor does not participate in overload resolution if std::decay<F>::type is the same type as std::packaged_task<R(ArgTypes...)>. 3) Constructs a
std::experimental::packaged_task object with a shared state and a copy of the task, initialized with std::forward<F>(f). Uses the provided allocator to allocate memory necessary to store the task, which is treated as a type-erased allocator (see below). This constructor does not participate in overload resolution if std::decay<F>::type is the same type as std::packaged_task<R(ArgTypes...)>. 4) The copy constructor is deleted,
std::experimental::packaged_task is move-only. 5) Constructs a
std::experimental::packaged_task with the shared state and task formerly owned by rhs, leaving rhs with no shared state and a moved-from task.
Type-erased allocator
The constructors of packaged_task taking an allocator argument alloc treats that argument as a type-erased allocator. The memory resource pointer used by packaged_task to allocate memory is determined using the allocator argument (if specified) as follows:
Type of alloc
|
value of the memory resource pointer |
| Non-existent (no allocator specified at time of construction) | The value of std::experimental::pmr::get_default_resource() at time of construction. |
| std::nullptr_t | The value of std::experimental::pmr::get_default_resource() at time of construction |
| A pointer type convertible to std::experimental::pmr::memory_resource* |
static_cast<std::experimental::pmr::memory_resource*>(alloc) |
| A specialization of std::experimental::pmr::polymorphic_allocator |
alloc.resource() |
| Any other type meeting the Allocator requirements | A pointer to a value of type std::experimental::pmr::resource_adaptor<A>(alloc), where A is the type of alloc. The pointer remains valid only for the lifetime of the packaged_task object.
|
| None of the above | The program is ill-formed. |
Parameters
| f | - | the callable target (function, member function, lambda-expression, functor) to execute |
| alloc | - | the allocator to use when storing the task |
| rhs | - | the std::experimental::packaged_task to move from
|
Exceptions
2-3) Any exceptions thrown by copy/move constructor of
f and possiblly std::bad_alloc if the allocation fails.4) (none)