NAME¶

std::experimental::packaged_task::packaged_task(libraryfundamentalsTS) - std::experimental::packaged_task::packaged_task(libraryfundamentalsTS)

Synopsis¶

packaged_task() noexcept; (1) (library fundamentals TS)
template< class F > (2) (library fundamentals TS)
explicit packaged_task( F&& f );
template< class F, class Allocator >
explicit packaged_task( std::allocator_arg_t, const (3) (library fundamentals TS)
Allocator& alloc, F&& f );
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 The value of std::experimental::pmr::get_default_resource() of construction) 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 static_cast<std::experimental::pmr::memory_resource*>(alloc) std::experimental::pmr::memory_resource* A specialization of alloc.resource() std::experimental::pmr::polymorphic_allocator
A pointer to a value of type Any other type meeting the Allocator std::experimental::pmr::resource_adaptor<A>(alloc), where A requirements 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)