thread Class
The latest version of this topic can be found at thread Class.
Defines an object that's used to observe and manage a thread of execution within an application.
Syntax
class thread;
Remarks
You can use a thread object to observe and manage a thread of execution within an application. A thread object that's created by using the default constructor is not associated with any thread of execution. A thread object that's constructed by using a callable object creates a new thread of execution and calls the callable object in that thread. Thread objects can be moved but not copied. Therefore, a thread of execution can be associated with only one thread object.
Every thread of execution has a unique identifier of type thread::id. The function this_thread::get_id returns the identifier of the calling thread. The member function thread::get_id returns the identifier of the thread that's managed by a thread object. For a default-constructed thread object, the thread::get_id method returns an object that has a value that's the same for all default-constructed thread objects and different from the value that's returned by this_thread::get_id for any thread of execution that could be joined at the time of the call.
Members
Public Classes
| Name | Description |
|---|---|
| thread::id Class | Uniquely identifies the associated thread. |
Public Constructors
| Name | Description |
|---|---|
| thread::thread Constructor | Constructs a thread object. |
Public Methods
| Name | Description |
|---|---|
| thread::detach Method | Detaches the associated thread from the thread object. |
| thread::get_id Method | Returns the unique identifier of the associated thread. |
| thread::hardware_concurrency Method | Static. Returns an estimate of the number of hardware thread contexts. |
| thread::join Method | Blocks until the associated thread completes. |
| thread::joinable Method | Specifies whether the associated thread is joinable. |
| thread::native_handle Method | Returns the implementation-specific type that represents the thread handle. |
| thread::swap Method | Swaps the object state with a specified thread object. |
Public Operators
| Name | Description |
|---|---|
| thread::operator= | Associates a thread with the current thread object. |
Requirements
Header: thread
Namespace: std
thread::detach Method
Detaches the associated thread. The operating system becomes responsible for releasing thread resources on termination.
void detach();
Remarks
After a call to detach, subsequent calls to get_id return id.
If the thread that's associated with the calling object is not joinable, the function throws a system_error that has an error code of invalid_argument.
If the thread that's associated with the calling object is invalid, the function throws a system_error that has an error code of no_such_process.
thread::get_id Method
Returns a unique identifier for the associated thread.
id get_id() const noexcept;
Return Value
A thread::id object that uniquely identifies the associated thread, or thread::id() if no thread is associated with the object.
thread::hardware_concurrency Method
Static method that returns an estimate of the number of hardware thread contexts.
static unsigned int hardware_concurrency() noexcept;
Return Value
An estimate of the number of hardware thread contexts. If the value cannot be computed or is not well defined, this method returns 0.
thread::id Class
Provides a unique identifier for each thread of execution in the process.
class thread::id {
id() noexcept;
};
Remarks
The default constructor creates an object that does not compare equal to the thread::id object for any existing thread.
All default-constructed thread::id objects compare equal.
thread::join Method
Blocks until the thread of execution that's associated with the calling object completes.
void join();
Remarks
If the call succeeds, subsequent calls to get_id for the calling object return a default thread::id that does not compare equal to the thread::id of any existing thread; if the call does not succeed, the value that's returned by get_id is unchanged.
thread::joinable Method
Specifies whether the associated thread is joinable.
bool joinable() const noexcept;
Return Value
true if the associated thread is joinable; otherwise, false.
Remarks
A thread object is joinable if get_id() != id().
thread::native_handle Method
Returns the implementation-specific type that represents the thread handle. The thread handle can be used in implementation-specific ways.
native_handle_type native_handle();
Return Value
native_handle_type is defined as a Win32 HANDLE that's cast as void *.
thread::operator=
Associates the thread of a specified object with the current object.
thread& operator=(thread&& Other) noexcept;
Parameters
Other
A thread object.
Return Value
*this
Remarks
The method calls detach if the calling object is joinable.
After the association is made, Other is set to a default-constructed state.
thread::swap Method
Swaps the object state with that of a specified thread object.
void swap(thread& Other) noexcept;
Parameters
Other
A thread object.
thread::thread Constructor
Constructs a thread object.
thread() noexcept;
template <class Fn, class... Args>
explicit thread(Fn&& F, Args&&... A);
thread(thread&& Other) noexcept;
Parameters
F
An application-defined function to be executed by the thread.
A
A list of arguments to be passed to F.
Other
An existing thread object.
Remarks
The first constructor constructs an object that's not associated with a thread of execution. The value that's returned by a call to get_id for the constructed object is thread::id().
The second constructor constructs an object that's associated with a new thread of execution and executes the pseudo-function INVOKE that's defined in <functional>. If not enough resources are available to start a new thread, the function throws a system_error object that has an error code of resource_unavailable_try_again. If the call to F terminates with an uncaught exception, terminate is called.
The third constructor constructs an object that's associated with the thread that's associated with Other. Other is then set to a default-constructed state.