32 Thread support library [thread]

32.4 Threads [thread.threads]

32.4.3 Class jthread [thread.jthread.class]

32.4.3.1 Constructors, move, and assignment [thread.jthread.cons]

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jthread() noexcept;
1
#
Effects: Constructs a jthread object that does not represent a thread of execution.
2
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Postconditions: get_­id() == id() is true and ssource.stop_­possible() is false.
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template<class F, class... Args> explicit jthread(F&& f, Args&&... args);
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Constraints: remove_­cvref_­t<F> is not the same type as jthread.
4
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Mandates: The following are all true:
  • (4.1)
    is_­constructible_­v<decay_­t<F>, F>,
  • (4.2)
    (is_­constructible_­v<decay_­t<Args>, Args> && ...),
  • (4.3)
    is_­move_­constructible_­v<decay_­t<F>>,
  • (4.4)
    (is_­move_­constructible_­v<decay_­t<Args>> && ...), and
  • (4.5)
    is_­invocable_­v<decay_­t<F>, decay_­t<Args>...> ||
    is_­invocable_­v<decay_­t<F>, stop_­token, decay_­t<Args>...>.
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Preconditions: decay_­t<F> and each type in decay_­t<Args> meet the Cpp17MoveConstructible requirements.
6
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Effects: Initializes ssource.
The new thread of execution executes 
invoke(decay-copy(std::forward<F>(f)), get_stop_token(),
       decay-copy(std::forward<Args>(args))...)
if that expression is well-formed, otherwise 
invoke(decay-copy(std::forward<F>(f)), decay-copy(std::forward<Args>(args))...)
with the calls to decay-copy being evaluated in the constructing thread.
Any return value from this invocation is ignored.
[ Note
:
This implies that any exceptions not thrown from the invocation of the copy of f will be thrown in the constructing thread, not the new thread.
— end note
 ]
If the invoke expression exits via an exception, terminate is called.
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Synchronization: The completion of the invocation of the constructor synchronizes with the beginning of the invocation of the copy of f.
8
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Postconditions: get_­id() != id() is true and ssource.stop_­possible() is true and *this represents the newly started thread.
[ Note
:
The calling thread can make a stop request only once, because it cannot replace this stop token.
— end note
 ]
9
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Throws: system_­error if unable to start the new thread.
10
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Error conditions:
  • (10.1)
    resource_­unavailable_­try_­again — the system lacked the necessary resources to create another thread, or the system-imposed limit on the number of threads in a process would be exceeded.
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jthread(jthread&& x) noexcept;
11
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Postconditions: x.get_­id() == id() and get_­id() returns the value of x.get_­id() prior to the start of construction.
ssource has the value of x.ssource prior to the start of construction and x.ssource.stop_­possible() is false.
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~jthread();
12
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Effects: If joinable() is true, calls request_­stop() and then join().
[ Note
:
Operations on *this are not synchronized.
— end note
 ]
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jthread& operator=(jthread&& x) noexcept;
13
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Effects: If joinable() is true, calls request_­stop() and then join().
Assigns the state of x to *this and sets x to a default constructed state.
14
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Postconditions: x.get_­id() == id() and get_­id() returns the value of x.get_­id() prior to the assignment.
ssource has the value of x.ssource prior to the assignment and x.ssource.stop_­possible() is false.
15
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Returns: *this.