33 Concurrency support library [thread]

33.4 Threads [thread.threads]

33.4.4 Class jthread [thread.jthread.class]

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

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jthread() noexcept;
1
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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.
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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> && ...), and
  • (4.3)
    is_­invocable_­v<decay_­t<F>, decay_­t<Args>...> ||
    is_­invocable_­v<decay_­t<F>, stop_­token, decay_­t<Args>...>.
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Effects: Initializes ssource.
The new thread of execution executes invoke(auto(std::forward<F>(f)), get_stop_token(), auto(std::forward<Args>(args))...) if that expression is well-formed, otherwise invoke(auto(std::forward<F>(f)), auto(std::forward<Args>(args))...) with the values produced by auto being materialized ([conv.rval]) in the constructing thread.
Any return value from this invocation is ignored.
[Note 1:
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.
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Postconditions: get_­id() != id() is true and ssource.stop_­possible() is true and *this represents the newly started thread.
[Note 2:
The calling thread can make a stop request only once, because it cannot replace this stop token.
— end note]
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Throws: system_­error if unable to start the new thread.
9
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Error conditions:
  • (9.1)
    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;
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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();
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Effects: If joinable() is true, calls request_­stop() and then join().
[Note 3:
Operations on *this are not synchronized.
— end note]
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jthread& operator=(jthread&& x) noexcept;
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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.
13
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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.
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Returns: *this.