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tids are non-copyable, only movable

master
Daniel Kolesa 2017-05-02 23:49:56 +02:00
parent 2c62b82ec4
commit 9f593eebd1
1 changed files with 12 additions and 8 deletions
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20
ostd/concurrency.hh
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@ -148,11 +148,13 @@ namespace detail {
* represents a spawned task, allowing you to wait for the task to be done
* as well as retrieve its return value. It also allows sane cross-task
* exception handling, as any exception is saved inside the internal
* shared state and propagated on get().
* state and propagated on get().
*
* The internal shared state is reference counted, but it's only safe to
* call get() once from one instance. It cannot be constructed normally,
* only as a return value or a copy.
* Tids are move constructible and assignable, but not copyable. They also
* cannot be constructed normally, only returned from the appropriate spawn
* function. The internal state stays alive for as long as necessary (always
* at least until the associated task finishes, but it can remain alive after
* that to either get the return value or propagate an exception).
*
* The `T` template parameter is the type of the result. It can be `void`,
* in which case get() returns nothing, but can still propagate exceptions.
@ -162,10 +164,10 @@ struct tid {
friend struct scheduler;
tid() = delete;
tid(tid const &) = delete;
tid &operator=(tid const &) = delete;
tid(tid const &) = default;
tid(tid &&) = default;
tid &operator=(tid const &) = default;
tid &operator=(tid &&) = default;
/** @brief Waits for the result and returns it.
@ -174,7 +176,9 @@ struct tid {
* the task, it will be rethrown here, allowing sane exception handling
* between different tasks and possibly threads.
*
* Effectively calls wait() before returning or throwing.
* Effectively calls wait() before returning or throwing. After this
* call is done, valid() will no longer be true. It is undefined to
* call this when valid() is not true.
*/
T get() {
auto p = std::move(p_state);
@ -188,7 +192,7 @@ struct tid {
/** @brief Waits for the associated task to finish.
*
* The behavior is undefined if valid() is true.
* The behavior is undefined when valid() is not true.
*/
void wait() const {
p_state->wait();