This commit makes several changes to `std::thread` in preparation for
final stabilization:
* It removes the ability to handle panics from `scoped` children; see
#20807 for discussion
* It adds a `JoinHandle` structure, now returned from `spawn`, which
makes it possible to join on children that do not share data from
their parent's stack. The child is automatically detached when the
handle is dropped, and the handle cannot be copied due to Posix
semantics.
* It moves all static methods from `std:🧵:Thread` to free
functions in `std::thread`. This was done in part because, due to the
above changes, there are effectively no direct `Thread` constructors,
and the static methods have tended to feel a bit awkward.
* Adds an `io::Result` around the `Builder` methods `scoped` and
`spawn`, making it possible to handle OS errors when creating
threads. The convenience free functions entail an unwrap.
* Stabilizes the entire module. Despite the fact that the API is
changing somewhat here, this is part of a long period of baking and
the changes are addressing all known issues prior to alpha2. If
absolutely necessary, further breaking changes can be made prior to beta.
Closes#20807
[breaking-change]
This commit is part of a series that introduces a `std::thread` API to
replace `std::task`.
In the new API, `spawn` returns a `JoinGuard`, which by default will
join the spawned thread when dropped. It can also be used to join
explicitly at any time, returning the thread's result. Alternatively,
the spawned thread can be explicitly detached (so no join takes place).
As part of this change, Rust processes now terminate when the main
thread exits, even if other detached threads are still running, moving
Rust closer to standard threading models. This new behavior may break code
that was relying on the previously implicit join-all.
In addition to the above, the new thread API also offers some built-in
support for building blocking abstractions in user space; see the module
doc for details.
Closes#18000
[breaking-change]
This commit merges the `rustrt` crate into `std`, undoing part of the
facade. This merger continues the paring down of the runtime system.
Code relying on the public API of `rustrt` will break; some of this API
is now available through `std::rt`, but is likely to change and/or be
removed very soon.
[breaking-change]
