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And final part!!!
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r=Mark-Simulacrum
Adjusted some doctests in libcore to use `should_panic`.
Fixes #73196 .
I grepped libstd and libcore for all the instances of this pattern that I could find, but its possible that I missed some of course. If anyone knows of any more, please let me know and I will add them to the PR.
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Previously, some doctests were spawning new threads and joining them to
indicate that a particular call should panic; this hurt readability, so
the tests have been adjusted to simply call the method and use the
`should_panic` marker.
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Small cell example update
r? @Dylan-DPC
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In the same vein as `Cell::take` and `Option::take`.
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Bump the bootstrap compiler
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Add undo_leak to reset RefCell borrow state
This method is complementary for the feature cell_leak added in an
earlier PR. It allows *safely* reverting the effects of leaking a borrow guard by
statically proving that such a guard could not longer exist. This was
not added to the existing `get_mut` out of concern of impacting the
complexity of the otherwise pure pointer cast and because the name
`get_mut` poorly communicates the intent of resetting remaining borrows.
This is a follow-up to #68712 and uses the same tracking issue, #69099,
as these methods deal with the same mechanism and the idea came up
[in a review comment](https://github.com/rust-lang/rust/pull/68712#discussion_r384670041).
@dtolnay who reviewed the prior PR.
cc @RalfJung
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This method is complementary for the feature refcell_leak added in an
earlier PR. It allows reverting the effects of leaking a borrow guard by
statically proving that such a guard could not longer exist. This was
not added to the existing `get_mut` out of concern of impacting the
complexity of the otherwise pure pointer cast and because the name
`get_mut` poorly communicates the intent of resetting remaining borrows.
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Add methods to 'leak' RefCell borrows as references with the lifetime of the original reference
Usually, references to the interior are only created by the `Deref` and
`DerefMut` impl of the guards `Ref` and `RefMut`. Note that `RefCell`
already has to cope with leaks of such guards which, when it occurs,
effectively makes it impossible to ever acquire a mutable guard or any
guard for `Ref` and `RefMut` respectively. It is already safe to use
this to create a reference to the inner of the ref cell that lives as
long as the reference to the `RefCell` itself, e.g.
```rust
fn leak(r: &RefCell<usize>) -> Option<&usize> {
let guard = r.try_borrow().ok()?;
let leaked = Box::leak(Box::new(guard));
Some(&*leaked)
}
```
The newly added methods allow the same reference conversion without an
indirection over a leaked allocation. It's placed on the `Ref`/`RefMut` to
compose with both borrow and try_borrow directly.
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Usually, references to the interior are only created by the `Deref` and
`DerefMut` impl of the guards `Ref` and `RefMut`. Note that `RefCell`
already has to cope with leaks of such guards which, when it occurs,
effectively makes it impossible to ever acquire a mutable guard or any
guard for `Ref` and `RefMut` respectively. It is already safe to use
this to create a reference to the inner of the ref cell that lives as
long as the reference to the `RefCell` itself, e.g.
```rust
fn leak(r: &RefCell<usize>) -> Option<&usize> {
let guard = r.try_borrow().ok()?;
let leaked = Box::leak(Box::new(guard));
Some(&*leaked)
}
```
The newly added methods allow the same reference conversion without an
indirection over a leaked allocation and composing with both borrow and
try_borrow without additional method combinations.
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functions with a `const` modifier
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Co-Authored-By: Mazdak Farrokhzad <twingoow@gmail.com>
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Have tidy ensure that we document all `unsafe` blocks in libcore
cc @rust-lang/libs
I documented a few and added ignore flags on the other files. We can incrementally document the files, but won't regress any files this way.
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To make `new` method appear first in documentation.
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Optimize RefCell read borrowing
Instead of doing two comparisons we can do only one with a bit of cleverness.
LLVM currently can't do this optimization itself on x86-64.
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Instead of doing two comparisons we can do only one with a bit of
cleverness.
LLVM currently can't do this optimization itself on x86-64.
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FCP: https://github.com/rust-lang/rust/issues/43038#issuecomment-499900463
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Stabilize RefCell::try_borrow_unguarded
Servo has been using this since https://github.com/servo/servo/pull/23196 to add a runtime check to some unsafe code, as discussed in PR https://github.com/rust-lang/rust/pull/59211. Stabilizing would help do more of the same in libraries that also have users on Stable.
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Servo has been using this since https://github.com/servo/servo/pull/23196 to add a runtime check to some unsafe code, as discussed in PR https://github.com/rust-lang/rust/pull/59211. Stabilizing would help do more of the same in libraries that also have users on Stable.
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