Remove `crate` visibility modifier
FCP to remove this syntax is just about complete in #53120. Once it completes, this should be merged ASAP to avoid merge conflicts.
The first two commits remove usage of the feature in this repository, while the last removes the feature itself.
Drop Tracking: Implement `fake_read` callback
This PR updates drop tracking's use of `ExprUseVisitor` so that we treat `fake_read` events as borrows. Without doing this, we were not handling match expressions correctly, which showed up as a breakage in the `addassign-yield.rs` test. We did not previously notice this because we still had rather large temporary scopes that we held borrows for, which changed in #94309.
This PR also includes a variant of the `addassign-yield.rs` test case to make sure we continue to have correct behavior here with drop tracking.
r? `@nikomatsakis`
Improve codegen of String::retain method
This pull-request improve the codegen of the `String::retain` method.
Using `unwrap_unchecked` helps the optimizer to not generate a panicking path that will never be taken for valid UTF-8 like string.
Using `encode_utf8` saves us from an expensive call to `memcpy`, as the optimizer is unable to realize that `ch_len <= 4` and so can generate much better assembly code.
https://rust.godbolt.org/z/z73ohenfc
Use GRND_INSECURE instead of /dev/urandom when possible
From reading the source code, it appears like the desired semantic of
std::unix::rand is to always provide some bytes and never block. For
that reason GRND_NONBLOCK is checked before calling getrandom(0), so
that getrandom(0) won't block. If it would block, then the function
falls back to using /dev/urandom, which for the time being doesn't
block. There are some drawbacks to using /dev/urandom, however, and so
getrandom(GRND_INSECURE) was created as a replacement for this exact
circumstance.
getrandom(GRND_INSECURE) is the same as /dev/urandom, except:
- It won't leave a warning in dmesg if used at early boot time, which is
a common occurance (and the reason why I found this issue);
- It won't introduce a tiny delay at early boot on newer kernels when
/dev/urandom tries to opportunistically create jitter entropy;
- It only requires 1 syscall, rather than 3.
Other than that, it returns the same "quality" of randomness as
/dev/urandom, and never blocks.
It's only available on kernels ≥5.6, so we try to use it, cache the
result of that attempt, and fall back to to the previous code if it
didn't work.
From reading the source code, it appears like the desired semantic of
std::unix::rand is to always provide some bytes and never block. For
that reason GRND_NONBLOCK is checked before calling getrandom(0), so
that getrandom(0) won't block. If it would block, then the function
falls back to using /dev/urandom, which for the time being doesn't
block. There are some drawbacks to using /dev/urandom, however, and so
getrandom(GRND_INSECURE) was created as a replacement for this exact
circumstance.
getrandom(GRND_INSECURE) is the same as /dev/urandom, except:
- It won't leave a warning in dmesg if used at early boot time, which is
a common occurance (and the reason why I found this issue);
- It won't introduce a tiny delay at early boot on newer kernels when
/dev/urandom tries to opportunistically create jitter entropy;
- It only requires 1 syscall, rather than 3.
Other than that, it returns the same "quality" of randomness as
/dev/urandom, and never blocks.
It's only available on kernels ≥5.6, so we try to use it, cache the
result of that attempt, and fall back to to the previous code if it
didn't work.
Cache more queries on disk
One of the principles of incremental compilation is to allow saving results on disk to avoid recomputing them.
This PR investigates persisting a lot of queries whose result are to be saved into metadata.
Some of the queries are cheap reads from HIR, but we may also want to get rid of these reads for incremental lowering.
Add complexity estimation of iterating over HashSet and HashMap
It is not obvious (at least for me) that complexity of iteration over hash tables depends on capacity and not length. Especially comparing with other containers like Vec or String. I think, this behaviour is worth mentioning.
I run benchmark which tests iteration time for maps with length 50 and different capacities and get this results:
```
capacity - time
64 - 203.87 ns
256 - 351.78 ns
1024 - 607.87 ns
4096 - 965.82 ns
16384 - 3.1188 us
```
If you want to dig why it behaves such way, you can look current implementation in [hashbrown code](f3a9f211d0/src/raw/mod.rs (L1933)).
Benchmarks code would be presented in PR related to this commit.
Do not emit the lint `unused_attributes` for *inherent* `#[doc(hidden)]` associated items
Fixes#97205 (embarrassing oversight from #96008).
`@rustbot` label A-lint
Minor tweaks to rustc book summary formatting.
This includes a few minor tweaks to the summary/titles of chapters for the rustc book:
* Use a consistent chapter capitalization and hyphenation.
* Move "Codegen Options" underneath "Command-line Arguments". I feel like they are two closely related chapters, where codegen is just a subset of the total arguments.
* Move "Target Tier Policy" underneath "Platform Support". That chapter includes that policy for platform support, and thus I feel it is more closely related to that grouping.
Reverse condition in Vec::retain_mut doctest
I find that the doctest for `Vec::retain_mut` is easier to read and understand when the `if` block corresponds to the path that returns `true` and the `else` block returns `false`. Having the `if` block be the `false` path led me to stare at the example for somewhat longer than I probably had to.
It is not obvious (at least for me) that complexity of iteration over hash tables depends on capacity and not length. Especially comparing with other containers like Vec or String. I think, this behaviour is worth mentioning.
I run benchmark which tests iteration time for maps with length 50 and different capacities and get this results:
```
capacity - time
64 - 203.87 ns
256 - 351.78 ns
1024 - 607.87 ns
4096 - 965.82 ns
16384 - 3.1188 us
```
If you want to dig why it behaves such way, you can look current implementation in [hashbrown code](f3a9f211d0/src/raw/mod.rs (L1933)).
Benchmarks code would be presented in PR related to this commit.
Rollup of 6 pull requests
Successful merges:
- #96565 (rustdoc: show implementations on `#[fundamental]` wrappers)
- #97179 (Add new lint to enforce whitespace after keywords)
- #97185 (interpret/validity: separately control checking numbers for being init and non-ptr)
- #97188 (Remove unneeded null pointer asserts in ptr2int casts)
- #97189 (Update .mailmap)
- #97192 (Say "last" instead of "rightmost" in the documentation for `std::str:rfind`)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
Say "last" instead of "rightmost" in the documentation for `std::str:rfind`
In the documentation comment for `std::str::rfind`, say "last" instead
of "rightmost" to describe the match that `rfind` finds. This follows the
spirit of #30459, for which `trim_left` and `trim_right` were replaced by
`trim_start` and `trim_end` to be more clear about how they work on
text which is displayed right-to-left.
Remove unneeded null pointer asserts in ptr2int casts
This removes an assert that a pointer with address 0 has no provenance. This change is needed to support permissive provenance work in Miri, and seems justified by `ptr.with_addr(0)` working and a discussion on Zulip regarding LLVM semantics.
r? `@RalfJung`
interpret/validity: separately control checking numbers for being init and non-ptr
This lets Miri control this in a more fine-grained way.
r? `@oli-obk`
generator_interior: Count match pattern bindings as borrowed for the whole guard expression
The test case `yielding-in-match-guard.rs` was failing with `-Zdrop-tracking` enabled. The reason is that the copy of a local (`y`) was not counted as a borrow in typeck, while MIR did consider this as borrowed.
The correct thing to do here is to count pattern bindings are borrowed for the whole guard. Instead, what we were doing is to record the type at the use site of the variable and check if the variable comes from a borrowed pattern. Due to the fix for #57017, we were considering too small of a scope for this variable, which meant it was not counted as borrowed.
Because we now unconditionally record the borrow, rather than only for bindings that are used, this PR is also able to remove a lot of the logic around match bindings that was there before.
r? `@nikomatsakis`
Use pointers in `cell::{Ref,RefMut}` to avoid `noalias`
When `Ref` and `RefMut` were based on references, they would get LLVM `noalias` attributes that were incorrect, because that alias guarantee is only true until the guard drops. A `&RefCell` on the same value can get a new borrow that aliases the previous guard, possibly leading to miscompilation. Using `NonNull` pointers in `Ref` and `RefCell` avoids `noalias`.
Fixes the library side of #63787, but we still might want to explore language solutions there.
