Compress amount of hashed bytes for `isize` values in StableHasher
This is another attempt to land https://github.com/rust-lang/rust/pull/92103, this time hopefully with a correct implementation w.r.t. stable hashing guarantees. The previous PR was [reverted](https://github.com/rust-lang/rust/pull/93014) because it could produce the [same hash](https://github.com/rust-lang/rust/pull/92103#issuecomment-1014625442) for different values even in quite simple situations. I have since added a basic [test](https://github.com/rust-lang/rust/pull/93193) that should guard against that situation, I also added a new test in this PR, specialised for this optimization.
## Why this optimization helps
Since the original PR, I have tried to analyze why this optimization even helps (and why it especially helps for `clap`). I found that the vast majority of stable-hashing `i64` actually comes from hashing `isize` (which is converted to `i64` in the stable hasher). I only found a single place where is this datatype used directly in the compiler, and this place has also been showing up in traces that I used to find out when is `isize` being hashed. This place is `rustc_span::FileName::DocTest`, however, I suppose that isizes also come from other places, but they might not be so easy to find (there were some other entries in the trace). `clap` hashes about 8.5 million `isize`s, and all of them fit into a single byte, which is why this optimization has helped it [quite a lot](https://github.com/rust-lang/rust/pull/92103#issuecomment-1005711861).
Now, I'm not sure if special casing `isize` is the correct solution here, maybe something could be done with that `isize` inside `DocTest` or in other places, but that's for another discussion I suppose. In this PR, instead of hardcoding a special case inside `SipHasher128`, I instead put it into `StableHasher`, and only used it for `isize` (I tested that for `i64` it doesn't help, or at least not for `clap` and other few benchmarks that I was testing).
## New approach
Since the most common case is a single byte, I added a fast path for hashing `isize` values which positive value fits within a single byte, and a cold path for the rest of the values.
To avoid the previous correctness problem, we need to make sure that each unique `isize` value will produce a unique hash stream to the hasher. By hash stream I mean a sequence of bytes that will be hashed (a different sequence should produce a different hash, but that is of course not guaranteed).
We have to distinguish different values that produce the same bit pattern when we combine them. For example, if we just simply skipped the leading zero bytes for values that fit within a single byte, `(0xFF, 0xFFFFFFFFFFFFFFFF)` and `(0xFFFFFFFFFFFFFFFF, 0xFF)` would send the same hash stream to the hasher, which must not happen.
To avoid this situation, values `[0, 0xFE]` are hashed as a single byte. When we hash a larger (treating `isize` as `u64`) value, we first hash an additional byte `0xFF`. Since `0xFF` cannot occur when we apply the single byte optimization, we guarantee that the hash streams will be unique when hashing two values `(a, b)` and `(b, a)` if `a != b`:
1) When both `a` and `b` are within `[0, 0xFE]`, their hash streams will be different.
2) When neither `a` and `b` are within `[0, 0xFE]`, their hash streams will be different.
3) When `a` is within `[0, 0xFE]` and `b` isn't, when we hash `(a, b)`, the hash stream will definitely not begin with `0xFF`. When we hash `(b, a)`, the hash stream will definitely begin with `0xFF`. Therefore the hash streams will be different.
r? `@the8472`
Support configuring whether to capture backtraces at runtime
Tracking issue: https://github.com/rust-lang/rust/issues/93346
This adds a new API to the `std::panic` module which configures whether and how the default panic hook will emit a backtrace when a panic occurs.
After discussion with `@yaahc` on [Zulip](https://rust-lang.zulipchat.com/#narrow/stream/219381-t-libs/topic/backtrace.20lib.20vs.2E.20panic), this PR chooses to avoid adjusting or seeking to provide a similar API for the (currently unstable) std::backtrace API. It seems likely that the users of that API may wish to expose more specific settings rather than just a global one (e.g., emulating the `env_logger`, `tracing` per-module configuration) to avoid the cost of capture in hot code. The API added here could plausibly be copied and/or re-exported directly from std::backtrace relatively easily, but I don't think that's the right call as of now.
```rust
mod panic {
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
#[non_exhaustive]
pub enum BacktraceStyle {
Short,
Full,
Off,
}
fn set_backtrace_style(BacktraceStyle);
fn get_backtrace_style() -> Option<BacktraceStyle>;
}
```
Several unresolved questions:
* Do we need to move to a thread-local or otherwise more customizable strategy for whether to capture backtraces? See [this comment](https://github.com/rust-lang/rust/pull/79085#issuecomment-727845826) for some potential use cases for this.
* Proposed answer: no, leave this for third-party hooks.
* Bikeshed on naming of all the options, as usual.
* Should BacktraceStyle be moved into `std::backtrace`?
* It's already somewhat annoying to import and/or re-type the `std::panic::` prefix necessary to use these APIs, probably adding a second module to the mix isn't worth it.
Note that PR #79085 proposed a much simpler API, but particularly in light of the desire to fully replace setting environment variables via `env::set_var` to control the backtrace API, a more complete API seems preferable. This PR likely subsumes that one.
Rollup of 8 pull requests
Successful merges:
- #92528 (Make `Fingerprint::combine_commutative` associative)
- #93221 ([borrowck] Fix help on mutating &self in async fns)
- #93542 (Prevent lifetime elision in type alias)
- #93546 (Validate that values in switch int terminator are unique)
- #93571 (better suggestion for duplicated `where` clause)
- #93574 (don't suggest adding `let` due to bad assignment expressions inside of `while` loop)
- #93590 (More let_else adoptions)
- #93592 (Remove unused dep from rustc_arena)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
don't suggest adding `let` due to bad assignment expressions inside of `while` loop
adds a check that our `lhs` expression is actually within the conditional part of the `while` loop, instead of anywhere in the `while` body.
fixes#93486
[borrowck] Fix help on mutating &self in async fns
Previously, when rustc was provided an async function that tried to
mutate through a shared reference to an implicit self (as shown in the
ui test), rustc would suggest modifying the parameter signature
to `&mut` + the fully qualified name of the ty (in the case of the repro
`S`). If a user modified their code to match the suggestion, the
compiler would not accept it.
This commit modifies the suggestion so that when rustc is provided the
ui test that is also attached in this commit, it suggests (correctly)
`&mut self`. We try to be careful about distinguishing between implicit
and explicit self annotations, since the latter seem to be handled
correctly already.
This is my first PR here so I'm pretty sure I probably missed something/could use better terminology. I also didn't try to make the match exhaustive since implicit self is the only real special case that I need to handle (that I'm aware of), and I'm pretty sure there's a cleaner way to do this so any advice would be greatly appreciated! (I'm also not terribly confident about how I wrote the ui tests)
here is your cc as requested `@compiler-errors`
This is an attempt to fix#93093
Make `Fingerprint::combine_commutative` associative
The previous implementation swapped lower and upper 64-bits of a result
of modular addition, so the function was non-associative.
r? `@Aaron1011`
Return an indexmap in `all_local_trait_impls` query
The data structure previously used here required that `DefId` be `Ord`. As part of #90317, we do not want `DefId` to implement `Ord`.
debuginfo: Make sure that type names for closure and generator environments are unique in debuginfo.
Before this change, closure/generator environments coming from different instantiations of the same generic function were all assigned the same name even though they were distinct types with potentially different data layout. Now we append the generic arguments of the originating function to the type name.
This commit also emits `{closure_env#0}` as the name of these types in order to disambiguate them from the accompanying closure function (which keeps being called `{closure#0}`). Previously both were assigned the same name.
NOTE: Changing debuginfo names like this can break pretty printers and other debugger plugins. I think it's OK in this particular case because the names we are changing were ambiguous anyway. In general though it would be great to have a process for doing changes like these.
Fix two incorrect "it's" (typos in comments)
Found one of these while reading the documentation online. The other came up because it's in the same file.
Add missing | between print options
The help text for the newly stabilized print option is missing a | between stack-protector-strategies and link-args.
Fix incorrect panic message in example
The panic message when calling the `connect()` should probably be a message about connection failure, not a message about binding address failure.
Document valid values of the char type
As discussed at #93392, the current documentation on what constitutes a valid char isn't very detailed and is partly on the MAX constant rather than the type itself.
This PR expands on that information, stating the actual numerical range, giving examples of what won't work, and also mentions how a `char` might be a valid USV but still not be a defined character (terminology checked against [Unicode 14.0, table 2-3](https://www.unicode.org/versions/Unicode14.0.0/ch02.pdf#M9.61673.TableTitle.Table.22.Types.of.Code.Points)).
Make dead code check a query.
Dead code check is run for each invocation of the compiler, even if no modifications were involved.
This PR makes dead code check a query keyed on the module. This allows to skip the check when a module has not changed.
To perform this, a query `live_symbols_and_ignored_derived_traits` is introduced to encapsulate the global analysis of finding live symbols. The second query `check_mod_deathness` outputs diagnostics for each module based on this first query's results.
Continue work on associated const equality
This actually implements some more complex logic for assigning associated consts to values.
Inside of projection candidates, it now defers to a separate function for either consts or
types. To reduce amount of code, projections are now generic over T, where T is either a Type or
a Const. I can add some comments back later, but this was the fastest way to implement it.
It also now finds the correct type of consts in type_of.
---
The current main TODO is finding the const of the def id for the LeafDef.
Right now it works if the function isn't called, but once you use the trait impl with the bound it fails inside projection.
I was hoping to get some help in getting the `&'tcx ty::Const<'tcx>`, in addition to a bunch of other `todo!()`s which I think may not be hit.
r? `@oli-obk`
Updates #92827
Change Termination::report return type to ExitCode
Related to https://github.com/rust-lang/rust/issues/43301
The goal of this change is to minimize the forward compatibility risks in stabilizing Termination. By using the opaque type `ExitCode` instead of an `i32` we leave room for us to evolve the API over time to provide what cross-platform consistency we can / minimize footguns when working with exit codes, where as stabilizing on `i32` would limit what changes we could make in the future in how we represent and construct exit codes.
Implement `RawWaker` and `Waker` getters for underlying pointers
implement #87021
New APIs:
- `RawWaker::data(&self) -> *const ()`
- `RawWaker::vtable(&self) -> &'static RawWakerVTable`
- ~`Waker::as_raw_waker(&self) -> &RawWaker`~ `Waker::as_raw(&self) -> &RawWaker`
This third one is an auxiliary function to make the two APIs above more useful. Since we can only get `&Waker` in `Future::poll`, without this, we need to `transmute` it into `&RawWaker` (relying on `repr(transparent)`) in order to access its data/vtable pointers.
~Not sure if it should be named `as_raw` or `as_raw_waker`. Seems we always use `as_<something-raw>` instead of just `as_raw`. But `as_raw_waker` seems not quite consistent with `Waker::from_raw`.~ As suggested in https://github.com/rust-lang/rust/pull/91828#discussion_r770729837, use `as_raw`.
Enable combining `+crt-static` and `relocation-model=pic` on `x86_64-unknown-linux-gnu`
Modern `gcc` versions support `-static-pie`, and `rustc` will already fall-back to `-static` if the local `gcc` is too old (and hence this change is optimistic rather than absolute). This brings the `-musl` and `-gnu` targets to feature compatibility (albeit with different default settings).
Of note a `-static` or `-static-pie` binary based on glibc that uses NSS-backed functions (`gethostbyname` or `getpwuid` etc.) need to have access to the `libnss_X.so.2` libraries and any of their dynamic dependencies.
I wasn't sure about the `# only`/`# ignore` changes (I've not got a `gnux32` toolchain to test with hence not also enabling `-static-pie` there).
Disable drop range analysis
The previous PR, #93165, still performed the drop range analysis despite ignoring the results. Unfortunately, there were ICEs in the analysis as well, so some packages failed to build (see the issue #93197 for an example). This change further disables the analysis and just provides dummy results in that case.
