Windows: No panic if function not (yet) available
In some situations (e.g. #97814) it is possible for required functions to be called before they've had a chance to be loaded. Therefore, we make it possible to recover from this situation simply by looking at error codes.
`@rustbot` label +O-windows
Add `#[inline]` to small fns of futex `RwLock`
The important methods like `read` and `write` were already inlined,
which can propagate all the way to inlining in user code, but these
small state functions were left behind as normal calls. They should
almost always be inlined as well, as they're just a few instructions.
Test NLL fix of bad lifetime inference for reference captured in closure.
This came up as a use-case for `thread::scope` API that only compiles successfully since `feature(nll)` got stabilized recently.
Closes#93203 which had been re-opened for tracking this very test case to be added.
Entry and_modify doc
This PR modifies the documentation for [HashMap](https://doc.rust-lang.org/std/collections/struct.HashMap.html#) and [BTreeMap](https://doc.rust-lang.org/std/collections/struct.BTreeMap.html#) by introducing examples for `and_modify`. `and_modify` is a function that tends to give more idiomatic rust code when dealing with these data structures -- yet it lacked examples and was hidden away. This PR adds that and addresses #98122.
I've made some choices which I tried to explain in my commits. This is my first time contributing to rust, so hopefully, I made the right choices.
os str capacity documentation
This is based on https://github.com/rust-lang/rust/pull/95394 , with expansion and consolidation
to address comments from `@dtolnay` and other `@rust-lang/libs-api` team members.
Add a `BorrowedFd::try_clone_to_owned` and accompanying documentation
Add a `BorrowedFd::try_clone_to_owned`, which returns a new `OwnedFd` sharing the underlying file description. And similar for `BorrowedHandle` and `BorrowedSocket` on WIndows.
This is similar to the existing `OwnedFd::try_clone`, but it's named differently to reflect that it doesn't return `Result<Self, ...>`. I'm open to suggestions for better names.
Also, extend the `unix::io` documentation to mention that `dup` is permitted on `BorrowedFd`.
This was originally requsted [here](https://github.com/rust-lang/rust/issues/88564#issuecomment-910786081). At the time I wasn't sure whether it was desirable, but it does have uses and it helps clarify the API. The documentation previously didn't rule out using `dup` on a `BorrowedFd`, but the API only offered convenient ways to do it from an `OwnedFd`. With this patch, the API allows one to do `try_clone` on any type where it's permitted.
The important methods like `read` and `write` were already inlined,
which can propagate all the way to inlining in user code, but these
small state functions were left behind as normal calls. They should
almost always be inlined as well, as they're just a few instructions.
STD support for the Nintendo 3DS
Rustc already supports compiling for the Nintendo 3DS using the `armv6k-nintendo-3ds` target (Tier 3). Until now though, only `core` and `alloc` were supported. This PR adds standard library support for the Nintendo 3DS. A notable exclusion is `std::thread` support, which will come in a follow-up PR as it requires more complicated changes.
This has been a joint effort by `@Meziu,` `@ian-h-chamberlain,` myself, and prior work by `@rust3ds` members.
### Background
The Nintendo 3DS (Horizon OS) is a mostly-UNIX looking system, with the caveat that it does not come with a full libc implementation out of the box. On the homebrew side (I'm not under NDA), the libc interface is partially implemented by the [devkitPro](https://devkitpro.org/wiki/devkitPro_pacman) toolchain and a user library like [`libctru`](https://github.com/devkitPro/libctru). This is important because there are [some possible legal barriers](https://github.com/rust-lang/rust/pull/88529#issuecomment-919938396) to linking directly to a library that uses the underlying platform APIs, since they might be considered a trade secret or under NDA.
To get around this, the standard library impl for the 3DS does not directly depend on any platform-level APIs. Instead, it expects standard libc functions to be linked in. The implementation of these libc functions is left to the user. Some functions are provided by the devkitPro toolchain, but in our testing, we used the following to fill in the other functions:
- [`libctru`] - provides more basic APIs, such as `nanosleep`. Linked in by way of [`ctru-sys`](https://github.com/Meziu/ctru-rs/tree/master/ctru-sys).
- [`pthread-3ds`](https://github.com/Meziu/pthread-3ds) - provides pthread APIs for `std::thread`. Implemented using [`libctru`].
- [`linker-fix-3ds`](https://github.com/Meziu/rust-linker-fix-3ds) - fulfills some other missing libc APIs. Implemented using [`libctru`].
For more details, see the `src/doc/rustc/src/platform-support/armv6k-nintendo-3ds.md` file added in this PR.
### Notes
We've already upstreamed changes to the [`libc`] crate to support this PR, as well as the upcoming threading PR. These changes have all been released as of 0.2.121, so we bump the crate version in this PR.
Edit: After some rebases, the version bump has already been merged so it doesn't appear in this PR.
A lot of the changes in this PR are straightforward, and follow in the footsteps of the ESP-IDF target: https://github.com/rust-lang/rust/pull/87666.
The 3DS does not support user space process spawning, so these APIs are unimplemented (similar to ESP-IDF).
[`libctru`]: https://github.com/devkitPro/libctru
[`libc`]: https://github.com/rust-lang/libc
Updated the HashMap's documentation to include two references to
add_modify.
The first is when the `Entry` API is mentioned at the beginning. I was
hesitant to change the "attack" example (although I believe that it is
perfect example of where `add_modify` should be used) because both uses
work equally, but one is more idiomatic (`add_modify`).
The second is with the `entry` function that is used for the `Entry`
API. The code example was a perfect use for `add_modify`, which is why
it was changed to reflect that.
This stabilizes the `Path::try_exists()` method which returns
`Result<bool, io::Error>` instead of `bool` allowing handling of errors
unrelated to the file not existing. (e.g permission errors)
Along with the stabilization it also:
* Warns that the `exists()` method is error-prone and suggests to use
the newly stabilized one.
* Suggests it instead of `metadata()` to handle errors.
* Mentions TOCTOU bugs to avoid false assumption that `try_exists()` is
completely safe fixed version of `exists()`.
* Renames the feature of still-unstable `std::fs::try_exists()` to
`fs_try_exists` to avoid name conflict.
The tracking issue #83186 remains open to track `fs_try_exists`.
Integrate measureme's hardware performance counter support.
*Note: this is a companion to https://github.com/rust-lang/measureme/pull/143, and duplicates some information with it for convenience*
**(much later) EDIT**: take any numbers with a grain of salt, they may have changed since initial PR open.
## Credits
I'd like to start by thanking `@alyssais,` `@cuviper,` `@edef1c,` `@glandium,` `@jix,` `@Mark-Simulacrum,` `@m-ou-se,` `@mystor,` `@nagisa,` `@puckipedia,` and `@yorickvP,` for all of their help with testing, and valuable insight and suggestions.
Getting here wouldn't have been possible without you!
(If I've forgotten anyone please let me know, I'm going off memory here, plus some discussion logs)
## Summary
This PR adds support to `-Z self-profile` for counting hardware events such as "instructions retired" (as opposed to being limited to time measurements), using the `rdpmc` instruction on `x86_64` Linux.
While other OSes may eventually be supported, preliminary research suggests some kind of kernel extension/driver is required to enable this, whereas on Linux any user can profile (at least) their own threads.
Supporting Linux on architectures other than x86_64 should be much easier (provided the hardware supports such performance counters), and was mostly not done due to a lack of readily available test hardware.
That said, 32-bit `x86` (aka `i686`) would be almost trivial to add and test once we land the initial `x86_64` version (as all the CPU detection code can be reused).
A new flag `-Z self-profile-counter` was added, to control which of the named `measureme` counters is used, and which defaults to `wall-time`, in order to keep `-Z self-profile`'s current functionality unchanged (at least for now).
The named counters so far are:
* `wall-time`: the existing time measurement
* name chosen for consistency with `perf.rust-lang.org`
* continues to use `std::time::Instant` for a nanosecond-precision "monotonic clock"
* `instructions:u`: the hardware performance counter usually referred to as "Instructions retired"
* here "retired" (roughly) means "fully executed"
* the `:u` suffix is from the Linux `perf` tool and indicates the counter only runs while userspace code is executing, and therefore counts no kernel instructions
* *see [Caveats/Subtracting IRQs](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#Subtracting-IRQs) for why this isn't entirely true and why `instructions-minus-irqs:u` should be preferred instead*
* `instructions-minus-irqs:u`: same as `instructions:u`, except the count of hardware interrupts ("IRQs" here for brevity) is subtracted
* *see [Caveats/Subtracting IRQs](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#Subtracting-IRQs) for why this should be preferred over `instructions:u`*
* `instructions-minus-r0420:u`: experimental counter, same as `instructions-minus-irqs:u` but subtracting an undocumented counter (`r0420:u`) instead of IRQs
* the `rXXXX` notation is again from Linux `perf`, and indicates a "raw" counter, with a hex representation of the low-level counter configuration - this was picked because we still don't *really* know what it is
* this only exists for (future) testing and isn't included/used in any comparisons/data we've put together so far
* *see [Challenges/Zen's undocumented 420 counter](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#Epilogue-Zen’s-undocumented-420-counter) for details on how this counter was found and what it does*
---
There are also some additional commits:
* ~~see [Challenges/Rebasing *shouldn't* affect the results, right?](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#Rebasing-*shouldn’t*-affect-the-results,-right) for details on the changes to `rustc_parse` and `rustc_trait_section` (the latter far more dubious, and probably shouldn't be merged, or not as-is)~~
* **EDIT**: the effects of these are no long quantifiable, the PR includes reverts for them
* ~~see [Challenges/`jemalloc`: purging will commence in ten seconds](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#jemalloc-purging-will-commence-in-ten-seconds) for details on the `jemalloc` change~~
* this is also separately found in #77162, and we probably want to avoid doing it by default, ideally we'd use the runtime control API `jemalloc` offers (assuming that can stop the timer that's already running, which I'm not sure about)
* **EDIT**: until we can do this based on `-Z` flags, this commit has also been reverted
* the `proc_macro` change was to avoid randomized hashing and therefore ASLR-like effects
---
**(much later) EDIT**: take any numbers with a grain of salt, they may have changed since initial PR open.
#### Write-up / report
Because of how extensive the full report ended up being, I've kept most of it [on `hackmd.io`](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view), but for convenient access, here are all the sections (with individual links):
<sup>(someone suggested I'd make a backup, so [here it is on the wayback machine](http://web.archive.org/web/20201127164748/https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view) - I'll need to remember to update that if I have to edit the write-up)</sup>
* [**Motivation**](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#Motivation)
* [**Results**](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#Results)
* [**Overhead**](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#Overhead)
*Preview (see the report itself for more details):*
|Counter|Total<br>`instructions-minus-irqs:u`|Overhead from "Baseline"<br>(for all 1903881<br>counter reads)|Overhead from "Baseline"<br>(per each counter read)|
|-|-|-|-|
|Baseline|63637621286 ±6||
|`instructions:u`|63658815885 ±2| +21194599 ±8| +11|
|`instructions-minus-irqs:u`|63680307361 ±13| +42686075 ±19| +22|
|`wall-time`|63951958376 ±10275|+314337090 ±10281|+165|
* [**"Macro" noise (self time)**](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#“Macro”-noise-(self-time))
*Preview (see the report itself for more details):*
|| `wall-time` (ns) | `instructions:u` | `instructions-minus-irqs:u`
-: | -: | -: | -:
`typeck` | 5478261360 ±283933373 (±~5.2%) | 17350144522 ±6392 (±~0.00004%) | 17351035832.5 ±4.5 (±~0.00000003%)
`expand_crate` | 2342096719 ±110465856 (±~4.7%) | 8263777916 ±2937 (±~0.00004%) | 8263708389 ±0 (±~0%)
`mir_borrowck` | 2216149671 ±119458444 (±~5.4%) | 8340920100 ±2794 (±~0.00003%) | 8341613983.5 ±2.5 (±~0.00000003%)
`mir_built` | 1269059734 ±91514604 (±~7.2%) | 4454959122 ±1618 (±~0.00004%) | 4455303811 ±1 (±~0.00000002%)
`resolve_crate` | 942154987.5 ±53068423.5 (±~5.6%) | 3951197709 ±39 (±~0.000001%) | 3951196865 ±0 (±~0%)
* [**"Micro" noise (individual sampling intervals)**](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#“Micro”-noise-(individual-sampling-intervals))
* [**Caveats**](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#Caveats)
* [**Disabling ASLR**](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#Disabling-ASLR)
* [**Non-deterministic proc macros**](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#Non-deterministic-proc-macros)
* [**Subtracting IRQs**](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#Subtracting-IRQs)
* [**Lack of support for multiple threads**](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#Lack-of-support-for-multiple-threads)
* [**Challenges**](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#Challenges)
* [**How do we even read hardware performance counters?**](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#How-do-we-even-read-hardware-performance-counters)
* [**ASLR: it's free entropy**](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#ASLR-it’s-free-entropy)
* [**The serializing instruction**](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#The-serializing-instruction)
* [**Getting constantly interrupted**](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#Getting-constantly-interrupted)
* [**AMD patented time-travel and dubbed it `SpecLockMap`<br><sup> or: "how we accidentally unlocked `rr` on AMD Zen"</sup>**](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#AMD-patented-time-travel-and-dubbed-it-SpecLockMapnbspnbspnbspnbspnbspnbspnbspnbspor-“how-we-accidentally-unlocked-rr-on-AMD-Zen”)
* [**`jemalloc`: purging will commence in ten seconds**](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#jemalloc-purging-will-commence-in-ten-seconds)
* [**Rebasing *shouldn't* affect the results, right?**](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#Rebasing-*shouldn’t*-affect-the-results,-right)
* [**Epilogue: Zen's undocumented 420 counter**](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#Epilogue-Zen’s-undocumented-420-counter)
Our condvar doesn't support setting attributes, like
pthread_condattr_setclock, which the current wait_timeout expects to
have configured.
Switch to a different implementation, following espidf.
Use `fcntl(fd, F_GETFD)` to detect if standard streams are open
In the previous implementation, if the standard streams were open,
but the RLIMIT_NOFILE value was below three, the poll would fail
with EINVAL:
> ERRORS: EINVAL The nfds value exceeds the RLIMIT_NOFILE value.
Switch to the existing fcntl based implementation to avoid the issue.
Fixes#96621.
std::io: Modify some ReadBuf method signatures to return `&mut Self`
This allows using `ReadBuf` in a builder-like style and to setup a `ReadBuf` and
pass it to `read_buf` in a single expression, e.g.,
```
// With this PR:
reader.read_buf(ReadBuf::uninit(buf).assume_init(init_len))?;
// Previously:
let mut buf = ReadBuf::uninit(buf);
buf.assume_init(init_len);
reader.read_buf(&mut buf)?;
```
r? `@sfackler`
cc https://github.com/rust-lang/rust/issues/78485, https://github.com/rust-lang/rust/issues/94741
`Mutex::lock()` and `RwLock::write()` are poison-guarded against panics,
in that they set the poison flag if a panic occurs while they're locked.
But if we're already in a panic (`thread::panicking()`), they leave the
poison flag alone.
That check is a bit of a waste for methods that never set the poison
flag though, namely `get_mut()`, `into_inner()`, and `RwLock::read()`.
These use-cases are now split to avoid that unnecessary call.
This allows to format into an `OsString` without unnecessary
allocations. E.g.
```
let mut temp_filename = path.into_os_string();
write!(&mut temp_filename, ".tmp.{}", process::id());
```
impl Read and Write for VecDeque<u8>
Implementing `Read` and `Write` for `VecDeque<u8>` fills in the VecDeque api surface where `Vec<u8>` and `Cursor<Vec<u8>>` already impl Read and Write. Not only for completeness, but VecDeque in particular is a very handy mock interface for a TCP echo service, if only it supported Read/Write.
Since this PR is just an impl trait, I don't think there is a way to limit it behind a feature flag, so it's "insta-stable". Please correct me if I'm wrong here, not trying to rush stability.
This commit adds a new unstable attribute, `#[doc(tuple_varadic)]`, that
shows a 1-tuple as `(T, ...)` instead of just `(T,)`, and links to a section
in the tuple primitive docs that talks about these.
In some situations it is possible for required functions to be called before they've had a chance to be loaded. Therefore, we make it possible to recover from this situation simply by looking at error codes.
Add documentation to `std::os::unix::io` describing Rust's stance on
`/proc/self/mem`, treating it as an external entity which is outside
the scope of Rust's safety guarantees.
Remove confusing sentence from `Mutex` docs
The docs were saying something about "statically initializing" the
mutex, and it's not clear what this means. Remove that part to avoid
confusion.
Remove migrate borrowck mode
Closes#58781Closes#43234
# Stabilization proposal
This PR proposes the stabilization of `#![feature(nll)]` and the removal of `-Z borrowck`. Current borrow checking behavior of item bodies is currently done by first infering regions *lexically* and reporting any errors during HIR type checking. If there *are* any errors, then MIR borrowck (NLL) never occurs. If there *aren't* any errors, then MIR borrowck happens and any errors there would be reported. This PR removes the lexical region check of item bodies entirely and only uses MIR borrowck. Because MIR borrowck could never *not* be run for a compiled program, this should not break any programs. It does, however, change diagnostics significantly and allows a slightly larger set of programs to compile.
Tracking issue: #43234
RFC: https://github.com/rust-lang/rfcs/blob/master/text/2094-nll.md
Version: 1.63 (2022-06-30 => beta, 2022-08-11 => stable).
## Motivation
Over time, the Rust borrow checker has become "smarter" and thus allowed more programs to compile. There have been three different implementations: AST borrowck, MIR borrowck, and polonius (well, in progress). Additionally, there is the "lexical region resolver", which (roughly) solves the constraints generated through HIR typeck. It is not a full borrow checker, but does emit some errors.
The AST borrowck was the original implementation of the borrow checker and was part of the initially stabilized Rust 1.0. In mid 2017, work began to implement the current MIR borrow checker and that effort ompleted by the end of 2017, for the most part. During 2018, efforts were made to migrate away from the AST borrow checker to the MIR borrow checker - eventually culminating into "migrate" mode - where HIR typeck with lexical region resolving following by MIR borrow checking - being active by default in the 2018 edition.
In early 2019, migrate mode was turned on by default in the 2015 edition as well, but with MIR borrowck errors emitted as warnings. By late 2019, these warnings were upgraded to full errors. This was followed by the complete removal of the AST borrow checker.
In the period since, various errors emitted by the MIR borrow checker have been improved to the point that they are mostly the same or better than those emitted by the lexical region resolver.
While there do remain some degradations in errors (tracked under the [NLL-diagnostics tag](https://github.com/rust-lang/rust/issues?q=is%3Aopen+is%3Aissue+label%3ANLL-diagnostics), those are sufficiently small and rare enough that increased flexibility of MIR borrow check-only is now a worthwhile tradeoff.
## What is stabilized
As said previously, this does not fundamentally change the landscape of accepted programs. However, there are a [few](https://github.com/rust-lang/rust/issues?q=is%3Aopen+is%3Aissue+label%3ANLL-fixed-by-NLL) cases where programs can compile under `feature(nll)`, but not otherwise.
There are two notable patterns that are "fixed" by this stabilization. First, the `scoped_threads` feature, which is a continutation of a pre-1.0 API, can sometimes emit a [weird lifetime error](https://github.com/rust-lang/rust/issues/95527) without NLL. Second, actually seen in the standard library. In the `Extend` impl for `HashMap`, there is an implied bound of `K: 'a` that is available with NLL on but not without - this is utilized in the impl.
As mentioned before, there are a large number of diagnostic differences. Most of them are better, but some are worse. None are serious or happen often enough to need to block this PR. The biggest change is the loss of error code for a number of lifetime errors in favor of more general "lifetime may not live long enough" error. While this may *seem* bad, the former error codes were just attempts to somewhat-arbitrarily bin together lifetime errors of the same type; however, on paper, they end up being roughly the same with roughly the same kinds of solutions.
## What isn't stabilized
This PR does not completely remove the lexical region resolver. In the future, it may be possible to remove that (while still keeping HIR typeck) or to remove it together with HIR typeck.
## Tests
Many test outputs get updated by this PR. However, there are number of tests specifically geared towards NLL under `src/test/ui/nll`
## History
* On 2017-07-14, [tracking issue opened](https://github.com/rust-lang/rust/issues/43234)
* On 2017-07-20, [initial empty MIR pass added](https://github.com/rust-lang/rust/pull/43271)
* On 2017-08-29, [RFC opened](https://github.com/rust-lang/rfcs/pull/2094)
* On 2017-11-16, [Integrate MIR type-checker with NLL](https://github.com/rust-lang/rust/pull/45825)
* On 2017-12-20, [NLL feature complete](https://github.com/rust-lang/rust/pull/46862)
* On 2018-07-07, [Don't run AST borrowck on mir mode](https://github.com/rust-lang/rust/pull/52083)
* On 2018-07-27, [Add migrate mode](https://github.com/rust-lang/rust/pull/52681)
* On 2019-04-22, [Enable migrate mode on 2015 edition](https://github.com/rust-lang/rust/pull/59114)
* On 2019-08-26, [Don't downgrade errors on 2015 edition](https://github.com/rust-lang/rust/pull/64221)
* On 2019-08-27, [Remove AST borrowck](https://github.com/rust-lang/rust/pull/64790)
Add note to documentation of HashSet::intersection
The functionality of the `std::collections::HashSet::intersection(...)` method was slightly surprising to me so I wanted to take a sec to contribute to the documentation for this method.
I've added a `Note:` section if that is appropriate.
Call the OS function to set the main thread's name on program init
Normally, `Thread::spawn` takes care of setting the thread's name, if
one was provided, but since the main thread wasn't created by calling
`Thread::spawn`, we need to call that function in `std::rt::init`.
This is mainly useful for system tools like debuggers and profilers
which might show the thread name to a user. Prior to these changes, gdb
and WinDbg would show all thread names except the main thread's name to
a user. I've validated that this patch resolves the issue for both
debuggers.
Lazily allocate and initialize pthread locks.
Lazily allocate and initialize pthread locks.
This allows {Mutex, Condvar, RwLock}::new() to be const, while still using the platform's native locks for features like priority inheritance and debug tooling. E.g. on macOS, we cannot directly use the (private) APIs that pthread's locks are implemented with, making it impossible for us to use anything other than pthread while still preserving priority inheritance, etc.
This PR doesn't yet make the public APIs const. That's for a separate PR with an FCP.
Tracking issue: https://github.com/rust-lang/rust/issues/93740
Tweak insert docs
For `{Hash, BTree}Map::insert`, I always have to take a few extra seconds to think about the slight weirdness about the fact that if we "did not" insert (which "sounds" false), we return true, and if we "did" insert, (which "sounds" true), we return false.
This tweaks the doc comments for the `insert` methods of those types (as well as what looks like a rustc internal data structure that I found just by searching the codebase for "If the set did") to first use the "Returns whether _something_" pattern used in e.g. `remove`, where we say that `remove` "returns whether the value was present".
Expose `get_many_mut` and `get_many_unchecked_mut` to HashMap
This pull-request expose the function [`get_many_mut`](https://docs.rs/hashbrown/0.12.0/hashbrown/struct.HashMap.html#method.get_many_mut) and [`get_many_unchecked_mut`](https://docs.rs/hashbrown/0.12.0/hashbrown/struct.HashMap.html#method.get_many_unchecked_mut) from `hashbrown` to the standard library `HashMap` type. They obviously keep the same API and are added under the (new) `map_many_mut` feature.
- `get_many_mut`: Attempts to get mutable references to `N` values in the map at once.
- `get_many_unchecked_mut`: Attempts to get mutable references to `N` values in the map at once, without validating that the values are unique.
library/std: Bump compiler_builtins
Some neat changes include faster float conversions & fixes for AVR 🙂
(note that's it's my first time upgrading `compiler_builtins`, so I'm not 100% sure if bumping `library/std/Cargo.toml` is enough; certainly seems to be so, though.)
Put a bound on collection misbehavior
As currently written, when a logic error occurs in a collection's trait parameters, this allows *completely arbitrary* misbehavior, so long as it does not cause undefined behavior in std. However, because the extent of misbehavior is not specified, it is allowed for *any* code in std to start misbehaving in arbitrary ways which are not formally UB; consider the theoretical example of a global which gets set on an observed logic error. Because the misbehavior is only bound by not resulting in UB from safe APIs and the crate-level encapsulation boundary of all of std, this makes writing user unsafe code that utilizes std theoretically impossible, as it now relies on undocumented QOI (quality of implementation) that unrelated parts of std cannot be caused to misbehave by a misuse of std::collections APIs.
In practice, this is a nonconcern, because std has reasonable QOI and an implementation that takes advantage of this freedom is essentially a malicious implementation and only compliant by the most langauage-lawyer reading of the documentation.
To close this hole, we just add a small clause to the existing logic error paragraph that ensures that any misbehavior is limited to the collection which observed the logic error, making it more plausible to prove the soundness of user unsafe code.
This is not meant to be formal; a formal refinement would likely need to mention that values derived from the collection can also misbehave after a logic error is observed, as well as define what it means to "observe" a logic error in the first place. This fix errs on the side of informality in order to close the hole without complicating a normal reading which can assume a reasonable nonmalicious QOI.
See also [discussion on IRLO][1].
[1]: https://internals.rust-lang.org/t/using-std-collections-and-unsafe-anything-can-happen/16640
r? rust-lang/libs-api ```@rustbot``` label +T-libs-api -T-libs
This technically adds a new guarantee to the documentation, though I argue as written it's one already implicitly provided.
Rollup of 6 pull requests
Successful merges:
- #97089 (Improve settings theme display)
- #97229 (Document the current aliasing rules for `Box<T>`.)
- #97371 (Suggest adding a semicolon to a closure without block)
- #97455 (Stabilize `toowned_clone_into`)
- #97565 (Add doc alias `memset` to `write_bytes`)
- #97569 (Remove `memset` alias from `fill_with`.)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
Implement [OsStr]::join
Implements join for `OsStr` and `OsString` slices:
```Rust
let strings = [OsStr::new("hello"), OsStr::new("dear"), OsStr::new("world")];
assert_eq!("hello dear world", strings.join(OsStr::new(" ")));
````
This saves one from converting to strings and back, or from implementing it manually.
This PR has been re-filed after #96744 was first accidentally merged and then reverted.
The change is instantly stable and thus:
r? rust-lang/libs-api `@rustbot` label +T-libs-api -T-libs
cc `@thomcc` `@m-ou-se` `@faptc`
Remove "sys isn't exported yet" phrase
The oldest occurence is from 9e224c2bf1,
which is from the pre-1.0 days. In the years since then, std::sys still
hasn't been exported, and the last attempt was met with strong criticism:
https://github.com/rust-lang/rust/pull/97151
Thus, removing the "yet" part makes a lot of sense.
Use Box::new() instead of box syntax in library tests
The tests inside `library/*` have no reason to use `box` syntax as they have 0 performance relevance. Therefore, we can safely remove them (instead of having to use alternatives like the one in #97293).
The oldest occurence is from 9e224c2bf1,
which is from the pre-1.0 days. In the years since then, std::sys still
hasn't been exported, and the last attempt was met with strong criticism:
https://github.com/rust-lang/rust/pull/97151
Thus, removing the "yet" part makes a lot of sense.
Finish bumping stage0
It looks like the last time had left some remaining cfg's -- which made me think
that the stage0 bump was actually successful. This brings us to a released 1.62
beta though.
This now brings us to cfg-clean, with the exception of check-cfg-features in bootstrap;
I'd prefer to leave that for a separate PR at this time since it's likely to be more tricky.
cc https://github.com/rust-lang/rust/pull/97147#issuecomment-1132845061
r? `@pietroalbini`
Normally, `Thread::spawn` takes care of setting the thread's name, if
one was provided, but since the main thread wasn't created by calling
`Thread::spawn`, we need to call that function in `std::rt::init`.
This is mainly useful for system tools like debuggers and profilers
which might show the thread name to a user. Prior to these changes, gdb
and WinDbg would show all thread names except the main thread's name to
a user. I've validated that this patch resolves the issue for both
debuggers.
It looks like the last time had left some remaining cfg's -- which made me think
that the stage0 bump was actually successful. This brings us to a released 1.62
beta though.
Add section on common message styles for Result::expect
Based on a question from https://github.com/rust-lang/project-error-handling/issues/50#issuecomment-1092339937
~~One thing I haven't decided on yet, should I duplicate this section on `Option::expect`, link to this section, or move it somewhere else and link to that location from both docs?~~: I ended up moving the section to `std::error` and referencing it from both `Result::expect` and `Option::expect`'s docs.
I think this section, when combined with the similar update I made on [`std::panic!`](https://doc.rust-lang.org/nightly/std/macro.panic.html#when-to-use-panic-vs-result) implies that we should possibly more aggressively encourage and support the "expect as precondition" style described in this section. The consensus among the libs team seems to be that panic should be used for bugs, not expected potential failure modes. The "expect as error message" style seems to align better with the panic for unrecoverable errors style where they're seen as normal errors where the only difference is a desire to kill the current execution unit (aka erlang style error handling). I'm wondering if we should be providing a panic hook similar to `human-panic` or more strongly recommending the "expect as precondition" style of expect message.
