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STD support for the ESP-IDF framework #87666

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@ivmarkov ivmarkov commented Jul 31, 2021

Dear all,

This PR is implementing libStd support for the ESP-IDF newlib-based framework, which is the open source SDK provided by Espressif for their MCU family (esp32, esp32s2, esp32c3 and all other forthcoming ones).

Note that this PR has a sibling PR against the libc crate, which implements proper declarations for all ESP-IDF APIs which are necessary for libStd support.

Implementation approach

The ESP-IDF framework - despite being bare metal - offers a relatively complete POSIX API based on newlib. pthread, BSD sockets, file descriptors, and even a small file-system VFS layer. Perhaps the only significant exception is the lack of support for processes, which is to be expected of course on bare metal.

Therefore, the libStd support is implemented as a set of (hopefully small) changes to the sys/unix family of modules, in the form of conditional-compilation branches based either on target_os = "espidf" or in a couple of cases - based on target_env = "newlib" (the latter was already there actually and is not part of this patch).

The PR also contains two new targets:

  • riscv32imc-esp-espidf
  • riscv32imac-esp-espidf

... which are essentially copies of riscv32imc-unknown-none-elf and riscv32imac-unknown-none-elf, but enriched with proper linker, linker_flavor, families, os, env etc. specifications so that (a) the proper conditional compilation branches in libStd are selected when compiling with these targets and (b) the correct linker is used.

Since support for atomics is a precondition for libStd, the riscv32imc-esp-espidf target additionally is configured in such a way, so as to emit libcalls to the __sync* & __atomic* GCC functions, which are already implemented in the ESP-IDF framework. If this modification is not acceptable, we can also live with only the riscv32imac-esp-espidf target as well. While the RiscV chips of Espressif lack native atomics support, the relevant instructions are transparently emulated in the ESP-IDF framework using invalid instruction trap. This modification was implemented specifically with Rust support in mind.

Target maintainers

In case this PR eventually gets merged, you can list myself as a Target Maintainer.

More importantly, Espressif (the chip vendor) is now actively involved and embracing all Rust-related efforts which were originally a community effort. In light of that, I suppose @MabezDev - who initiated the Rust-on-Espressif efforts back in time and who now works for Espressif won't object to being listed as a maintainer as well.

EDIT: I was hinted (thanks, @Urgau) that answering the Tier 3 policy explicitly might be helpful. Answers below.

Tier 3 Target Policy - answers

A proposed target or target-specific patch that substantially changes code shared with other targets (not just target-specific code) must be reviewed and approved by the appropriate team for that shared code before acceptance.

Hopefully, the changes introduced by the ESP-IDF libStd support are rather on the small side. They are completely contained within the sys/unix set of modules (that is, aside from the obviously necessary one-liners in the unwind crate and in build.rs).

A tier 3 target must have a designated developer or developers (the "target maintainers") on record to be CCed when issues arise regarding the target. (The mechanism to track and CC such developers may evolve over time.)

@ivmarkov
@MabezDev

Targets must use naming consistent with any existing targets; for instance, a target for the same CPU or OS as an existing Rust target should use the same name for that CPU or OS. Targets should normally use the same names and naming conventions as used elsewhere in the broader ecosystem beyond Rust (such as in other toolchains), unless they have a very good reason to diverge. Changing the name of a target can be highly disruptive, especially once the target reaches a higher tier, so getting the name right is important even for a tier 3 target.

The two introduced targets follow as much as possible the naming conventions of the other targets. I.e. taking the bare-metal riscv32imac_unknown_none_elf as a base:

  • The name of the new target was derived by replacing none with espidf to designate the target_os.
  • _elf was removed, as the non-bare metal targets seem not to have it
  • -newlib was deliberately NOT added at the end, as I believe the chance of having two simultaneously active separate targets for the ESP-IDF framework with different C libraries (say, newlib vs musl) is way too small
  • Finally, we replaced the middle unknown with esp which is kind of the name of the whole chipset MCU family (and abbreviation from Espressif which is too long). It will stay esp for all RiscV32-based MCUs of the company, as they all use the riscv32imc instruction set. By necessity however (disambiguation), it will be esp32 or esp32s2 or esp32s3 for the Xtensa-based MCUs as all of these have their own variation of the Xtensa architecture. (The Xtensa targets are not part of this PR, even though they would use 1:1 the same LibStd implementation provided here, as they depend on the upstreaming of the Xtensa architecture support in LLVM; this upstreaming this is currently in progress.)

There was also a preceding discussion on the topic here.

Target names should not introduce undue confusion or ambiguity unless absolutely necessary to maintain ecosystem compatibility. For example, if the name of the target makes people extremely likely to form incorrect beliefs about what it targets, the name should be changed or augmented to disambiguate it.

We are explicitly putting an -espidf suffix to designate that the target is specifically for Rust + ESP-IDF

Tier 3 targets may have unusual requirements to build or use, but must not create legal issues or impose onerous legal terms for the Rust project or for Rust developers or users.

Agreed.

The target must not introduce license incompatibilities.

To the best of our knowledge, it doesn't.

Anything added to the Rust repository must be under the standard Rust license (MIT OR Apache-2.0).

MIT + Apache 2.0

The target must not cause the Rust tools or libraries built for any other host (even when supporting cross-compilation to the target) to depend on any new dependency less permissive than the Rust licensing policy. This applies whether the dependency is a Rust crate that would require adding new license exceptions (as specified by the tidy tool in the rust-lang/rust repository), or whether the dependency is a native library or binary. In other words, the introduction of the target must not cause a user installing or running a version of Rust or the Rust tools to be subject to any new license requirements.

Requirements are not changed for any other target.

If the target supports building host tools (such as rustc or cargo), those host tools must not depend on proprietary (non-FOSS) libraries, other than ordinary runtime libraries supplied by the platform and commonly used by other binaries built for the target. For instance, rustc built for the target may depend on a common proprietary C runtime library or console output library, but must not depend on a proprietary code generation library or code optimization library. Rust's license permits such combinations, but the Rust project has no interest in maintaining such combinations within the scope of Rust itself, even at tier 3.

The targets are for bare-metal environment which is not hosting build tools or a compiler.

Targets should not require proprietary (non-FOSS) components to link a functional binary or library.

The linker used by the targets is the GCC linker from the GCC toolchain cross-compiled for riscv. GNU GPL.

"onerous" here is an intentionally subjective term. At a minimum, "onerous" legal/licensing terms include but are not limited to: non-disclosure requirements, non-compete requirements, contributor license agreements (CLAs) or equivalent, "non-commercial"/"research-only"/etc terms, requirements conditional on the employer or employment of any particular Rust developers, revocable terms, any requirements that create liability for the Rust project or its developers or users, or any requirements that adversely affect the livelihood or prospects of the Rust project or its developers or users.
Neither this policy nor any decisions made regarding targets shall create any binding agreement or estoppel by any party. If any member of an approving Rust team serves as one of the maintainers of a target, or has any legal or employment requirement (explicit or implicit) that might affect their decisions regarding a target, they must recuse themselves from any approval decisions regarding the target's tier status, though they may otherwise participate in discussions.
This requirement does not prevent part or all of this policy from being cited in an explicit contract or work agreement (e.g. to implement or maintain support for a target). This requirement exists to ensure that a developer or team responsible for reviewing and approving a target does not face any legal threats or obligations that would prevent them from freely exercising their judgment in such approval, even if such judgment involves subjective matters or goes beyond the letter of these requirements.

Agreed.

Tier 3 targets should attempt to implement as much of the standard libraries as possible and appropriate (core for most targets, alloc for targets that can support dynamic memory allocation, std for targets with an operating system or equivalent layer of system-provided functionality), but may leave some code unimplemented (either unavailable or stubbed out as appropriate), whether because the target makes it impossible to implement or challenging to implement. The authors of pull requests are not obligated to avoid calling any portions of the standard library on the basis of a tier 3 target not implementing those portions.

The targets implement libStd almost in its entirety, except for the missing support for process, as this is a bare metal platform. The process sys\unix module is currently stubbed to return "not implemented" errors.

The target must provide documentation for the Rust community explaining how to build for the target, using cross-compilation if possible. If the target supports running tests (even if they do not pass), the documentation must explain how to run tests for the target, using emulation if possible or dedicated hardware if necessary.

Target does not (yet) support running tests. We would gladly provide all documentation how to build for the target (where?). It is currently hosted in this README.md file, but will likely be moved to the esp-rs organization. Since the build for the target is driven by cargo and all other tooling is downloaded automatically during the build, there is no need for extensive documentation.

Tier 3 targets must not impose burden on the authors of pull requests, or other developers in the community, to maintain the target. In particular, do not post comments (automated or manual) on a PR that derail or suggest a block on the PR based on a tier 3 target. Do not send automated messages or notifications (via any medium, including via @) to a PR author or others involved with a PR regarding a tier 3 target, unless they have opted into such messages.

Agreed.

Backlinks such as those generated by the issue/PR tracker when linking to an issue or PR are not considered a violation of this policy, within reason. However, such messages (even on a separate repository) must not generate notifications to anyone involved with a PR who has not requested such notifications.

Agreed.

Patches adding or updating tier 3 targets must not break any existing tier 2 or tier 1 target, and must not knowingly break another tier 3 target without approval of either the compiler team or the maintainers of the other tier 3 target.

To the best of our knowledge, we believe we are not breaking any other target (be it tier 1, 2 or 3).

In particular, this may come up when working on closely related targets, such as variations of the same architecture with different features. Avoid introducing unconditional uses of features that another variation of the target may not have; use conditional compilation or runtime detection, as appropriate, to let each target run code supported by that target.

To the best of our knowledge, we have not introduced any unconditional use of a feature that affects any other target.

If a tier 3 target stops meeting these requirements, or the target maintainers no longer have interest or time, or the target shows no signs of activity and has not built for some time, or removing the target would improve the quality of the Rust codebase, we may post a PR to remove it; any such PR will be CCed to the target maintainers (and potentially other people who have previously worked on the target), to check potential interest in improving the situation.

Agreed.

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Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @dtolnay (or someone else) soon.

Please see the contribution instructions for more information.

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⚠️ Warning ⚠️

@rust-highfive rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jul 31, 2021
@dtolnay dtolnay added the T-libs Relevant to the library team, which will review and decide on the PR/issue. label Jul 31, 2021
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dtolnay commented Jul 31, 2021

r? @rust-lang/libs

@rust-highfive rust-highfive assigned kennytm and unassigned dtolnay Jul 31, 2021
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@ivmarkov ivmarkov force-pushed the master branch 3 times, most recently from c7966fd to b1e8daa Compare July 31, 2021 17:30
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the8472 commented Jul 31, 2021

Note that as part of only supporting fallible allocation in the linux kernel (rust-lang/rfcs#3140) there is ongoing discussion around making std features optional and how to support that on the cargo side. rust-lang/rfcs#3146

I'm not sure what exactly the roadmap on those parts are but it sounds like it would be appropriate here if you only want to support a subset of the standard library in the beginning. But putting whole modules behind feature gates that have yet to be introduced instead of stubbing them could require some work.

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ivmarkov commented Aug 1, 2021

Note that as part of only supporting fallible allocation in the linux kernel (rust-lang/rfcs#3140) there is ongoing discussion around making std features optional and how to support that on the cargo side. rust-lang/rfcs#3146

I'm not sure what exactly the roadmap on those parts are but it sounds like it would be appropriate here if you only want to support a subset of the standard library in the beginning. But putting whole modules behind feature gates that have yet to be introduced instead of stubbing them could require some work.

That's very useful info, thanks for sharing!

My problem with it is a little bit that this patch set has been in development since approx last November, and waiting for another Cargo nightly feature to first of all hit nightly, and then suffering through its stabilization pains, change of semantics and so on might be a bit too much. Especially considering that we are already sailing in an ocean of Cargo unstable features, that - when changed or regressed - did hit us in the past:

So I would rather take a conservative approach here and stub what is not supported, if there is no strong, well-grounded objection from the Rust maintainers.

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bors commented Aug 2, 2021

☔ The latest upstream changes (presumably #87535) made this pull request unmergeable. Please resolve the merge conflicts.

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Amanieu commented Aug 2, 2021

Since support for atomics is a precondition for libStd, the riscv32imc-esp-espidf target additionally is configured in such a way, so as to emit libcalls to the __sync* & __atomic* GCC functions, which are already implemented in the ESP-IDF framework. If this modification is not acceptable, we can also live with only the riscv32imac-esp-espidf target as well. While the RiscV chips of Espressif lack native atomics support, the relevant instructions are transparently emulated in the ESP-IDF framework using invalid instruction trap. This modification was implemented specifically with Rust support in mind.

This is fine as long as the underlying implementation is lock-free (doesn't use a lock internally to emulate atomics). The requirement here is that a signal/interrupt handler should never deadlock if it tries to use an Atomic* which the interrupted thread was in the middle of accessing.

Generally this is implemented by disabling interrupt handlers or by having the interrupt handler restart the atomic sequence in the interrupted thread upon returning. We already have something similar for ARMv4 on Linux (atomic instructions were introduced in ARMv6) where support for atomic operations is provided by the kernel: https://github.com/rust-lang/compiler-builtins/blob/master/src/arm_linux.rs

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Now that libc 0.2.99 is released, I've forced pushed the following two updates:

  • Modification of ./Cargo.lock and ./library/std/Cargo.toml - only change is that the libc dependency is now raised to 0.2.99
  • I've rebased all commits so far into a single one to keep the rust master branch history cleaner. Other than the rebase, no changes to the already reviewed code

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Amanieu commented Aug 10, 2021

@bors r+

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bors commented Aug 10, 2021

📌 Commit 459eaa6 has been approved by Amanieu

@bors bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Aug 10, 2021
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bors commented Aug 12, 2021

⌛ Testing commit 459eaa6 with merge 6bed1f0...

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bors commented Aug 12, 2021

☀️ Test successful - checks-actions
Approved by: Amanieu
Pushing 6bed1f0 to master...

@bors bors added the merged-by-bors This PR was explicitly merged by bors. label Aug 12, 2021
@bors bors merged commit 6bed1f0 into rust-lang:master Aug 12, 2021
@rustbot rustbot added this to the 1.56.0 milestone Aug 12, 2021
This was referenced Aug 12, 2021
wip-sync pushed a commit to NetBSD/pkgsrc-wip that referenced this pull request Oct 22, 2021
Pkgsrc changes:
 * Remove one now-longer-applicable patch, adjust a few others
 * Bump bootstrap requirements to 1.55.0.

Upstream changes:

Version 1.56.0 (2021-10-21)
========================

Language
--------

- [The 2021 Edition is now stable.][rust#88100]
  See [the edition guide][rust-2021-edition-guide] for more details.
- [The pattern in `binding @ pattern` can now also introduce new bindings.]
  [rust#85305]
- [Union field access is permitted in `const fn`.][rust#85769]

[rust-2021-edition-guide]: https://doc.rust-lang.org/nightly/edition-guide/rust-2021/index.html

Compiler
--------

- [Upgrade to LLVM 13.][rust#87570]
- [Support memory, address, and thread sanitizers on
  aarch64-unknown-freebsd.][rust#88023]
- [Allow specifying a deployment target version for all iOS targets][rust#87699]
- [Warnings can be forced on with `--force-warn`.][rust#87472]
  This feature is primarily intended for usage by `cargo fix`,
  rather than end users.
- [Promote `aarch64-apple-ios-sim` to Tier 2\*.][rust#87760]
- [Add `powerpc-unknown-freebsd` at Tier 3\*.][rust#87370]
- [Add `riscv32imc-esp-espidf` at Tier 3\*.][rust#87666]

\* Refer to Rust's [platform support page][platform-support-doc] for more
information on Rust's tiered platform support.

Libraries
---------

- [Allow writing of incomplete UTF-8 sequences via stdout/stderr on Windows.]
  [rust#83342]
  The Windows console still requires valid Unicode, but this change allows
  splitting a UTF-8 character across multiple write calls. This allows, for
  instance, programs that just read and write data buffers (e.g. copying a file
  to stdout) without regard for Unicode or character boundaries.
- [Prefer `AtomicU{64,128}` over Mutex for Instant backsliding protection.]
  [rust#83093]
  For this use case, atomics scale much better under contention.
- [Implement `Extend<(A, B)>` for `(Extend<A>, Extend<B>)`][rust#85835]
- [impl Default, Copy, Clone for std::io::Sink and std::io::Empty][rust#86744]
- [`impl From<[(K, V); N]>` for all collections.][rust#84111]
- [Remove `P: Unpin` bound on impl Future for Pin.][rust#81363]
- [Treat invalid environment variable names as non-existent.][rust#86183]
  Previously, the environment functions would panic if given a
  variable name with an internal null character or equal sign (`=`).
  Now, these functions will just treat such names as non-existent
  variables, since the OS cannot represent the existence of a
  variable with such a name.

Stabilised APIs
---------------

- [`std::os::unix::fs::chroot`]
- [`UnsafeCell::raw_get`]
- [`BufWriter::into_parts`]
- [`core::panic::{UnwindSafe, RefUnwindSafe, AssertUnwindSafe}`]
  These APIs were previously stable in `std`, but are now also available
  in `core`.
- [`Vec::shrink_to`]
- [`String::shrink_to`]
- [`OsString::shrink_to`]
- [`PathBuf::shrink_to`]
- [`BinaryHeap::shrink_to`]
- [`VecDeque::shrink_to`]
- [`HashMap::shrink_to`]
- [`HashSet::shrink_to`]

These APIs are now usable in const contexts:

- [`std::mem::transmute`]
- [`[T]::first`][`slice::first`]
- [`[T]::split_first`][`slice::split_first`]
- [`[T]::last`][`slice::last`]
- [`[T]::split_last`][`slice::split_last`]

Cargo
-----

- [Cargo supports specifying a minimum supported Rust version in Cargo.toml.]
  [`rust-version`] This has no effect at present on dependency
  version selection.  We encourage crates to specify their minimum
  supported Rust version, and we encourage CI systems that support
  Rust code to include a crate's specified minimum version in the
  text matrix for that crate by default.

Compatibility notes
-------------------

- [Update to new argument parsing rules on Windows.][rust#87580]
  This adjusts Rust's standard library to match the behavior of the standard
  libraries for C/C++. The rules have changed slightly over time, and this PR
  brings us to the latest set of rules (changed in 2008).
- [Disallow the aapcs calling convention on aarch64][rust#88399]
  This was already not supported by LLVM; this change surfaces this lack of
  support with a better error message.
- [Make `SEMICOLON_IN_EXPRESSIONS_FROM_MACROS` warn by default][rust#87385]
- [Warn when an escaped newline skips multiple lines.][rust#87671]
- [Calls to `libc::getpid` / `std::process::id` from `Command::pre_exec`
  may return different values on glibc <= 2.24.][rust#81825] Rust
  now invokes the `clone3` system call directly, when available,
  to use new functionality available via that system call. Older
  versions of glibc cache the result of `getpid`, and only update
  that cache when calling glibc's clone/fork functions, so a direct
  system call bypasses that cache update. glibc 2.25 and newer no
  longer cache `getpid` for exactly this reason.

Internal changes
----------------
These changes provide no direct user facing benefits, but represent
significant improvements to the internals and overall performance
of rustc and related tools.

- [LLVM is compiled with PGO in published x86_64-unknown-linux-gnu
  artifacts.][rust#88069] This improves the performance of most Rust builds.

- [Unify representation of macros in internal data structures.][rust#88019]
  This change fixes a host of bugs with the handling of macros by the compiler,
  as well as rustdoc.

[`std::os::unix::fs::chroot`]: https://doc.rust-lang.org/stable/std/os/unix/fs/fn.chroot.html
[`Iterator::intersperse`]: https://doc.rust-lang.org/stable/std/iter/trait.Iterator.html#method.intersperse
[`Iterator::intersperse_with`]: https://doc.rust-lang.org/stable/std/iter/trait.Iterator.html#method.intersperse
[`UnsafeCell::raw_get`]: https://doc.rust-lang.org/stable/std/cell/struct.UnsafeCell.html#method.raw_get
[`BufWriter::into_parts`]: https://doc.rust-lang.org/stable/std/io/struct.BufWriter.html#method.into_parts
[`core::panic::{UnwindSafe, RefUnwindSafe, AssertUnwindSafe}`]: rust-lang/rust#84662
[`Vec::shrink_to`]: https://doc.rust-lang.org/stable/std/vec/struct.Vec.html#method.shrink_to
[`String::shrink_to`]: https://doc.rust-lang.org/stable/std/string/struct.String.html#method.shrink_to
[`OsString::shrink_to`]: https://doc.rust-lang.org/stable/std/ffi/struct.OsString.html#method.shrink_to
[`PathBuf::shrink_to`]: https://doc.rust-lang.org/stable/std/path/struct.PathBuf.html#method.shrink_to
[`BinaryHeap::shrink_to`]: https://doc.rust-lang.org/stable/std/collections/struct.BinaryHeap.html#method.shrink_to
[`VecDeque::shrink_to`]: https://doc.rust-lang.org/stable/std/collections/struct.VecDeque.html#method.shrink_to
[`HashMap::shrink_to`]: https://doc.rust-lang.org/stable/std/collections/hash_map/struct.HashMap.html#method.shrink_to
[`HashSet::shrink_to`]: https://doc.rust-lang.org/stable/std/collections/hash_set/struct.HashSet.html#method.shrink_to
[`std::mem::transmute`]: https://doc.rust-lang.org/stable/std/mem/fn.transmute.html
[`slice::first`]: https://doc.rust-lang.org/stable/std/primitive.slice.html#method.first
[`slice::split_first`]: https://doc.rust-lang.org/stable/std/primitive.slice.html#method.split_first
[`slice::last`]: https://doc.rust-lang.org/stable/std/primitive.slice.html#method.last
[`slice::split_last`]: https://doc.rust-lang.org/stable/std/primitive.slice.html#method.split_last
[`rust-version`]: https://doc.rust-lang.org/nightly/cargo/reference/manifest.html#the-rust-version-field
[rust#87671]: rust-lang/rust#87671
[rust#86183]: rust-lang/rust#86183
[rust#87385]: rust-lang/rust#87385
[rust#88100]: rust-lang/rust#88100
[rust#86860]: rust-lang/rust#86860
[rust#84039]: rust-lang/rust#84039
[rust#86492]: rust-lang/rust#86492
[rust#88363]: rust-lang/rust#88363
[rust#85305]: rust-lang/rust#85305
[rust#87832]: rust-lang/rust#87832
[rust#88069]: rust-lang/rust#88069
[rust#87472]: rust-lang/rust#87472
[rust#87699]: rust-lang/rust#87699
[rust#87570]: rust-lang/rust#87570
[rust#88023]: rust-lang/rust#88023
[rust#87760]: rust-lang/rust#87760
[rust#87370]: rust-lang/rust#87370
[rust#87580]: rust-lang/rust#87580
[rust#83342]: rust-lang/rust#83342
[rust#83093]: rust-lang/rust#83093
[rust#88177]: rust-lang/rust#88177
[rust#88548]: rust-lang/rust#88548
[rust#88551]: rust-lang/rust#88551
[rust#88299]: rust-lang/rust#88299
[rust#88220]: rust-lang/rust#88220
[rust#85835]: rust-lang/rust#85835
[rust#86879]: rust-lang/rust#86879
[rust#86744]: rust-lang/rust#86744
[rust#84662]: rust-lang/rust#84662
[rust#86593]: rust-lang/rust#86593
[rust#81050]: rust-lang/rust#81050
[rust#81363]: rust-lang/rust#81363
[rust#84111]: rust-lang/rust#84111
[rust#85769]: rust-lang/rust#85769 (comment)
[rust#88490]: rust-lang/rust#88490
[rust#88269]: rust-lang/rust#88269
[rust#84176]: rust-lang/rust#84176
[rust#88399]: rust-lang/rust#88399
[rust#88227]: rust-lang/rust#88227
[rust#88200]: rust-lang/rust#88200
[rust#82776]: rust-lang/rust#82776
[rust#88077]: rust-lang/rust#88077
[rust#87728]: rust-lang/rust#87728
[rust#87050]: rust-lang/rust#87050
[rust#87619]: rust-lang/rust#87619
[rust#81825]: rust-lang/rust#81825 (comment)
[rust#88019]: rust-lang/rust#88019
[rust#87666]: rust-lang/rust#87666
netbsd-srcmastr pushed a commit to NetBSD/pkgsrc that referenced this pull request Nov 20, 2021
Pkgsrc changes:
 * Bump bootstrap kit version to 1.55.0.
 * Adjust patches as needed, some no longer apply (so removed)
 * Update checksum adjustments.
 * Avoid rust-llvm on SunOS
 * Optionally build docs
 * Remove reference to closed/old PR#54621

Upstream changes:

Version 1.56.1 (2021-11-01)
===========================

- New lints to detect the presence of bidirectional-override Unicode
  codepoints in the compiled source code ([CVE-2021-42574])

[CVE-2021-42574]: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-42574

Version 1.56.0 (2021-10-21)
========================

Language
--------

- [The 2021 Edition is now stable.][rust#88100]
  See [the edition guide][rust-2021-edition-guide] for more details.
- [The pattern in `binding @ pattern` can now also introduce new bindings.]
  [rust#85305]
- [Union field access is permitted in `const fn`.][rust#85769]

[rust-2021-edition-guide]:
  https://doc.rust-lang.org/nightly/edition-guide/rust-2021/index.html

Compiler
--------

- [Upgrade to LLVM 13.][rust#87570]
- [Support memory, address, and thread sanitizers on aarch64-unknown-freebsd.]
  [rust#88023]
- [Allow specifying a deployment target version for all iOS targets][rust#87699]
- [Warnings can be forced on with `--force-warn`.][rust#87472]
  This feature is primarily intended for usage by `cargo fix`, rather than
  end users.
- [Promote `aarch64-apple-ios-sim` to Tier 2\*.][rust#87760]
- [Add `powerpc-unknown-freebsd` at Tier 3\*.][rust#87370]
- [Add `riscv32imc-esp-espidf` at Tier 3\*.][rust#87666]

\* Refer to Rust's [platform support page][platform-support-doc] for more
information on Rust's tiered platform support.

Libraries
---------

- [Allow writing of incomplete UTF-8 sequences via stdout/stderr on Windows.]
  [rust#83342]
  The Windows console still requires valid Unicode, but this change allows
  splitting a UTF-8 character across multiple write calls. This allows, for
  instance, programs that just read and write data buffers (e.g. copying a file
  to stdout) without regard for Unicode or character boundaries.
- [Prefer `AtomicU{64,128}` over Mutex for Instant backsliding protection.]
  [rust#83093]
  For this use case, atomics scale much better under contention.
- [Implement `Extend<(A, B)>` for `(Extend<A>, Extend<B>)`][rust#85835]
- [impl Default, Copy, Clone for std::io::Sink and std::io::Empty][rust#86744]
- [`impl From<[(K, V); N]>` for all collections.][rust#84111]
- [Remove `P: Unpin` bound on impl Future for Pin.][rust#81363]
- [Treat invalid environment variable names as non-existent.][rust#86183]
  Previously, the environment functions would panic if given a
  variable name with an internal null character or equal sign (`=`).
  Now, these functions will just treat such names as non-existent
  variables, since the OS cannot represent the existence of a
  variable with such a name.

Stabilised APIs
---------------

- [`std::os::unix::fs::chroot`]
- [`UnsafeCell::raw_get`]
- [`BufWriter::into_parts`]
- [`core::panic::{UnwindSafe, RefUnwindSafe, AssertUnwindSafe}`]
  These APIs were previously stable in `std`, but are now also available
  in `core`.
- [`Vec::shrink_to`]
- [`String::shrink_to`]
- [`OsString::shrink_to`]
- [`PathBuf::shrink_to`]
- [`BinaryHeap::shrink_to`]
- [`VecDeque::shrink_to`]
- [`HashMap::shrink_to`]
- [`HashSet::shrink_to`]

These APIs are now usable in const contexts:

- [`std::mem::transmute`]
- [`[T]::first`][`slice::first`]
- [`[T]::split_first`][`slice::split_first`]
- [`[T]::last`][`slice::last`]
- [`[T]::split_last`][`slice::split_last`]

Cargo
-----

- [Cargo supports specifying a minimum supported Rust version in Cargo.toml.]
  [`rust-version`]
  This has no effect at present on dependency version selection.
  We encourage crates to specify their minimum supported Rust
  version, and we encourage CI systems that support Rust code to
  include a crate's specified minimum version in the text matrix
  for that crate by default.

Compatibility notes
-------------------

- [Update to new argument parsing rules on Windows.][rust#87580]
  This adjusts Rust's standard library to match the behavior of the standard
  libraries for C/C++. The rules have changed slightly over time, and this PR
  brings us to the latest set of rules (changed in 2008).
- [Disallow the aapcs calling convention on aarch64][rust#88399]
  This was already not supported by LLVM; this change surfaces this lack of
  support with a better error message.
- [Make `SEMICOLON_IN_EXPRESSIONS_FROM_MACROS` warn by default][rust#87385]
- [Warn when an escaped newline skips multiple lines.][rust#87671]
- [Calls to `libc::getpid` / `std::process::id` from `Command::pre_exec`
  may return different values on glibc <= 2.24.][rust#81825]
  Rust now invokes the `clone3` system call directly, when available,
  to use new functionality available via that system call. Older
  versions of glibc cache the result of `getpid`, and only update
  that cache when calling glibc's clone/fork functions, so a direct
  system call bypasses that cache update. glibc 2.25 and newer no
  longer cache `getpid` for exactly this reason.

Internal changes
----------------
These changes provide no direct user facing benefits, but represent
significant improvements to the internals and overall performance
of rustc and related tools.

- [LLVM is compiled with PGO in published x86_64-unknown-linux-gnu artifacts.]
  [rust#88069]
  This improves the performance of most Rust builds.
- [Unify representation of macros in internal data structures.][rust#88019]
  This change fixes a host of bugs with the handling of macros by the compiler,
  as well as rustdoc.

[`std::os::unix::fs::chroot`]: https://doc.rust-lang.org/stable/std/os/unix/fs/fn.chroot.html
[`Iterator::intersperse`]: https://doc.rust-lang.org/stable/std/iter/trait.Iterator.html#method.intersperse
[`Iterator::intersperse_with`]: https://doc.rust-lang.org/stable/std/iter/trait.Iterator.html#method.intersperse
[`UnsafeCell::raw_get`]: https://doc.rust-lang.org/stable/std/cell/struct.UnsafeCell.html#method.raw_get
[`BufWriter::into_parts`]: https://doc.rust-lang.org/stable/std/io/struct.BufWriter.html#method.into_parts
[`core::panic::{UnwindSafe, RefUnwindSafe, AssertUnwindSafe}`]: rust-lang/rust#84662
[`Vec::shrink_to`]: https://doc.rust-lang.org/stable/std/vec/struct.Vec.html#method.shrink_to
[`String::shrink_to`]: https://doc.rust-lang.org/stable/std/string/struct.String.html#method.shrink_to
[`OsString::shrink_to`]: https://doc.rust-lang.org/stable/std/ffi/struct.OsString.html#method.shrink_to
[`PathBuf::shrink_to`]: https://doc.rust-lang.org/stable/std/path/struct.PathBuf.html#method.shrink_to
[`BinaryHeap::shrink_to`]: https://doc.rust-lang.org/stable/std/collections/struct.BinaryHeap.html#method.shrink_to
[`VecDeque::shrink_to`]: https://doc.rust-lang.org/stable/std/collections/struct.VecDeque.html#method.shrink_to
[`HashMap::shrink_to`]: https://doc.rust-lang.org/stable/std/collections/hash_map/struct.HashMap.html#method.shrink_to
[`HashSet::shrink_to`]: https://doc.rust-lang.org/stable/std/collections/hash_set/struct.HashSet.html#method.shrink_to
[`std::mem::transmute`]: https://doc.rust-lang.org/stable/std/mem/fn.transmute.html
[`slice::first`]: https://doc.rust-lang.org/stable/std/primitive.slice.html#method.first
[`slice::split_first`]: https://doc.rust-lang.org/stable/std/primitive.slice.html#method.split_first
[`slice::last`]: https://doc.rust-lang.org/stable/std/primitive.slice.html#method.last
[`slice::split_last`]: https://doc.rust-lang.org/stable/std/primitive.slice.html#method.split_last
[`rust-version`]: https://doc.rust-lang.org/nightly/cargo/reference/manifest.html#the-rust-version-field
[rust#87671]: rust-lang/rust#87671
[rust#86183]: rust-lang/rust#86183
[rust#87385]: rust-lang/rust#87385
[rust#88100]: rust-lang/rust#88100
[rust#86860]: rust-lang/rust#86860
[rust#84039]: rust-lang/rust#84039
[rust#86492]: rust-lang/rust#86492
[rust#88363]: rust-lang/rust#88363
[rust#85305]: rust-lang/rust#85305
[rust#87832]: rust-lang/rust#87832
[rust#88069]: rust-lang/rust#88069
[rust#87472]: rust-lang/rust#87472
[rust#87699]: rust-lang/rust#87699
[rust#87570]: rust-lang/rust#87570
[rust#88023]: rust-lang/rust#88023
[rust#87760]: rust-lang/rust#87760
[rust#87370]: rust-lang/rust#87370
[rust#87580]: rust-lang/rust#87580
[rust#83342]: rust-lang/rust#83342
[rust#83093]: rust-lang/rust#83093
[rust#88177]: rust-lang/rust#88177
[rust#88548]: rust-lang/rust#88548
[rust#88551]: rust-lang/rust#88551
[rust#88299]: rust-lang/rust#88299
[rust#88220]: rust-lang/rust#88220
[rust#85835]: rust-lang/rust#85835
[rust#86879]: rust-lang/rust#86879
[rust#86744]: rust-lang/rust#86744
[rust#84662]: rust-lang/rust#84662
[rust#86593]: rust-lang/rust#86593
[rust#81050]: rust-lang/rust#81050
[rust#81363]: rust-lang/rust#81363
[rust#84111]: rust-lang/rust#84111
[rust#85769]: rust-lang/rust#85769 (comment)
[rust#88490]: rust-lang/rust#88490
[rust#88269]: rust-lang/rust#88269
[rust#84176]: rust-lang/rust#84176
[rust#88399]: rust-lang/rust#88399
[rust#88227]: rust-lang/rust#88227
[rust#88200]: rust-lang/rust#88200
[rust#82776]: rust-lang/rust#82776
[rust#88077]: rust-lang/rust#88077
[rust#87728]: rust-lang/rust#87728
[rust#87050]: rust-lang/rust#87050
[rust#87619]: rust-lang/rust#87619
[rust#81825]: rust-lang/rust#81825 (comment)
[rust#88019]: rust-lang/rust#88019
[rust#87666]: rust-lang/rust#87666

Version 1.55.0 (2021-09-09)
============================

Language
--------
- [You can now write open "from" range patterns (`X..`), which will start
  at `X` and will end at the maximum value of the integer.][83918]
- [You can now explicitly import the prelude of different editions
  through `std::prelude` (e.g. `use std::prelude::rust_2021::*;`).][86294]

Compiler
--------
- [Added tier 3\* support for `powerpc64le-unknown-freebsd`.][83572]

\* Refer to Rust's [platform support page][platform-support-doc] for more
   information on Rust's tiered platform support.

Libraries
---------

- [Updated std's float parsing to use the Eisel-Lemire algorithm.][86761]
  These improvements should in general provide faster string parsing of floats,
  no longer reject certain valid floating point values, and reduce
  the produced code size for non-stripped artifacts.
- [`string::Drain` now implements `AsRef<str>` and `AsRef<[u8]>`.][86858]

Stabilised APIs
---------------

- [`Bound::cloned`]
- [`Drain::as_str`]
- [`IntoInnerError::into_error`]
- [`IntoInnerError::into_parts`]
- [`MaybeUninit::assume_init_mut`]
- [`MaybeUninit::assume_init_ref`]
- [`MaybeUninit::write`]
- [`array::map`]
- [`ops::ControlFlow`]
- [`x86::_bittest`]
- [`x86::_bittestandcomplement`]
- [`x86::_bittestandreset`]
- [`x86::_bittestandset`]
- [`x86_64::_bittest64`]
- [`x86_64::_bittestandcomplement64`]
- [`x86_64::_bittestandreset64`]
- [`x86_64::_bittestandset64`]

The following previously stable functions are now `const`.

- [`str::from_utf8_unchecked`]


Cargo
-----
- [Cargo will now deduplicate compiler diagnostics to the terminal when invoking
  rustc in parallel such as when using `cargo test`.][cargo/9675]
- [The package definition in `cargo metadata` now includes the `"default_run"`
  field from the manifest.][cargo/9550]
- [Added `cargo d` as an alias for `cargo doc`.][cargo/9680]
- [Added `{lib}` as formatting option for `cargo tree` to print the `"lib_name"`
  of packages.][cargo/9663]

Rustdoc
-------
- [Added "Go to item on exact match" search option.][85876]
- [The "Implementors" section on traits no longer shows redundant
  method definitions.][85970]
- [Trait implementations are toggled open by default.][86260] This should
  make the implementations more searchable by tools like `CTRL+F` in
  your browser.
- [Intra-doc links should now correctly resolve associated items (e.g. methods)
  through type aliases.][86334]
- [Traits which are marked with `#[doc(hidden)]` will no longer appear in the
  "Trait Implementations" section.][86513]


Compatibility Notes
-------------------
- [std functions that return an `io::Error` will no longer use the
  `ErrorKind::Other` variant.][85746] This is to better reflect that these
  kinds of errors could be categorised [into newer more specific `ErrorKind`
  variants][79965], and that they do not represent a user error.
- [Using environment variable names with `process::Command` on Windows now
  behaves as expected.][85270] Previously using envionment variables with
  `Command` would cause them to be ASCII-uppercased.
- [Rustdoc will now warn on using rustdoc lints that aren't prefixed
  with `rustdoc::`][86849]

[86849]: rust-lang/rust#86849
[86513]: rust-lang/rust#86513
[86334]: rust-lang/rust#86334
[86260]: rust-lang/rust#86260
[85970]: rust-lang/rust#85970
[85876]: rust-lang/rust#85876
[83572]: rust-lang/rust#83572
[86294]: rust-lang/rust#86294
[86858]: rust-lang/rust#86858
[86761]: rust-lang/rust#86761
[85769]: rust-lang/rust#85769
[85746]: rust-lang/rust#85746
[85305]: rust-lang/rust#85305
[85270]: rust-lang/rust#85270
[84111]: rust-lang/rust#84111
[83918]: rust-lang/rust#83918
[79965]: rust-lang/rust#79965
[87370]: rust-lang/rust#87370
[87298]: rust-lang/rust#87298
[cargo/9663]: rust-lang/cargo#9663
[cargo/9675]: rust-lang/cargo#9675
[cargo/9550]: rust-lang/cargo#9550
[cargo/9680]: rust-lang/cargo#9680
[cargo/9663]: rust-lang/cargo#9663
[`array::map`]: https://doc.rust-lang.org/stable/std/primitive.array.html#method.map
[`Bound::cloned`]: https://doc.rust-lang.org/stable/std/ops/enum.Bound.html#method.cloned
[`Drain::as_str`]: https://doc.rust-lang.org/stable/std/string/struct.Drain.html#method.as_str
[`IntoInnerError::into_error`]: https://doc.rust-lang.org/stable/std/io/struct.IntoInnerError.html#method.into_error
[`IntoInnerError::into_parts`]: https://doc.rust-lang.org/stable/std/io/struct.IntoInnerError.html#method.into_parts
[`MaybeUninit::assume_init_mut`]: https://doc.rust-lang.org/stable/std/mem/union.MaybeUninit.html#method.assume_init_mut
[`MaybeUninit::assume_init_ref`]: https://doc.rust-lang.org/stable/std/mem/union.MaybeUninit.html#method.assume_init_ref
[`MaybeUninit::write`]: https://doc.rust-lang.org/stable/std/mem/union.MaybeUninit.html#method.write
[`Seek::rewind`]: https://doc.rust-lang.org/stable/std/io/trait.Seek.html#method.rewind
[`ops::ControlFlow`]: https://doc.rust-lang.org/stable/std/ops/enum.ControlFlow.html
[`str::from_utf8_unchecked`]: https://doc.rust-lang.org/stable/std/str/fn.from_utf8_unchecked.html
[`x86::_bittest`]: https://doc.rust-lang.org/stable/core/arch/x86/fn._bittest.html
[`x86::_bittestandcomplement`]: https://doc.rust-lang.org/stable/core/arch/x86/fn._bittestandcomplement.html
[`x86::_bittestandreset`]: https://doc.rust-lang.org/stable/core/arch/x86/fn._bittestandreset.html
[`x86::_bittestandset`]: https://doc.rust-lang.org/stable/core/arch/x86/fn._bittestandset.html
[`x86_64::_bittest64`]: https://doc.rust-lang.org/stable/core/arch/x86_64/fn._bittest64.html
[`x86_64::_bittestandcomplement64`]: https://doc.rust-lang.org/stable/core/arch/x86_64/fn._bittestandcomplement64.html
[`x86_64::_bittestandreset64`]: https://doc.rust-lang.org/stable/core/arch/x86_64/fn._bittestandreset64.html
[`x86_64::_bittestandset64`]: https://doc.rust-lang.org/stable/core/arch/x86_64/fn._bittestandset64.html
bors added a commit to rust-lang-ci/rust that referenced this pull request Jun 15, 2022
…gisa

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](rust-lang#88529 (comment)) 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: rust-lang#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
workingjubilee pushed a commit to tcdi/postgrestd that referenced this pull request Sep 15, 2022
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](rust-lang/rust#88529 (comment)) 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: rust-lang/rust#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
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this pull request Jan 8, 2024
Add `riscv32imafc-esp-espidf` tier 3 target for the ESP32-P4.

The tier 3 target answers in the original PR are still relevant, so please review them here: rust-lang#87666 (comment)

cc: `@ivmarkov`
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this pull request Jan 8, 2024
Add `riscv32imafc-esp-espidf` tier 3 target for the ESP32-P4.

The tier 3 target answers in the original PR are still relevant, so please review them here: rust-lang#87666 (comment)

cc: ``@ivmarkov``
rust-timer added a commit to rust-lang-ci/rust that referenced this pull request Jan 9, 2024
Rollup merge of rust-lang#119738 - esp-rs:esp32p4-espidf, r=Nilstrieb

Add `riscv32imafc-esp-espidf` tier 3 target for the ESP32-P4.

The tier 3 target answers in the original PR are still relevant, so please review them here: rust-lang#87666 (comment)

cc: ``@ivmarkov``
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