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Lower transmutes from int to pointer type as gep on null #121282

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merged 1 commit into from
Mar 12, 2024

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saethlin
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@saethlin saethlin commented Feb 19, 2024

I thought of this while looking at #121242. See that PR's description for why this lowering is preferable.

The UI test that's being changed here crashes without changing the transmutes into casts. Based on that, this PR should not be merged without a crater build-and-test run.

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r? @fmease

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@rustbot rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Feb 19, 2024
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@bors try @rust-timer queue

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@rustbot rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Feb 19, 2024
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bors commented Feb 19, 2024

⌛ Trying commit 903dd09 with merge d073071...

bors added a commit to rust-lang-ci/rust that referenced this pull request Feb 19, 2024
…e, r=<try>

Lower transmutes from int to pointer type as gep on null

I thought of this while looking at rust-lang#121242

The UI test that's being changed here crashes without changing the transmutes into casts. Based on that, this PR should not be merged without a crater build-and-test run.
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bors commented Feb 19, 2024

☀️ Try build successful - checks-actions
Build commit: d073071 (d073071d77ce0f93b4fd8cc567a1e2b9e1b22126)

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Finished benchmarking commit (d073071): comparison URL.

Overall result: no relevant changes - no action needed

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.

@bors rollup=never
@rustbot label: -S-waiting-on-perf -perf-regression

Instruction count

This benchmark run did not return any relevant results for this metric.

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

mean range count
Regressions ❌
(primary)
- - 0
Regressions ❌
(secondary)
3.5% [3.5%, 3.5%] 1
Improvements ✅
(primary)
- - 0
Improvements ✅
(secondary)
- - 0
All ❌✅ (primary) - - 0

Cycles

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

mean range count
Regressions ❌
(primary)
- - 0
Regressions ❌
(secondary)
2.1% [2.1%, 2.2%] 2
Improvements ✅
(primary)
- - 0
Improvements ✅
(secondary)
- - 0
All ❌✅ (primary) - - 0

Binary size

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

mean range count
Regressions ❌
(primary)
0.1% [0.1%, 0.1%] 1
Regressions ❌
(secondary)
- - 0
Improvements ✅
(primary)
- - 0
Improvements ✅
(secondary)
- - 0
All ❌✅ (primary) 0.1% [0.1%, 0.1%] 1

Bootstrap: 640.336s -> 641.418s (0.17%)
Artifact size: 308.82 MiB -> 308.83 MiB (0.00%)

@rustbot rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Feb 19, 2024
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@craterbot run mode=build-and-test

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👌 Experiment pr-121282 created and queued.
🤖 Automatically detected try build d073071
🔍 You can check out the queue and this experiment's details.

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

@craterbot craterbot added S-waiting-on-crater Status: Waiting on a crater run to be completed. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Feb 19, 2024
@saethlin saethlin added the T-opsem Relevant to the opsem team label Feb 19, 2024
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@craterbot abort

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🗑️ Experiment pr-121282 deleted!

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

@craterbot craterbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-crater Status: Waiting on a crater run to be completed. labels Feb 20, 2024
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@craterbot run mode=build-and-test start=master#61223975d46f794466efa832bc7562b9707ecc46+rustflags=-Copt-level=3 end=try#d073071d77ce0f93b4fd8cc567a1e2b9e1b22126+rustflags=-Copt-level=3

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👌 Experiment pr-121282 created and queued.
🔍 You can check out the queue and this experiment's details.

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

@craterbot craterbot added S-waiting-on-crater Status: Waiting on a crater run to be completed. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Feb 20, 2024
@@ -49,7 +49,7 @@ pub fn ptr_to_int(p: *mut u16) -> usize {
}

// CHECK: define{{.*}}ptr @int_to_ptr([[USIZE]] %i)
// CHECK: %_0 = inttoptr [[USIZE]] %i to ptr
// CHECK: %_0 = getelementptr i8, ptr null, i64 %i
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I think to make this pass on non-64-bit you need

Suggested change
// CHECK: %_0 = getelementptr i8, ptr null, i64 %i
// CHECK: %_0 = getelementptr i8, ptr null, [[USIZE]] %i

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🚧 Experiment pr-121282 is now running

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

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bors commented Mar 12, 2024

☀️ Test successful - checks-actions
Approved by: scottmcm
Pushing 0fa7fea to master...

@bors bors added the merged-by-bors This PR was explicitly merged by bors. label Mar 12, 2024
@bors bors merged commit 0fa7fea into rust-lang:master Mar 12, 2024
12 checks passed
@rustbot rustbot added this to the 1.78.0 milestone Mar 12, 2024
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Finished benchmarking commit (0fa7fea): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

This benchmark run did not return any relevant results for this metric.

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

mean range count
Regressions ❌
(primary)
2.6% [2.6%, 2.6%] 1
Regressions ❌
(secondary)
2.8% [2.8%, 2.8%] 1
Improvements ✅
(primary)
- - 0
Improvements ✅
(secondary)
-7.8% [-7.8%, -7.8%] 1
All ❌✅ (primary) 2.6% [2.6%, 2.6%] 1

Cycles

This benchmark run did not return any relevant results for this metric.

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 672.319s -> 672.448s (0.02%)
Artifact size: 310.04 MiB -> 310.05 MiB (0.00%)

@saethlin saethlin deleted the gep-null-means-no-provenance branch March 12, 2024 13:40
bors added a commit to rust-lang/crater that referenced this pull request Mar 18, 2024
Ignore some more crates

Adding all the spurious failures I identified in rust-lang/rust#121282 (comment)

I'm also not sure what `blacklist.md` is for, but it hasn't been updated in 6 years so I imagine it's not important.
bors added a commit to rust-lang/crater that referenced this pull request Mar 20, 2024
Ignore some more crates

Adding all the spurious failures I identified in rust-lang/rust#121282 (comment)

I'm also not sure what `blacklist.md` is for, but it hasn't been updated in 6 years so I imagine it's not important.
bors added a commit to rust-lang/crater that referenced this pull request Mar 20, 2024
Ignore some more crates

Adding all the spurious failures I identified in rust-lang/rust#121282 (comment)

I'm also not sure what `blacklist.md` is for, but it hasn't been updated in 6 years so I imagine it's not important.
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this pull request Mar 23, 2024
transmute: caution against int2ptr transmutation

This came up in rust-lang#121282.
Cc `@saethlin` `@scottmcm`

Eventually we'll add a proper description of provenance that we can reference, but that's a bunch of work and it's unclear who will have the time to do that when. Meanwhile, let's at least do what we can without mentioning provenance explicitly.
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this pull request Mar 23, 2024
transmute: caution against int2ptr transmutation

This came up in rust-lang#121282.
Cc ``@saethlin`` ``@scottmcm``

Eventually we'll add a proper description of provenance that we can reference, but that's a bunch of work and it's unclear who will have the time to do that when. Meanwhile, let's at least do what we can without mentioning provenance explicitly.
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this pull request Mar 24, 2024
transmute: caution against int2ptr transmutation

This came up in rust-lang#121282.
Cc ```@saethlin``` ```@scottmcm```

Eventually we'll add a proper description of provenance that we can reference, but that's a bunch of work and it's unclear who will have the time to do that when. Meanwhile, let's at least do what we can without mentioning provenance explicitly.
workingjubilee added a commit to workingjubilee/rustc that referenced this pull request Mar 24, 2024
transmute: caution against int2ptr transmutation

This came up in rust-lang#121282.
Cc ````@saethlin```` ````@scottmcm````

Eventually we'll add a proper description of provenance that we can reference, but that's a bunch of work and it's unclear who will have the time to do that when. Meanwhile, let's at least do what we can without mentioning provenance explicitly.
workingjubilee added a commit to workingjubilee/rustc that referenced this pull request Mar 24, 2024
transmute: caution against int2ptr transmutation

This came up in rust-lang#121282.
Cc `````@saethlin````` `````@scottmcm`````

Eventually we'll add a proper description of provenance that we can reference, but that's a bunch of work and it's unclear who will have the time to do that when. Meanwhile, let's at least do what we can without mentioning provenance explicitly.
rust-timer added a commit to rust-lang-ci/rust that referenced this pull request Mar 24, 2024
Rollup merge of rust-lang#122379 - RalfJung:int2ptr-transmute, r=m-ou-se

transmute: caution against int2ptr transmutation

This came up in rust-lang#121282.
Cc ```@saethlin``` ```@scottmcm```

Eventually we'll add a proper description of provenance that we can reference, but that's a bunch of work and it's unclear who will have the time to do that when. Meanwhile, let's at least do what we can without mentioning provenance explicitly.
RenjiSann pushed a commit to RenjiSann/rust that referenced this pull request Mar 25, 2024
transmute: caution against int2ptr transmutation

This came up in rust-lang#121282.
Cc ```@saethlin``` ```@scottmcm```

Eventually we'll add a proper description of provenance that we can reference, but that's a bunch of work and it's unclear who will have the time to do that when. Meanwhile, let's at least do what we can without mentioning provenance explicitly.
wip-sync pushed a commit to NetBSD/pkgsrc-wip that referenced this pull request May 4, 2024
Pkgsrc changes:
 * Adapt checksums and patches, some have beene intregrated upstream.

Upstream chnages:

Version 1.78.0 (2024-05-02)
===========================

Language
--------
- [Stabilize `#[cfg(target_abi = ...)]`]
  (rust-lang/rust#119590)
- [Stabilize the `#[diagnostic]` namespace and
  `#[diagnostic::on_unimplemented]` attribute]
  (rust-lang/rust#119888)
- [Make async-fn-in-trait implementable with concrete signatures]
  (rust-lang/rust#120103)
- [Make matching on NaN a hard error, and remove the rest of
  `illegal_floating_point_literal_pattern`]
  (rust-lang/rust#116284)
- [static mut: allow mutable reference to arbitrary types, not just
  slices and arrays]
  (rust-lang/rust#117614)
- [Extend `invalid_reference_casting` to include references casting
  to bigger memory layout]
  (rust-lang/rust#118983)
- [Add `non_contiguous_range_endpoints` lint for singleton gaps
  after exclusive ranges]
  (rust-lang/rust#118879)
- [Add `wasm_c_abi` lint for use of older wasm-bindgen versions]
  (rust-lang/rust#117918)
  This lint currently only works when using Cargo.
- [Update `indirect_structural_match` and `pointer_structural_match`
  lints to match RFC]
  (rust-lang/rust#120423)
- [Make non-`PartialEq`-typed consts as patterns a hard error]
  (rust-lang/rust#120805)
- [Split `refining_impl_trait` lint into `_reachable`, `_internal` variants]
  (rust-lang/rust#121720)
- [Remove unnecessary type inference when using associated types
  inside of higher ranked `where`-bounds]
  (rust-lang/rust#119849)
- [Weaken eager detection of cyclic types during type inference]
  (rust-lang/rust#119989)
- [`trait Trait: Auto {}`: allow upcasting from `dyn Trait` to `dyn Auto`]
  (rust-lang/rust#119338)

Compiler
--------

- [Made `INVALID_DOC_ATTRIBUTES` lint deny by default]
  (rust-lang/rust#111505)
- [Increase accuracy of redundant `use` checking]
  (rust-lang/rust#117772)
- [Suggest moving definition if non-found macro_rules! is defined later]
  (rust-lang/rust#121130)
- [Lower transmutes from int to pointer type as gep on null]
  (rust-lang/rust#121282)

Target changes:

- [Windows tier 1 targets now require at least Windows 10]
  (rust-lang/rust#115141)
 - [Enable CMPXCHG16B, SSE3, SAHF/LAHF and 128-bit Atomics in tier 1 Windows]
  (rust-lang/rust#120820)
- [Add `wasm32-wasip1` tier 2 (without host tools) target]
  (rust-lang/rust#120468)
- [Add `wasm32-wasip2` tier 3 target]
  (rust-lang/rust#119616)
- [Rename `wasm32-wasi-preview1-threads` to `wasm32-wasip1-threads`]
  (rust-lang/rust#122170)
- [Add `arm64ec-pc-windows-msvc` tier 3 target]
  (rust-lang/rust#119199)
- [Add `armv8r-none-eabihf` tier 3 target for the Cortex-R52]
  (rust-lang/rust#110482)
- [Add `loongarch64-unknown-linux-musl` tier 3 target]
  (rust-lang/rust#121832)

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

Libraries
---------

- [Bump Unicode to version 15.1.0, regenerate tables]
  (rust-lang/rust#120777)
- [Make align_offset, align_to well-behaved in all cases]
  (rust-lang/rust#121201)
- [PartialEq, PartialOrd: document expectations for transitive chains]
  (rust-lang/rust#115386)
- [Optimize away poison guards when std is built with panic=abort]
  (rust-lang/rust#100603)
- [Replace pthread `RwLock` with custom implementation]
  (rust-lang/rust#110211)
- [Implement unwind safety for Condvar on all platforms]
  (rust-lang/rust#121768)
- [Add ASCII fast-path for `char::is_grapheme_extended`]
  (rust-lang/rust#121138)

Stabilized APIs
---------------

- [`impl Read for &Stdin`]
  (https://doc.rust-lang.org/stable/std/io/struct.Stdin.html#impl-Read-for-%26Stdin)
- [Accept non `'static` lifetimes for several `std::error::Error`
  related implementations] (rust-lang/rust#113833)
- [Make `impl<Fd: AsFd>` impl take `?Sized`]
  (rust-lang/rust#114655)
- [`impl From<TryReserveError> for io::Error`]
  (https://doc.rust-lang.org/stable/std/io/struct.Error.html#impl-From%3CTryReserveError%3E-for-Error)

These APIs are now stable in const contexts:

- [`Barrier::new()`]
  (https://doc.rust-lang.org/stable/std/sync/struct.Barrier.html#method.new)

Cargo
-----

- [Stabilize lockfile v4](rust-lang/cargo#12852)
- [Respect `rust-version` when generating lockfile]
  (rust-lang/cargo#12861)
- [Control `--charset` via auto-detecting config value]
  (rust-lang/cargo#13337)
- [Support `target.<triple>.rustdocflags` officially]
  (rust-lang/cargo#13197)
- [Stabilize global cache data tracking]
  (rust-lang/cargo#13492)

Misc
----

- [rustdoc: add `--test-builder-wrapper` arg to support wrappers
  such as RUSTC_WRAPPER when building doctests]
  (rust-lang/rust#114651)

Compatibility Notes
-------------------

- [Many unsafe precondition checks now run for user code with debug
  assertions enabled] (rust-lang/rust#120594)
  This change helps users catch undefined behavior in their code,
  though the details of how much is checked are generally not
  stable.
- [riscv only supports split_debuginfo=off for now]
  (rust-lang/rust#120518)
- [Consistently check bounds on hidden types of `impl Trait`]
  (rust-lang/rust#121679)
- [Change equality of higher ranked types to not rely on subtyping]
  (rust-lang/rust#118247)
- [When called, additionally check bounds on normalized function return type]
  (rust-lang/rust#118882)
- [Expand coverage for `arithmetic_overflow` lint]
  (rust-lang/rust#119432)

Internal Changes
----------------

These changes do not affect any public interfaces of Rust, but they represent
significant improvements to the performance or internals of rustc and related
tools.

- [Update to LLVM 18](rust-lang/rust#120055)
- [Build `rustc` with 1CGU on `x86_64-pc-windows-msvc`]
  (rust-lang/rust#112267)
- [Build `rustc` with 1CGU on `x86_64-apple-darwin`]
  (rust-lang/rust#112268)
- [Introduce `run-make` V2 infrastructure, a `run_make_support`
  library and port over 2 tests as example]
  (rust-lang/rust#113026)
- [Windows: Implement condvar, mutex and rwlock using futex]
  (rust-lang/rust#121956)
Liorst4 added a commit to Liorst4/liorforth that referenced this pull request May 24, 2024
…Cell`

Reduces the amount of `unsafe` in the code.

Looks like in newer rustc versions, this causes crashes.
Could be related to rust-lang/rust#121282
@Liorst4
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Liorst4 commented May 24, 2024

Is there a difference between casting an isize to a pointer using as and using std::mem::transmute?

@saethlin @scottmcm

When this change was proposed it crashed on one of my projects #121282 (comment)

@saethlin discussed this with me here: Liorst4/liorforth#1

The discussion didn't go very deep into the issue, and it left me kind of confused.
I assumed its a bug in the patch and @saethlin was going to fix it before pushing it into master.

Now when I run the test in release the test crashes.
To fix it, all I needed to do is change a std::mem::transmute cast into an as cast.
Liorst4/liorforth@fba984a
But I don't really understand why, shouldn't these be the same thing? Is there something I'm missing? Alignment issues?

Code that fails now

type Byte = u8;

type Cell = isize;

#[repr(packed(1))]
struct CountedString {
    len: Byte,
    data: [Byte; 0],
}

#[no_mangle]
fn test_breaks() {
    let buffer: [u8; 6] = [5, b'h', b'e', b'l', b'l', b'o'];
    let counted_string_address: Cell = (&buffer).as_ptr() as Cell;
    
    // Using `transmute` to cast
    let counted_string: &CountedString = unsafe {
        std::mem::transmute::<Cell, *const CountedString>(counted_string_address)
            .as_ref()
            .unwrap()
    };

    let counted_string_as_slice: &[u8] = unsafe {
        std::slice::from_raw_parts(counted_string.data.as_ptr(), counted_string.len as usize)
    };
    let counted_string_as_rust_string = std::str::from_utf8(counted_string_as_slice).unwrap();
    println!("{}", counted_string_as_rust_string);
}

#[no_mangle]
fn test_works() {
    let buffer: [u8; 6] = [5, b'h', b'e', b'l', b'l', b'o'];
    let counted_string_address: Cell = (&buffer).as_ptr() as Cell;
    
    // Using `as` to cast
    let counted_string: &CountedString = unsafe {
        (counted_string_address as *const CountedString)
            .as_ref()
            .unwrap()
    };

    let counted_string_as_slice: &[u8] = unsafe {
        std::slice::from_raw_parts(counted_string.data.as_ptr(), counted_string.len as usize)
    };
    let counted_string_as_rust_string = std::str::from_utf8(counted_string_as_slice).unwrap();
    println!("{}", counted_string_as_rust_string);
}

pub fn main() {
    test_works();
    test_breaks();
}

https://gcc.godbolt.org/z/b8ba9Y7G5

@saethlin
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Yes there is a difference. To quote the RFC https://rust-lang.github.io/rfcs/3559-rust-has-provenance.html

Furthermore, the section on “Integer types” is extended to say that integers do not have provenance, and therefore transmuting (via transmute or type punning) from a pointer to an integer is a lossy operation and might even be UB. (The exact semantics of that operation involve some subtle trade-offs and are not decided by this RFC.)

as is a different operation from transmute for other types as well. Conversions between integers and floating point, for example.

@Liorst4
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Liorst4 commented May 24, 2024

Yes there is a difference. To quote the RFC https://rust-lang.github.io/rfcs/3559-rust-has-provenance.html

Furthermore, the section on “Integer types” is extended to say that integers do not have provenance, and therefore transmuting (via transmute or type punning) from a pointer to an integer is a lossy operation and might even be UB. (The exact semantics of that operation involve some subtle trade-offs and are not decided by this RFC.)

as is a different operation from transmute for other types as well. Conversions between integers and floating point, for example.

OK, thanks, this clears stuff up 👍

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scottmcm commented May 24, 2024

@Liorst4 Reminder that you can also confirm this using Miri. This PR changed only codegen, which doesn't affect Miri, but your test_breaks example also fails in Miri: https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=46c3f8c80ae90b5fb22dd59023628e88

error: Undefined Behavior: out-of-bounds pointer use: 0x25d44[noalloc] is a dangling pointer (it has no provenance)
   --> /playground/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/ptr/const_ptr.rs:358:57
    |
358 |         if self.is_null() { None } else { unsafe { Some(&*self) } }
    |                                                         ^^^^^^ out-of-bounds pointer use: 0x25d44[noalloc] is a dangling pointer (it has no provenance)
    |
    = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
    = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
    = note: BACKTRACE:
    = note: inside `std::ptr::const_ptr::<impl *const CountedString>::as_ref::<'_>` at /playground/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/ptr/const_ptr.rs:358:57: 358:63
note: inside `test_breaks`
   --> src/main.rs:18:9
    |
18  | /         std::mem::transmute::<Cell, *const CountedString>(counted_string_address)
19  | |             .as_ref()
    | |_____________________^
note: inside `main`
   --> src/main.rs:31:5
    |
31  |     test_breaks();
    |     ^^^^^^^^^^^^^

(Miri has diagnosed this for a long time; this PR just means that LLVM also knows about the UB.)

netbsd-srcmastr pushed a commit to NetBSD/pkgsrc that referenced this pull request Oct 13, 2024
This is based on the pkgsrc-wip rust180 package, retaining
the main pkgsrc changes as best as I could.

Pkgsrc changes:
 * Adapt checksums and patches.
 * Make this work again on big-endian aarch64 (at least on NetBSD).
 * Make the choice of GCC = 12 work for sparc64 by testing options
   after options.mk is included (which is required...).  Makes this
   work on NetBSD/sparc64 10.0 again.

Upstream chnages:

Version 1.80.1 (2024-08-08)
===========================

- [Fix miscompilation in the jump threading MIR optimization when
  comparing floats]
  (rust-lang/rust#128271)
- [Revert changes to the `dead_code` lint from 1.80.0]
  (rust-lang/rust#128618)

Version 1.80.0 (2024-07-25)
==========================

Language
--------
- [Document maximum allocation size]
  (rust-lang/rust#116675)
- [Allow zero-byte offsets and ZST read/writes on arbitrary pointers]
  (rust-lang/rust#117329)
- [Support C23's variadics without a named parameter]
  (rust-lang/rust#124048)
- [Stabilize `exclusive_range_pattern` feature]
  (rust-lang/rust#124459)
- [Guarantee layout and ABI of `Result` in some scenarios]
  (rust-lang/rust#124870)

Compiler
--------
- [Update cc crate to v1.0.97 allowing additional spectre mitigations
  on MSVC targets]
  (rust-lang/rust#124892)
- [Allow field reordering on types marked `repr(packed(1))`]
  (rust-lang/rust#125360)
- [Add a lint against never type fallback affecting unsafe code]
  (rust-lang/rust#123939)
- [Disallow cast with trailing braced macro in let-else]
  (rust-lang/rust#125049)
- [Expand `for_loops_over_fallibles` lint to lint on fallibles
  behind references.]
  (rust-lang/rust#125156)
- [self-contained linker: retry linking without `-fuse-ld=lld` on
  CCs that don't support it]
  (rust-lang/rust#125417)
- [Do not parse CVarArgs (`...`) as a type in trait bounds]
  (rust-lang/rust#125863)
- Improvements to LLDB formatting [#124458]
  (rust-lang/rust#124458) [#124500]
  (rust-lang/rust#124500)
- [For the wasm32-wasip2 target default to PIC and do not use `-fuse-ld=lld`]
  (rust-lang/rust#124858)
- [Add x86_64-unknown-linux-none as a tier 3 target]
  (rust-lang/rust#125023)
- [Lint on `foo.into_iter()` resolving to `&Box<[T]>: IntoIterator`]
  (rust-lang/rust#124097)

Libraries
---------
- [Add `size_of` and `size_of_val` and `align_of` and `align_of_val`
  to the prelude]
  (rust-lang/rust#123168)
- [Abort a process when FD ownership is violated]
  (rust-lang/rust#124210)
- [io::Write::write_fmt: panic if the formatter fails when the
  stream does not fail]
  (rust-lang/rust#125012)
- [Panic if `PathBuf::set_extension` would add a path separator]
  (rust-lang/rust#125070)
- [Add assert_unsafe_precondition to unchecked_{add,sub,neg,mul,shl,shr}
  methods] (rust-lang/rust#121571)
- [Update `c_char` on AIX to use the correct type]
  (rust-lang/rust#122986)
- [`offset_of!` no longer returns a temporary]
  (rust-lang/rust#124484)
- [Handle sigma in `str.to_lowercase` correctly]
  (rust-lang/rust#124773)
- [Raise `DEFAULT_MIN_STACK_SIZE` to at least 64KiB]
  (rust-lang/rust#126059)

Stabilized APIs
---------------
- [`impl Default for Rc<CStr>`]
  (https://doc.rust-lang.org/beta/alloc/rc/struct.Rc.html#impl-Default-for-Rc%3CCStr%3E)
- [`impl Default for Rc<str>`]
  (https://doc.rust-lang.org/beta/alloc/rc/struct.Rc.html#impl-Default-for-Rc%3Cstr%3E)
- [`impl Default for Rc<[T]>`]
  (https://doc.rust-lang.org/beta/alloc/rc/struct.Rc.html#impl-Default-for-Rc%3C%5BT%5D%3E)
- [`impl Default for Arc<str>`]
  (https://doc.rust-lang.org/beta/alloc/sync/struct.Arc.html#impl-Default-for-Arc%3Cstr%3E)
- [`impl Default for Arc<CStr>`]
  (https://doc.rust-lang.org/beta/alloc/sync/struct.Arc.html#impl-Default-for-Arc%3CCStr%3E)
- [`impl Default for Arc<[T]>`]
  (https://doc.rust-lang.org/beta/alloc/sync/struct.Arc.html#impl-Default-for-Arc%3C%5BT%5D%3E)
- [`impl IntoIterator for Box<[T]>`]
  (https://doc.rust-lang.org/beta/alloc/boxed/struct.Box.html#impl-IntoIterator-for-Box%3C%5BI%5D,+A%3E)
- [`impl FromIterator<String> for Box<str>`]
  (https://doc.rust-lang.org/beta/alloc/boxed/struct.Box.html#impl-FromIterator%3CString%3E-for-Box%3Cstr%3E)
- [`impl FromIterator<char> for Box<str>`]
  (https://doc.rust-lang.org/beta/alloc/boxed/struct.Box.html#impl-FromIterator%3Cchar%3E-for-Box%3Cstr%3E)
- [`LazyCell`]
  (https://doc.rust-lang.org/beta/core/cell/struct.LazyCell.html)
- [`LazyLock`]
  (https://doc.rust-lang.org/beta/std/sync/struct.LazyLock.html)
- [`Duration::div_duration_f32`]
  (https://doc.rust-lang.org/beta/std/time/struct.Duration.html#method.div_duration_f32)
- [`Duration::div_duration_f64`]
  (https://doc.rust-lang.org/beta/std/time/struct.Duration.html#method.div_duration_f64)
- [`Option::take_if`]
  (https://doc.rust-lang.org/beta/std/option/enum.Option.html#method.take_if)
- [`Seek::seek_relative`]
  (https://doc.rust-lang.org/beta/std/io/trait.Seek.html#method.seek_relative)
- [`BinaryHeap::as_slice`]
  (https://doc.rust-lang.org/beta/std/collections/struct.BinaryHeap.html#method.as_slice)
- [`NonNull::offset`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.offset)
- [`NonNull::byte_offset`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.byte_offset)
- [`NonNull::add`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.add)
- [`NonNull::byte_add`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.byte_add)
- [`NonNull::sub`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.sub)
- [`NonNull::byte_sub`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.byte_sub)
- [`NonNull::offset_from`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.offset_from)
- [`NonNull::byte_offset_from`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.byte_offset_from)
- [`NonNull::read`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.read)
- [`NonNull::read_volatile`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.read_volatile)
- [`NonNull::read_unaligned`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.read_unaligned)
- [`NonNull::write`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.write)
- [`NonNull::write_volatile`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.write_volatile)
- [`NonNull::write_unaligned`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.write_unaligned)
- [`NonNull::write_bytes`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.write_bytes)
- [`NonNull::copy_to`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.copy_to)
- [`NonNull::copy_to_nonoverlapping`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.copy_to_nonoverlapping)
- [`NonNull::copy_from`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.copy_from)
- [`NonNull::copy_from_nonoverlapping`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.copy_from_nonoverlapping)
- [`NonNull::replace`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.replace)
- [`NonNull::swap`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.swap)
- [`NonNull::drop_in_place`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.drop_in_place)
- [`NonNull::align_offset`]
  (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.align_offset)
- [`<[T]>::split_at_checked`]
  (https://doc.rust-lang.org/beta/std/primitive.slice.html#method.split_at_checked)
- [`<[T]>::split_at_mut_checked`]
  (https://doc.rust-lang.org/beta/std/primitive.slice.html#method.split_at_mut_checked)
- [`str::split_at_checked`]
  (https://doc.rust-lang.org/beta/std/primitive.str.html#method.split_at_checked)
- [`str::split_at_mut_checked`]
  (https://doc.rust-lang.org/beta/std/primitive.str.html#method.split_at_mut_checked)
- [`str::trim_ascii`]
  (https://doc.rust-lang.org/beta/std/primitive.str.html#method.trim_ascii)
- [`str::trim_ascii_start`]
  (https://doc.rust-lang.org/beta/std/primitive.str.html#method.trim_ascii_start)
- [`str::trim_ascii_end`]
  (https://doc.rust-lang.org/beta/std/primitive.str.html#method.trim_ascii_end)
- [`<[u8]>::trim_ascii`]
  (https://doc.rust-lang.org/beta/core/primitive.slice.html#method.trim_ascii)
- [`<[u8]>::trim_ascii_start`]
  (https://doc.rust-lang.org/beta/core/primitive.slice.html#method.trim_ascii_start)
- [`<[u8]>::trim_ascii_end`]
  (https://doc.rust-lang.org/beta/core/primitive.slice.html#method.trim_ascii_end)
- [`Ipv4Addr::BITS`]
  (https://doc.rust-lang.org/beta/core/net/struct.Ipv4Addr.html#associatedconstant.BITS)
- [`Ipv4Addr::to_bits`]
  (https://doc.rust-lang.org/beta/core/net/struct.Ipv4Addr.html#method.to_bits)
- [`Ipv4Addr::from_bits`]
  (https://doc.rust-lang.org/beta/core/net/struct.Ipv4Addr.html#method.from_bits)
- [`Ipv6Addr::BITS`]
  (https://doc.rust-lang.org/beta/core/net/struct.Ipv6Addr.html#associatedconstant.BITS)
- [`Ipv6Addr::to_bits`]
  (https://doc.rust-lang.org/beta/core/net/struct.Ipv6Addr.html#method.to_bits)
- [`Ipv6Addr::from_bits`]
  (https://doc.rust-lang.org/beta/core/net/struct.Ipv6Addr.html#method.from_bits)
- [`Vec::<[T; N]>::into_flattened`]
  (https://doc.rust-lang.org/beta/alloc/vec/struct.Vec.html#method.into_flattened)
- [`<[[T; N]]>::as_flattened`]
  (https://doc.rust-lang.org/beta/core/primitive.slice.html#method.as_flattened)
- [`<[[T; N]]>::as_flattened_mut`]
  (https://doc.rust-lang.org/beta/core/primitive.slice.html#method.as_flattened_mut)

These APIs are now stable in const contexts:

- [`<[T]>::last_chunk`]
  (https://doc.rust-lang.org/beta/core/primitive.slice.html#method.last_chunk)
- [`BinaryHeap::new`]
  (https://doc.rust-lang.org/beta/std/collections/struct.BinaryHeap.html#method.new)

Cargo
-----

- [Stabilize `-Zcheck-cfg` as always enabled]
  (rust-lang/cargo#13571)
- [Warn, rather than fail publish, if a target is excluded]
  (rust-lang/cargo#13713)
- [Add special `check-cfg` lint config for the `unexpected_cfgs` lint]
  (rust-lang/cargo#13913)
- [Stabilize `cargo update --precise <yanked>`]
  (rust-lang/cargo#13974)
- [Don't change file permissions on `Cargo.toml` when using `cargo add`]
  (rust-lang/cargo#13898)
- [Support using `cargo fix` on IPv6-only networks]
  (rust-lang/cargo#13907)

Rustdoc
-----

- [Allow searching for references]
  (rust-lang/rust#124148)
- [Stabilize `custom_code_classes_in_docs` feature]
  (rust-lang/rust#124577)
- [fix: In cross-crate scenarios show enum variants on type aliases of enums]
  (rust-lang/rust#125300)

Compatibility Notes
-------------------

- [rustfmt estimates line lengths differently when using non-ascii characters]
  (rust-lang/rustfmt#6203)
- [Type aliases are now handled correctly in orphan check]
  (rust-lang/rust#117164)
- [Allow instructing rustdoc to read from stdin via `-`]
  (rust-lang/rust#124611)
- [`std::env::{set_var, remove_var}` can no longer be converted to
  safe function pointers and no longer implement the `Fn` family of
  traits]
  (rust-lang/rust#124636)
- [Warn (or error) when `Self` constructor from outer item is
  referenced in inner nested item]
  (rust-lang/rust#124187)
- [Turn `indirect_structural_match` and `pointer_structural_match`
  lints into hard errors]
  (rust-lang/rust#124661)
- [Make `where_clause_object_safety` lint a regular object safety violation]
  (rust-lang/rust#125380)
- [Turn `proc_macro_back_compat` lint into a hard error.]
  (rust-lang/rust#125596)
- [Detect unused structs even when implementing private traits]
  (rust-lang/rust#122382)
- [`std::sync::ReentrantLockGuard<T>` is no longer `Sync` if `T: !Sync`]
  (rust-lang/rust#125527) which means
  [`std::io::StdoutLock` and `std::io::StderrLock` are no longer
  Sync] (rust-lang/rust#127340)

Internal Changes
----------------

These changes do not affect any public interfaces of Rust, but they represent
significant improvements to the performance or internals of rustc and related
tools.

- Misc improvements to size of generated html by rustdoc e.g. [#124738]
  (rust-lang/rust#124738) and [#123734]
  (rust-lang/rust#123734)
- [MSVC targets no longer depend on libc]
  (rust-lang/rust#124050)


Version 1.79.0 (2024-06-13)
==========================

Language
--------
- [Stabilize inline `const {}` expressions.]
  (rust-lang/rust#104087)
- [Prevent opaque types being instantiated twice with different
  regions within the same function.]
  (rust-lang/rust#116935)
- [Stabilize WebAssembly target features that are in phase 4 and 5.]
  (rust-lang/rust#117457)
- [Add the `redundant_lifetimes` lint to detect lifetimes which
  are semantically redundant.]
  (rust-lang/rust#118391)
- [Stabilize the `unnameable_types` lint for public types that can't be named.]
  (rust-lang/rust#120144)
- [Enable debuginfo in macros, and stabilize `-C collapse-macro-debuginfo`
  and `#[collapse_debuginfo]`.]
  (rust-lang/rust#120845)
- [Propagate temporary lifetime extension into `if` and `match` expressions.]
  (rust-lang/rust#121346)
- [Restrict promotion of `const fn` calls.]
  (rust-lang/rust#121557)
- [Warn against refining impls of crate-private traits with
  `refining_impl_trait` lint.]
  (rust-lang/rust#121720)
- [Stabilize associated type bounds (RFC 2289).]
  (rust-lang/rust#122055)
- [Stabilize importing `main` from other modules or crates.]
  (rust-lang/rust#122060)
- [Check return types of function types for well-formedness]
  (rust-lang/rust#115538)
- [Rework `impl Trait` lifetime inference]
  (rust-lang/rust#116891)
- [Change inductive trait solver cycles to be ambiguous]
  (rust-lang/rust#122791)

Compiler
--------
- [Define `-C strip` to only affect binaries, not artifacts like `.pdb`.]
  (rust-lang/rust#115120)
- [Stabilize `-Crelro-level` for controlling runtime link hardening.]
  (rust-lang/rust#121694)
- [Stabilize checking of `cfg` names and values at compile-time
  with `--check-cfg`.]
  (rust-lang/rust#123501)
  *Note that this only stabilizes the compiler part, the Cargo part
  is still unstable in this release.*
- [Add `aarch64-apple-visionos` and `aarch64-apple-visionos-sim`
  tier 3 targets.]
  (rust-lang/rust#121419)
- [Add `riscv32ima-unknown-none-elf` tier 3 target.]
  (rust-lang/rust#122696)
- [Promote several Windows targets to tier 2]
  (rust-lang/rust#121712):
  `aarch64-pc-windows-gnullvm`, `i686-pc-windows-gnullvm`, and
  `x86_64-pc-windows-gnullvm`.

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

Libraries
---------

- [Implement `FromIterator` for `(impl Default + Extend, impl
  Default + Extend)`.]
  (rust-lang/rust#107462)
- [Implement `{Div,Rem}Assign<NonZero<X>>` on `X`.]
  (rust-lang/rust#121952)
- [Document overrides of `clone_from()` in core/std.]
  (rust-lang/rust#122201)
- [Link MSVC default lib in core.]
  (rust-lang/rust#122268)
- [Caution against using `transmute` between pointers and integers.]
  (rust-lang/rust#122379)
- [Enable frame pointers for the standard library.]
  (rust-lang/rust#122646)

Stabilized APIs
---------------

- [`{integer}::unchecked_add`]
  (https://doc.rust-lang.org/stable/core/primitive.i32.html#method.unchecked_add)
- [`{integer}::unchecked_mul`]
  (https://doc.rust-lang.org/stable/core/primitive.i32.html#method.unchecked_mul)
- [`{integer}::unchecked_sub`]
  (https://doc.rust-lang.org/stable/core/primitive.i32.html#method.unchecked_sub)
- [`<[T]>::split_at_unchecked`]
  (https://doc.rust-lang.org/stable/core/primitive.slice.html#method.split_at_unchecked)
- [`<[T]>::split_at_mut_unchecked`]
  (https://doc.rust-lang.org/stable/core/primitive.slice.html#method.split_at_mut_unchecked)
- [`<[u8]>::utf8_chunks`]
  (https://doc.rust-lang.org/stable/core/primitive.slice.html#method.utf8_chunks)
- [`str::Utf8Chunks`]
  (https://doc.rust-lang.org/stable/core/str/struct.Utf8Chunks.html)
- [`str::Utf8Chunk`]
  (https://doc.rust-lang.org/stable/core/str/struct.Utf8Chunk.html)
- [`<*const T>::is_aligned`]
  (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.is_aligned)
- [`<*mut T>::is_aligned`]
  (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.is_aligned-1)
- [`NonNull::is_aligned`]
  (https://doc.rust-lang.org/stable/core/ptr/struct.NonNull.html#method.is_aligned)
- [`<*const [T]>::len`]
  (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.len)
- [`<*mut [T]>::len`]
  (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.len-1)
- [`<*const [T]>::is_empty`]
  (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.is_empty)
- [`<*mut [T]>::is_empty`]
  (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.is_empty-1)
- [`NonNull::<[T]>::is_empty`]
  (https://doc.rust-lang.org/stable/core/ptr/struct.NonNull.html#method.is_empty)
- [`CStr::count_bytes`]
  (https://doc.rust-lang.org/stable/core/ffi/c_str/struct.CStr.html#method.count_bytes)
- [`io::Error::downcast`]
  (https://doc.rust-lang.org/stable/std/io/struct.Error.html#method.downcast)
- [`num::NonZero<T>`]
  (https://doc.rust-lang.org/stable/core/num/struct.NonZero.html)
- [`path::absolute`]
  (https://doc.rust-lang.org/stable/std/path/fn.absolute.html)
- [`proc_macro::Literal::byte_character`]
  (https://doc.rust-lang.org/stable/proc_macro/struct.Literal.html#method.byte_character)
- [`proc_macro::Literal::c_string`]
  (https://doc.rust-lang.org/stable/proc_macro/struct.Literal.html#method.c_string)

These APIs are now stable in const contexts:

- [`Atomic*::into_inner`]
  (https://doc.rust-lang.org/stable/core/sync/atomic/struct.AtomicUsize.html#method.into_inner)
- [`io::Cursor::new`]
  (https://doc.rust-lang.org/stable/std/io/struct.Cursor.html#method.new)
- [`io::Cursor::get_ref`]
  (https://doc.rust-lang.org/stable/std/io/struct.Cursor.html#method.get_ref)
- [`io::Cursor::position`]
  (https://doc.rust-lang.org/stable/std/io/struct.Cursor.html#method.position)
- [`io::empty`]
  (https://doc.rust-lang.org/stable/std/io/fn.empty.html)
- [`io::repeat`]
  (https://doc.rust-lang.org/stable/std/io/fn.repeat.html)
- [`io::sink`]
  (https://doc.rust-lang.org/stable/std/io/fn.sink.html)
- [`panic::Location::caller`]
  (https://doc.rust-lang.org/stable/std/panic/struct.Location.html#method.caller)
- [`panic::Location::file`]
  (https://doc.rust-lang.org/stable/std/panic/struct.Location.html#method.file)
- [`panic::Location::line`]
  (https://doc.rust-lang.org/stable/std/panic/struct.Location.html#method.line)
- [`panic::Location::column`]
  (https://doc.rust-lang.org/stable/std/panic/struct.Location.html#method.column)

Cargo
-----

- [Prevent dashes in `lib.name`, always normalizing to `_`.]
  (rust-lang/cargo#12783)
- [Stabilize MSRV-aware version requirement selection in `cargo add`.]
  (rust-lang/cargo#13608)
- [Switch to using `gitoxide` by default for listing files.]
  (rust-lang/cargo#13696)

Rustdoc
-----

- [Always display stability version even if it's the same as the
  containing item.]
  (rust-lang/rust#118441)
- [Show a single search result for items with multiple paths.]
  (rust-lang/rust#119912)
- [Support typing `/` in docs to begin a search.]
  (rust-lang/rust#123355)

Misc
----

Compatibility Notes
-------------------

- [Update the minimum external LLVM to 17.]
  (rust-lang/rust#122649)
- [`RustcEncodable` and `RustcDecodable` are soft-destabilized, to
  be removed from the prelude in next edition.]
  (rust-lang/rust#116016)
- [The `wasm_c_abi` future-incompatibility lint will warn about use of the
  non-spec-compliant C ABI.]
  (rust-lang/rust#117918)
  Use `wasm-bindgen v0.2.88` to generate forward-compatible bindings.
- [Check return types of function types for well-formedness]
  (rust-lang/rust#115538)

Version 1.78.0 (2024-05-02)
===========================

Language
--------
- [Stabilize `#[cfg(target_abi = ...)]`]
  (rust-lang/rust#119590)
- [Stabilize the `#[diagnostic]` namespace and
  `#[diagnostic::on_unimplemented]` attribute]
  (rust-lang/rust#119888)
- [Make async-fn-in-trait implementable with concrete signatures]
  (rust-lang/rust#120103)
- [Make matching on NaN a hard error, and remove the rest of
  `illegal_floating_point_literal_pattern`]
  (rust-lang/rust#116284)
- [static mut: allow mutable reference to arbitrary types, not just
  slices and arrays]
  (rust-lang/rust#117614)
- [Extend `invalid_reference_casting` to include references casting
  to bigger memory layout]
  (rust-lang/rust#118983)
- [Add `non_contiguous_range_endpoints` lint for singleton gaps
  after exclusive ranges]
  (rust-lang/rust#118879)
- [Add `wasm_c_abi` lint for use of older wasm-bindgen versions]
  (rust-lang/rust#117918)
  This lint currently only works when using Cargo.
- [Update `indirect_structural_match` and `pointer_structural_match`
  lints to match RFC]
  (rust-lang/rust#120423)
- [Make non-`PartialEq`-typed consts as patterns a hard error]
  (rust-lang/rust#120805)
- [Split `refining_impl_trait` lint into `_reachable`, `_internal` variants]
  (rust-lang/rust#121720)
- [Remove unnecessary type inference when using associated types
  inside of higher ranked `where`-bounds]
  (rust-lang/rust#119849)
- [Weaken eager detection of cyclic types during type inference]
  (rust-lang/rust#119989)
- [`trait Trait: Auto {}`: allow upcasting from `dyn Trait` to `dyn Auto`]
  (rust-lang/rust#119338)

Compiler
--------

- [Made `INVALID_DOC_ATTRIBUTES` lint deny by default]
  (rust-lang/rust#111505)
- [Increase accuracy of redundant `use` checking]
  (rust-lang/rust#117772)
- [Suggest moving definition if non-found macro_rules! is defined later]
  (rust-lang/rust#121130)
- [Lower transmutes from int to pointer type as gep on null]
  (rust-lang/rust#121282)

Target changes:

- [Windows tier 1 targets now require at least Windows 10]
  (rust-lang/rust#115141)
 - [Enable CMPXCHG16B, SSE3, SAHF/LAHF and 128-bit Atomics in tier 1 Windows]
  (rust-lang/rust#120820)
- [Add `wasm32-wasip1` tier 2 (without host tools) target]
  (rust-lang/rust#120468)
- [Add `wasm32-wasip2` tier 3 target]
  (rust-lang/rust#119616)
- [Rename `wasm32-wasi-preview1-threads` to `wasm32-wasip1-threads`]
  (rust-lang/rust#122170)
- [Add `arm64ec-pc-windows-msvc` tier 3 target]
  (rust-lang/rust#119199)
- [Add `armv8r-none-eabihf` tier 3 target for the Cortex-R52]
  (rust-lang/rust#110482)
- [Add `loongarch64-unknown-linux-musl` tier 3 target]
  (rust-lang/rust#121832)

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

Libraries
---------

- [Bump Unicode to version 15.1.0, regenerate tables]
  (rust-lang/rust#120777)
- [Make align_offset, align_to well-behaved in all cases]
  (rust-lang/rust#121201)
- [PartialEq, PartialOrd: document expectations for transitive chains]
  (rust-lang/rust#115386)
- [Optimize away poison guards when std is built with panic=abort]
  (rust-lang/rust#100603)
- [Replace pthread `RwLock` with custom implementation]
  (rust-lang/rust#110211)
- [Implement unwind safety for Condvar on all platforms]
  (rust-lang/rust#121768)
- [Add ASCII fast-path for `char::is_grapheme_extended`]
  (rust-lang/rust#121138)

Stabilized APIs
---------------

- [`impl Read for &Stdin`]
  (https://doc.rust-lang.org/stable/std/io/struct.Stdin.html#impl-Read-for-%26Stdin)
- [Accept non `'static` lifetimes for several `std::error::Error`
  related implementations] (rust-lang/rust#113833)
- [Make `impl<Fd: AsFd>` impl take `?Sized`]
  (rust-lang/rust#114655)
- [`impl From<TryReserveError> for io::Error`]
  (https://doc.rust-lang.org/stable/std/io/struct.Error.html#impl-From%3CTryReserveError%3E-for-Error)

These APIs are now stable in const contexts:

- [`Barrier::new()`]
  (https://doc.rust-lang.org/stable/std/sync/struct.Barrier.html#method.new)

Cargo
-----

- [Stabilize lockfile v4](rust-lang/cargo#12852)
- [Respect `rust-version` when generating lockfile]
  (rust-lang/cargo#12861)
- [Control `--charset` via auto-detecting config value]
  (rust-lang/cargo#13337)
- [Support `target.<triple>.rustdocflags` officially]
  (rust-lang/cargo#13197)
- [Stabilize global cache data tracking]
  (rust-lang/cargo#13492)

Misc
----

- [rustdoc: add `--test-builder-wrapper` arg to support wrappers
  such as RUSTC_WRAPPER when building doctests]
  (rust-lang/rust#114651)

Compatibility Notes
-------------------

- [Many unsafe precondition checks now run for user code with debug
  assertions enabled] (rust-lang/rust#120594)
  This change helps users catch undefined behavior in their code,
  though the details of how much is checked are generally not
  stable.
- [riscv only supports split_debuginfo=off for now]
  (rust-lang/rust#120518)
- [Consistently check bounds on hidden types of `impl Trait`]
  (rust-lang/rust#121679)
- [Change equality of higher ranked types to not rely on subtyping]
  (rust-lang/rust#118247)
- [When called, additionally check bounds on normalized function return type]
  (rust-lang/rust#118882)
- [Expand coverage for `arithmetic_overflow` lint]
  (rust-lang/rust#119432)

Internal Changes
----------------

These changes do not affect any public interfaces of Rust, but they represent
significant improvements to the performance or internals of rustc and related
tools.

- [Update to LLVM 18](rust-lang/rust#120055)
- [Build `rustc` with 1CGU on `x86_64-pc-windows-msvc`]
  (rust-lang/rust#112267)
- [Build `rustc` with 1CGU on `x86_64-apple-darwin`]
  (rust-lang/rust#112268)
- [Introduce `run-make` V2 infrastructure, a `run_make_support`
  library and port over 2 tests as example]
  (rust-lang/rust#113026)
- [Windows: Implement condvar, mutex and rwlock using futex]
  (rust-lang/rust#121956)


Version 1.77.0 (2024-03-21)
==========================

- [Reveal opaque types within the defining body for exhaustiveness checking.]
  (rust-lang/rust#116821)
- [Stabilize C-string literals.]
  (rust-lang/rust#117472)
- [Stabilize THIR unsafeck.]
  (rust-lang/rust#117673)
- [Add lint `static_mut_refs` to warn on references to mutable statics.]
  (rust-lang/rust#117556)
- [Support async recursive calls (as long as they have indirection).]
  (rust-lang/rust#117703)
- [Undeprecate lint `unstable_features` and make use of it in the compiler.]
  (rust-lang/rust#118639)
- [Make inductive cycles in coherence ambiguous always.]
  (rust-lang/rust#118649)
- [Get rid of type-driven traversal in const-eval interning]
  (rust-lang/rust#119044),
  only as a [future compatiblity lint]
  (rust-lang/rust#122204) for now.
- [Deny braced macro invocations in let-else.]
  (rust-lang/rust#119062)

Compiler
--------

- [Include lint `soft_unstable` in future breakage reports.]
  (rust-lang/rust#116274)
- [Make `i128` and `u128` 16-byte aligned on x86-based targets.]
  (rust-lang/rust#116672)
- [Use `--verbose` in diagnostic output.]
  (rust-lang/rust#119129)
- [Improve spacing between printed tokens.]
  (rust-lang/rust#120227)
- [Merge the `unused_tuple_struct_fields` lint into `dead_code`.]
  (rust-lang/rust#118297)
- [Error on incorrect implied bounds in well-formedness check]
  (rust-lang/rust#118553),
  with a temporary exception for Bevy.
- [Fix coverage instrumentation/reports for non-ASCII source code.]
  (rust-lang/rust#119033)
- [Fix `fn`/`const` items implied bounds and well-formedness check.]
  (rust-lang/rust#120019)
- [Promote `riscv32{im|imafc}-unknown-none-elf` targets to tier 2.]
  (rust-lang/rust#118704)
- Add several new tier 3 targets:
  - [`aarch64-unknown-illumos`]
    (rust-lang/rust#112936)
  - [`hexagon-unknown-none-elf`]
    (rust-lang/rust#117601)
  - [`riscv32imafc-esp-espidf`]
    (rust-lang/rust#119738)
  - [`riscv32im-risc0-zkvm-elf`]
    (rust-lang/rust#117958)

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

Libraries
---------

- [Implement `From<&[T; N]>` for `Cow<[T]>`.]
  (rust-lang/rust#113489)
- [Remove special-case handling of `vec.split_off
  (0)`.](rust-lang/rust#119917)

Stabilized APIs
---------------

- [`array::each_ref`]
  (https://doc.rust-lang.org/stable/std/primitive.array.html#method.each_ref)
- [`array::each_mut`]
  (https://doc.rust-lang.org/stable/std/primitive.array.html#method.each_mut)
- [`core::net`]
  (https://doc.rust-lang.org/stable/core/net/index.html)
- [`f32::round_ties_even`]
  (https://doc.rust-lang.org/stable/std/primitive.f32.html#method.round_ties_even)
- [`f64::round_ties_even`]
  (https://doc.rust-lang.org/stable/std/primitive.f64.html#method.round_ties_even)
- [`mem::offset_of!`]
  (https://doc.rust-lang.org/stable/std/mem/macro.offset_of.html)
- [`slice::first_chunk`]
  (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.first_chunk)
- [`slice::first_chunk_mut`]
  (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.first_chunk_mut)
- [`slice::split_first_chunk`]
  (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.split_first_chunk)
- [`slice::split_first_chunk_mut`]
  (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.split_first_chunk_mut)
- [`slice::last_chunk`]
  (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.last_chunk)
- [`slice::last_chunk_mut`]
  (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.last_chunk_mut)
- [`slice::split_last_chunk`]
  (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.split_last_chunk)
- [`slice::split_last_chunk_mut`]
  (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.split_last_chunk_mut)
- [`slice::chunk_by`]
  (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.chunk_by)
- [`slice::chunk_by_mut`]
  (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.chunk_by_mut)
- [`Bound::map`]
  (https://doc.rust-lang.org/stable/std/ops/enum.Bound.html#method.map)
- [`File::create_new`]
  (https://doc.rust-lang.org/stable/std/fs/struct.File.html#method.create_new)
- [`Mutex::clear_poison`]
  (https://doc.rust-lang.org/stable/std/sync/struct.Mutex.html#method.clear_poison)
- [`RwLock::clear_poison`]
  (https://doc.rust-lang.org/stable/std/sync/struct.RwLock.html#method.clear_poison)

Cargo
-----

- [Extend the build directive syntax with `cargo::`.]
  (rust-lang/cargo#12201)
- [Stabilize metadata `id` format as `PackageIDSpec`.]
  (rust-lang/cargo#12914)
- [Pull out as `cargo-util-schemas` as a crate.]
  (rust-lang/cargo#13178)
- [Strip all debuginfo when debuginfo is not requested.]
  (rust-lang/cargo#13257)
- [Inherit jobserver from env for all kinds of runners.]
  (rust-lang/cargo#12776)
- [Deprecate rustc plugin support in cargo.]
  (rust-lang/cargo#13248)

Rustdoc
-----

- [Allows links in markdown headings.]
  (rust-lang/rust#117662)
- [Search for tuples and unit by type with `()`.]
  (rust-lang/rust#118194)
- [Clean up the source sidebar's hide button.]
  (rust-lang/rust#119066)
- [Prevent JS injection from `localStorage`.]
  (rust-lang/rust#120250)

Misc
----

- [Recommend version-sorting for all sorting in style guide.]
  (rust-lang/rust#115046)

Internal Changes
----------------

These changes do not affect any public interfaces of Rust, but they represent
significant improvements to the performance or internals of rustc and related
tools.

- [Add more weirdness to `weird-exprs.rs`.]
  (rust-lang/rust#119028)
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