…ent, r=oli-obk

closure field capturing: don't depend on alignment of packed fields

This fixes the closure field capture part of rust-lang#115305: field capturing always stops at projections into packed structs, no matter the alignment of the field. This means changing a private field type from `u8` to `u64` can never change how closures capture fields, which is probably what we want.

Here's an example where, before this PR, changing the type of a private field in a repr(Rust) struct can change the output of a program:

```rust
#![allow(dead_code)]

mod m {
    // before patch
    #[derive(Default)]
    pub struct S1(u8);
    // after patch
    #[derive(Default)]
    pub struct S2(u64);
}

struct NoisyDrop;
impl Drop for NoisyDrop {
    fn drop(&mut self) {
        eprintln!("dropped!");
    }
}

#[repr(packed)]
struct MyType {
    field: m::S1, // output changes when this becomes S2
    other_field: NoisyDrop,
    third_field: Vec<()>,
}

fn test(r: MyType) {
    let c = || {
        let _val = std::ptr::addr_of!(r.field);
        let _val = r.third_field;
    };
    drop(c);
    eprintln!("before dropping");
}

fn main() {
    test(MyType {
        field: Default::default(),
        other_field: NoisyDrop,
        third_field: Vec::new(),
    });
}
```

Of course this is a breaking change for the same reason that doing field capturing in the first place was a breaking change. Packed fields are relatively rare and depending on drop order is relatively rare, so I don't expect this to have much impact, but it's hard to be sure and even a crater run will only tell us so much.

Also see the [nomination comment](rust-lang#115315 (comment)).

Cc `@rust-lang/wg-rfc-2229` `@ehuss`

…i-obk

closure field capturing: don't depend on alignment of packed fields

This fixes the closure field capture part of rust-lang/rust#115305: field capturing always stops at projections into packed structs, no matter the alignment of the field. This means changing a private field type from `u8` to `u64` can never change how closures capture fields, which is probably what we want.

Here's an example where, before this PR, changing the type of a private field in a repr(Rust) struct can change the output of a program:

```rust
#![allow(dead_code)]

mod m {
    // before patch
    #[derive(Default)]
    pub struct S1(u8);
    // after patch
    #[derive(Default)]
    pub struct S2(u64);
}

struct NoisyDrop;
impl Drop for NoisyDrop {
    fn drop(&mut self) {
        eprintln!("dropped!");
    }
}

#[repr(packed)]
struct MyType {
    field: m::S1, // output changes when this becomes S2
    other_field: NoisyDrop,
    third_field: Vec<()>,
}

fn test(r: MyType) {
    let c = || {
        let _val = std::ptr::addr_of!(r.field);
        let _val = r.third_field;
    };
    drop(c);
    eprintln!("before dropping");
}

fn main() {
    test(MyType {
        field: Default::default(),
        other_field: NoisyDrop,
        third_field: Vec::new(),
    });
}
```

Of course this is a breaking change for the same reason that doing field capturing in the first place was a breaking change. Packed fields are relatively rare and depending on drop order is relatively rare, so I don't expect this to have much impact, but it's hard to be sure and even a crater run will only tell us so much.

Also see the [nomination comment](rust-lang/rust#115315 (comment)).

Cc `@rust-lang/wg-rfc-2229` `@ehuss`

Pkgsrc changes:

 * Remove NetBSD-8 support (embedded LLVm requires newer C++
   than what is in -8; it's conceivable that this could still
   build with an external LLVM)
 * undo powerpc 9.0 file naming tweak, since we no longer support -8.
 * Remove patch to LLVM for powerpc now included by upstream.
 * Minor adjustments, checksum changes etc.


Upstream changes:

Version 1.74.1 (2023-12-07)
===========================

- [Resolved spurious STATUS_ACCESS_VIOLATIONs in LLVM]
  (rust-lang/rust#118464)
- [Clarify guarantees for std::mem::discriminant]
  (rust-lang/rust#118006)
- [Fix some subtyping-related regressions]
  (rust-lang/rust#116415)

Version 1.74.0 (2023-11-16)
==========================

Language
--------

- [Codify that `std::mem::Discriminant<T>` does not depend on any
  lifetimes in T]
  (rust-lang/rust#104299)
- [Replace `private_in_public` lint with `private_interfaces` and
  `private_bounds` per RFC 2145]
  (rust-lang/rust#113126)
  Read more in
  [RFC 2145](https://rust-lang.github.io/rfcs/2145-type-privacy.html).
- [Allow explicit `#[repr(Rust)]`]
  (rust-lang/rust#114201)
- [closure field capturing: don't depend on alignment of packed fields]
  (rust-lang/rust#115315)
- [Enable MIR-based drop-tracking for `async` blocks]
  (rust-lang/rust#107421)

Compiler
--------

- [stabilize combining +bundle and +whole-archive link modifiers]
  (rust-lang/rust#113301)
- [Stabilize `PATH` option for `--print KIND=PATH`]
  (rust-lang/rust#114183)
- [Enable ASAN/LSAN/TSAN for `*-apple-ios-macabi`]
  (rust-lang/rust#115644)
- [Promote loongarch64-unknown-none* to Tier 2]
  (rust-lang/rust#115368)
- [Add `i686-pc-windows-gnullvm` as a tier 3 target]
  (rust-lang/rust#115687)

Libraries
---------

- [Implement `From<OwnedFd/Handle>` for ChildStdin/out/err]
  (rust-lang/rust#98704)
- [Implement `From<{&,&mut} [T; N]>` for `Vec<T>` where `T: Clone`]
  (rust-lang/rust#111278)
- [impl Step for IP addresses]
  (rust-lang/rust#113748)
- [Implement `From<[T; N]>` for `Rc<[T]>` and `Arc<[T]>`]
  (rust-lang/rust#114041)
- [`impl TryFrom<char> for u16`]
  (rust-lang/rust#114065)
- [Stabilize `io_error_other` feature]
  (rust-lang/rust#115453)
- [Stabilize the `Saturating` type]
  (rust-lang/rust#115477)
- [Stabilize const_transmute_copy]
  (rust-lang/rust#115520)

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

- [`core::num::Saturating`]
  (https://doc.rust-lang.org/stable/std/num/struct.Saturating.html)
- [`impl From<io::Stdout> for std::process::Stdio`]
  (https://doc.rust-lang.org/stable/std/process/struct.Stdio.html#impl-From%3CStdout%3E-for-Stdio)
- [`impl From<io::Stderr> for std::process::Stdio`]
  (https://doc.rust-lang.org/stable/std/process/struct.Stdio.html#impl-From%3CStderr%3E-for-Stdio)
- [`impl From<OwnedHandle> for std::process::Child{Stdin, Stdout, Stderr}`]
  (https://doc.rust-lang.org/stable/std/process/struct.Stdio.html#impl-From%3CStderr%3E-for-Stdio)
- [`impl From<OwnedFd> for std::process::Child{Stdin, Stdout, Stderr}`]
  (https://doc.rust-lang.org/stable/std/process/struct.Stdio.html#impl-From%3CStderr%3E-for-Stdio)
- [`std::ffi::OsString::from_encoded_bytes_unchecked`]
  (https://doc.rust-lang.org/stable/std/ffi/struct.OsString.html#method.from_encoded_bytes_unchecked)
- [`std::ffi::OsString::into_encoded_bytes`]
  (https://doc.rust-lang.org/stable/std/ffi/struct.OsString.html#method.into_encoded_bytes)
- [`std::ffi::OsStr::from_encoded_bytes_unchecked`]
  (https://doc.rust-lang.org/stable/std/ffi/struct.OsStr.html#method.from_encoded_bytes_unchecked)
- [`std::ffi::OsStr::as_encoded_bytes`]
  (https://doc.rust-lang.org/stable/std/ffi/struct.OsStr.html#method.as_encoded_bytes)
- [`std::io::Error::other`]
  (https://doc.rust-lang.org/stable/std/io/struct.Error.html#method.other)
- [`impl TryFrom<char> for u16`]
  (https://doc.rust-lang.org/stable/std/primitive.u16.html#impl-TryFrom%3Cchar%3E-for-u16)
- [`impl<T: Clone, const N: usize> From<&[T; N]> for Vec<T>`]
  (https://doc.rust-lang.org/stable/std/vec/struct.Vec.html#impl-From%3C%26%5BT;+N%5D%3E-for-Vec%3CT,+Global%3E)
- [`impl<T: Clone, const N: usize> From<&mut [T; N]> for Vec<T>`]
  (https://doc.rust-lang.org/stable/std/vec/struct.Vec.html#impl-From%3C%26mut+%5BT;+N%5D%3E-for-Vec%3CT,+Global%3E)
- [`impl<T, const N: usize> From<[T; N]> for Arc<[T]>`]
  (https://doc.rust-lang.org/stable/std/sync/struct.Arc.html#impl-From%3C%5BT;+N%5D%3E-for-Arc%3C%5BT%5D,+Global%3E)
- [`impl<T, const N: usize> From<[T; N]> for Rc<[T]>`]
  (https://doc.rust-lang.org/stable/std/rc/struct.Rc.html#impl-From%3C%5BT;+N%5D%3E-for-Rc%3C%5BT%5D,+Global%3E)

These APIs are now stable in const contexts:

- [`core::mem::transmute_copy`]
  (https://doc.rust-lang.org/beta/std/mem/fn.transmute_copy.html)
- [`str::is_ascii`]
  (https://doc.rust-lang.org/beta/std/primitive.str.html#method.is_ascii)
- [`[u8]::is_ascii`]
  (https://doc.rust-lang.org/beta/std/primitive.slice.html#method.is_ascii)

Cargo
-----

- [fix: Set MSRV for internal packages]
  (rust-lang/cargo#12381)
- [config: merge lists in precedence order]
  (rust-lang/cargo#12515)
- [fix(update): Clarify meaning of --aggressive as --recursive]
  (rust-lang/cargo#12544)
- [fix(update): Make `-p` more convenient by being positional]
  (rust-lang/cargo#12545)
- [feat(help): Add styling to help output ]
  (rust-lang/cargo#12578)
- [feat(pkgid): Allow incomplete versions when unambigious]
  (rust-lang/cargo#12614)
- [feat: stabilize credential-process and registry-auth]
  (rust-lang/cargo#12649)
- [feat(cli): Add '-n' to dry-run]
  (rust-lang/cargo#12660)
- [Add support for `target.'cfg(..)'.linker`]
  (rust-lang/cargo#12535)
- [Stabilize `--keep-going`]
  (rust-lang/cargo#12568)
- [feat: Stabilize lints]
  (rust-lang/cargo#12648)

Rustdoc
-------

- [Add warning block support in rustdoc]
  (rust-lang/rust#106561)
- [Accept additional user-defined syntax classes in fenced code blocks]
  (rust-lang/rust#110800)
- [rustdoc-search: add support for type parameters]
  (rust-lang/rust#112725)
- [rustdoc: show inner enum and struct in type definition for concrete type]
  (rust-lang/rust#114855)

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

- [Raise minimum supported Apple OS versions]
  (rust-lang/rust#104385)
- [make Cell::swap panic if the Cells partially overlap]
  (rust-lang/rust#114795)
- [Reject invalid crate names in `--extern`]
  (rust-lang/rust#116001)
- [Don't resolve generic impls that may be shadowed by dyn built-in impls]
  (rust-lang/rust#114941)

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.

None this cycle.

…i-obk

closure field capturing: don't depend on alignment of packed fields

This fixes the closure field capture part of rust-lang/rust#115305: field capturing always stops at projections into packed structs, no matter the alignment of the field. This means changing a private field type from `u8` to `u64` can never change how closures capture fields, which is probably what we want.

Here's an example where, before this PR, changing the type of a private field in a repr(Rust) struct can change the output of a program:

```rust
#![allow(dead_code)]

mod m {
    // before patch
    #[derive(Default)]
    pub struct S1(u8);
    // after patch
    #[derive(Default)]
    pub struct S2(u64);
}

struct NoisyDrop;
impl Drop for NoisyDrop {
    fn drop(&mut self) {
        eprintln!("dropped!");
    }
}

#[repr(packed)]
struct MyType {
    field: m::S1, // output changes when this becomes S2
    other_field: NoisyDrop,
    third_field: Vec<()>,
}

fn test(r: MyType) {
    let c = || {
        let _val = std::ptr::addr_of!(r.field);
        let _val = r.third_field;
    };
    drop(c);
    eprintln!("before dropping");
}

fn main() {
    test(MyType {
        field: Default::default(),
        other_field: NoisyDrop,
        third_field: Vec::new(),
    });
}
```

Of course this is a breaking change for the same reason that doing field capturing in the first place was a breaking change. Packed fields are relatively rare and depending on drop order is relatively rare, so I don't expect this to have much impact, but it's hard to be sure and even a crater run will only tell us so much.

Also see the [nomination comment](rust-lang/rust#115315 (comment)).

Cc `@rust-lang/wg-rfc-2229` `@ehuss`

…i-obk

closure field capturing: don't depend on alignment of packed fields

This fixes the closure field capture part of rust-lang/rust#115305: field capturing always stops at projections into packed structs, no matter the alignment of the field. This means changing a private field type from `u8` to `u64` can never change how closures capture fields, which is probably what we want.

Here's an example where, before this PR, changing the type of a private field in a repr(Rust) struct can change the output of a program:

```rust
#![allow(dead_code)]

mod m {
    // before patch
    #[derive(Default)]
    pub struct S1(u8);
    // after patch
    #[derive(Default)]
    pub struct S2(u64);
}

struct NoisyDrop;
impl Drop for NoisyDrop {
    fn drop(&mut self) {
        eprintln!("dropped!");
    }
}

#[repr(packed)]
struct MyType {
    field: m::S1, // output changes when this becomes S2
    other_field: NoisyDrop,
    third_field: Vec<()>,
}

fn test(r: MyType) {
    let c = || {
        let _val = std::ptr::addr_of!(r.field);
        let _val = r.third_field;
    };
    drop(c);
    eprintln!("before dropping");
}

fn main() {
    test(MyType {
        field: Default::default(),
        other_field: NoisyDrop,
        third_field: Vec::new(),
    });
}
```

Of course this is a breaking change for the same reason that doing field capturing in the first place was a breaking change. Packed fields are relatively rare and depending on drop order is relatively rare, so I don't expect this to have much impact, but it's hard to be sure and even a crater run will only tell us so much.

Also see the [nomination comment](rust-lang/rust#115315 (comment)).

Cc `@rust-lang/wg-rfc-2229` `@ehuss`