atomicrmw on pointers: move integer-pointer cast hacks into backend
Conceptually, we want to have atomic operations on pointers of the form `fn atomic_add(ptr: *mut T, offset: usize, ...)`. However, LLVM does not directly support such operations (https://github.com/llvm/llvm-project/issues/120837), so we have to cast the `offset` to a pointer somewhere.
This PR moves that hack into the LLVM backend, so that the standard library, intrinsic, and Miri all work with the conceptual operation we actually want. Hopefully, one day LLVM will gain a way to represent these operations without integer-pointer casts, and then the hack will disappear entirely.
Cc ```@nikic``` -- this is the best we can do right now, right?
Fixes https://github.com/rust-lang/rust/issues/134617
doc(library): Fix Markdown in `Iterator::by_ref`
This patch fixes the Markdown formatting in `std::core::iter::Iterator::by_ref`. Code is used inside a link without the backticks around the code.
bump bootstrap compiler to 1.90 beta
There were significantly less `cfg(bootstrap)` and `cfg(not(bootstrap))` this release. Presumably due to the fact that we change the bootstrap stage orderings to reduce the need for them and it was successful 🙏
Stabilize const TypeId::of
fixesrust-lang/rust#77125
# Stabilization report for `const_type_id`
## General design
### What is the RFC for this feature and what changes have occurred to the user-facing design since the RFC was finalized?
N/A the constness was never RFCed
### What behavior are we committing to that has been controversial? Summarize the major arguments pro/con.
`const_type_id` was kept unstable because we are currently unable to stabilize the `PartialEq` impl for it (in const contexts), so we feared people would transmute the type id to an integer and compare that integer.
### Are there extensions to this feature that remain unstable? How do we know that we are not accidentally committing to those?
`TypeId::eq` is not const at this time, and will only become const once const traits are stable.
## Has a Call for Testing period been conducted? If so, what feedback was received?
This feature has been unstable for a long time, and most people just worked around it on stable by storing a pointer to `TypeId::of` and calling that at "runtime" (usually LLVM devirtualized the function pointer and inlined the call so there was no real performance difference).
A lot of people seem to be using the `const_type_id` feature gate (600 results for the feature gate on github: https://github.com/search?q=%22%23%21%5Bfeature%28const_type_id%29%5D%22&type=code)
We have had very little feedback except desire for stabilization being expressed.
## Implementation quality
Until these three PRs
* https://github.com/rust-lang/rust/pull/142789
* https://github.com/rust-lang/rust/pull/143696
* https://github.com/rust-lang/rust/pull/143736
there was no difference between the const eval feature and the runtime feature except that we prevented you from using `TypeId::of` at compile-time. These three recent PRs have hardened the internals of `TypeId`:
* it now contains an array of pointers instead of integers
* these pointers at compile-time (and in miri) contain provenance that makes them unique and prevents inspection. Both miri and CTFE will in fact error if you mess with the bits or the provenance of the pointers in any way and then try to use the `TypeId` for an equality check. This also guards against creating values of type `TypeId` by any means other than `TypeId::of`
### Summarize the major parts of the implementation and provide links into the code (or to PRs)
N/A see above
### Summarize existing test coverage of this feature
Since we are not stabilizing any operations on `TypeId` except for creating `TypeId`s, the test coverage of the runtime implementation of `TypeId` covers all the interesting use cases not in the list below
#### Hardening against transmutes
* https://github.com/rust-lang/rust/blob/master/tests/ui/consts/const_transmute_type_id.rs
* https://github.com/rust-lang/rust/blob/master/tests/ui/consts/const_transmute_type_id2.rs
* https://github.com/rust-lang/rust/blob/master/tests/ui/consts/const_transmute_type_id3.rs
* https://github.com/rust-lang/rust/blob/master/tests/ui/consts/const_transmute_type_id4.rs
* https://github.com/rust-lang/rust/blob/master/tests/ui/consts/const_transmute_type_id5.rs
#### TypeId::eq is still unstable
* https://github.com/rust-lang/rust/blob/master/tests/ui/consts/const_cmp_type_id.rs
### What outstanding bugs in the issue tracker involve this feature? Are they stabilization-blocking?
https://github.com/rust-lang/rust/issues/129014 is still unresolved, but it affects more the runtime version of `TypeId` than the compile-time.
### What FIXMEs are still in the code for that feature and why is it ok to leave them there?
none
### Summarize contributors to the feature by name for recognition and assuredness that people involved in the feature agree with stabilization
* `@eddyb`
* `@RalfJung`
### Which tools need to be adjusted to support this feature. Has this work been done?
N/A
## Type system and execution rules
### What compilation-time checks are done that are needed to prevent undefined behavior?
Already covered above. Transmuting types with private fields to expose those fields has always been library UB, but for the specific case of `TypeId` CTFE and Miri will detect it if that is done in any way other than for reconstructing the exact same `TypeId` in another location.
### Does the feature's implementation need checks to prevent UB or is it sound by default and needs opt in in places to perform the dangerous/unsafe operations? If it is not sound by default, what is the rationale?
N/A
### Can users use this feature to introduce undefined behavior, or use this feature to break the abstraction of Rust and expose the underlying assembly-level implementation? (Describe.)
N/A
### What updates are needed to the reference/specification? (link to PRs when they exist)
Nothing more than what needs to exist for `TypeId` already.
## Common interactions
### Does this feature introduce new expressions and can they produce temporaries? What are the lifetimes of those temporaries?
N/A
### What other unstable features may be exposed by this feature?
N/A
Miri: non-deterministic floating point operations in `foreign_items`
Part of [rust-lang/miri/#3555](https://github.com/rust-lang/miri/issues/3555#issue-2278914000), this pr does the `foreign_items` work.
Some things have changed since rust-lang/rust#138062 and rust-lang/rust#142514. I moved the "helpers" used for creating fixed outputs and clamping operations to their defined ranges to `math.rs`. These are now also extended to handle the floating-point operations in `foreign_items`. Tests in `miri/tests/float.rs` were changed/added.
Failing tests in `std` were extracted, run under miri with `-Zmiri-many-seeds=0..1000` and changed accordingly. Double checked with `-Zmiri-many-seeds`.
I noticed that the C standard doesn't specify the output ranges for all of its mathematical operations; it just specifies them as:
```
Returns
The sinh functions return sinh x.
```
So I used [Wolfram|Alpha](https://www.wolframalpha.com/).
Fix some doc links for intrinsics
This fixes a few intrinsic docs that had a link directly to itself instead of to the correct function in the `mem` module.
Document Poisoning in `LazyCell` and `LazyLock`
Currently, there is no documentation of poisoning behavior in either `LazyCell` or `LazyLock`, even though both of them can be observed as poisoned by users.
`LazyCell` [plagyround example](https://play.rust-lang.org/?version=stable&mode=debug&edition=2024&gist=9cf38b8dc56db100848f54085c2c697d)
`LazyLock` [playground example](https://play.rust-lang.org/?version=stable&mode=debug&edition=2024&gist=f1cd6f9fe16636e347ebb695a0ce30c0)
# Open Questions
- [x] Is it worth making the implementation of `LazyLock` more complicated to ensure that the the panic message is `"LazyLock instance has previously been poisoned"` instead of `"Once instance has previously been poisoned"`? See the `LazyLock` playground link above for more context.
- [x] Does it make sense to move `LazyLock` into the `poison` module? It is certainly a poison-able type, but at the same time it is slightly different from the 4 other types currently in the `poison` module in that it is unrecoverable. I think this is more of a libs-api question.
``@rustbot`` label +T-libs-api
Please let me know if these open questions deserve a separate issue / PR!
Use `as_array` in PartialEq for arrays
Now that `as_array` exists we might as well use it here, since it's a bit more convenient than getting the correct type out of `try_into`.
`AlignmentEnum` should just be `repr(usize)` now
These used to use specific sizes because they were compiled on all widths. But now that the types themselves are `#[cfg]`'d, we can save some conversions by having it always be `repr(usize)`.
Update safety comment for new_unchecked in niche_types
Change the safety comment on `new_unchecked` to mention the valid range instead of 0. I noticed this while working on https://github.com/model-checking/verify-rust-std
Improve formatting of doc code blocks
We don't currently apply automatic formatting to doc comment code blocks. As a
result, it has built up various idiosyncracies, which make such automatic
formatting difficult. Some of those idiosyncracies also make things harder for
human readers or other tools.
This PR makes a few improvements to doc code formatting, in the hopes of making
future automatic formatting easier, as well as in many cases providing net
readability improvements.
I would suggest reading each commit separately, as each commit contains one
class of changes.
Fix Ord, Eq and Hash implementation of panic::Location
Fixes https://github.com/rust-lang/rust/issues/144486.
Now properly compares/hashes the filename rather than the pointer to the string.
Fix typo in `DropGuard` doc
Follows-up rust-lang/rust#144236 (I happened to see the typo yesterday but didn’t think it should delay the PR’s merge so I kept quiet, sorryyyyy).
