Add some track_caller info to precondition panics
Currently, when you encounter a precondition check, you'll always get the caller location of the implementation of the precondition checks. But with this PR, you'll be told the location of the invalid call. Which is useful.
I thought of this while looking at https://github.com/rust-lang/rust/pull/129642#issuecomment-2311703898.
The changes to `tests/ui/const*` happen because the const-eval interpreter skips `#[track_caller]` frames in its backtraces.
The perf implications of this are:
* Increased debug binary sizes. The caller_location implementation requires that the additional data we want to display here be stored in const allocations, which are deduplicated but not across crates. There is no impact on optimized build sizes. The panic path and the caller location data get optimized out.
* The compile time hit to opt-incr-patched bitmaps happens because the patch changes the line number of some function calls with precondition checks, causing us to go from 0 dirty CGUs to 1 dirty CGU.
* The other compile time hits are marginal but real, and due to doing a handful of new queries. Adding more useful data isn't completely free.
speed up charsearcher for ascii chars
attempt at fixing rust-lang/rust#82471
this implementation should be valid because ascii characters are always one byte and there are no continuation bytes that overlap with ascii characters
im not completely sure that this is _always_ an improvement but it seems to be an improvement for this case and i dont think it can significantly regress any cases
Implement a lint for implicit autoref of raw pointer dereference - take 2
*[t-lang nomination comment](https://github.com/rust-lang/rust/pull/123239#issuecomment-2727551097)*
This PR aims at implementing a lint for implicit autoref of raw pointer dereference, it is based on #103735 with suggestion and improvements from https://github.com/rust-lang/rust/pull/103735#issuecomment-1370420305.
The goal is to catch cases like this, where the user probably doesn't realise it just created a reference.
```rust
pub struct Test {
data: [u8],
}
pub fn test_len(t: *const Test) -> usize {
unsafe { (*t).data.len() } // this calls <[T]>::len(&self)
}
```
Since #103735 already went 2 times through T-lang, where they T-lang ended-up asking for a more restricted version (which is what this PR does), I would prefer this PR to be reviewed first before re-nominating it for T-lang.
----
Compared to the PR it is as based on, this PR adds 3 restrictions on the outer most expression, which must either be:
1. A deref followed by any non-deref place projection (that intermediate deref will typically be auto-inserted)
2. A method call annotated with `#[rustc_no_implicit_refs]`.
3. A deref followed by a `addr_of!` or `addr_of_mut!`. See bottom of post for details.
There are several points that are not 100% clear to me when implementing the modifications:
- ~~"4. Any number of automatically inserted deref/derefmut calls." I as never able to trigger this. Am I missing something?~~ Fixed
- Are "index" and "field" enough?
----
cc `@JakobDegen` `@WaffleLapkin`
r? `@RalfJung`
try-job: dist-various-1
try-job: dist-various-2
specify explicit safety guidance for from_utf8_unchecked
The PR addresses missing safety guidelines in two APIs by adding explicit text to the cross-linked reference.
Optimize multi-char string patterns
Uses specialization for `[T]::contains` from #130991 to optimize multi-char patterns in string searches.
Requesting a perf run to see if this actually has an effect 🙏
(I think that adding `char` to the list of types for which the `SliceContains` is specialized is a good idea, even if it doesn't show up on perf - might be helpful for downstream users)
Remove `#[cfg(not(test))]` gates in `core`
These gates are unnecessary now that unit tests for `core` are in a separate package, `coretests`, instead of in the same files as the source code. They previously prevented the two `core` versions from conflicting with each other.
Use `std::mem::{size_of, size_of_val, align_of, align_of_val}` from the
prelude instead of importing or qualifying them.
These functions were added to all preludes in Rust 1.80.
These gates are unnecessary now that unit tests for `core` are in a
separate package, `coretests`, instead of in the same files as the
source code. They previously prevented the two `core` versions from
conflicting with each other.
Add `MAX_LEN_UTF8` and `MAX_LEN_UTF16` Constants
This pull request adds the `MAX_LEN_UTF8` and `MAX_LEN_UTF16` constants as per #45795, gated behind the `char_max_len` feature.
The constants are currently applied in the `alloc`, `core` and `std` libraries.
fix docs for inherent str constructors
related to #131114
when implementing inherent str constructors in #136517, i forgot to change the docs, so the code examples still imported the `std::str` module and used the constructor from there, instead of using "itself" (the inherent constructor).
Stabilize `const_is_char_boundary` and `const_str_split_at`.
Tracking issues: #131516, #131518
Stabilized const API:
```rs
// in `core`
impl str {
// const_is_char_boundary feature
const fn is_char_boundary(&self, index: usize) -> bool;
// const_str_split_at feature, depends on const_is_char_boundary
const fn split_at(&self, mid: usize) -> (&str, &str);
const fn split_at_mut(&mut self, mid: usize) -> (&mut str, &mut str);
const fn split_at_checked(&self, mid: usize) -> Option<(&str, &str)>;
const fn split_at_mut_checked(&mut self, mid: usize) -> Option<(&mut str, &mut str)>;
}
```
This will allow safely splitting string slices during const-eval.
Closes#131516, Closes#131518
This will need FCP.
r? libs-api
IIUC these do not use any new const language features (i.e. they are implementable manually on stable 1.83.0 using `unsafe`: [playground link](https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=3679632cd1041084796241b7ac8edfbd)).
Cc ``@rust-lang/wg-const-eval`` (I don't know if I have the permissions for this ping; if not, someone else please ping wg-const-eval if it is necessary)
Use attributes for `dangling_pointers_from_temporaries` lint
Checking for dangling pointers by function name isn't ideal, and leaves out certain pointer-returning methods that don't follow the `as_ptr` naming convention. Using an attribute for this lint cleans things up and allows more thorough coverage of other methods, such as `UnsafeCell::get()`.
add const_eval_select macro to reduce redundancy
I played around a bit with a macro to make const_eval_select invocations look a bit nicer and avoid repeating the argument lists. Here's what I got. What do you think?
I didn't apply this everywhere yet because I wanted to gather feedback first.
The second commit moves the macros from https://github.com/rust-lang/rust/pull/132542 into a more sensible place. It didn't seem worth its own PR and would conflict with this PR if done separately.
Cc ``@oli-obk`` ``@saethlin`` ``@tgross35``
try-job: dist-aarch64-msvc
Operations like is_aligned would return actively wrong results at compile-time,
i.e. calling it on the same pointer at compiletime and runtime could yield
different results. That's no good.
Instead of having hacks to make align_offset kind-of work in const-eval, just
use const_eval_select in the few places where it makes sense, which also ensures
those places are all aware they need to make sure the fallback behavior is
consistent.
