Insert null checks for pointer dereferences when debug assertions are enabled
Similar to how the alignment is already checked, this adds a check
for null pointer dereferences in debug mode. It is implemented similarly
to the alignment check as a `MirPass`.
This inserts checks in the same places as the `CheckAlignment` pass and additionally
also inserts checks for `Borrows`, so code like
```rust
let ptr: *const u32 = std::ptr::null();
let val: &u32 = unsafe { &*ptr };
```
will have a check inserted on dereference. This is done because null references
are UB. The alignment check doesn't cover these places, because in `&(*ptr).field`,
the exact requirement is that the final reference must be aligned. This is something to
consider further enhancements of the alignment check.
For now this is implemented as a separate `MirPass`, to make it easy to disable
this check if necessary.
This is related to a 2025H1 project goal for better UB checks in debug
mode: https://github.com/rust-lang/rust-project-goals/pull/177.
r? `@saethlin`
Similar to how the alignment is already checked, this adds a check
for null pointer dereferences in debug mode. It is implemented similarly
to the alignment check as a MirPass.
This is related to a 2025H1 project goal for better UB checks in debug
mode: https://github.com/rust-lang/rust-project-goals/pull/177.
float::min/max: mention the non-determinism around signed 0
Turns out this can actually produce different results on different machines [in practice](https://github.com/rust-lang/rust/issues/83984#issuecomment-2623859230); that seems worth documenting. I assume LLVM will happily const-fold these operations so so there could be different results for the same input even on the same machine, depending on whether things get const-folded or not.
`@nikic` I remember there was an LLVM soundness fix regarding scalar evolution for loops that had to recognize certain operations as non-deterministic... it seems to me that pass would also have to avoid predicting the result of `llvm.{min,max}num`, for the same reason?
r? `@tgross35`
Cc `@rust-lang/libs-api`
If this lands we should also make Miri non-deterministic here.
Fixes https://github.com/rust-lang/rust/issues/83984
Stabilize `const_black_box`
This has been unstably const since #92226, but a tracking issue was never created. Per [discussion on Zulip][zulip], there should not be any blockers to making this const-stable. The function does not provide any functionality at compile time but does allow code reuse between const- and non-const functions, so stabilize it here.
[zulip]: https://rust-lang.zulipchat.com/#narrow/channel/146212-t-compiler.2Fconst-eval/topic/const_black_box
Improve documentation for file locking
Add notes to each method stating that locks get dropped on close.
Clarify the return values of the try methods: they're only defined if
the lock is held via a *different* file handle/descriptor. That goes
along with the documentation that calling them while holding a lock via
the *same* file handle/descriptor may deadlock.
Document the behavior of unlock if no lock is held.
r? `@m-ou-se`
(Documentation changes requested in https://github.com/rust-lang/rust/issues/130994 .)
Remove minor future footgun in `impl Debug for MaybeUninit`
No longer breaks if `MaybeUninit` moves modules (technically it could break if `MaybeUninit` were renamed but realistically that will never happen)
Debug impl originally added in #133282
Add `AsyncFn*` to `core` prelude
In https://github.com/rust-lang/rust/pull/132611 these got added to the `std` prelude only, which looks like an oversight.
r? libs-api
cc `@compiler-errors`
uefi: Implement path
This PR is split off from https://github.com/rust-lang/rust/pull/135368 to reduce noise.
UEFI paths can be of 4 types:
1. Absolute Shell Path: Uses shell mappings
2. Absolute Device Path: this is what we want
3. Relative root: path relative to the current root.
4. Relative
Absolute shell path can be identified with `:` and Absolute Device path can be identified with `/`. Relative root path will start with `\`.
The algorithm is mostly taken from edk2 UEFI shell implementation and is somewhat simple. Check for the path type in order.
For Absolute Shell path, use `EFI_SHELL->GetDevicePathFromMap` to get a BorrowedDevicePath for the volume.
For Relative paths, we use the current working directory to construct the new path.
BorrowedDevicePath abstraction is needed to interact with `EFI_SHELL->GetDevicePathFromMap` which returns a Device Path Protocol with the lifetime of UEFI shell.
Absolute Shell paths cannot exist if UEFI shell is missing.
cc `@nicholasbishop`
Implement `int_from_ascii` (#134821)
Provides unstable `T::from_ascii()` and `T::from_ascii_radix()` for integer types `T`, as drafted in tracking issue #134821.
To deduplicate documentation without additional macros, implementations of `isize` and `usize` no longer delegate to equivalent integer types. After #132870 they are inlined anyway.
Add notes to each method stating that locks get dropped on close.
Clarify the return values of the try methods: they're only defined if
the lock is held via a *different* file handle/descriptor. That goes
along with the documentation that calling them while holding a lock via
the *same* file handle/descriptor may deadlock.
Document the behavior of unlock if no lock is held.
Cleanup docs for Allocator
This is an attempt to remove ungrammatical constructions and clean up the prose. I've sometimes had to try hard to understand what was being stated, so it is possible that I've misunderstood the original meaning. In particular, I did not see a difference between:
- the borrow-checker lifetime of the allocator type itself.
- as long as at least one of the allocator instance and all of its clones has not been dropped.
optimize slice::ptr_rotate for small rotates
r? `@scottmcm`
This swaps the positions and numberings of algorithms 1 and 2 in `slice::ptr_rotate`, and pulls the entire outer loop into algorithm 3 since it was redundant for the first two. Effectively, `ptr_rotate` now always does the `memcpy`+`memmove`+`memcpy` sequence if the shifts fit into the stack buffer.
With this change, an `IndexMap`-style `move_index` function is optimized correctly.
Assembly comparisons:
- `move_index`, before: https://godbolt.org/z/Kr616KnYM
- `move_index`, after: https://godbolt.org/z/1aoov6j8h
- the code from `#89714`, before: https://godbolt.org/z/Y4zaPxEG6
- the code from `#89714`, after: https://godbolt.org/z/1dPx83axc
related to #89714
some relevant discussion in https://internals.rust-lang.org/t/idea-shift-move-to-efficiently-move-elements-in-a-vec/22184
Behavior tests pass locally. I can't get any consistent microbenchmark results on my machine, but the assembly diffs look promising.
Rollup of 8 pull requests
Successful merges:
- #133382 (Suggest considering casting fn item as fn pointer in more cases)
- #136092 (Test pipes also when not running on Windows and Linux simultaneously)
- #136190 (Remove duplicated code in RISC-V asm bad-reg test)
- #136192 (ci: remove unused windows runner)
- #136205 (Properly check that array length is valid type during built-in unsizing in index)
- #136211 (Update mdbook to 0.4.44)
- #136212 (Tweak `&mut self` suggestion span)
- #136214 (Make crate AST mutation accessible for driver callback)
r? `@ghost`
`@rustbot` modify labels: rollup
uefi: process: Fix args
- While working on process env support, I found that args were currently broken. Not sure how I missed it in the PR, but well here is the fix.
- Additionally, no point in adding space at the end of args.
