Improve diagnostics for pointer arithmetic += and -= (fixes#137391)
**Description**:
This PR improves the diagnostic message for cases where a binary assignment operation like `ptr += offset` or `ptr -= offset` is attempted on `*mut T`. These operations are not allowed, and the compiler previously suggested calling `.add()` or `.wrapping_add()`, which is misleading if not assigned.
This PR updates the diagnostics to suggest assigning the result of `.wrapping_add()` or `.wrapping_sub()` back to the pointer, e.g.:
**Examples**
For this code
```rust
let mut arr = [0u8; 10];
let mut ptr = arr.as_mut_ptr();
ptr += 2;
```
it will say:
```rust
10 | ptr += 2;
| ---^^^^^
| |
| cannot use `+=` on type `*mut u8`
|
help: consider replacing `ptr += offset` with `ptr = ptr.wrapping_add(offset)` or `ptr.add(offset)`
|
10 - ptr += 2;
10 + ptr = ptr.wrapping_add(2);
```
**Related issue**: #137391
cc `@nabijaczleweli` for context (issue author)
Construct OutputType using macro and print [=FILENAME] help info
Closes#139805
Use define_output_types to define variants of OutputType, as well as refactor all of its methods for clarity. This way no variant is missed when pattern matching or output help messages.
On top of that, I optimized for `emit` help messages.
r? ```@jieyouxu```
jsondocck: Require command is at start of line
In one place we use `///``@``` instead of `//``@`.`` The test-runner allowed it, but it probably shouldn't. Ran into by ``@lolbinarycat`` in https://github.com/rust-lang/rust/pull/132748#issuecomment-2816469322:
```
error: unknown disambiguator `?(`
##[error] --> /checkout/tests/rustdoc-json/fns/return_type_alias.rs:3:25
|
3 | ///@ set foo = "$.index[?(``@.name=='Foo')].id"``
| ^^
|
```
Maybe it's also worth erroring on this like we added in #137103
r? ``@GuillaumeGomez``
rustdoc-json: Improve test for auto-trait impls
The TODO is fixable now due-to #138763. While I was here I realized there's probably a a few more things we should also test.
r? ```@GuillaumeGomez```
Fix error when an intra doc link is trying to resolve an empty associated item
Fixes https://github.com/rust-lang/rust/issues/140026.
Assigning ```@nnethercote``` since they're the one who wrote the initial change.
I updated rustdoc code instead of compiler's because I think it makes more sense that the caller ensures on their side that the name they're looking for isn't empty.
r? ```@nnethercote```
Advent of `tests/ui` (misc cleanups and improvements) [4/N]
Some `tests/ui/` housekeeping, to trim down number of tests directly under `tests/ui/`. Part of #133895.
### Review advice
- Best reviewed commit-by-commit.
- I can squash commits before merge, commits are separate to make it easier to review.
Clarify why SGX code specifies linkage/symbol names for certain statics
Specifying linkage/symbol name is solely to ensure a single instance between the `std` crate and its unit tests.
Also update the symbol names as items have moved around a bit. The actual name isn't that important, it just needs to be unique. But for debugging it can be useful for it to point to the right place.
Hermit: Unify `std::env::args` with Unix
The only differences between these implementations of `std::env::args` are that Unix uses relaxed ordering, but Hermit uses acquire/release, and Unix truncates `argv` at the first null pointer, but Hermit doesn't. Since Hermit aims for Unix compatibility, unify it with Unix.
The atomic orderings were established in https://github.com/rust-lang/rust/pull/74006 (cc `@euclio)` for Unix and https://github.com/rust-lang/rust/pull/100579 (cc `@joboet)` for Hermit and, before those, they used mutexes and non-atomic statics. I think the difference in orderings is simply from them being changed at different times. The commented explanation for using acquire/release for Hermit is “to broadcast writes by the OS”. I'm not experienced enough with atomics to accurately judge, but I think acquire/release is stronger than needed. Either way, they should match.
Truncating at the first null pointer seems desirable, though I don't know whether it is necessary in practice on Hermit.
cc `@mkroening` `@stlankes` for Hermit
Stabilize `naked_functions`
tracking issue: https://github.com/rust-lang/rust/issues/90957
request for stabilization on tracking issue: https://github.com/rust-lang/rust/issues/90957#issuecomment-2539270352
reference PR: https://github.com/rust-lang/reference/pull/1689
# Request for Stabilization
Two years later, we're ready to try this again. Even though this issue is already marked as having passed FCP, given the amount of time that has passed and the changes in implementation strategy, we should follow the process again.
## Summary
The `naked_functions` feature has two main parts: the `#[naked]` function attribute, and the `naked_asm!` macro.
An example of a naked function:
```rust
const THREE: usize = 3;
#[naked]
pub extern "sysv64" fn add_n(number: usize) -> usize {
// SAFETY: the validity of the used registers
// is guaranteed according to the "sysv64" ABI
unsafe {
core::arch::naked_asm!(
"add rdi, {}",
"mov rax, rdi",
"ret",
const THREE,
)
}
}
```
When the `#[naked]` attribute is applied to a function, the compiler won't emit a [function prologue](https://en.wikipedia.org/wiki/Function_prologue_and_epilogue) or epilogue when generating code for this function. This attribute is analogous to [`__attribute__((naked))`](https://developer.arm.com/documentation/100067/0608/Compiler-specific-Function--Variable--and-Type-Attributes/--attribute----naked---function-attribute) in C. The use of this feature allows the programmer to have precise control over the assembly that is generated for a given function.
The body of a naked function must consist of a single `naked_asm!` invocation, a heavily restricted variant of the `asm!` macro: the only legal operands are `const` and `sym`, and the only legal options are `raw` and `att_syntax`. In lieu of specifying operands, the `naked_asm!` within a naked function relies on the function's calling convention to determine the validity of registers.
## Documentation
The Rust Reference: https://github.com/rust-lang/reference/pull/1689
(Previous PR: https://github.com/rust-lang/reference/pull/1153)
## Tests
* [tests/run-make/naked-symbol-visiblity](https://github.com/rust-lang/rust/tree/master/tests/codegen/naked-fn) verifies that `pub`, `#[no_mangle]` and `#[linkage = "..."]` work correctly for naked functions
* [tests/codegen/naked-fn](https://github.com/rust-lang/rust/tree/master/tests/codegen/naked-fn) has tests for function alignment, use of generics, and validates the exact assembly output on linux, macos, windows and thumb
* [tests/ui/asm/naked-*](https://github.com/rust-lang/rust/tree/master/tests/ui/asm) tests for incompatible attributes, generating errors around incorrect use of `naked_asm!`, etc
## Interaction with other (unstable) features
### [fn_align](https://github.com/rust-lang/rust/issues/82232)
Combining `#[naked]` with `#[repr(align(N))]` works well, and is tested e.g. here
- https://github.com/rust-lang/rust/blob/master/tests/codegen/naked-fn/aligned.rs
- https://github.com/rust-lang/rust/blob/master/tests/codegen/naked-fn/min-function-alignment.rs
It's tested extensively because we do need to explicitly support the `repr(align)` attribute (and make sure we e.g. don't mistake powers of two for number of bytes).
## History
This feature was originally proposed in [RFC 1201](https://github.com/rust-lang/rfcs/pull/1201), filed on 2015-07-10 and accepted on 2016-03-21. Support for this feature was added in [#32410](https://github.com/rust-lang/rust/pull/32410), landing on 2016-03-23. Development languished for several years as it was realized that the semantics given in RFC 1201 were insufficiently specific. To address this, a minimal subset of naked functions was specified by [RFC 2972](https://github.com/rust-lang/rfcs/pull/2972), filed on 2020-08-07 and accepted on 2021-11-16. Prior to the acceptance of RFC 2972, all of the stricter behavior specified by RFC 2972 was implemented as a series of warn-by-default lints that would trigger on existing uses of the `naked` attribute; these lints became hard errors in [#93153](https://github.com/rust-lang/rust/pull/93153) on 2022-01-22. As a result, today RFC 2972 has completely superseded RFC 1201 in describing the semantics of the `naked` attribute.
More recently, the `naked_asm!` macro was added to replace the earlier use of a heavily restricted `asm!` invocation. The `naked_asm!` name is clearer in error messages, and provides a place for documenting the specific requirements of inline assembly in naked functions.
The implementation strategy was changed to emitting a global assembly block. In effect, an extern function
```rust
extern "C" fn foo() {
core::arch::naked_asm!("ret")
}
```
is emitted as something similar to
```rust
core::arch::global_asm!(
"foo:",
"ret"
);
extern "C" {
fn foo();
}
```
The codegen approach was chosen over the llvm naked function attribute because:
- the rust compiler can guarantee the behavior (no sneaky additional instructions, no inlining, etc.)
- behavior is the same on all backends (llvm, cranelift, gcc, etc)
Finally, there is now an allow list of compatible attributes on naked functions, so that e.g. `#[inline]` is rejected with an error. The `#[target_feature]` attribute on naked functions was later made separately unstable, because implementing it is complex and we did not want to block naked functions themselves on how target features work on them. See also https://github.com/rust-lang/rust/issues/138568.
relevant PRs for these recent changes
- https://github.com/rust-lang/rust/pull/127853
- https://github.com/rust-lang/rust/pull/128651
- https://github.com/rust-lang/rust/pull/128004
- https://github.com/rust-lang/rust/pull/138570
-
### Various historical notes
#### `noreturn`
[RFC 2972](https://github.com/rust-lang/rfcs/blob/master/text/2972-constrained-naked.md) mentions that naked functions
> must have a body which contains only a single asm!() statement which:
> iii. must contain the noreturn option.
Instead of `asm!`, the current implementation mandates that the body contain a single `naked_asm!` statement. The `naked_asm!` macro is a heavily restricted version of the `asm!` macro, making it easier to talk about and document the rules of assembly in naked functions and give dedicated error messages.
For `naked_asm!`, the behavior of the `asm!`'s `noreturn` option is implicit. The `noreturn` option means that it is UB for control flow to fall through the end of the assembly block. With `asm!`, this option is usually used for blocks that diverge (and thus have no return and can be typed as `!`). With `naked_asm!`, the intent is different: usually naked funtions do return, but they must do so from within the assembly block. The `noreturn` option was used so that the compiler would not itself also insert a `ret` instruction at the very end.
#### padding / `ud2`
A `naked_asm!` block that violates the safety assumption that control flow must not fall through the end of the assembly block is UB. Because no return instruction is emitted, whatever bytes follow the naked function will be executed, resulting in truly undefined behavior. There has been discussion whether rustc should emit an invalid instruction (e.g. `ud2` on x86) after the `naked_asm!` block to at least fail early in the case of an invalid `naked_asm!`. It was however decided that it is more useful to guarantee that `#[naked]` functions NEVER contain any instructions besides those in the `naked_asm!` block.
# unresolved questions
None
r? ``@Amanieu``
I've validated the tests on x86_64 and aarch64
Use `output_base_dir` for `mir_dump_dir`
It just occurred to me that the problem might be due to multiple revisions using the same dump directory (and therefore deleting the other revision's dir). This fixes that by simply using the normal per-test output directory, which is revision safe.
Relocate tests in `tests/ui`
Part of #133895
Moved tests from a top-level directory into a more appropriate subdirectory.
If there is anything else that could be improved, please let me know!
r? jieyouxu
Don't ICE on pending obligations from deep normalization in a loop
See the comment I left inline in `compiler/rustc_trait_selection/src/traits/normalize.rs`.
Fixes https://github.com/rust-lang/rust/issues/133868
r? lcnr
SystemTime doc tweaks
* Change the `UNIX_EPOCH` link in the `SystemTime` docs to point to the associated constant, not the module level constant. The former seems to be the recommended way to access it, since aiui the only reason the module constant exists in the first place is that associated constants weren't stable yet at the time.
* Reword the comment in the `SystemTime` example - "an error occurred!" is a tad misleading; I feel like it implies a system error out of our control while `SystemTimeError` is more of a logic error.
I was originally just gonna do the first thing but I noticed the second and figured I may as well.
I'm also somewhat surprised that there aren't more in-depth module level docs for `std::time`; they don't even mention `SystemTime` at all. I might make another PR for that but mainly just wanted to flag it.
replace broken links armv7-rtems-eabihf.md
Hi team , i found broken link in `src/doc/rustc/src/platform-support/armv7-rtems-eabihf.md` and replace
thanks
Make target maintainers more easily pingable
Put them all on the same line with just their GitHub handles to make it very easy to copy and paste (with ctrl-shift-v!!!) the names.
We have no use for email, so I removed all the emails, we don't care about people's full names either.
This is a pretty big PR with lots of changes. I may have gotten one or two wrong, who knows. I went over it fairly aggressively, removing all information I deemed unnecessary.
> [!Caution]
> When copying these usernames, use **ctrl-shift-v** to avoid pasting them as links
r? RalfJung you indirectly asked for this :) (anyone is welcome to review)
Add target-specific NaN payloads for the missing tier 2 targets
This PR adds target-specific NaN payloads for the remaining tier 2 targets:
- `arm64ec`: This target is a mix of `x86_64` and `aarch64`, meaning as they both have no extra payloads `arm64ec` also has no extra payloads.
- `loongarch64`: Per [LoongArch Reference Manual - Volume 1: Basic Architecture](https://github.com/loongson/LoongArch-Documentation/releases/download/2023.04.20/LoongArch-Vol1-v1.10-EN.pdf) section 3.1.1.3, LoongArch does quieting NaN propagation with the Rust preferred NaN as its default NaN, meaning it has no extra payloads.
- `nvptx64`: Per [PTX ISA documentation](https://docs.nvidia.com/cuda/parallel-thread-execution/index.html#floating-point-instructions) section 9.7.3 (and section 9.7.4 for `f16`), all payloads are possible. The documentation explicitly states that `f16` and `f32` operations result in an unspecified NaN payload, while for `f64` it states "NaN payloads are supported" without specifying how or what payload will be generated if there are no input NaNs.
- `powerpc` and `powerpc64`: Per [Power Instruction Set Architecture](https://files.openpower.foundation/s/9izgC5Rogi5Ywmm/download/OPF_PowerISA_v3.1C.pdf) Book I section 4.3.2, PowerPC does quieting NaN propagation with the Rust preferred NaN being generated if no there are no input NaNs, meaning it has no extra payloads.
- `s390x`: Per [IBM z/Architecture Principles of Operation](https://www.vm.ibm.com/library/other/22783213.pdf#page=965) page 9-3, s390x does quieting NaN propagation with the Rust's preferred NaN as its default NaN, meaning it has no extra payloads.
Tracking issue: #128288
cc ``@RalfJung``
``@rustbot`` label +T-lang
Also cc relevant target maintainers of tier 2 targets:
- `arm64ec`: ``@dpaoliello``
- `loongarch64`: ``@heiher`` ``@xiangzhai`` ``@zhaixiaojuan`` ``@xen0n``
- `nvptx64`: ``@RDambrosio016`` ``@kjetilkjeka``
- `powerpc`: the only documented maintainer is ``@BKPepe`` for the tier 3 `powerpc-unknown-linux-muslspe`.
- `powerpc64`: ``@daltenty`` ``@gilamn5tr`` ``@Gelbpunkt`` ``@famfo`` ``@neuschaefer``
- `s390x`: ``@uweigand`` ``@cuviper``
Put them all on the same line with just their GitHub handles to make it
very easy to copy and paste (with ctrl-shift-v!!!) the names.
We have no use for email, so I removed all the emails, we don't care
about people's full names either.
Co-authored-by: Thalia Archibald <thalia@archibald.dev>
Switch exploit mitigations to mdbook footnotes
This updates the exploit mitigations chapter in the rustc book to use the footnote feature of mdbook instead of manually implementing footnotes with HTML.
