This commit intends to fill out some of the remaining pieces of the
C-unwind ABI. This has a number of other changes with it though to move
this design space forward a bit. Notably contained within here is:
* On `panic=unwind`, the `extern "C"` ABI is now considered as "may
unwind". This fixes a longstanding soundness issue where if you
`panic!()` in an `extern "C"` function defined in Rust that's actually
UB because the LLVM representation for the function has the `nounwind`
attribute, but then you unwind.
* Whether or not a function unwinds now mainly considers the ABI of the
function instead of first checking the panic strategy. This fixes a
miscompile of `extern "C-unwind"` with `panic=abort` because that ABI
can still unwind.
* The aborting stub for non-unwinding ABIs with `panic=unwind` has been
reimplemented. Previously this was done as a small tweak during MIR
generation, but this has been moved to a separate and dedicated MIR
pass. This new pass will, for appropriate functions and function
calls, insert a `cleanup` landing pad for any function call that may
unwind within a function that is itself not allowed to unwind. Note
that this subtly changes some behavior from before where previously on
an unwind which was caught-to-abort it would run active destructors in
the function, and now it simply immediately aborts the process.
* The `#[unwind]` attribute has been removed and all users in tests and
such are now using `C-unwind` and `#![feature(c_unwind)]`.
I think this is largely the last piece of the RFC to implement.
Unfortunately I believe this is still not stabilizable as-is because
activating the feature gate changes the behavior of the existing `extern
"C"` ABI in a way that has no replacement. My thinking for how to enable
this is that we add support for the `C-unwind` ABI on stable Rust first,
and then after it hits stable we change the behavior of the `C` ABI.
That way anyone straddling stable/beta/nightly can switch to `C-unwind`
safely.
Make const panic!("..") work in Rust 2021.
During const eval, this replaces calls to core::panicking::panic_fmt and std::panicking::being_panic_fmt with a call to a new const fn: core::panicking::const_panic_fmt. That function uses fmt::Arguments::as_str() to get the str and calls panic_str with that instead.
panic!() invocations with formatting arguments are still not accepted, as the creation of such a fmt::Arguments cannot be done in constant functions right now.
r? `@RalfJung`
Remove P: Unpin bound on impl Future for Pin
We can safely produce a `Pin<&mut P::Target>` without moving out of the `Pin` by using `Pin::as_mut` directly.
The `Unpin` bound was originally added in #56939 following the recommendation of ``@withoutboats`` in https://github.com/rust-lang/rust/issues/55766#issue-378417538
That comment does not give explicit justification for why the bound should be added. The relevant context was:
> [ ] Remove `impl<P> Unpin for Pin<P>`
>
> This impl is not justified by our standard justification for unpin impls: there is no pointer direction between `Pin<P>` and `P`. Its usefulness is covered by the impls for pointers themselves.
>
> This futures impl (link to the impl changed in this PR) will need to change to add a `P: Unpin` bound.
The decision to remove the unconditional impl of `Unpin for Pin` is sound (these days there is just an auto-impl for when `P: Unpin`). But, I think the decision to also add the `Unpin` bound for `impl Future` may have been unnecessary. Or if that's not the case, I'd be very interested to have the argument for why written down somewhere. The bound _appears_ to not be needed, as demonstrated by the change requiring no unsafe code and by the existence of `Pin::as_mut`.
During const eval, this replaces calls to core::panicking::panic_fmt and
std::panicking::being_panic_fmt with a call to a new const fn:
core::panicking::const_panic_fmt. That function uses
fmt::Arguments::as_str() to get the str and calls panic_str with that
instead.
panic!() invocations with formatting arguments are still not accepted,
as the creation of such a fmt::Arguments cannot be done in constant
functions right now.
std: Stabilize wasm simd intrinsics
This commit performs two changes to stabilize Rust support for
WebAssembly simd intrinsics:
* The stdarch submodule is updated to pull in rust-lang/stdarch#1179.
* The `wasm_target_feature` feature gate requirement for the `simd128`
feature has been removed, stabilizing the name `simd128`.
This should conclude the FCP started on #74372 and...
Closes#74372
This commit performs two changes to stabilize Rust support for
WebAssembly simd intrinsics:
* The stdarch submodule is updated to pull in rust-lang/stdarch#1179.
* The `wasm_target_feature` feature gate requirement for the `simd128`
feature has been removed, stabilizing the name `simd128`.
This should conclude the FCP started on #74372 and...
Closes#74372
to_digit simplification (less jumps)
I just realised we might be able to make use of the fact that changing case in ascii is easy to help simplify to_digit some more.
It looks a bit cleaner and it looks like it's less jumps and there's less instructions in the generated assembly:
https://godbolt.org/z/84Erh5dhz
The benchmarks don't really tell me much. Maybe a slight improvement on the var radix.
Before:
```
test char::methods::bench_to_digit_radix_10 ... bench: 53,819 ns/iter (+/- 8,314)
test char::methods::bench_to_digit_radix_16 ... bench: 57,265 ns/iter (+/- 10,730)
test char::methods::bench_to_digit_radix_2 ... bench: 55,077 ns/iter (+/- 5,431)
test char::methods::bench_to_digit_radix_36 ... bench: 56,549 ns/iter (+/- 3,248)
test char::methods::bench_to_digit_radix_var ... bench: 43,848 ns/iter (+/- 3,189)
test char::methods::bench_to_digit_radix_10 ... bench: 51,707 ns/iter (+/- 10,946)
test char::methods::bench_to_digit_radix_16 ... bench: 52,835 ns/iter (+/- 2,689)
test char::methods::bench_to_digit_radix_2 ... bench: 51,012 ns/iter (+/- 2,746)
test char::methods::bench_to_digit_radix_36 ... bench: 53,210 ns/iter (+/- 8,645)
test char::methods::bench_to_digit_radix_var ... bench: 40,386 ns/iter (+/- 4,711)
test char::methods::bench_to_digit_radix_10 ... bench: 54,088 ns/iter (+/- 5,677)
test char::methods::bench_to_digit_radix_16 ... bench: 55,972 ns/iter (+/- 17,229)
test char::methods::bench_to_digit_radix_2 ... bench: 52,083 ns/iter (+/- 2,425)
test char::methods::bench_to_digit_radix_36 ... bench: 54,132 ns/iter (+/- 1,548)
test char::methods::bench_to_digit_radix_var ... bench: 41,250 ns/iter (+/- 5,299)
```
After:
```
test char::methods::bench_to_digit_radix_10 ... bench: 48,907 ns/iter (+/- 19,449)
test char::methods::bench_to_digit_radix_16 ... bench: 52,673 ns/iter (+/- 8,122)
test char::methods::bench_to_digit_radix_2 ... bench: 48,509 ns/iter (+/- 2,885)
test char::methods::bench_to_digit_radix_36 ... bench: 50,526 ns/iter (+/- 4,610)
test char::methods::bench_to_digit_radix_var ... bench: 38,618 ns/iter (+/- 3,180)
test char::methods::bench_to_digit_radix_10 ... bench: 54,202 ns/iter (+/- 6,994)
test char::methods::bench_to_digit_radix_16 ... bench: 56,585 ns/iter (+/- 8,448)
test char::methods::bench_to_digit_radix_2 ... bench: 50,548 ns/iter (+/- 1,674)
test char::methods::bench_to_digit_radix_36 ... bench: 52,749 ns/iter (+/- 2,576)
test char::methods::bench_to_digit_radix_var ... bench: 40,215 ns/iter (+/- 3,327)
test char::methods::bench_to_digit_radix_10 ... bench: 50,233 ns/iter (+/- 22,272)
test char::methods::bench_to_digit_radix_16 ... bench: 50,841 ns/iter (+/- 19,981)
test char::methods::bench_to_digit_radix_2 ... bench: 50,386 ns/iter (+/- 4,555)
test char::methods::bench_to_digit_radix_36 ... bench: 52,369 ns/iter (+/- 2,737)
test char::methods::bench_to_digit_radix_var ... bench: 40,417 ns/iter (+/- 2,766)
```
I removed the likely as it resulted in a few less instructions. (It's not been in there long - I added it in the last to_digit iteration).
Remove `doc(include)`
This nightly feature is redundant now that `extended_key_value_attributes` is stable (https://github.com/rust-lang/rust/pull/83366). `@rust-lang/rustdoc` not sure if you think this needs FCP; there was already an FCP in #82539, but technically it was for deprecating, not removing the feature altogether.
This should not be merged before #83366.
cc `@petrochenkov`
## User-facing changes
- Intra-doc links to primitives that currently go to rust-lang.org/nightly/std/primitive.x.html will start going to channel that rustdoc was built with. Nightly will continue going to /nightly; Beta will link to /beta; stable compilers will link to /1.52.1 (or whatever version they were built as).
- Cross-crate links from std to core currently go to /nightly unconditionally. They will start going to /1.52.0 on stable channels (but remain the same on nightly channels).
- Intra-crate links from std to std (or core to core) currently go to the same URL they are hosted at; they will continue to do so. Notably, this is different from everything else because it can preserve the distinction between /stable and /1.52.0 by using relative links.
Note that "links" includes both intra-doc links and rustdoc's own
automatically generated hyperlinks.
## Implementation changes
- Update the testsuite to allow linking to /beta and /1.52.1 in docs
- Use an html_root_url for the standard library that's dependent on the channel
This avoids linking to nightly docs on stable.
- Update rustdoc to use channel-dependent links for primitives from an
unknown crate
- Set DOC_RUST_LANG_ORG_CHANNEL from bootstrap to ensure it's in sync
- Include doc.rust-lang.org in the channel
# Stabilization report
## Summary
This stabilizes using macro expansion in key-value attributes, like so:
```rust
#[doc = include_str!("my_doc.md")]
struct S;
#[path = concat!(env!("OUT_DIR"), "/generated.rs")]
mod m;
```
See the changes to the reference for details on what macros are allowed;
see Petrochenkov's excellent blog post [on internals](https://internals.rust-lang.org/t/macro-expansion-points-in-attributes/11455)
for alternatives that were considered and rejected ("why accept no more
and no less?")
This has been available on nightly since 1.50 with no major issues.
## Notes
### Accepted syntax
The parser accepts arbitrary Rust expressions in this position, but any expression other than a macro invocation will ultimately lead to an error because it is not expected by the built-in expression forms (e.g., `#[doc]`). Note that decorators and the like may be able to observe other expression forms.
### Expansion ordering
Expansion of macro expressions in "inert" attributes occurs after decorators have executed, analogously to macro expressions appearing in the function body or other parts of decorator input.
There is currently no way for decorators to accept macros in key-value position if macro expansion must be performed before the decorator executes (if the macro can simply be copied into the output for later expansion, that can work).
## Test cases
- https://github.com/rust-lang/rust/blob/master/src/test/ui/attributes/key-value-expansion-on-mac.rs
- https://github.com/rust-lang/rust/blob/master/src/test/rustdoc/external-doc.rs
The feature has also been dogfooded extensively in the compiler and
standard library:
- https://github.com/rust-lang/rust/pull/83329
- https://github.com/rust-lang/rust/pull/83230
- https://github.com/rust-lang/rust/pull/82641
- https://github.com/rust-lang/rust/pull/80534
## Implementation history
- Initial proposal: https://github.com/rust-lang/rust/issues/55414#issuecomment-554005412
- Experiment to see how much code it would break: https://github.com/rust-lang/rust/pull/67121
- Preliminary work to restrict expansion that would conflict with this
feature: https://github.com/rust-lang/rust/pull/77271
- Initial implementation: https://github.com/rust-lang/rust/pull/78837
- Fix for an ICE: https://github.com/rust-lang/rust/pull/80563
## Unresolved Questions
~~https://github.com/rust-lang/rust/pull/83366#issuecomment-805180738 listed some concerns, but they have been resolved as of this final report.~~
## Additional Information
There are two workarounds that have a similar effect for `#[doc]`
attributes on nightly. One is to emulate this behavior by using a limited version of this feature that was stabilized for historical reasons:
```rust
macro_rules! forward_inner_docs {
($e:expr => $i:item) => {
#[doc = $e]
$i
};
}
forward_inner_docs!(include_str!("lib.rs") => struct S {});
```
This also works for other attributes (like `#[path = concat!(...)]`).
The other is to use `doc(include)`:
```rust
#![feature(external_doc)]
#[doc(include = "lib.rs")]
struct S {}
```
The first works, but is non-trivial for people to discover, and
difficult to read and maintain. The second is a strange special-case for
a particular use of the macro. This generalizes it to work for any use
case, not just including files.
I plan to remove `doc(include)` when this is stabilized. The
`forward_inner_docs` workaround will still compile without warnings, but
I expect it to be used less once it's no longer necessary.
Make unchecked_{add,sub,mul} inherent methods unstably const
The intrinsics are marked as being stably const (even though they're not stable by nature of being intrinsics), but the currently-unstable inherent versions are not marked as const. This fixes this inconsistency. Split out of #85017,
r? `@oli-obk`
Disallows `#![feature(no_coverage)]` on stable and beta (using standard crate-level gating)
Fixes: #84836
Removes the function-level feature gating solution originally implemented, and solves the same problem using `allow_internal_unstable`, so normal crate-level feature gating mechanism can still be used (which disallows the feature on stable and beta).
I tested this, building the compiler with and without `CFG_DISABLE_UNSTABLE_FEATURES=1`
With unstable features disabled, I get the expected result as shown here:
```shell
$ ./build/x86_64-unknown-linux-gnu/stage1/bin/rustc src/test/run-make-fulldeps/coverage/no_cov_crate.rs
error[E0554]: `#![feature]` may not be used on the dev release channel
--> src/test/run-make-fulldeps/coverage/no_cov_crate.rs:2:1
|
2 | #![feature(no_coverage)]
| ^^^^^^^^^^^^^^^^^^^^^^^^
error: aborting due to previous error
For more information about this error, try `rustc --explain E0554`.
```
r? ````@Mark-Simulacrum````
cc: ````@tmandry```` ````@wesleywiser````
using allow_internal_unstable (as recommended)
Fixes: #84836
```shell
$ ./build/x86_64-unknown-linux-gnu/stage1/bin/rustc src/test/run-make-fulldeps/coverage/no_cov_crate.rs
error[E0554]: `#![feature]` may not be used on the dev release channel
--> src/test/run-make-fulldeps/coverage/no_cov_crate.rs:2:1
|
2 | #![feature(no_coverage)]
| ^^^^^^^^^^^^^^^^^^^^^^^^
error: aborting due to previous error
For more information about this error, try `rustc --explain E0554`.
```
further split up const_fn feature flag
This continues the work on splitting up `const_fn` into separate feature flags:
* `const_fn_trait_bound` for `const fn` with trait bounds
* `const_fn_unsize` for unsizing coercions in `const fn` (looks like only `dyn` unsizing is still guarded here)
I don't know if there are even any things left that `const_fn` guards... at least libcore and liballoc do not need it any more.
`@oli-obk` are you currently able to do reviews?
Added CharIndices::offset function
The CharIndices iterator has a field internally called front_offset, that I think would be very useful to have access to.
You can already do something like ``char_indices.next().map(|(offset, _)| offset)``, but that is wordy, in addition to not handling the case where the iterator has ended, where you'd want the offset to be equal to the length.
I'm very new to the open source world and the rust repository, so I'm sorry if I missed a step or did something weird.
Rename `#[doc(spotlight)]` to `#[doc(notable_trait)]`
Fixes#80936.
"spotlight" is not a very specific or self-explaining name.
Additionally, the dialog that it triggers is called "Notable traits".
So, "notable trait" is a better name.
* Rename `#[doc(spotlight)]` to `#[doc(notable_trait)]`
* Rename `#![feature(doc_spotlight)]` to `#![feature(doc_notable_trait)]`
* Update documentation
* Improve documentation
r? `@Manishearth`
The `Unpin` bound was originally added in #56939 following the
recommendation of @withoutboats in
https://github.com/rust-lang/rust/issues/55766#issue-378417538
That comment does not give explicit justification for why the bound
should be added. The relevant context was:
> [ ] Remove `impl<P> Unpin for Pin<P>`
>
> This impl is not justified by our standard justification for unpin
> impls: there is no pointer direction between `Pin<P>` and `P`. Its
> usefulness is covered by the impls for pointers themselves.
>
> This futures impl (link to the impl changed in this PR) will need to
> change to add a `P: Unpin` bound.
The decision to remove the unconditional impl of `Unpin for Pin` is
sound (these days there is just an auto-impl for when `P: Unpin`). But,
I think the decision to also add the `Unpin` bound for `impl Future` may
have been unnecessary. Or if that's not the case, I'd be very interested
to have the argument for why written down somewhere. The bound _appears_
to not be needed, since the presence of a `Pin<P>` should indicate that
it's safe to project to `Pin<&mut P::Target>` just like for
`Pin::as_mut`.
"spotlight" is not a very specific or self-explaining name.
Additionally, the dialog that it triggers is called "Notable traits".
So, "notable trait" is a better name.
* Rename `#[doc(spotlight)]` to `#[doc(notable_trait)]`
* Rename `#![feature(doc_spotlight)]` to `#![feature(doc_notable_trait)]`
* Update documentation
* Improve documentation
