linker flavors
- only the stable values for `-Clink-self-contained` can be used on stable until we
have more feedback on the interface
- `-Zunstable-options` is required to use unstable linker flavors
Fix loading target specs in compiletest not working with custom targets
In https://github.com/rust-lang/rust/pull/112454#issuecomment-1611351168 it was pointed out that the PR broke blessing mir-opt tests. Since #112418, blessing mir-opt tests generates "synthetic targets", which are custom target specs. Those specs are not included in `--print=all-target-specs-json`, and #112454 required that the current target was returned by that flag.
This PR fixes the breakage by loading the target spec for the current target explicitly, if a custom target is detected.
r? `@oli-obk`
Fix unset e_flags in ELF files generated for AVR targets
Closes#106576
~~Sort-of blocked by gimli-rs/object#500~~ (merged)
I'm not sure whether the list of AVR CPU names is okay here. Maybe it could be moved out-of-line to improve the readability of the function.
Use structured suggestion when telling user about `for<'a>`
```
error[E0637]: `&` without an explicit lifetime name cannot be used here
--> $DIR/E0637.rs:13:13
|
LL | T: Into<&u32>,
| ^ explicit lifetime name needed here
|
help: consider introducing a higher-ranked lifetime here
|
LL | T: for<'a> Into<&'a u32>,
| +++++++ ++
```
Encode item bounds for `DefKind::ImplTraitPlaceholder`
This was lost in a refactoring -- `hir::ItemKind::OpaqueTy` doesn't always map to `DefKind::Opaque`, specifically for RPITITs, so the check was migrated subtly wrong, and unfortunately I never had a test for this 🙃Fixes#113155
r? ``@cjgillot``
Account for late-bound vars from parent arg-position impl trait
We should be reporting an error like we do for late-bound args coming from a parent APIT.
Fixes#113016
suggest `slice::swap` for `mem::swap(&mut x[0], &mut x[1])` borrowck error
Recently saw someone ask why this code (example slightly modified):
```rs
fn main() {
let mut foo = [1, 2];
std::mem::swap(&mut foo[0], &mut foo[1]);
}
```
triggers this error and how to fix it:
```
error[E0499]: cannot borrow `foo[_]` as mutable more than once at a time
--> src/main.rs:4:33
|
4 | std::mem::swap(&mut foo[0], &mut foo[1]);
| -------------- ----------- ^^^^^^^^^^^ second mutable borrow occurs here
| | |
| | first mutable borrow occurs here
| first borrow later used by call
|
= help: consider using `.split_at_mut(position)` or similar method to obtain two mutable non-overlapping sub-slices
```
The current help message is nice and goes in the right direction, but I think we can do better for this specific instance and suggest `slice::swap`, which makes this compile
Stabilize `const_cstr_methods`
This PR seeks to stabilize `const_cstr_methods`. Fixes most of #101719
## New const stable API
```rust
impl CStr {
// depends: memchr
pub const fn from_bytes_with_nul(bytes: &[u8]) -> Result<&Self, FromBytesWithNulError> {...}
// depends: const_slice_index
pub const fn to_bytes(&self) -> &[u8] {}
// depends: pointer casts
pub const fn to_bytes_with_nul(&self) -> &[u8] {}
// depends: str::from_utf8
pub const fn to_str(&self) -> Result<&str, str::Utf8Error> {}
}
```
I don't think any of these methods will have any issue when `CStr` becomes a thin pointer as long as `memchr` is const (which also allows for const `strlen`) .
## Notes
- `from_bytes_until_nul` relies on `const_slice_index`, which relies on `const_trait_impls`, and generally this should be avoided. After talking with Oli, it should be OK in this case because we could replace the ranges with pointer tricks if needed (worst case being those feature gates disappear). https://github.com/rust-lang/rust/pull/107624#discussion_r1101468480
- Making `from_ptr` const is deferred because it depends on `const_eval_select`. I have moved this under the new flag `const_cstr_from_ptr` https://github.com/rust-lang/rust/pull/107624#discussion_r1101555239
cc ``@oli-obk`` I think you're the const expert
``@rustbot`` modify labels: +T-libs-api +needs-fcp
```
error[E0637]: `&` without an explicit lifetime name cannot be used here
--> $DIR/E0637.rs:13:13
|
LL | T: Into<&u32>,
| ^ explicit lifetime name needed here
|
help: consider introducing a higher-ranked lifetime here
|
LL | T: for<'a> Into<&'a u32>,
| +++++++ ++
```
Normalize opaques with late-bound vars again
We have a hack in the compiler where if an opaque has escaping late-bound vars, we skip revealing it even though we *could* reveal it from a technical perspective. First of all, this is weird, since we really should be revealing all opaques in `Reveal::All` mode. Second of all, it causes subtle bugs (linked below).
I attempted to fix this in #100980, which was unfortunately reverted due to perf regressions on codebases that used really deeply nested futures in some interesting ways. The worst of which was #103423, which caused the project to hang on build. Another one was #104842, which was just a slow-down, but not a hang. I took some time afterwards to investigate how to rework `normalize_erasing_regions` to take advantage of better caching, but that effort kinda fizzled out (#104133).
However, recently, I was made aware of more bugs whose root cause is not revealing opaques during codegen. That made me want to fix this again -- in the process, interestingly, I took the the minimized example from https://github.com/rust-lang/rust/issues/103423#issuecomment-1292947043, and it doesn't seem to hang any more...
Thinking about this harder, there have been some changes to the way we lower and typecheck async futures that may have reduced the pathologically large number of outlives obligations (see description of #103423) that we were encountering when normalizing opaques with bound vars the last time around:
* #104321 (lower `async { .. }` directly as a generator that implements `Future`, removing the `from_generator` shim)
* #104833 (removing an `identity_future` fn that was wrapping desugared future generators)
... so given that I can see:
* No significant regression on rust perf bot (https://github.com/rust-lang/rust/pull/107620#issuecomment-1600070317)
* No timeouts in crater run I did (https://github.com/rust-lang/rust/pull/107620#issuecomment-1605428952, rechecked failing crates in https://github.com/rust-lang/rust/pull/107620#issuecomment-1605973434)
... and given that this PR:
* Fixes#104601
* Fixes#107557
* Fixes#109464
* Allows us to remove a `DefiningAnchor::Bubble` from codegen (75a8f68183)
I'm inclined to give this another shot at landing this. Best case, it just works -- worst case, we get more examples to study how we need to improve the compiler to make this work.
r? types
Make the `Elaboratable` trait take clauses
We only ever elaborate clauses, so make this explicit in the trait's definition rather than having a bunch of `.expect_clause()` calls everywhere.
Convert `run-make/coverage-reports` tests to use a custom compiletest mode
I was frustrated by the fact that most of the coverage tests are glued together with makefiles and shell scripts, so I tried my hand at converting most of them over to a newly-implemented `run-coverage` mode/suite in compiletest.
This ~~*mostly*~~ resolves#85009, ~~though I've left a small number of the existing tests as-is because they would require more work to fix/support~~.
---
I had time to go back and add support for the more troublesome tests that I had initially skipped over, so this PR now manages to completely get rid of `run-make/coverage-reports`.
---
The patches are arranged as follows:
- Declare the new mode/suite in bootstrap
- Small changes to compiletest that will be used by the new mode
- Implement the new mode in compiletest
- Migrate most of the tests over
- Add more code to bootstrap and compiletest to support the remaining tests
- Migrate the remaining tests (with some temporary hacks to avoid re-blessing them)
- Remove the temporary hacks and re-bless the migrated tests
- Remove the unused remnants of `run-make/coverage-reports`
Support for native WASM exceptions
### Motivation
Currently, rustc does not support native WASM exceptions. It does support JavaScript based exceptions for the wasm32-emscripten-target, but this requires back&forth with javascript for many calls, which is very slow.
Native wasm support for exceptions is quite common: Clang+LLVM implemented them years ago, and all major browsers support them by now. They enable zero-cost exceptions, at least with regard to runtime-performance-cost. They may increase startup-time and code size, though.
### Important: This PR does not change default behaviour
Exceptions usually add a lot of code in form of unwinding blocks, increasing the binary size. Most users probably do not want that, especially which regard to web development.
Therefore, wasm exceptions play a similar role as WASM-threads: rustc should support them, like clang does, but users who want to use it have to use some command-line magic like rustflags to opt in.
### What does this PR do?
As stated above, the default behaviour is not changed. It is already possible to opt-in into wasm exceptions using the command line. Unfortunately, the LLVM IR is invalid and the LLVM backend crashes.
```
rustc <sourcefile>
--target wasm32-unknown-unknown
-C panic=unwind
-C llvm-args=-wasm-enable-eh
-C target-feature=+exception-handling
```
As it turns out, LLVM is quite picky when it comes to IR for exception handling. If the IR does not look exactly like it should, some LLVM-assertions fail and the code generation crashes.
This PR adds the necessary modifications to the code generator to make it work. It also adds `exception-handling` as a wasm target feature.
### What this PR does not / what is missing
This PR is not a full fledges solution. It is the first step. A few parts are still missing; however, it is already useable (see next section).
Currently missing:
* The std library has to be adapted. Currently, only [no_std] crates work
* Usually, nested exceptions abort the program (i.e. a panic during the cleanup of another panic). This is currently not done yet.
- Currently, code inside cleanup handlers does not unwind
- To fix this requires a little more work: The code generator currently maintains a single terminate block per function for this. Unfortunately, WASM requires funclet based exception handling. Therefore, we need to create a terminate block per funclet. This is probably not a big problem, but I want to keep this PR simple.
### How to use the compiler given this PR?
This PR does not add any command line flags or features. It uses those which are already there. To compile with exceptions enabled, you need
* to set the panic strategy to unwind, i.e. `-C panic=unwind`
* to enable the exception-handling target feature, i.e. `-C target-feature=+exception-handling`
* to tell LLVM about the exception handling, i.e. `-C llvm-args=-wasm-enable-eh`
Since the standard library has not been adapted, you can only use it in [no_std] crates as of now. The intrinsic `core::intrinsics::r#try` works. To throw exceptions, you need the ```@llvm.wasm.throw``` intrinsic.
I created a sample application which works for me: https://github.com/mirkootter/rust-wasm-demos
This example can be run at https://webassembly.sh
