do not allow ABI mismatches inside repr(C) types
In https://github.com/rust-lang/rust/pull/115476 we allowed ABI mismatches inside `repr(C)` types. This wasn't really discussed much; I added it because from how I understand calling conventions, this should actually be safe in practice. However I entirely forgot to actually allow this in Miri, and in the mean time I have learned that too much ABI compatibility can be a problem for CFI (it can reject fewer calls so that gives an attacker more room to play with).
So I propose we take back that part about ABI compatibility in `repr(C)`. It is anyway something that C and C++ do not allow, as far as I understand.
In the future we might want to introduce a class of ABI compatibilities where we say "this is a bug and it may lead to aborting the process, but it won't lead to arbitrary misbehavior -- worst case it'll just transmute the arguments from the caller type to the callee type". That would give CFI leeway to reject such calls without introducing the risk of arbitrary UB. (The UB can still happen if the transmute leads to bad results, of course, but it wouldn't be due to ABI weirdness.)
#115476 hasn't reached beta yet so if we land this before Dec 22nd we can just pretend this all never happened. ;) Otherwise we should do a beta backport (of the docs change at least).
Cc `@rust-lang/opsem` `@rust-lang/types`
coverage: Check for `async fn` explicitly, without needing a heuristic
The old code used a heuristic to detect async functions and adjust their coverage spans to produce better output. But there's no need to resort to a heuristic when we can just look back at the original definition and check whether the current function is actually an `async fn`.
In addition to being generally nicer, this also gets rid of the one piece of code that specifically cares about `CoverageSpan::is_closure` representing an actual closure. All remaining code that inspects that field just uses it as an indication that the span is a hole that should be carved out of other spans, and then discarded.
That opens up the possibility of introducing other kinds of “hole” spans, e.g. for nested functions/types/macros, and having them all behave uniformly.
---
`@rustbot` label +A-code-coverage
Rollup of 7 pull requests
Successful merges:
- #118691 (Add check for possible CStr literals in pre-2021)
- #118973 (rustc_codegen_ssa: Don't drop `IncorrectCguReuseType` , make `rustc_expected_cgu_reuse` attr work)
- #119071 (-Znext-solver: adapt overflow rules to avoid breakage)
- #119089 (effects: fix a comment)
- #119094 (Add function ABI and type layout to StableMIR)
- #119102 (Add arm-none-eabi and armv7r-none-eabi platform-support documentation.)
- #119107 (subtype_predicate: remove unnecessary probe)
Failed merges:
- #119135 (Fix crash due to `CrateItem::kind()` not handling constructors)
- #119141 (Add method to get instance instantiation arguments)
r? `@ghost`
`@rustbot` modify labels: rollup
subtype_predicate: remove unnecessary probe
There is no reason to probe here. The failure either results in an actual type error, in which cases the probe is useless, or it is used inside of evaluate, in which case we're already inside of the `fn evaluation_probe`, so it is also not necessary.
Add arm-none-eabi and armv7r-none-eabi platform-support documentation.
Mostly collecting existing information that's common to all arm-none-eabi targets and putting it in one file and adding a new file with specific details about armv7r.
Add function ABI and type layout to StableMIR
This change introduces a new module to StableMIR named `abi` with information from `rustc_target::abi` and `rustc_abi`, that allow users to retrieve more low level information required to perform bit-precise analysis.
The layout of a type can be retrieved via `Ty::layout`, and the instance ABI can be retrieved via `Instance::fn_abi()`.
To properly handle errors while retrieve layout information, we had to implement a few layout related traits.
r? ```@compiler-errors```
-Znext-solver: adapt overflow rules to avoid breakage
Do not erase overflow constraints if they are from equating the impl header when normalizing[^1].
This should be the minimal change to not break crates depending on the old project behavior of "apply impl constraints while only lazily evaluating any nested goals".
Fixes https://github.com/rust-lang/trait-system-refactor-initiative/issues/70, see https://hackmd.io/ATf4hN0NRY-w2LIVgeFsVg for the reasoning behind this.
Only keeping constraints on overflow for `normalize-to` goals as that's the only thing needed for backcompat. It also allows us to not track the origin of root obligations. The issue with root goals would be something like the following:
```rust
trait Foo {}
trait Bar {}
trait FooBar {}
impl<T: Foo + Bar> FooBar for T {}
// These two should behave the same, rn we can drop constraints for both,
// but if we don't drop `Misc` goals we would only drop the constraints for
// `FooBar` unless we track origins of root obligations.
fn func1<T: Foo + Bar>() {}
fn func2<T: FooBaz>() {}
```
[^1]: mostly, the actual rules are slightly different
r? ``@compiler-errors``
rustc_codegen_ssa: Don't drop `IncorrectCguReuseType` , make `rustc_expected_cgu_reuse` attr work
In [100753], `IncorrectCguReuseType` accidentally stopped being emitted by removing `diag.span_err(...)`. Begin emitting it again rather than just blindly dropping it, and adjust tests accordingly.
We assume that there are no bugs and that the currently actual CGU reuse is correct. If there are bugs, they will be discovered and fixed eventually, and the tests will then be updated.
[100753]: 706452eba7 (diff-048389738ddcbe0f9765291a29db1fed9a5f03693d4781cfb5aaa97ffb3c7f84)Closes#118972
Add check for possible CStr literals in pre-2021
Fixes [#118654](https://github.com/rust-lang/rust/issues/118654)
Adds information to errors caused by possible CStr literals in pre-2021.
The lexer separates `c"str"` into two tokens if the edition is less than 2021, which later causes an error when parsing. This error now has a more helpful message that directs them to information about editions. However, the user might also have written `c "str"` in a later edition, so to not confuse people who _are_ using a recent edition, I also added a note about whitespace.
We could probably figure out exactly which scenario has been encountered by examining spans and editions, but I figured it would be better not to overcomplicate the creation of the error too much.
This is my first code PR and I tried to follow existing conventions as much as possible, but I probably missed something, so let me know!
The old code used a heuristic to detect async functions and adjust their
coverage spans to produce better output. But there's no need to resort to a
heuristic when we can just check whether the current function is actually an
`async fn`.
Fix arm64e-apple-ios target
- [x] [Remove legacy `bitcode` defaults](https://github.com/rust-lang/rust/pull/117364)
- [x] Use LLVM features
Now we have warnings such as
```
'+paca' is not a recognized feature for this target (ignoring feature)
'+pacg' is not a recognized feature for this target (ignoring feature)
```
Because we should use LLVM features.
Yeet unnecessary param envs
We don't need to pass in param-envs around in the lexical region resolution code (or in `MatchAgainstFreshVars` in the solver), since it is only used to eval some consts in `structurally_relate_tys` which I removed.
This is in preparation for normalizing the outlives clauses in `ParamEnv` for the new trait solver.
r? lcnr
add more niches to rawvec
Previously RawVec only had a single niche in its `NonNull` pointer. With this change it now has `isize::MAX` niches since half the value-space of the capacity field is never needed, we can't have a capacity larger than isize::MAX.
match lowering: Remove the `make_target_blocks` hack
This hack was introduced 4 years ago in [`a1d0266` (#60730)](a1d0266878) to improve LLVM optimization time, specifically noticed in the `encoding` benchmark. Measurements today indicate it is no longer needed.
r? `@matthewjasper`
Make exhaustiveness usable outside of rustc
With this PR, `rustc_pattern_analysis` compiles on stable (with the `stable` feature)! `rust-analyzer` will be able to use it to provide match-related diagnostics and refactors.
Two questions:
- Should I name the feature `nightly` instead of `rustc` for consistency with other crates? `rustc` makes more sense imo.
- `typed-arena` is an optional dependency but tidy made me add it to the allow-list anyway. Can I avoid that somehow?
r? `@compiler-errors`
Subtree sync for rustc_codegen_cranelift
The main highlight is a couple of fixes around size, alignment and field offset computations for foreign and packed unsized types. As well as a fix for the signature of simd_scatter which a recent PR accidentally messed up.
r? `@ghost`
`@rustbot` label +A-codegen +A-cranelift +T-compiler
Rollup of 4 pull requests
Successful merges:
- #119087 (Update books)
- #119091 (Use alias-eq in structural normalization)
- #119098 (Adjust the ignore-compare-mode-next-solver for hangs)
- #119100 (Add the function body span to StableMIR)
r? `@ghost`
`@rustbot` modify labels: rollup
Add the function body span to StableMIR
We were missing the body span, which differs from the function definition span, since it covers the entire function body.
r? `@ouz-a`
Adjust the ignore-compare-mode-next-solver for hangs
Some new tests hang, some old tests don't hang.
r? lcnr or anyone in `@rust-lang/initiative-trait-system-refactor`
