In the stabilization attempt of `#[unix_sigpipe = "sig_dfl"]`, a concern
was raised related to using a language attribute for the feature: Long
term, we want `fn lang_start()` to be definable by any crate, not just
libstd. Having a special language attribute in that case becomes
awkward.
So as a first step towards towards the next stabilization attempt, this
PR changes the `#[unix_sigpipe = "..."]` attribute to a compiler flag
`-Zon-broken-pipe=...` to remove that concern, since now the language
is not "contaminated" by this feature.
Another point was also raised, namely that the ui should not leak
**how** it does things, but rather what the **end effect** is. The new
flag uses the proposed naming. This is of course something that can be
iterated on further before stabilization.
`-Z debug-macros` is "stabilized" by enabling it by default and removing.
`-Z collapse-macro-debuginfo` is stabilized as `-C collapse-macro-debuginfo`.
It now supports all typical boolean values (`parse_opt_bool`) in addition to just yes/no.
Default value of `collapse_debuginfo` was changed from `false` to `external` (i.e. collapsed if external, not collapsed if local).
`#[collapse_debuginfo]` attribute without a value is no longer supported to avoid guessing the default.
Implement Modified Condition/Decision Coverage
This is an implementation based on llvm backend support (>= 18) by `@evodius96` and branch coverage support by `@Zalathar.`
### Major changes:
* Add -Zcoverage-options=mcdc as switch. Now coverage options accept either `no-branch`, `branch`, or `mcdc`. `mcdc` also enables `branch` because it is essential to work.
* Add coverage mapping for MCDCBranch and MCDCDecision. Note that MCDCParameter evolves from llvm 18 to llvm 19. The mapping in rust side mainly references to 19 and is casted to 18 types in llvm wrapper.
* Add wrapper for mcdc instrinc functions from llvm. And inject associated statements to mir.
* Add BcbMappingKind::Decision, I'm not sure is it proper but can't find a better way temporarily.
* Let coverage-dump support parsing MCDCBranch and MCDCDecision from llvm ir.
* Add simple tests to check whether mcdc works.
* Same as clang, currently rustc does not generate instrument for decision with more than 6 condtions or only 1 condition due to considerations of resource.
### Implementation Details
1. To get information about conditions and decisions, `MCDCState` in `BranchInfoBuilder` is used during hir lowering to mir. For expressions with logical op we call `Builder::visit_coverage_branch_operation` to record its sub conditions, generate condition ids for them and save their spans (to construct the span of whole decision). This process mainly references to the implementation in clang and is described in comments over `MCDCState::record_conditions`. Also true marks and false marks introduced by branch coverage are used to detect where the decision evaluation ends: the next id of the condition == 0.
2. Once the `MCDCState::decision_stack` popped all recorded conditions, we can ensure that the decision is checked over and push it into `decision_spans`. We do not manually insert decision span to avoid complexity from then_else_break in nested if scopes.
3. When constructing CoverageSpans, add condition info to BcbMappingKind::Branch and decision info to BcbMappingKind::Decision. If the branch mapping has non-zero condition id it will be transformed to MCDCBranch mapping and insert `CondBitmapUpdate` statements to its evaluated blocks. While decision bcb mapping will insert `TestVectorBitmapUpdate` in all its end blocks.
### Usage
```bash
echo "[build]\nprofiler=true" >> config.toml
./x build --stage 1
./x test tests/coverage/mcdc_if.rs
```
to build the compiler and run tests.
```shell
export PATH=path/to/llvm-build:$PATH
rustup toolchain link mcdc build/host/stage1
cargo +mcdc rustc --bin foo -- -Cinstrument-coverage -Zcoverage-options=mcdc
cd target/debug
LLVM_PROFILE_FILE="foo.profraw" ./foo
llvm-profdata merge -sparse foo.profraw -o foo.profdata
llvm-cov show ./foo -instr-profile=foo.profdata --show-mcdc
```
to check "foo" code.
### Problems to solve
For now decision mapping will insert statements to its all end blocks, which may be optimized by inserting a final block of the decision. To do this we must also trace the evaluated value at each end of the decision and join them separately.
This implementation is not heavily tested so there should be some unrevealed issues. We are going to check our rust products in the next. Please let me know if you had any suggestions or comments.
Introduce perma-unstable `wasm-c-abi` flag
Now that `wasm-bindgen` v0.2.88 supports the spec-compliant C ABI, the idea is to switch to that in a future version of Rust. In the meantime it would be good to let people test and play around with it.
This PR introduces a new perma-unstable `-Zwasm-c-abi` compiler flag, which switches to the new spec-compliant C ABI when targeting `wasm32-unknown-unknown`.
Alternatively, we could also stabilize this and then deprecate it when we switch. I will leave this to the Rust maintainers to decide.
This is a companion PR to #117918, but they could be merged independently.
MCP: https://github.com/rust-lang/compiler-team/issues/703
Tracking issue: https://github.com/rust-lang/rust/issues/122532
Add `-Z external-clangrt`
This adds the unstable `-Z external-clangrt` flag that will prevent rustc from emitting linker paths for the in-tree LLVM sanitizer runtime library.
This adds the unstable `-Z external-sanitizer-runtime` flag that will
prevent rustc from emitting linker paths for the in-tree LLVM sanitizer
runtime library.
coverage: Remove or migrate all unstable values of `-Cinstrument-coverage`
(This PR was substantially overhauled from its original version, which migrated all of the existing unstable values intact.)
This PR takes the three nightly-only values that are currently accepted by `-Cinstrument-coverage`, completely removes two of them (`except-unused-functions` and `except-unused-generics`), and migrates the third (`branch`) over to a newly-introduced unstable flag `-Zcoverage-options`.
I have a few motivations for wanting to do this:
- It's unclear whether anyone actually uses the `except-unused-*` values, so this serves as an opportunity to either remove them, or prompt existing users to object to their removal.
- After #117199, the stable values of `-Cinstrument-coverage` treat it as a boolean-valued flag, so having nightly-only extra values feels out-of-place.
- Nightly-only values also require extra ad-hoc code to make sure they aren't accidentally exposed to stable users.
- The new system allows multiple different settings to be toggled independently, which isn't possible in the current single-value system.
- The new system makes it easier to introduce new behaviour behind an unstable toggle, and then gather nightly-user feedback before possibly making it the default behaviour for all users.
- The new system also gives us a convenient place to put relatively-narrow options that won't ever be the default, but that nightly users might still want access to.
- It's likely that we will eventually want to give stable users more fine-grained control over coverage instrumentation. The new flag serves as a prototype of what that stable UI might eventually look like.
The `branch` option is a placeholder that currently does nothing. It will be used by #122322 to opt into branch coverage instrumentation.
---
I see `-Zcoverage-options` as something that will exist more-or-less indefinitely, though individual sub-options might come and go as appropriate. I think there will always be some demand for nightly-only toggles, so I don't see `-Zcoverage-options` itself ever being stable, though we might eventually stabilize something similar to it.
Verify that query keys result in unique dep nodes
This implements checking that query keys result into unique dep nodes as mentioned in https://github.com/rust-lang/rust/pull/112469.
We could do a perf check to see how expensive this is.
r? `@michaelwoerister`
This new nightly-only flag can be used to toggle fine-grained flags that
control the details of coverage instrumentation.
Currently the only supported flag value is `branch` (or `no-branch`), which is
a placeholder for upcoming support for branch coverage. Other flag values can
be added in the future, to prototype proposed new behaviour, or to enable
special non-default behaviour.
Rework `untranslatable_diagnostic` lint
Currently it only checks calls to functions marked with `#[rustc_lint_diagnostics]`. This PR changes it to check calls to any function with an `impl Into<{D,Subd}iagnosticMessage>` parameter. This greatly improves its coverage and doesn't rely on people remembering to add `#[rustc_lint_diagnostics]`. It also lets us add `#[rustc_lint_diagnostics]` to a number of functions that don't have an `impl Into<{D,Subd}iagnosticMessage>`, such as `Diag::span`.
r? ``@davidtwco``
Currently it only checks calls to functions marked with
`#[rustc_lint_diagnostics]`. This commit changes it to check calls to
any function with an `impl Into<{D,Subd}iagMessage>` parameter. This
greatly improves its coverage and doesn't rely on people remembering to
add `#[rustc_lint_diagnostics]`.
The commit also adds `#[allow(rustc::untranslatable_diagnostic)`]
attributes to places that need it that are caught by the improved lint.
These places that might be easy to convert to translatable diagnostics.
Finally, it also:
- Expands and corrects some comments.
- Does some minor formatting improvements.
- Adds missing `DecorateLint` cases to
`tests/ui-fulldeps/internal-lints/diagnostics.rs`.
Adds initial support for DataFlowSanitizer to the Rust compiler. It
currently supports `-Zsanitizer-dataflow-abilist`. Additional options
for it can be passed to LLVM command line argument processor via LLVM
arguments using `llvm-args` codegen option (e.g.,
`-Cllvm-args=-dfsan-combine-pointer-labels-on-load=false`).
bjorn3 says:
> On errors we don't finalize the incr comp cache, but non-fatal diagnostics are cached afaik.
Otherwise we would have to replay the query in question, which we may not be able to do if the query
key is not reconstructible from the dep node fingerprint.
So we must track these flags to avoid replaying incorrect diagnostics.
Improved collapse_debuginfo attribute, added command-line flag
Improved attribute collapse_debuginfo with variants: `#[collapse_debuginfo=(no|external|yes)]`.
Added command-line flag for default behaviour.
Work-in-progress: will add more tests.
cc https://github.com/rust-lang/rust/issues/100758
Remove `-Zdont-buffer-diagnostics`.
It was added in #54232. It seems like it was aimed at NLL development, which is well in the past. Also, it looks like `-Ztreat-err-as-bug` can be used to achieve the same effect. So it doesn't seem necessary.
r? ``@pnkfelix``
Add -Zuse-sync-unwind
Currently Rust uses async unwind by default, but async unwind will bring non-negligible size overhead. it would be nice to allow users to choose this.
In addition, async unwind currently prevents LLVM from generate compact unwind for MachO, if one wishes to generate compact unwind for MachO, then also needs this flag.
It was added in #54232. It seems like it was aimed at NLL development,
which is well in the past. Also, it looks like `-Ztreat-err-as-bug` can
be used to achieve the same effect. So it doesn't seem necessary.
Remove `-Zreport-delayed-bugs`.
It's not used within the repository in any way (e.g. in tests), and doesn't seem useful.
It was added in #52568.
r? ````@oli-obk````
Remove `-Zdump-mir-spanview`
The `-Zdump-mir-spanview` flag was added back in #76074, as a development/debugging aid for the initial work on what would eventually become `-Cinstrument-coverage`. It causes the compiler to emit an HTML file containing a function's source code, with various spans highlighted based on the contents of MIR.
When the suggestion was made to [triage and remove unnecessary `-Z` flags (Zulip)](https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/.60-Z.60.20option.20triage), I noted that this flag could potentially be worth removing, but I wanted to keep it around to see whether I found it useful for my own coverage work.
But when I actually tried to use it, I ran into various issues (e.g. it crashes on `tests/coverage/closure.rs`). If I can't trust it to work properly without a full overhaul, then instead of diving down a rabbit hole of trying to fix arcane span-handling bugs, it seems better to just remove this obscure old code entirely.
---
````@rustbot```` label +A-code-coverage
