A bit more polish on const eval errors
This PR adds a bit more polish to the const eval errors:
- a slight improvement to the PME messages from #85633: I mentioned there that the erroneous item's paths were dependent on the environment, and could be displayed fully qualified or not. This can obscure the items when they come from a dependency. This PR uses the pretty-printing code ensuring the items' paths are not trimmed.
- whenever there are generics involved in an item where const evaluation errors out, the error message now displays the instance and its const arguments, so that we can see which instantiated item and compile-time values lead to the error.
So we get this slight improvement for our beloved `stdarch` example, on nightly:
```
error[E0080]: evaluation of constant value failed
--> ./stdarch/crates/core_arch/src/macros.rs:8:9
|
8 | assert!(IMM >= MIN && IMM <= MAX, "IMM value not in expected range");
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'IMM value not in expected range', /rustc/9111b8ae9793f18179a1336417618fc07a9cac85/library/core/src/../../stdarch/crates/core_arch/src/macros.rs:8:9
|
```
to this PR's:
```
error[E0080]: evaluation of `core::core_arch::macros::ValidateConstImm::<51_i32, 0_i32, 15_i32>::VALID` failed
--> ./stdarch/crates/core_arch/src/macros.rs:8:9
|
8 | assert!(IMM >= MIN && IMM <= MAX, "IMM value not in expected range");
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'IMM value not in expected range', ./stdarch/crates/core_arch/src/macros.rs:8:9
|
```
with this PR.
Of course this is an idea from Oli, so maybe r? `@oli-obk` if they have the time.
This commit updates the compiler's handling of the `#[target_feature]`
attribute when applied to functions on WebAssembly-based targets. The
compiler in general requires that any functions with `#[target_feature]`
are marked as `unsafe` as well, but this commit relaxes the restriction
for WebAssembly targets where the attribute can be applied to safe
functions as well.
The reason this is done is that the motivation for this feature of the
compiler is not applicable for WebAssembly targets. In general the
`#[target_feature]` attribute is used to enhance target CPU features
enabled beyond the basic level for the rest of the compilation. If done
improperly this means that your program could execute an instruction
that the CPU you happen to be running on does not understand. This is
considered undefined behavior where it is unknown what will happen (e.g.
it's not a deterministic `SIGILL`).
For WebAssembly, however, the target is different. It is not possible
for a running WebAssembly program to execute an instruction that the
engine does not understand. If this were the case then the program would
not have validated in the first place and would not run at all. Even if
this were allowed in some hypothetical future where engines have some
form of runtime feature detection (which they do not right now) any
implementation of such a feature would generate a trap if a module
attempts to execute an instruction the module does not understand. This
deterministic trap behavior would still not fall into the category of
undefined behavior because the trap is deterministic.
For these reasons the `#[target_feature]` attribute is now allowed on
safe functions, but only for WebAssembly targets. This notably enables
the wasm-SIMD intrinsics proposed for stabilization in #74372 to be
marked as safe generally instead of today where they're all `unsafe` due
to the historical implementation of `#[target_feature]` in the compiler.
const-eval: disallow unwinding across functions that `!fn_can_unwind()`
Following https://github.com/rust-lang/miri/pull/1776#discussion_r633074343, so r? `@RalfJung`
This PR turns `unwind` in `StackPopCleanup::Goto` into a new enum `StackPopUnwind`, with a `NotAllowed` variant to indicate that unwinding is not allowed. This variant is chosen based on `rustc_middle::ty::layout::fn_can_unwind()` in `eval_fn_call()` when pushing the frame. A check is added in `unwind_to_block()` to report UB if unwinding happens across a `StackPopUnwind::NotAllowed` frame.
Tested with Miri `HEAD` with [minor changes](https://github.com/rust-lang/miri/compare/HEAD..9cf3c7f0d86325a586fbcbf2acdc9232b861f1d8) and the rust-lang/miri#1776 branch with [these changes](d866c1c52f..626638fbfe).
Post-monomorphization errors traces MVP
This PR works towards better diagnostics for the errors encountered in #85155 and similar.
We can encounter post-monomorphization errors (PMEs) when collecting mono items. The current diagnostics are confusing for these cases when they happen in a dependency (but are acceptable when they happen in the local crate).
These kinds of errors will be more likely now that `stdarch` uses const generics for its intrinsics' immediate arguments, and validates these const arguments with a mechanism that triggers such PMEs.
(Not to mention that the errors happen during codegen, so only when building code that actually uses these code paths. Check builds don't trigger them, neither does unused code)
So in this PR, we detect these kinds of errors during the mono item graph walk: if any error happens while collecting a node or its neighbors, we print a diagnostic about the current collection step, so that the user has at least some context of which erroneous code and dependency triggered the error.
The diagnostics for issue #85155 now have this note showing the source of the erroneous const argument:
```
note: the above error was encountered while instantiating `fn std::arch::x86_64::_mm_blend_ps::<51_i32>`
--> issue-85155.rs:11:24
|
11 | let _blended = _mm_blend_ps(a, b, 0x33);
| ^^^^^^^^^^^^^^^^^^^^^^^^
error: aborting due to previous error
```
Note that #85155 is a reduced version of a case happening in the wild, to indirect users of the `rustfft` crate, as seen in https://github.com/ejmahler/RustFFT/issues/74. The crate had a few of these out-of-range immediates. Here's how the diagnostics in this PR would have looked on one of its examples before it was fixed:
<details>
```
error[E0080]: evaluation of constant value failed
--> ./stdarch/crates/core_arch/src/macros.rs:8:9
|
8 | assert!(IMM >= MIN && IMM <= MAX, "IMM value not in expected range");
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'IMM value not in expected range', ./stdarch/crates/core_arch/src/macros.rs:8:9
|
= note: this error originates in the macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
note: the above error was encountered while instantiating `fn _mm_blend_ps::<51_i32>`
--> /tmp/RustFFT/src/avx/avx_vector.rs:1314:23
|
1314 | let blended = _mm_blend_ps(rows[0], rows[2], 0x33);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
note: the above error was encountered while instantiating `fn _mm_permute_pd::<5_i32>`
--> /tmp/RustFFT/src/avx/avx_vector.rs:1859:9
|
1859 | _mm_permute_pd(self, 0x05)
| ^^^^^^^^^^^^^^^^^^^^^^^^^^
note: the above error was encountered while instantiating `fn _mm_permute_pd::<15_i32>`
--> /tmp/RustFFT/src/avx/avx_vector.rs:1863:32
|
1863 | (_mm_movedup_pd(self), _mm_permute_pd(self, 0x0F))
| ^^^^^^^^^^^^^^^^^^^^^^^^^^
error: aborting due to previous error
For more information about this error, try `rustc --explain E0080`.
error: could not compile `rustfft`
To learn more, run the command again with --verbose.
```
</details>
I've developed and discussed this with them, so maybe r? `@oli-obk` -- but feel free to redirect to someone else of course.
(I'm not sure we can say that this PR definitely closes issue 85155, as it's still unclear exactly which diagnostics and information would be interesting to report in such cases -- and we've discussed printing backtraces before. I have prototypes of some complete and therefore noisy backtraces I showed Oli, but we decided to not include them in this PR for now)
Emit a diagnostic when the monomorphized item collector
encounters errors during a step of the recursive item collection.
These post-monomorphization errors otherwise only show the
erroneous expression without a trace, making them very obscure
and hard to pinpoint whenever they happen in dependencies.
CTFE get_alloc_extra_mut: also provide ref to MemoryExtra
This would let me use mutable references in more places in Stacked Borrows, avoiding some `RefCell` overhead. :)
r? `@oli-obk`
CTFE core engine allocation & memory API improvemenets
This is a first step towards https://github.com/rust-lang/miri/issues/841.
- make `Allocation` API offset-based (no more making up `Pointer`s just to access an `Allocation`)
- make `Memory` API higher-level (combine checking for access and getting access into one operation)
The Miri-side PR is at https://github.com/rust-lang/miri/pull/1804.
r? `@oli-obk`
- make Allocation API offset-based (no more Pointer)
- make Memory API higher-level (combine checking for access and getting access into one operation)
This adds a new lint to `rustc` that is used in rustdoc when a code
block is empty or cannot be parsed as valid Rust code.
Previously this was unconditionally a warning. As such some
documentation comments were (unknowingly) abusing this to pass despite
the `-Dwarnings` used when compiling `rustc`, this should not be the
case anymore.
Remove CrateNum parameter for queries that only work on local crate
The pervasive `CrateNum` parameter is a remnant of the multi-crate rustc idea.
Using `()` as query key in those cases avoids having to worry about the validity of the query key.
CTFE validation: handle pointers in str
I also finally learned how I can match *some* NOTEs in a ui test without matching all of them, and applied that to some const tests in the 2nd commit where I added NOTE because I did not know what I was doing. I can separate this into its own PR if you prefer.
Fixes https://github.com/rust-lang/rust/issues/83182
r? `@oli-obk`
coverage bug fixes and some refactoring
This replaces the relevant commits (2 and 3) from PR #85082, and also corrects an error querying for coverageinfo.
1. `coverageinfo` query needs to use the same MIR as codegen
I ran into an error trying to fix dead block coverage and realized the
`coverageinfo` query is getting a different MIR compared to the
codegenned MIR, which can sometimes be a problem during mapgen.
I changed that query to use the `InstandeDef` (which includes the
generic parameter substitutions, prosibly specific to const params)
instead of the `DefId` (without unknown/default const substitutions).
2. Simplified body_span and filtered span code
Some code cleanup extracted from future (but unfinished) commit to fix
coverage in attr macro functions.
3. Spanview needs the relevant body_span used for coverage
The coverage body_span doesn't always match the function body_span.
r? ```@tmandry```
I ran into an error trying to fix dead block coverage and realized the
`coverageinfo` query is getting a different MIR compared to the
codegenned MIR, which can sometimes be a problem during mapgen.
I changed that query to use the `InstandeDef` (which includes the
generic parameter substitutions, prosibly specific to const params)
instead of the `DefId` (without unknown/default const substitutions).
Fix `--remap-path-prefix` not correctly remapping `rust-src` component paths and unify handling of path mapping with virtualized paths
This PR fixes#73167 ("Binaries end up containing path to the rust-src component despite `--remap-path-prefix`") by preventing real local filesystem paths from reaching compilation output if the path is supposed to be remapped.
`RealFileName::Named` introduced in #72767 is now renamed as `LocalPath`, because this variant wraps a (most likely) valid local filesystem path.
`RealFileName::Devirtualized` is renamed as `Remapped` to be used for remapped path from a real path via `--remap-path-prefix` argument, as well as real path inferred from a virtualized (during compiler bootstrapping) `/rustc/...` path. The `local_path` field is now an `Option<PathBuf>`, as it will be set to `None` before serialisation, so it never reaches any build output. Attempting to serialise a non-`None` `local_path` will cause an assertion faliure.
When a path is remapped, a `RealFileName::Remapped` variant is created. The original path is preserved in `local_path` field and the remapped path is saved in `virtual_name` field. Previously, the `local_path` is directly modified which goes against its purpose of "suitable for reading from the file system on the local host".
`rustc_span::SourceFile`'s fields `unmapped_path` (introduced by #44940) and `name_was_remapped` (introduced by #41508 when `--remap-path-prefix` feature originally added) are removed, as these two pieces of information can be inferred from the `name` field: if it's anything other than a `FileName::Real(_)`, or if it is a `FileName::Real(RealFileName::LocalPath(_))`, then clearly `name_was_remapped` would've been false and `unmapped_path` would've been `None`. If it is a `FileName::Real(RealFileName::Remapped{local_path, virtual_name})`, then `name_was_remapped` would've been true and `unmapped_path` would've been `Some(local_path)`.
cc `@eddyb` who implemented `/rustc/...` path devirtualisation
This PR implements span quoting, allowing proc-macros to produce spans
pointing *into their own crate*. This is used by the unstable
`proc_macro::quote!` macro, allowing us to get error messages like this:
```
error[E0412]: cannot find type `MissingType` in this scope
--> $DIR/auxiliary/span-from-proc-macro.rs:37:20
|
LL | pub fn error_from_attribute(_args: TokenStream, _input: TokenStream) -> TokenStream {
| ----------------------------------------------------------------------------------- in this expansion of procedural macro `#[error_from_attribute]`
...
LL | field: MissingType
| ^^^^^^^^^^^ not found in this scope
|
::: $DIR/span-from-proc-macro.rs:8:1
|
LL | #[error_from_attribute]
| ----------------------- in this macro invocation
```
Here, `MissingType` occurs inside the implementation of the proc-macro
`#[error_from_attribute]`. Previosuly, this would always result in a
span pointing at `#[error_from_attribute]`
This will make many proc-macro-related error message much more useful -
when a proc-macro generates code containing an error, users will get an
error message pointing directly at that code (within the macro
definition), instead of always getting a span pointing at the macro
invocation site.
This is implemented as follows:
* When a proc-macro crate is being *compiled*, it causes the `quote!`
macro to get run. This saves all of the sapns in the input to `quote!`
into the metadata of *the proc-macro-crate* (which we are currently
compiling). The `quote!` macro then expands to a call to
`proc_macro::Span::recover_proc_macro_span(id)`, where `id` is an
opaque identifier for the span in the crate metadata.
* When the same proc-macro crate is *run* (e.g. it is loaded from disk
and invoked by some consumer crate), the call to
`proc_macro::Span::recover_proc_macro_span` causes us to load the span
from the proc-macro crate's metadata. The proc-macro then produces a
`TokenStream` containing a `Span` pointing into the proc-macro crate
itself.
The recursive nature of 'quote!' can be difficult to understand at
first. The file `src/test/ui/proc-macro/quote-debug.stdout` shows
the output of the `quote!` macro, which should make this eaier to
understand.
This PR also supports custom quoting spans in custom quote macros (e.g.
the `quote` crate). All span quoting goes through the
`proc_macro::quote_span` method, which can be called by a custom quote
macro to perform span quoting. An example of this usage is provided in
`src/test/ui/proc-macro/auxiliary/custom-quote.rs`
Custom quoting currently has a few limitations:
In order to quote a span, we need to generate a call to
`proc_macro::Span::recover_proc_macro_span`. However, proc-macros
support renaming the `proc_macro` crate, so we can't simply hardcode
this path. Previously, the `quote_span` method used the path
`crate::Span` - however, this only works when it is called by the
builtin `quote!` macro in the same crate. To support being called from
arbitrary crates, we need access to the name of the `proc_macro` crate
to generate a path. This PR adds an additional argument to `quote_span`
to specify the name of the `proc_macro` crate. Howver, this feels kind
of hacky, and we may want to change this before stabilizing anything
quote-related.
Additionally, using `quote_span` currently requires enabling the
`proc_macro_internals` feature. The builtin `quote!` macro
has an `#[allow_internal_unstable]` attribute, but this won't work for
custom quote implementations. This will likely require some additional
tricks to apply `allow_internal_unstable` to the span of
`proc_macro::Span::recover_proc_macro_span`.
Add primary marker on codegen unit and generate main wrapper on primary codegen.
This is the codegen part of changes extracted from #84062.
This add a marker called `primary` on each codegen units, where exactly one codegen unit will be `primary = true` at a time. This specific codegen unit will take charge of generating `main` wrapper when `main` is imported from a foreign crate after the implementation of RFC 1260.
cc #28937
I'm not sure who should i ask for review for codegen changes, so feel free to reassign.
r? `@nagisa`
Report coverage `0` of dead blocks
Fixes: #84018
With `-Z instrument-coverage`, coverage reporting of dead blocks
(for example, blocks dropped because a conditional branch is dropped,
based on const evaluation) is now supported.
If `instrument-coverage` is enabled, `simplify::remove_dead_blocks()`
finds all dropped coverage `Statement`s and adds their `code_region`s as
`Unreachable` coverage `Statement`s to the `START_BLOCK`, so they are
still included in the coverage map.
Check out the resulting changes in the test coverage reports in this PR (in [commit 1](0b0d293c7c)).
r? `@tmandry`
cc: `@wesleywiser`
CTFE inbounds-error-messages tweak
* use CheckInAllocMsg::PointerArithmeticTest for ptr_offset error
* nicer errors for some null pointer cases
r? `@oli-obk`
Coverage instruments closure bodies in macros (not the macro body)
Fixes: #84884
This solution might be considered a compromise, but I think it is the
better choice.
The results in the `closure.rs` test correctly resolve all test cases
broken as described in #84884.
One test pattern (in both `closure_macro.rs` and
`closure_macro_async.rs`) was also affected, and removes coverage
statistics for the lines inside the closure, because the closure
includes a macro. (The coverage remains at the callsite of the macro, so
we lose some detail, but there isn't a perfect choice with macros.
Often macro implementations are split across the macro and the callsite,
and there doesn't appear to be a single "right choice" for which body
should be covered. For the current implementation, we can't do both.
The callsite is most likely to be the preferred site for coverage.
r? `@tmandry`
cc: `@wesleywiser`
Fixes: #84884
This solution might be considered a compromise, but I think it is the
better choice.
The results in the `closure.rs` test correctly resolve all test cases
broken as described in #84884.
One test pattern (in both `closure_macro.rs` and
`closure_macro_async.rs`) was also affected, and removes coverage
statistics for the lines inside the closure, because the closure
includes a macro. (The coverage remains at the callsite of the macro, so
we lose some detail, but there isn't a perfect choice with macros.
Often macro implementations are split across the macro and the callsite,
and there doesn't appear to be a single "right choice" for which body
should be covered. For the current implementation, we can't do both.
The callsite is most likely to be the preferred site for coverage.
I applied this fix to all `MacroKinds`, not just `Bang`.
I'm trying to resolve an issue of lost coverage in a
`MacroKind::Attr`-based, function-scoped macro. Instead of only
searching for a body_span that is "not a function-like macro" (that is,
MacroKind::Bang), I'm expanding this to all `MacroKind`s. Maybe I should
expand this to `ExpnKind::Desugaring` and `ExpnKind::AstPass` (or
subsets, depending on their sub-kinds) as well, but I'm not sure that's
a good idea.
I'd like to add a test of the `Attr` macro on functions, but I need time
to figure out how to constract a good, simple example without external
crate dependencies. For the moment, all tests still work as expected (no
change), this new commit shouldn't have a negative affect, and more
importantly, I believe it will have a positive effect. I will try to
confirm this.
