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Emit error when calling/declaring functions with unavailable vectors.

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On some architectures, vector types may have a different ABI when
relevant target features are enabled.

As discussed in https://github.com/rust-lang/lang-team/issues/235, this
turns out to very easily lead to unsound code.

This commit makes it an error to declare or call functions using those
vector types in a context in which the corresponding target features are
disabled, if using an ABI for which the difference is relevant.
This commit is contained in:
Luca Versari 2024-07-13 19:35:05 +02:00
parent 7342830c05
commit 5af56cac38
16 changed files with 448 additions and 53 deletions
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67
compiler/rustc_lint_defs/src/builtin.rs
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@ -16,6 +16,7 @@ declare_lint_pass! {
/// that are used by other parts of the compiler.
HardwiredLints => [
// tidy-alphabetical-start
ABI_UNSUPPORTED_VECTOR_TYPES,
ABSOLUTE_PATHS_NOT_STARTING_WITH_CRATE,
AMBIGUOUS_ASSOCIATED_ITEMS,
AMBIGUOUS_GLOB_IMPORTS,
@ -5078,3 +5079,69 @@ declare_lint! {
};
crate_level_only
}
declare_lint! {
/// The `abi_unsupported_vector_types` lint detects function definitions and calls
/// whose ABI depends on enabling certain target features, but those features are not enabled.
///
/// ### Example
///
/// ```rust,ignore (fails on non-x86_64)
/// extern "C" fn missing_target_feature(_: std::arch::x86_64::__m256) {
/// todo!()
/// }
///
/// #[target_feature(enable = "avx")]
/// unsafe extern "C" fn with_target_feature(_: std::arch::x86_64::__m256) {
/// todo!()
/// }
///
/// fn main() {
/// let v = unsafe { std::mem::zeroed() };
/// unsafe { with_target_feature(v); }
/// }
/// ```
///
/// ```text
/// warning: ABI error: this function call uses a avx vector type, which is not enabled in the caller
/// --> lint_example.rs:18:12
/// |
/// | unsafe { with_target_feature(v); }
/// | ^^^^^^^^^^^^^^^^^^^^^^ function called here
/// |
/// = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
/// = note: for more information, see issue #116558 <https://github.com/rust-lang/rust/issues/116558>
/// = help: consider enabling it globally (-C target-feature=+avx) or locally (#[target_feature(enable="avx")])
/// = note: `#[warn(abi_unsupported_vector_types)]` on by default
///
///
/// warning: ABI error: this function definition uses a avx vector type, which is not enabled
/// --> lint_example.rs:3:1
/// |
/// | pub extern "C" fn with_target_feature(_: std::arch::x86_64::__m256) {
/// | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ function defined here
/// |
/// = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
/// = note: for more information, see issue #116558 <https://github.com/rust-lang/rust/issues/116558>
/// = help: consider enabling it globally (-C target-feature=+avx) or locally (#[target_feature(enable="avx")])
/// ```
///
///
///
/// ### Explanation
///
/// The C ABI for `__m256` requires the value to be passed in an AVX register,
/// which is only possible when the `avx` target feature is enabled.
/// Therefore, `missing_target_feature` cannot be compiled without that target feature.
/// A similar (but complementary) message is triggered when `with_target_feature` is called
/// by a function that does not enable the `avx` target feature.
///
/// Note that this lint is very similar to the `-Wpsabi` warning in `gcc`/`clang`.
pub ABI_UNSUPPORTED_VECTOR_TYPES,
Warn,
"this function call or definition uses a vector type which is not enabled",
@future_incompatible = FutureIncompatibleInfo {
reason: FutureIncompatibilityReason::FutureReleaseErrorDontReportInDeps,
reference: "issue #116558 <https://github.com/rust-lang/rust/issues/116558>",
};
}