-
Notifications
You must be signed in to change notification settings - Fork 13.4k
Make two transmute-related MIR lints into HIR lint #141551
New issue
Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.
By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.
Already on GitHub? Sign in to your account
Merged
+488
−407
Merged
Changes from all commits
Commits
Show all changes
3 commits
Select commit
Hold shift + click to select a range
File filter
Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
There are no files selected for viewing
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,278 @@ | ||
| use rustc_errors::Applicability; | ||
| use rustc_hir::def::{DefKind, Res}; | ||
| use rustc_hir::def_id::LocalDefId; | ||
| use rustc_hir::{self as hir}; | ||
| use rustc_macros::LintDiagnostic; | ||
| use rustc_middle::ty::{self, Ty}; | ||
| use rustc_session::{declare_lint, impl_lint_pass}; | ||
| use rustc_span::sym; | ||
|
|
||
| use crate::{LateContext, LateLintPass}; | ||
|
|
||
| declare_lint! { | ||
| /// The `ptr_to_integer_transmute_in_consts` lint detects pointer to integer | ||
| /// transmute in const functions and associated constants. | ||
| /// | ||
| /// ### Example | ||
| /// | ||
| /// ```rust | ||
| /// const fn foo(ptr: *const u8) -> usize { | ||
| /// unsafe { | ||
| /// std::mem::transmute::<*const u8, usize>(ptr) | ||
| /// } | ||
| /// } | ||
| /// ``` | ||
| /// | ||
| /// {{produces}} | ||
| /// | ||
| /// ### Explanation | ||
| /// | ||
| /// Transmuting pointers to integers in a `const` context is undefined behavior. | ||
| /// Any attempt to use the resulting integer will abort const-evaluation. | ||
| /// | ||
| /// But sometimes the compiler might not emit an error for pointer to integer transmutes | ||
| /// inside const functions and associated consts because they are evaluated only when referenced. | ||
| /// Therefore, this lint serves as an extra layer of defense to prevent any undefined behavior | ||
| /// from compiling without any warnings or errors. | ||
| /// | ||
| /// See [std::mem::transmute] in the reference for more details. | ||
| /// | ||
| /// [std::mem::transmute]: https://doc.rust-lang.org/std/mem/fn.transmute.html | ||
| pub PTR_TO_INTEGER_TRANSMUTE_IN_CONSTS, | ||
| Warn, | ||
| "detects pointer to integer transmutes in const functions and associated constants", | ||
| } | ||
|
|
||
| declare_lint! { | ||
| /// The `unnecessary_transmutes` lint detects transmutations that have safer alternatives. | ||
| /// | ||
| /// ### Example | ||
| /// | ||
| /// ```rust | ||
| /// fn bytes_at_home(x: [u8; 4]) -> u32 { | ||
| /// unsafe { std::mem::transmute(x) } | ||
| /// } | ||
| /// ``` | ||
| /// | ||
| /// {{produces}} | ||
| /// | ||
| /// ### Explanation | ||
| /// | ||
| /// Using an explicit method is preferable over calls to | ||
| /// [`transmute`](https://doc.rust-lang.org/std/mem/fn.transmute.html) as | ||
| /// they more clearly communicate the intent, are easier to review, and | ||
| /// are less likely to accidentally result in unsoundness. | ||
| pub UNNECESSARY_TRANSMUTES, | ||
| Warn, | ||
| "detects transmutes that can also be achieved by other operations" | ||
| } | ||
|
|
||
| pub(crate) struct CheckTransmutes; | ||
|
|
||
| impl_lint_pass!(CheckTransmutes => [PTR_TO_INTEGER_TRANSMUTE_IN_CONSTS, UNNECESSARY_TRANSMUTES]); | ||
|
|
||
| impl<'tcx> LateLintPass<'tcx> for CheckTransmutes { | ||
| fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'tcx>) { | ||
| let hir::ExprKind::Call(callee, [arg]) = expr.kind else { | ||
| return; | ||
| }; | ||
| let hir::ExprKind::Path(qpath) = callee.kind else { | ||
| return; | ||
| }; | ||
| let Res::Def(DefKind::Fn, def_id) = cx.qpath_res(&qpath, callee.hir_id) else { | ||
| return; | ||
| }; | ||
| if !cx.tcx.is_intrinsic(def_id, sym::transmute) { | ||
| return; | ||
| }; | ||
| let body_owner_def_id = cx.tcx.hir_enclosing_body_owner(expr.hir_id); | ||
| let const_context = cx.tcx.hir_body_const_context(body_owner_def_id); | ||
| let args = cx.typeck_results().node_args(callee.hir_id); | ||
|
|
||
| let src = args.type_at(0); | ||
| let dst = args.type_at(1); | ||
|
|
||
| check_ptr_transmute_in_const(cx, expr, body_owner_def_id, const_context, src, dst); | ||
| check_unnecessary_transmute(cx, expr, callee, arg, const_context, src, dst); | ||
| } | ||
| } | ||
|
|
||
| /// Check for transmutes that exhibit undefined behavior. | ||
| /// For example, transmuting pointers to integers in a const context. | ||
| /// | ||
| /// Why do we consider const functions and associated constants only? | ||
| /// | ||
| /// Generally, undefined behavior in const items are handled by the evaluator. | ||
| /// But, const functions and associated constants are evaluated only when referenced. | ||
| /// This can result in undefined behavior in a library going unnoticed until | ||
| /// the function or constant is actually used. | ||
| /// | ||
| /// Therefore, we only consider const functions and associated constants here and leave | ||
| /// other const items to be handled by the evaluator. | ||
| fn check_ptr_transmute_in_const<'tcx>( | ||
| cx: &LateContext<'tcx>, | ||
| expr: &'tcx hir::Expr<'tcx>, | ||
| body_owner_def_id: LocalDefId, | ||
| const_context: Option<hir::ConstContext>, | ||
| src: Ty<'tcx>, | ||
| dst: Ty<'tcx>, | ||
| ) { | ||
| if matches!(const_context, Some(hir::ConstContext::ConstFn)) | ||
| || matches!(cx.tcx.def_kind(body_owner_def_id), DefKind::AssocConst) | ||
| { | ||
| if src.is_raw_ptr() && dst.is_integral() { | ||
| cx.tcx.emit_node_span_lint( | ||
| PTR_TO_INTEGER_TRANSMUTE_IN_CONSTS, | ||
| expr.hir_id, | ||
| expr.span, | ||
| UndefinedTransmuteLint, | ||
| ); | ||
| } | ||
| } | ||
| } | ||
|
|
||
| /// Check for transmutes that overlap with stdlib methods. | ||
| /// For example, transmuting `[u8; 4]` to `u32`. | ||
| /// | ||
| /// We chose not to lint u8 -> bool transmutes, see #140431. | ||
| fn check_unnecessary_transmute<'tcx>( | ||
| cx: &LateContext<'tcx>, | ||
| expr: &'tcx hir::Expr<'tcx>, | ||
| callee: &'tcx hir::Expr<'tcx>, | ||
| arg: &'tcx hir::Expr<'tcx>, | ||
| const_context: Option<hir::ConstContext>, | ||
| src: Ty<'tcx>, | ||
| dst: Ty<'tcx>, | ||
| ) { | ||
| let callee_span = callee.span.find_ancestor_inside(expr.span).unwrap_or(callee.span); | ||
| let (sugg, help) = match (src.kind(), dst.kind()) { | ||
| // dont check the length; transmute does that for us. | ||
| // [u8; _] => primitive | ||
| (ty::Array(t, _), ty::Uint(_) | ty::Float(_) | ty::Int(_)) | ||
| if *t.kind() == ty::Uint(ty::UintTy::U8) => | ||
| { | ||
| ( | ||
| Some(vec![(callee_span, format!("{dst}::from_ne_bytes"))]), | ||
| Some( | ||
| "there's also `from_le_bytes` and `from_be_bytes` if you expect a particular byte order", | ||
| ), | ||
| ) | ||
| } | ||
| // primitive => [u8; _] | ||
| (ty::Uint(_) | ty::Float(_) | ty::Int(_), ty::Array(t, _)) | ||
| if *t.kind() == ty::Uint(ty::UintTy::U8) => | ||
| { | ||
| ( | ||
| Some(vec![(callee_span, format!("{src}::to_ne_bytes"))]), | ||
| Some( | ||
| "there's also `to_le_bytes` and `to_be_bytes` if you expect a particular byte order", | ||
| ), | ||
| ) | ||
| } | ||
| // char → u32 | ||
| (ty::Char, ty::Uint(ty::UintTy::U32)) => { | ||
| (Some(vec![(callee_span, "u32::from".to_string())]), None) | ||
| } | ||
| // char (→ u32) → i32 | ||
| (ty::Char, ty::Int(ty::IntTy::I32)) => ( | ||
| Some(vec![ | ||
| (callee_span, "u32::from".to_string()), | ||
| (expr.span.shrink_to_hi(), ".cast_signed()".to_string()), | ||
| ]), | ||
| None, | ||
| ), | ||
| // u32 → char | ||
| (ty::Uint(ty::UintTy::U32), ty::Char) => ( | ||
| Some(vec![(callee_span, "char::from_u32_unchecked".to_string())]), | ||
| Some("consider using `char::from_u32(…).unwrap()`"), | ||
| ), | ||
| // i32 → char | ||
| (ty::Int(ty::IntTy::I32), ty::Char) => ( | ||
| Some(vec![ | ||
| (callee_span, "char::from_u32_unchecked(i32::cast_unsigned".to_string()), | ||
| (expr.span.shrink_to_hi(), ")".to_string()), | ||
| ]), | ||
| Some("consider using `char::from_u32(i32::cast_unsigned(…)).unwrap()`"), | ||
| ), | ||
| // uNN → iNN | ||
| (ty::Uint(_), ty::Int(_)) => { | ||
| (Some(vec![(callee_span, format!("{src}::cast_signed"))]), None) | ||
| } | ||
| // iNN → uNN | ||
| (ty::Int(_), ty::Uint(_)) => { | ||
| (Some(vec![(callee_span, format!("{src}::cast_unsigned"))]), None) | ||
| } | ||
| // fNN → usize, isize | ||
| (ty::Float(_), ty::Uint(ty::UintTy::Usize) | ty::Int(ty::IntTy::Isize)) => ( | ||
| Some(vec![ | ||
| (callee_span, format!("{src}::to_bits")), | ||
| (expr.span.shrink_to_hi(), format!(" as {dst}")), | ||
| ]), | ||
| None, | ||
| ), | ||
| // fNN (→ uNN) → iNN | ||
| (ty::Float(_), ty::Int(..)) => ( | ||
| Some(vec![ | ||
| (callee_span, format!("{src}::to_bits")), | ||
| (expr.span.shrink_to_hi(), ".cast_signed()".to_string()), | ||
| ]), | ||
| None, | ||
| ), | ||
| // fNN → uNN | ||
| (ty::Float(_), ty::Uint(..)) => { | ||
| (Some(vec![(callee_span, format!("{src}::to_bits"))]), None) | ||
| } | ||
| // xsize → fNN | ||
| (ty::Uint(ty::UintTy::Usize) | ty::Int(ty::IntTy::Isize), ty::Float(_)) => ( | ||
| Some(vec![ | ||
| (callee_span, format!("{dst}::from_bits")), | ||
| (arg.span.shrink_to_hi(), " as _".to_string()), | ||
| ]), | ||
| None, | ||
| ), | ||
| // iNN (→ uNN) → fNN | ||
| (ty::Int(_), ty::Float(_)) => ( | ||
| Some(vec![ | ||
| (callee_span, format!("{dst}::from_bits({src}::cast_unsigned")), | ||
| (expr.span.shrink_to_hi(), ")".to_string()), | ||
| ]), | ||
| None, | ||
| ), | ||
| // uNN → fNN | ||
| (ty::Uint(_), ty::Float(_)) => { | ||
| (Some(vec![(callee_span, format!("{dst}::from_bits"))]), None) | ||
| } | ||
| // bool → x8 in const context since `From::from` is not const yet | ||
| // FIXME: Consider arg expr's precedence to avoid parentheses. | ||
| // FIXME(const_traits): Remove this when `From::from` is constified. | ||
| (ty::Bool, ty::Int(..) | ty::Uint(..)) if const_context.is_some() => ( | ||
| Some(vec![ | ||
| (callee_span, "".to_string()), | ||
| (expr.span.shrink_to_hi(), format!(" as {dst}")), | ||
| ]), | ||
| None, | ||
| ), | ||
| // bool → x8 using `x8::from` | ||
| (ty::Bool, ty::Int(..) | ty::Uint(..)) => { | ||
| (Some(vec![(callee_span, format!("{dst}::from"))]), None) | ||
| } | ||
| _ => return, | ||
| }; | ||
|
|
||
| cx.tcx.node_span_lint(UNNECESSARY_TRANSMUTES, expr.hir_id, expr.span, |diag| { | ||
| diag.primary_message("unnecessary transmute"); | ||
| if let Some(sugg) = sugg { | ||
| diag.multipart_suggestion("replace this with", sugg, Applicability::MachineApplicable); | ||
| } | ||
| if let Some(help) = help { | ||
| diag.help(help); | ||
| } | ||
| }); | ||
| } | ||
|
|
||
| #[derive(LintDiagnostic)] | ||
| #[diag(lint_undefined_transmute)] | ||
| #[note] | ||
| #[note(lint_note2)] | ||
| #[help] | ||
| pub(crate) struct UndefinedTransmuteLint; | ||
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Oops, something went wrong.
Oops, something went wrong.
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
There was a problem hiding this comment.
Choose a reason for hiding this comment
The reason will be displayed to describe this comment to others. Learn more.
I chose to be lazy and use the old diagnostic machinery for the
UNNECESSARY_TRANSMUTESlint, since it's kind of a pain in the ass to make it work "correctly" w/ the new machinery.