1 use crate::{LateContext, LateLintPass, LintContext};
3 use rustc_attr as attr;
4 use rustc_data_structures::fx::FxHashSet;
5 use rustc_errors::{fluent, Applicability, DiagnosticMessage};
7 use rustc_hir::{is_range_literal, Expr, ExprKind, Node};
8 use rustc_macros::LintDiagnostic;
9 use rustc_middle::ty::layout::{IntegerExt, LayoutOf, SizeSkeleton};
10 use rustc_middle::ty::subst::SubstsRef;
11 use rustc_middle::ty::{self, AdtKind, DefIdTree, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable};
12 use rustc_span::source_map;
13 use rustc_span::symbol::sym;
14 use rustc_span::{Span, Symbol, DUMMY_SP};
15 use rustc_target::abi::{Abi, WrappingRange};
16 use rustc_target::abi::{Integer, TagEncoding, Variants};
17 use rustc_target::spec::abi::Abi as SpecAbi;
21 use std::ops::ControlFlow;
25 /// The `unused_comparisons` lint detects comparisons made useless by
26 /// limits of the types involved.
40 /// A useless comparison may indicate a mistake, and should be fixed or
44 "comparisons made useless by limits of the types involved"
48 /// The `overflowing_literals` lint detects literal out of range for its
53 /// ```rust,compile_fail
61 /// It is usually a mistake to use a literal that overflows the type where
62 /// it is used. Either use a literal that is within range, or change the
63 /// type to be within the range of the literal.
66 "literal out of range for its type"
70 /// The `variant_size_differences` lint detects enums with widely varying
75 /// ```rust,compile_fail
76 /// #![deny(variant_size_differences)]
87 /// It can be a mistake to add a variant to an enum that is much larger
88 /// than the other variants, bloating the overall size required for all
89 /// variants. This can impact performance and memory usage. This is
90 /// triggered if one variant is more than 3 times larger than the
91 /// second-largest variant.
93 /// Consider placing the large variant's contents on the heap (for example
94 /// via [`Box`]) to keep the overall size of the enum itself down.
96 /// This lint is "allow" by default because it can be noisy, and may not be
97 /// an actual problem. Decisions about this should be guided with
98 /// profiling and benchmarking.
100 /// [`Box`]: https://doc.rust-lang.org/std/boxed/index.html
101 VARIANT_SIZE_DIFFERENCES,
103 "detects enums with widely varying variant sizes"
106 #[derive(Copy, Clone)]
107 pub struct TypeLimits {
108 /// Id of the last visited negated expression
109 negated_expr_id: Option<hir::HirId>,
112 impl_lint_pass!(TypeLimits => [UNUSED_COMPARISONS, OVERFLOWING_LITERALS]);
115 pub fn new() -> TypeLimits {
116 TypeLimits { negated_expr_id: None }
120 /// Attempts to special-case the overflowing literal lint when it occurs as a range endpoint.
121 /// Returns `true` iff the lint was overridden.
122 fn lint_overflowing_range_endpoint<'tcx>(
123 cx: &LateContext<'tcx>,
127 expr: &'tcx hir::Expr<'tcx>,
128 parent_expr: &'tcx hir::Expr<'tcx>,
131 // We only want to handle exclusive (`..`) ranges,
132 // which are represented as `ExprKind::Struct`.
133 let mut overwritten = false;
134 if let ExprKind::Struct(_, eps, _) = &parent_expr.kind {
138 // We can suggest using an inclusive range
139 // (`..=`) instead only if it is the `end` that is
140 // overflowing and only by 1.
141 if eps[1].expr.hir_id == expr.hir_id && lit_val - 1 == max {
142 cx.struct_span_lint(OVERFLOWING_LITERALS, parent_expr.span, |lint| {
143 let mut err = lint.build(fluent::lint::range_endpoint_out_of_range);
144 err.set_arg("ty", ty);
145 if let Ok(start) = cx.sess().source_map().span_to_snippet(eps[0].span) {
146 use ast::{LitIntType, LitKind};
147 // We need to preserve the literal's suffix,
148 // as it may determine typing information.
149 let suffix = match lit.node {
150 LitKind::Int(_, LitIntType::Signed(s)) => s.name_str(),
151 LitKind::Int(_, LitIntType::Unsigned(s)) => s.name_str(),
152 LitKind::Int(_, LitIntType::Unsuffixed) => "",
155 let suggestion = format!("{}..={}{}", start, lit_val - 1, suffix);
158 fluent::lint::suggestion,
160 Applicability::MachineApplicable,
171 // For `isize` & `usize`, be conservative with the warnings, so that the
172 // warnings are consistent between 32- and 64-bit platforms.
173 fn int_ty_range(int_ty: ty::IntTy) -> (i128, i128) {
175 ty::IntTy::Isize => (i64::MIN.into(), i64::MAX.into()),
176 ty::IntTy::I8 => (i8::MIN.into(), i8::MAX.into()),
177 ty::IntTy::I16 => (i16::MIN.into(), i16::MAX.into()),
178 ty::IntTy::I32 => (i32::MIN.into(), i32::MAX.into()),
179 ty::IntTy::I64 => (i64::MIN.into(), i64::MAX.into()),
180 ty::IntTy::I128 => (i128::MIN, i128::MAX),
184 fn uint_ty_range(uint_ty: ty::UintTy) -> (u128, u128) {
185 let max = match uint_ty {
186 ty::UintTy::Usize => u64::MAX.into(),
187 ty::UintTy::U8 => u8::MAX.into(),
188 ty::UintTy::U16 => u16::MAX.into(),
189 ty::UintTy::U32 => u32::MAX.into(),
190 ty::UintTy::U64 => u64::MAX.into(),
191 ty::UintTy::U128 => u128::MAX,
196 fn get_bin_hex_repr(cx: &LateContext<'_>, lit: &hir::Lit) -> Option<String> {
197 let src = cx.sess().source_map().span_to_snippet(lit.span).ok()?;
198 let firstch = src.chars().next()?;
201 match src.chars().nth(1) {
202 Some('x' | 'b') => return Some(src),
210 fn report_bin_hex_error(
211 cx: &LateContext<'_>,
212 expr: &hir::Expr<'_>,
218 let size = Integer::from_attr(&cx.tcx, ty).size();
219 cx.struct_span_lint(OVERFLOWING_LITERALS, expr.span, |lint| {
220 let (t, actually) = match ty {
221 attr::IntType::SignedInt(t) => {
222 let actually = if negative {
223 -(size.sign_extend(val) as i128)
225 size.sign_extend(val) as i128
227 (t.name_str(), actually.to_string())
229 attr::IntType::UnsignedInt(t) => {
230 let actually = size.truncate(val);
231 (t.name_str(), actually.to_string())
234 let mut err = lint.build(fluent::lint::overflowing_bin_hex);
236 // If the value is negative,
237 // emits a note about the value itself, apart from the literal.
238 err.note(fluent::lint::negative_note);
239 err.note(fluent::lint::negative_becomes_note);
241 err.note(fluent::lint::positive_note);
243 if let Some(sugg_ty) =
244 get_type_suggestion(cx.typeck_results().node_type(expr.hir_id), val, negative)
246 err.set_arg("suggestion_ty", sugg_ty);
247 if let Some(pos) = repr_str.chars().position(|c| c == 'i' || c == 'u') {
248 let (sans_suffix, _) = repr_str.split_at(pos);
251 fluent::lint::suggestion,
252 format!("{}{}", sans_suffix, sugg_ty),
253 Applicability::MachineApplicable,
256 err.help(fluent::lint::help);
259 err.set_arg("ty", t);
260 err.set_arg("lit", repr_str);
261 err.set_arg("dec", val);
262 err.set_arg("actually", actually);
267 // This function finds the next fitting type and generates a suggestion string.
268 // It searches for fitting types in the following way (`X < Y`):
269 // - `iX`: if literal fits in `uX` => `uX`, else => `iY`
273 // No suggestion for: `isize`, `usize`.
274 fn get_type_suggestion(t: Ty<'_>, val: u128, negative: bool) -> Option<&'static str> {
277 macro_rules! find_fit {
278 ($ty:expr, $val:expr, $negative:expr,
279 $($type:ident => [$($utypes:expr),*] => [$($itypes:expr),*]),+) => {
281 let _neg = if negative { 1 } else { 0 };
284 $(if !negative && val <= uint_ty_range($utypes).1 {
285 return Some($utypes.name_str())
287 $(if val <= int_ty_range($itypes).1 as u128 + _neg {
288 return Some($itypes.name_str())
298 ty::Int(i) => find_fit!(i, val, negative,
299 I8 => [U8] => [I16, I32, I64, I128],
300 I16 => [U16] => [I32, I64, I128],
301 I32 => [U32] => [I64, I128],
302 I64 => [U64] => [I128],
303 I128 => [U128] => []),
304 ty::Uint(u) => find_fit!(u, val, negative,
305 U8 => [U8, U16, U32, U64, U128] => [],
306 U16 => [U16, U32, U64, U128] => [],
307 U32 => [U32, U64, U128] => [],
308 U64 => [U64, U128] => [],
309 U128 => [U128] => []),
314 fn lint_int_literal<'tcx>(
315 cx: &LateContext<'tcx>,
316 type_limits: &TypeLimits,
317 e: &'tcx hir::Expr<'tcx>,
322 let int_type = t.normalize(cx.sess().target.pointer_width);
323 let (min, max) = int_ty_range(int_type);
324 let max = max as u128;
325 let negative = type_limits.negated_expr_id == Some(e.hir_id);
327 // Detect literal value out of range [min, max] inclusive
328 // avoiding use of -min to prevent overflow/panic
329 if (negative && v > max + 1) || (!negative && v > max) {
330 if let Some(repr_str) = get_bin_hex_repr(cx, lit) {
331 report_bin_hex_error(
334 attr::IntType::SignedInt(ty::ast_int_ty(t)),
342 let par_id = cx.tcx.hir().get_parent_node(e.hir_id);
343 if let Node::Expr(par_e) = cx.tcx.hir().get(par_id) {
344 if let hir::ExprKind::Struct(..) = par_e.kind {
345 if is_range_literal(par_e)
346 && lint_overflowing_range_endpoint(cx, lit, v, max, e, par_e, t.name_str())
348 // The overflowing literal lint was overridden.
354 cx.struct_span_lint(OVERFLOWING_LITERALS, e.span, |lint| {
355 let mut err = lint.build(fluent::lint::overflowing_int);
356 err.set_arg("ty", t.name_str());
361 .span_to_snippet(lit.span)
362 .expect("must get snippet from literal"),
364 err.set_arg("min", min);
365 err.set_arg("max", max);
366 err.note(fluent::lint::note);
367 if let Some(sugg_ty) =
368 get_type_suggestion(cx.typeck_results().node_type(e.hir_id), v, negative)
370 err.set_arg("suggestion_ty", sugg_ty);
371 err.help(fluent::lint::help);
378 fn lint_uint_literal<'tcx>(
379 cx: &LateContext<'tcx>,
380 e: &'tcx hir::Expr<'tcx>,
384 let uint_type = t.normalize(cx.sess().target.pointer_width);
385 let (min, max) = uint_ty_range(uint_type);
386 let lit_val: u128 = match lit.node {
387 // _v is u8, within range by definition
388 ast::LitKind::Byte(_v) => return,
389 ast::LitKind::Int(v, _) => v,
392 if lit_val < min || lit_val > max {
393 let parent_id = cx.tcx.hir().get_parent_node(e.hir_id);
394 if let Node::Expr(par_e) = cx.tcx.hir().get(parent_id) {
396 hir::ExprKind::Cast(..) => {
397 if let ty::Char = cx.typeck_results().expr_ty(par_e).kind() {
398 cx.struct_span_lint(OVERFLOWING_LITERALS, par_e.span, |lint| {
399 lint.build(fluent::lint::only_cast_u8_to_char)
402 fluent::lint::suggestion,
403 format!("'\\u{{{:X}}}'", lit_val),
404 Applicability::MachineApplicable,
411 hir::ExprKind::Struct(..) if is_range_literal(par_e) => {
412 let t = t.name_str();
413 if lint_overflowing_range_endpoint(cx, lit, lit_val, max, e, par_e, t) {
414 // The overflowing literal lint was overridden.
421 if let Some(repr_str) = get_bin_hex_repr(cx, lit) {
422 report_bin_hex_error(
425 attr::IntType::UnsignedInt(ty::ast_uint_ty(t)),
432 cx.struct_span_lint(OVERFLOWING_LITERALS, e.span, |lint| {
433 lint.build(fluent::lint::overflowing_uint)
434 .set_arg("ty", t.name_str())
439 .span_to_snippet(lit.span)
440 .expect("must get snippet from literal"),
444 .note(fluent::lint::note)
450 fn lint_literal<'tcx>(
451 cx: &LateContext<'tcx>,
452 type_limits: &TypeLimits,
453 e: &'tcx hir::Expr<'tcx>,
456 match *cx.typeck_results().node_type(e.hir_id).kind() {
459 ast::LitKind::Int(v, ast::LitIntType::Signed(_) | ast::LitIntType::Unsuffixed) => {
460 lint_int_literal(cx, type_limits, e, lit, t, v)
465 ty::Uint(t) => lint_uint_literal(cx, e, lit, t),
467 let is_infinite = match lit.node {
468 ast::LitKind::Float(v, _) => match t {
469 ty::FloatTy::F32 => v.as_str().parse().map(f32::is_infinite),
470 ty::FloatTy::F64 => v.as_str().parse().map(f64::is_infinite),
474 if is_infinite == Ok(true) {
475 cx.struct_span_lint(OVERFLOWING_LITERALS, e.span, |lint| {
476 lint.build(fluent::lint::overflowing_literal)
477 .set_arg("ty", t.name_str())
482 .span_to_snippet(lit.span)
483 .expect("must get snippet from literal"),
485 .note(fluent::lint::note)
494 impl<'tcx> LateLintPass<'tcx> for TypeLimits {
495 fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx hir::Expr<'tcx>) {
497 hir::ExprKind::Unary(hir::UnOp::Neg, ref expr) => {
498 // propagate negation, if the negation itself isn't negated
499 if self.negated_expr_id != Some(e.hir_id) {
500 self.negated_expr_id = Some(expr.hir_id);
503 hir::ExprKind::Binary(binop, ref l, ref r) => {
504 if is_comparison(binop) && !check_limits(cx, binop, &l, &r) {
505 cx.struct_span_lint(UNUSED_COMPARISONS, e.span, |lint| {
506 lint.build(fluent::lint::unused_comparisons).emit();
510 hir::ExprKind::Lit(ref lit) => lint_literal(cx, self, e, lit),
514 fn is_valid<T: cmp::PartialOrd>(binop: hir::BinOp, v: T, min: T, max: T) -> bool {
516 hir::BinOpKind::Lt => v > min && v <= max,
517 hir::BinOpKind::Le => v >= min && v < max,
518 hir::BinOpKind::Gt => v >= min && v < max,
519 hir::BinOpKind::Ge => v > min && v <= max,
520 hir::BinOpKind::Eq | hir::BinOpKind::Ne => v >= min && v <= max,
525 fn rev_binop(binop: hir::BinOp) -> hir::BinOp {
529 hir::BinOpKind::Lt => hir::BinOpKind::Gt,
530 hir::BinOpKind::Le => hir::BinOpKind::Ge,
531 hir::BinOpKind::Gt => hir::BinOpKind::Lt,
532 hir::BinOpKind::Ge => hir::BinOpKind::Le,
539 cx: &LateContext<'_>,
544 let (lit, expr, swap) = match (&l.kind, &r.kind) {
545 (&hir::ExprKind::Lit(_), _) => (l, r, true),
546 (_, &hir::ExprKind::Lit(_)) => (r, l, false),
549 // Normalize the binop so that the literal is always on the RHS in
551 let norm_binop = if swap { rev_binop(binop) } else { binop };
552 match *cx.typeck_results().node_type(expr.hir_id).kind() {
554 let (min, max) = int_ty_range(int_ty);
555 let lit_val: i128 = match lit.kind {
556 hir::ExprKind::Lit(ref li) => match li.node {
559 ast::LitIntType::Signed(_) | ast::LitIntType::Unsuffixed,
565 is_valid(norm_binop, lit_val, min, max)
567 ty::Uint(uint_ty) => {
568 let (min, max): (u128, u128) = uint_ty_range(uint_ty);
569 let lit_val: u128 = match lit.kind {
570 hir::ExprKind::Lit(ref li) => match li.node {
571 ast::LitKind::Int(v, _) => v,
576 is_valid(norm_binop, lit_val, min, max)
582 fn is_comparison(binop: hir::BinOp) -> bool {
597 /// The `improper_ctypes` lint detects incorrect use of types in foreign
604 /// static STATIC: String;
612 /// The compiler has several checks to verify that types used in `extern`
613 /// blocks are safe and follow certain rules to ensure proper
614 /// compatibility with the foreign interfaces. This lint is issued when it
615 /// detects a probable mistake in a definition. The lint usually should
616 /// provide a description of the issue, along with possibly a hint on how
620 "proper use of libc types in foreign modules"
623 declare_lint_pass!(ImproperCTypesDeclarations => [IMPROPER_CTYPES]);
626 /// The `improper_ctypes_definitions` lint detects incorrect use of
627 /// [`extern` function] definitions.
629 /// [`extern` function]: https://doc.rust-lang.org/reference/items/functions.html#extern-function-qualifier
634 /// # #![allow(unused)]
635 /// pub extern "C" fn str_type(p: &str) { }
642 /// There are many parameter and return types that may be specified in an
643 /// `extern` function that are not compatible with the given ABI. This
644 /// lint is an alert that these types should not be used. The lint usually
645 /// should provide a description of the issue, along with possibly a hint
646 /// on how to resolve it.
647 IMPROPER_CTYPES_DEFINITIONS,
649 "proper use of libc types in foreign item definitions"
652 declare_lint_pass!(ImproperCTypesDefinitions => [IMPROPER_CTYPES_DEFINITIONS]);
654 #[derive(Clone, Copy)]
655 pub(crate) enum CItemKind {
660 struct ImproperCTypesVisitor<'a, 'tcx> {
661 cx: &'a LateContext<'tcx>,
665 enum FfiResult<'tcx> {
667 FfiPhantom(Ty<'tcx>),
668 FfiUnsafe { ty: Ty<'tcx>, reason: DiagnosticMessage, help: Option<DiagnosticMessage> },
671 pub(crate) fn nonnull_optimization_guaranteed<'tcx>(
673 def: ty::AdtDef<'tcx>,
675 tcx.has_attr(def.did(), sym::rustc_nonnull_optimization_guaranteed)
678 /// `repr(transparent)` structs can have a single non-ZST field, this function returns that
680 pub fn transparent_newtype_field<'a, 'tcx>(
682 variant: &'a ty::VariantDef,
683 ) -> Option<&'a ty::FieldDef> {
684 let param_env = tcx.param_env(variant.def_id);
685 variant.fields.iter().find(|field| {
686 let field_ty = tcx.type_of(field.did);
687 let is_zst = tcx.layout_of(param_env.and(field_ty)).map_or(false, |layout| layout.is_zst());
692 /// Is type known to be non-null?
693 fn ty_is_known_nonnull<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>, mode: CItemKind) -> bool {
696 ty::FnPtr(_) => true,
698 ty::Adt(def, _) if def.is_box() && matches!(mode, CItemKind::Definition) => true,
699 ty::Adt(def, substs) if def.repr().transparent() && !def.is_union() => {
700 let marked_non_null = nonnull_optimization_guaranteed(tcx, *def);
706 // `UnsafeCell` has its niche hidden.
707 if def.is_unsafe_cell() {
713 .filter_map(|variant| transparent_newtype_field(cx.tcx, variant))
714 .any(|field| ty_is_known_nonnull(cx, field.ty(tcx, substs), mode))
720 /// Given a non-null scalar (or transparent) type `ty`, return the nullable version of that type.
721 /// If the type passed in was not scalar, returns None.
722 fn get_nullable_type<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> Option<Ty<'tcx>> {
724 Some(match *ty.kind() {
725 ty::Adt(field_def, field_substs) => {
726 let inner_field_ty = {
727 let first_non_zst_ty = field_def
730 .filter_map(|v| transparent_newtype_field(cx.tcx, v));
732 first_non_zst_ty.clone().count(),
734 "Wrong number of fields for transparent type"
738 .expect("No non-zst fields in transparent type.")
739 .ty(tcx, field_substs)
741 return get_nullable_type(cx, inner_field_ty);
743 ty::Int(ty) => tcx.mk_mach_int(ty),
744 ty::Uint(ty) => tcx.mk_mach_uint(ty),
745 ty::RawPtr(ty_mut) => tcx.mk_ptr(ty_mut),
746 // As these types are always non-null, the nullable equivalent of
747 // Option<T> of these types are their raw pointer counterparts.
748 ty::Ref(_region, ty, mutbl) => tcx.mk_ptr(ty::TypeAndMut { ty, mutbl }),
750 // There is no nullable equivalent for Rust's function pointers -- you
751 // must use an Option<fn(..) -> _> to represent it.
755 // We should only ever reach this case if ty_is_known_nonnull is extended
759 "get_nullable_type: Unhandled scalar kind: {:?} while checking {:?}",
767 /// Check if this enum can be safely exported based on the "nullable pointer optimization". If it
768 /// can, return the type that `ty` can be safely converted to, otherwise return `None`.
769 /// Currently restricted to function pointers, boxes, references, `core::num::NonZero*`,
770 /// `core::ptr::NonNull`, and `#[repr(transparent)]` newtypes.
771 /// FIXME: This duplicates code in codegen.
772 pub(crate) fn repr_nullable_ptr<'tcx>(
773 cx: &LateContext<'tcx>,
776 ) -> Option<Ty<'tcx>> {
777 debug!("is_repr_nullable_ptr(cx, ty = {:?})", ty);
778 if let ty::Adt(ty_def, substs) = ty.kind() {
779 let field_ty = match &ty_def.variants().raw[..] {
780 [var_one, var_two] => match (&var_one.fields[..], &var_two.fields[..]) {
781 ([], [field]) | ([field], []) => field.ty(cx.tcx, substs),
787 if !ty_is_known_nonnull(cx, field_ty, ckind) {
791 // At this point, the field's type is known to be nonnull and the parent enum is Option-like.
792 // If the computed size for the field and the enum are different, the nonnull optimization isn't
793 // being applied (and we've got a problem somewhere).
794 let compute_size_skeleton = |t| SizeSkeleton::compute(t, cx.tcx, cx.param_env).unwrap();
795 if !compute_size_skeleton(ty).same_size(compute_size_skeleton(field_ty)) {
796 bug!("improper_ctypes: Option nonnull optimization not applied?");
799 // Return the nullable type this Option-like enum can be safely represented with.
800 let field_ty_abi = &cx.layout_of(field_ty).unwrap().abi;
801 if let Abi::Scalar(field_ty_scalar) = field_ty_abi {
802 match field_ty_scalar.valid_range(cx) {
803 WrappingRange { start: 0, end }
804 if end == field_ty_scalar.size(&cx.tcx).unsigned_int_max() - 1 =>
806 return Some(get_nullable_type(cx, field_ty).unwrap());
808 WrappingRange { start: 1, .. } => {
809 return Some(get_nullable_type(cx, field_ty).unwrap());
811 WrappingRange { start, end } => {
812 unreachable!("Unhandled start and end range: ({}, {})", start, end)
820 impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
821 /// Check if the type is array and emit an unsafe type lint.
822 fn check_for_array_ty(&mut self, sp: Span, ty: Ty<'tcx>) -> bool {
823 if let ty::Array(..) = ty.kind() {
824 self.emit_ffi_unsafe_type_lint(
827 fluent::lint::improper_ctypes_array_reason,
828 Some(fluent::lint::improper_ctypes_array_help),
836 /// Checks if the given field's type is "ffi-safe".
837 fn check_field_type_for_ffi(
839 cache: &mut FxHashSet<Ty<'tcx>>,
840 field: &ty::FieldDef,
841 substs: SubstsRef<'tcx>,
842 ) -> FfiResult<'tcx> {
843 let field_ty = field.ty(self.cx.tcx, substs);
844 if field_ty.has_opaque_types() {
845 self.check_type_for_ffi(cache, field_ty)
847 let field_ty = self.cx.tcx.normalize_erasing_regions(self.cx.param_env, field_ty);
848 self.check_type_for_ffi(cache, field_ty)
852 /// Checks if the given `VariantDef`'s field types are "ffi-safe".
853 fn check_variant_for_ffi(
855 cache: &mut FxHashSet<Ty<'tcx>>,
857 def: ty::AdtDef<'tcx>,
858 variant: &ty::VariantDef,
859 substs: SubstsRef<'tcx>,
860 ) -> FfiResult<'tcx> {
863 if def.repr().transparent() {
864 // Can assume that at most one field is not a ZST, so only check
865 // that field's type for FFI-safety.
866 if let Some(field) = transparent_newtype_field(self.cx.tcx, variant) {
867 self.check_field_type_for_ffi(cache, field, substs)
869 // All fields are ZSTs; this means that the type should behave
870 // like (), which is FFI-unsafe
871 FfiUnsafe { ty, reason: fluent::lint::improper_ctypes_struct_zst, help: None }
874 // We can't completely trust repr(C) markings; make sure the fields are
876 let mut all_phantom = !variant.fields.is_empty();
877 for field in &variant.fields {
878 match self.check_field_type_for_ffi(cache, &field, substs) {
882 FfiPhantom(..) if def.is_enum() => {
885 reason: fluent::lint::improper_ctypes_enum_phantomdata,
894 if all_phantom { FfiPhantom(ty) } else { FfiSafe }
898 /// Checks if the given type is "ffi-safe" (has a stable, well-defined
899 /// representation which can be exported to C code).
900 fn check_type_for_ffi(&self, cache: &mut FxHashSet<Ty<'tcx>>, ty: Ty<'tcx>) -> FfiResult<'tcx> {
903 let tcx = self.cx.tcx;
905 // Protect against infinite recursion, for example
906 // `struct S(*mut S);`.
907 // FIXME: A recursion limit is necessary as well, for irregular
909 if !cache.insert(ty) {
914 ty::Adt(def, substs) => {
915 if def.is_box() && matches!(self.mode, CItemKind::Definition) {
916 if ty.boxed_ty().is_sized(tcx.at(DUMMY_SP), self.cx.param_env) {
921 reason: fluent::lint::improper_ctypes_box,
926 if def.is_phantom_data() {
927 return FfiPhantom(ty);
929 match def.adt_kind() {
930 AdtKind::Struct | AdtKind::Union => {
931 if !def.repr().c() && !def.repr().transparent() {
934 reason: if def.is_struct() {
935 fluent::lint::improper_ctypes_struct_layout_reason
937 fluent::lint::improper_ctypes_union_layout_reason
939 help: if def.is_struct() {
940 Some(fluent::lint::improper_ctypes_struct_layout_help)
942 Some(fluent::lint::improper_ctypes_union_layout_help)
947 let is_non_exhaustive =
948 def.non_enum_variant().is_field_list_non_exhaustive();
949 if is_non_exhaustive && !def.did().is_local() {
952 reason: if def.is_struct() {
953 fluent::lint::improper_ctypes_struct_non_exhaustive
955 fluent::lint::improper_ctypes_union_non_exhaustive
961 if def.non_enum_variant().fields.is_empty() {
964 reason: if def.is_struct() {
965 fluent::lint::improper_ctypes_struct_fieldless_reason
967 fluent::lint::improper_ctypes_union_fieldless_reason
969 help: if def.is_struct() {
970 Some(fluent::lint::improper_ctypes_struct_fieldless_help)
972 Some(fluent::lint::improper_ctypes_union_fieldless_help)
977 self.check_variant_for_ffi(cache, ty, def, def.non_enum_variant(), substs)
980 if def.variants().is_empty() {
981 // Empty enums are okay... although sort of useless.
985 // Check for a repr() attribute to specify the size of the
987 if !def.repr().c() && !def.repr().transparent() && def.repr().int.is_none()
989 // Special-case types like `Option<extern fn()>`.
990 if repr_nullable_ptr(self.cx, ty, self.mode).is_none() {
993 reason: fluent::lint::improper_ctypes_enum_repr_reason,
994 help: Some(fluent::lint::improper_ctypes_enum_repr_help),
999 if def.is_variant_list_non_exhaustive() && !def.did().is_local() {
1002 reason: fluent::lint::improper_ctypes_non_exhaustive,
1007 // Check the contained variants.
1008 for variant in def.variants() {
1009 let is_non_exhaustive = variant.is_field_list_non_exhaustive();
1010 if is_non_exhaustive && !variant.def_id.is_local() {
1013 reason: fluent::lint::improper_ctypes_non_exhaustive_variant,
1018 match self.check_variant_for_ffi(cache, ty, def, variant, substs) {
1029 ty::Char => FfiUnsafe {
1031 reason: fluent::lint::improper_ctypes_char_reason,
1032 help: Some(fluent::lint::improper_ctypes_char_help),
1035 ty::Int(ty::IntTy::I128) | ty::Uint(ty::UintTy::U128) => {
1036 FfiUnsafe { ty, reason: fluent::lint::improper_ctypes_128bit, help: None }
1039 // Primitive types with a stable representation.
1040 ty::Bool | ty::Int(..) | ty::Uint(..) | ty::Float(..) | ty::Never => FfiSafe,
1042 ty::Slice(_) => FfiUnsafe {
1044 reason: fluent::lint::improper_ctypes_slice_reason,
1045 help: Some(fluent::lint::improper_ctypes_slice_help),
1048 ty::Dynamic(..) => {
1049 FfiUnsafe { ty, reason: fluent::lint::improper_ctypes_dyn, help: None }
1052 ty::Str => FfiUnsafe {
1054 reason: fluent::lint::improper_ctypes_str_reason,
1055 help: Some(fluent::lint::improper_ctypes_str_help),
1058 ty::Tuple(..) => FfiUnsafe {
1060 reason: fluent::lint::improper_ctypes_tuple_reason,
1061 help: Some(fluent::lint::improper_ctypes_tuple_help),
1064 ty::RawPtr(ty::TypeAndMut { ty, .. }) | ty::Ref(_, ty, _)
1066 matches!(self.mode, CItemKind::Definition)
1067 && ty.is_sized(self.cx.tcx.at(DUMMY_SP), self.cx.param_env)
1073 ty::RawPtr(ty::TypeAndMut { ty, .. })
1074 if match ty.kind() {
1075 ty::Tuple(tuple) => tuple.is_empty(),
1082 ty::RawPtr(ty::TypeAndMut { ty, .. }) | ty::Ref(_, ty, _) => {
1083 self.check_type_for_ffi(cache, ty)
1086 ty::Array(inner_ty, _) => self.check_type_for_ffi(cache, inner_ty),
1089 if self.is_internal_abi(sig.abi()) {
1092 reason: fluent::lint::improper_ctypes_fnptr_reason,
1093 help: Some(fluent::lint::improper_ctypes_fnptr_help),
1097 let sig = tcx.erase_late_bound_regions(sig);
1098 if !sig.output().is_unit() {
1099 let r = self.check_type_for_ffi(cache, sig.output());
1107 for arg in sig.inputs() {
1108 let r = self.check_type_for_ffi(cache, *arg);
1119 ty::Foreign(..) => FfiSafe,
1121 // While opaque types are checked for earlier, if a projection in a struct field
1122 // normalizes to an opaque type, then it will reach this branch.
1124 FfiUnsafe { ty, reason: fluent::lint::improper_ctypes_opaque, help: None }
1127 // `extern "C" fn` functions can have type parameters, which may or may not be FFI-safe,
1128 // so they are currently ignored for the purposes of this lint.
1129 ty::Param(..) | ty::Projection(..) if matches!(self.mode, CItemKind::Definition) => {
1134 | ty::Projection(..)
1140 | ty::GeneratorWitness(..)
1141 | ty::Placeholder(..)
1142 | ty::FnDef(..) => bug!("unexpected type in foreign function: {:?}", ty),
1146 fn emit_ffi_unsafe_type_lint(
1150 note: DiagnosticMessage,
1151 help: Option<DiagnosticMessage>,
1153 let lint = match self.mode {
1154 CItemKind::Declaration => IMPROPER_CTYPES,
1155 CItemKind::Definition => IMPROPER_CTYPES_DEFINITIONS,
1158 self.cx.struct_span_lint(lint, sp, |lint| {
1159 let item_description = match self.mode {
1160 CItemKind::Declaration => "block",
1161 CItemKind::Definition => "fn",
1163 let mut diag = lint.build(fluent::lint::improper_ctypes);
1164 diag.set_arg("ty", ty);
1165 diag.set_arg("desc", item_description);
1166 diag.span_label(sp, fluent::lint::label);
1167 if let Some(help) = help {
1171 if let ty::Adt(def, _) = ty.kind() {
1172 if let Some(sp) = self.cx.tcx.hir().span_if_local(def.did()) {
1173 diag.span_note(sp, fluent::lint::note);
1180 fn check_for_opaque_ty(&mut self, sp: Span, ty: Ty<'tcx>) -> bool {
1181 struct ProhibitOpaqueTypes<'a, 'tcx> {
1182 cx: &'a LateContext<'tcx>,
1185 impl<'a, 'tcx> ty::visit::TypeVisitor<'tcx> for ProhibitOpaqueTypes<'a, 'tcx> {
1186 type BreakTy = Ty<'tcx>;
1188 fn visit_ty(&mut self, ty: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
1190 ty::Opaque(..) => ControlFlow::Break(ty),
1191 // Consider opaque types within projections FFI-safe if they do not normalize
1192 // to more opaque types.
1193 ty::Projection(..) => {
1194 let ty = self.cx.tcx.normalize_erasing_regions(self.cx.param_env, ty);
1196 // If `ty` is an opaque type directly then `super_visit_with` won't invoke
1197 // this function again.
1198 if ty.has_opaque_types() {
1201 ControlFlow::CONTINUE
1204 _ => ty.super_visit_with(self),
1209 if let Some(ty) = ty.visit_with(&mut ProhibitOpaqueTypes { cx: self.cx }).break_value() {
1210 self.emit_ffi_unsafe_type_lint(ty, sp, fluent::lint::improper_ctypes_opaque, None);
1217 fn check_type_for_ffi_and_report_errors(
1222 is_return_type: bool,
1224 // We have to check for opaque types before `normalize_erasing_regions`,
1225 // which will replace opaque types with their underlying concrete type.
1226 if self.check_for_opaque_ty(sp, ty) {
1227 // We've already emitted an error due to an opaque type.
1231 // it is only OK to use this function because extern fns cannot have
1232 // any generic types right now:
1233 let ty = self.cx.tcx.normalize_erasing_regions(self.cx.param_env, ty);
1235 // C doesn't really support passing arrays by value - the only way to pass an array by value
1236 // is through a struct. So, first test that the top level isn't an array, and then
1237 // recursively check the types inside.
1238 if !is_static && self.check_for_array_ty(sp, ty) {
1242 // Don't report FFI errors for unit return types. This check exists here, and not in
1243 // `check_foreign_fn` (where it would make more sense) so that normalization has definitely
1245 if is_return_type && ty.is_unit() {
1249 match self.check_type_for_ffi(&mut FxHashSet::default(), ty) {
1250 FfiResult::FfiSafe => {}
1251 FfiResult::FfiPhantom(ty) => {
1252 self.emit_ffi_unsafe_type_lint(
1255 fluent::lint::improper_ctypes_only_phantomdata,
1259 // If `ty` is a `repr(transparent)` newtype, and the non-zero-sized type is a generic
1260 // argument, which after substitution, is `()`, then this branch can be hit.
1261 FfiResult::FfiUnsafe { ty, .. } if is_return_type && ty.is_unit() => {}
1262 FfiResult::FfiUnsafe { ty, reason, help } => {
1263 self.emit_ffi_unsafe_type_lint(ty, sp, reason, help);
1268 fn check_foreign_fn(&mut self, id: hir::HirId, decl: &hir::FnDecl<'_>) {
1269 let def_id = self.cx.tcx.hir().local_def_id(id);
1270 let sig = self.cx.tcx.fn_sig(def_id);
1271 let sig = self.cx.tcx.erase_late_bound_regions(sig);
1273 for (input_ty, input_hir) in iter::zip(sig.inputs(), decl.inputs) {
1274 self.check_type_for_ffi_and_report_errors(input_hir.span, *input_ty, false, false);
1277 if let hir::FnRetTy::Return(ref ret_hir) = decl.output {
1278 let ret_ty = sig.output();
1279 self.check_type_for_ffi_and_report_errors(ret_hir.span, ret_ty, false, true);
1283 fn check_foreign_static(&mut self, id: hir::HirId, span: Span) {
1284 let def_id = self.cx.tcx.hir().local_def_id(id);
1285 let ty = self.cx.tcx.type_of(def_id);
1286 self.check_type_for_ffi_and_report_errors(span, ty, true, false);
1289 fn is_internal_abi(&self, abi: SpecAbi) -> bool {
1292 SpecAbi::Rust | SpecAbi::RustCall | SpecAbi::RustIntrinsic | SpecAbi::PlatformIntrinsic
1297 impl<'tcx> LateLintPass<'tcx> for ImproperCTypesDeclarations {
1298 fn check_foreign_item(&mut self, cx: &LateContext<'_>, it: &hir::ForeignItem<'_>) {
1299 let mut vis = ImproperCTypesVisitor { cx, mode: CItemKind::Declaration };
1300 let abi = cx.tcx.hir().get_foreign_abi(it.hir_id());
1302 if !vis.is_internal_abi(abi) {
1304 hir::ForeignItemKind::Fn(ref decl, _, _) => {
1305 vis.check_foreign_fn(it.hir_id(), decl);
1307 hir::ForeignItemKind::Static(ref ty, _) => {
1308 vis.check_foreign_static(it.hir_id(), ty.span);
1310 hir::ForeignItemKind::Type => (),
1316 impl<'tcx> LateLintPass<'tcx> for ImproperCTypesDefinitions {
1319 cx: &LateContext<'tcx>,
1320 kind: hir::intravisit::FnKind<'tcx>,
1321 decl: &'tcx hir::FnDecl<'_>,
1322 _: &'tcx hir::Body<'_>,
1326 use hir::intravisit::FnKind;
1328 let abi = match kind {
1329 FnKind::ItemFn(_, _, header, ..) => header.abi,
1330 FnKind::Method(_, sig, ..) => sig.header.abi,
1334 let mut vis = ImproperCTypesVisitor { cx, mode: CItemKind::Definition };
1335 if !vis.is_internal_abi(abi) {
1336 vis.check_foreign_fn(hir_id, decl);
1341 declare_lint_pass!(VariantSizeDifferences => [VARIANT_SIZE_DIFFERENCES]);
1343 impl<'tcx> LateLintPass<'tcx> for VariantSizeDifferences {
1344 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1345 if let hir::ItemKind::Enum(ref enum_definition, _) = it.kind {
1346 let t = cx.tcx.type_of(it.def_id);
1347 let ty = cx.tcx.erase_regions(t);
1348 let Ok(layout) = cx.layout_of(ty) else { return };
1349 let Variants::Multiple {
1350 tag_encoding: TagEncoding::Direct, tag, ref variants, ..
1351 } = &layout.variants else {
1355 let tag_size = tag.size(&cx.tcx).bytes();
1358 "enum `{}` is {} bytes large with layout:\n{:#?}",
1360 layout.size.bytes(),
1364 let (largest, slargest, largest_index) = iter::zip(enum_definition.variants, variants)
1365 .map(|(variant, variant_layout)| {
1366 // Subtract the size of the enum tag.
1367 let bytes = variant_layout.size().bytes().saturating_sub(tag_size);
1369 debug!("- variant `{}` is {} bytes large", variant.ident, bytes);
1373 .fold((0, 0, 0), |(l, s, li), (idx, size)| {
1376 } else if size > s {
1383 // We only warn if the largest variant is at least thrice as large as
1384 // the second-largest.
1385 if largest > slargest * 3 && slargest > 0 {
1386 cx.struct_span_lint(
1387 VARIANT_SIZE_DIFFERENCES,
1388 enum_definition.variants[largest_index].span,
1390 lint.build(fluent::lint::variant_size_differences)
1391 .set_arg("largest", largest)
1401 /// The `invalid_atomic_ordering` lint detects passing an `Ordering`
1402 /// to an atomic operation that does not support that ordering.
1406 /// ```rust,compile_fail
1407 /// # use core::sync::atomic::{AtomicU8, Ordering};
1408 /// let atom = AtomicU8::new(0);
1409 /// let value = atom.load(Ordering::Release);
1410 /// # let _ = value;
1417 /// Some atomic operations are only supported for a subset of the
1418 /// `atomic::Ordering` variants. Passing an unsupported variant will cause
1419 /// an unconditional panic at runtime, which is detected by this lint.
1421 /// This lint will trigger in the following cases: (where `AtomicType` is an
1422 /// atomic type from `core::sync::atomic`, such as `AtomicBool`,
1423 /// `AtomicPtr`, `AtomicUsize`, or any of the other integer atomics).
1425 /// - Passing `Ordering::Acquire` or `Ordering::AcqRel` to
1426 /// `AtomicType::store`.
1428 /// - Passing `Ordering::Release` or `Ordering::AcqRel` to
1429 /// `AtomicType::load`.
1431 /// - Passing `Ordering::Relaxed` to `core::sync::atomic::fence` or
1432 /// `core::sync::atomic::compiler_fence`.
1434 /// - Passing `Ordering::Release` or `Ordering::AcqRel` as the failure
1435 /// ordering for any of `AtomicType::compare_exchange`,
1436 /// `AtomicType::compare_exchange_weak`, or `AtomicType::fetch_update`.
1437 INVALID_ATOMIC_ORDERING,
1439 "usage of invalid atomic ordering in atomic operations and memory fences"
1442 declare_lint_pass!(InvalidAtomicOrdering => [INVALID_ATOMIC_ORDERING]);
1444 impl InvalidAtomicOrdering {
1445 fn inherent_atomic_method_call<'hir>(
1446 cx: &LateContext<'_>,
1448 recognized_names: &[Symbol], // used for fast path calculation
1449 ) -> Option<(Symbol, &'hir [Expr<'hir>])> {
1450 const ATOMIC_TYPES: &[Symbol] = &[
1466 if let ExprKind::MethodCall(ref method_path, args, _) = &expr.kind
1467 && recognized_names.contains(&method_path.ident.name)
1468 && let Some(m_def_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id)
1469 && let Some(impl_did) = cx.tcx.impl_of_method(m_def_id)
1470 && let Some(adt) = cx.tcx.type_of(impl_did).ty_adt_def()
1471 // skip extension traits, only lint functions from the standard library
1472 && cx.tcx.trait_id_of_impl(impl_did).is_none()
1473 && let parent = cx.tcx.parent(adt.did())
1474 && cx.tcx.is_diagnostic_item(sym::atomic_mod, parent)
1475 && ATOMIC_TYPES.contains(&cx.tcx.item_name(adt.did()))
1477 return Some((method_path.ident.name, args));
1482 fn match_ordering(cx: &LateContext<'_>, ord_arg: &Expr<'_>) -> Option<Symbol> {
1483 let ExprKind::Path(ref ord_qpath) = ord_arg.kind else { return None };
1484 let did = cx.qpath_res(ord_qpath, ord_arg.hir_id).opt_def_id()?;
1486 let atomic_ordering = tcx.get_diagnostic_item(sym::Ordering);
1487 let name = tcx.item_name(did);
1488 let parent = tcx.parent(did);
1489 [sym::Relaxed, sym::Release, sym::Acquire, sym::AcqRel, sym::SeqCst].into_iter().find(
1492 && (Some(parent) == atomic_ordering
1493 // needed in case this is a ctor, not a variant
1494 || tcx.opt_parent(parent) == atomic_ordering)
1499 fn check_atomic_load_store(cx: &LateContext<'_>, expr: &Expr<'_>) {
1500 if let Some((method, args)) = Self::inherent_atomic_method_call(cx, expr, &[sym::load, sym::store])
1501 && let Some((ordering_arg, invalid_ordering)) = match method {
1502 sym::load => Some((&args[1], sym::Release)),
1503 sym::store => Some((&args[2], sym::Acquire)),
1506 && let Some(ordering) = Self::match_ordering(cx, ordering_arg)
1507 && (ordering == invalid_ordering || ordering == sym::AcqRel)
1509 cx.struct_span_lint(INVALID_ATOMIC_ORDERING, ordering_arg.span, |diag| {
1510 if method == sym::load {
1511 diag.build(fluent::lint::atomic_ordering_load)
1512 .help(fluent::lint::help)
1515 debug_assert_eq!(method, sym::store);
1516 diag.build(fluent::lint::atomic_ordering_store)
1517 .help(fluent::lint::help)
1524 fn check_memory_fence(cx: &LateContext<'_>, expr: &Expr<'_>) {
1525 if let ExprKind::Call(ref func, ref args) = expr.kind
1526 && let ExprKind::Path(ref func_qpath) = func.kind
1527 && let Some(def_id) = cx.qpath_res(func_qpath, func.hir_id).opt_def_id()
1528 && matches!(cx.tcx.get_diagnostic_name(def_id), Some(sym::fence | sym::compiler_fence))
1529 && Self::match_ordering(cx, &args[0]) == Some(sym::Relaxed)
1531 cx.struct_span_lint(INVALID_ATOMIC_ORDERING, args[0].span, |diag| {
1532 diag.build(fluent::lint::atomic_ordering_fence)
1533 .help(fluent::lint::help)
1539 fn check_atomic_compare_exchange(cx: &LateContext<'_>, expr: &Expr<'_>) {
1540 let Some((method, args)) = Self::inherent_atomic_method_call(cx, expr, &[sym::fetch_update, sym::compare_exchange, sym::compare_exchange_weak])
1543 let fail_order_arg = match method {
1544 sym::fetch_update => &args[2],
1545 sym::compare_exchange | sym::compare_exchange_weak => &args[4],
1549 let Some(fail_ordering) = Self::match_ordering(cx, fail_order_arg) else { return };
1551 if matches!(fail_ordering, sym::Release | sym::AcqRel) {
1552 #[derive(LintDiagnostic)]
1553 #[lint(lint::atomic_ordering_invalid)]
1555 struct InvalidAtomicOrderingDiag {
1558 fail_order_arg_span: Span,
1561 cx.emit_spanned_lint(
1562 INVALID_ATOMIC_ORDERING,
1563 fail_order_arg.span,
1564 InvalidAtomicOrderingDiag { method, fail_order_arg_span: fail_order_arg.span },
1570 impl<'tcx> LateLintPass<'tcx> for InvalidAtomicOrdering {
1571 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
1572 Self::check_atomic_load_store(cx, expr);
1573 Self::check_memory_fence(cx, expr);
1574 Self::check_atomic_compare_exchange(cx, expr);