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};
15 use rustc_target::abi::{Abi, Size, WrappingRange};
16 use rustc_target::abi::{Integer, TagEncoding, Variants};
17 use rustc_target::spec::abi::Abi as SpecAbi;
20 use std::ops::ControlFlow;
23 /// The `unused_comparisons` lint detects comparisons made useless by
24 /// limits of the types involved.
38 /// A useless comparison may indicate a mistake, and should be fixed or
42 "comparisons made useless by limits of the types involved"
46 /// The `overflowing_literals` lint detects literal out of range for its
51 /// ```rust,compile_fail
59 /// It is usually a mistake to use a literal that overflows the type where
60 /// it is used. Either use a literal that is within range, or change the
61 /// type to be within the range of the literal.
64 "literal out of range for its type"
68 /// The `variant_size_differences` lint detects enums with widely varying
73 /// ```rust,compile_fail
74 /// #![deny(variant_size_differences)]
85 /// It can be a mistake to add a variant to an enum that is much larger
86 /// than the other variants, bloating the overall size required for all
87 /// variants. This can impact performance and memory usage. This is
88 /// triggered if one variant is more than 3 times larger than the
89 /// second-largest variant.
91 /// Consider placing the large variant's contents on the heap (for example
92 /// via [`Box`]) to keep the overall size of the enum itself down.
94 /// This lint is "allow" by default because it can be noisy, and may not be
95 /// an actual problem. Decisions about this should be guided with
96 /// profiling and benchmarking.
98 /// [`Box`]: https://doc.rust-lang.org/std/boxed/index.html
99 VARIANT_SIZE_DIFFERENCES,
101 "detects enums with widely varying variant sizes"
104 #[derive(Copy, Clone)]
105 pub struct TypeLimits {
106 /// Id of the last visited negated expression
107 negated_expr_id: Option<hir::HirId>,
110 impl_lint_pass!(TypeLimits => [UNUSED_COMPARISONS, OVERFLOWING_LITERALS]);
113 pub fn new() -> TypeLimits {
114 TypeLimits { negated_expr_id: None }
118 /// Attempts to special-case the overflowing literal lint when it occurs as a range endpoint (`expr..MAX+1`).
119 /// Returns `true` iff the lint was emitted.
120 fn lint_overflowing_range_endpoint<'tcx>(
121 cx: &LateContext<'tcx>,
125 expr: &'tcx hir::Expr<'tcx>,
128 // We only want to handle exclusive (`..`) ranges,
129 // which are represented as `ExprKind::Struct`.
130 let par_id = cx.tcx.hir().get_parent_node(expr.hir_id);
131 let Node::ExprField(field) = cx.tcx.hir().get(par_id) else { return false };
132 let field_par_id = cx.tcx.hir().get_parent_node(field.hir_id);
133 let Node::Expr(struct_expr) = cx.tcx.hir().get(field_par_id) else { return false };
134 if !is_range_literal(struct_expr) {
137 let ExprKind::Struct(_, eps, _) = &struct_expr.kind else { return false };
142 // We can suggest using an inclusive range
143 // (`..=`) instead only if it is the `end` that is
144 // overflowing and only by 1.
145 if !(eps[1].expr.hir_id == expr.hir_id && lit_val - 1 == max) {
148 let Ok(start) = cx.sess().source_map().span_to_snippet(eps[0].span) else { return false };
151 OVERFLOWING_LITERALS,
153 fluent::lint_range_endpoint_out_of_range,
155 use ast::{LitIntType, LitKind};
157 lint.set_arg("ty", ty);
159 // We need to preserve the literal's suffix,
160 // as it may determine typing information.
161 let suffix = match lit.node {
162 LitKind::Int(_, LitIntType::Signed(s)) => s.name_str(),
163 LitKind::Int(_, LitIntType::Unsigned(s)) => s.name_str(),
164 LitKind::Int(_, LitIntType::Unsuffixed) => "",
167 let suggestion = format!("{}..={}{}", start, lit_val - 1, suffix);
168 lint.span_suggestion(
172 Applicability::MachineApplicable,
179 // We've just emitted a lint, special cased for `(...)..MAX+1` ranges,
180 // return `true` so the callers don't also emit a lint
184 // For `isize` & `usize`, be conservative with the warnings, so that the
185 // warnings are consistent between 32- and 64-bit platforms.
186 fn int_ty_range(int_ty: ty::IntTy) -> (i128, i128) {
188 ty::IntTy::Isize => (i64::MIN.into(), i64::MAX.into()),
189 ty::IntTy::I8 => (i8::MIN.into(), i8::MAX.into()),
190 ty::IntTy::I16 => (i16::MIN.into(), i16::MAX.into()),
191 ty::IntTy::I32 => (i32::MIN.into(), i32::MAX.into()),
192 ty::IntTy::I64 => (i64::MIN.into(), i64::MAX.into()),
193 ty::IntTy::I128 => (i128::MIN, i128::MAX),
197 fn uint_ty_range(uint_ty: ty::UintTy) -> (u128, u128) {
198 let max = match uint_ty {
199 ty::UintTy::Usize => u64::MAX.into(),
200 ty::UintTy::U8 => u8::MAX.into(),
201 ty::UintTy::U16 => u16::MAX.into(),
202 ty::UintTy::U32 => u32::MAX.into(),
203 ty::UintTy::U64 => u64::MAX.into(),
204 ty::UintTy::U128 => u128::MAX,
209 fn get_bin_hex_repr(cx: &LateContext<'_>, lit: &hir::Lit) -> Option<String> {
210 let src = cx.sess().source_map().span_to_snippet(lit.span).ok()?;
211 let firstch = src.chars().next()?;
214 match src.chars().nth(1) {
215 Some('x' | 'b') => return Some(src),
223 fn report_bin_hex_error(
224 cx: &LateContext<'_>,
225 expr: &hir::Expr<'_>,
233 OVERFLOWING_LITERALS,
235 fluent::lint_overflowing_bin_hex,
237 let (t, actually) = match ty {
238 attr::IntType::SignedInt(t) => {
239 let actually = if negative {
240 -(size.sign_extend(val) as i128)
242 size.sign_extend(val) as i128
244 (t.name_str(), actually.to_string())
246 attr::IntType::UnsignedInt(t) => {
247 let actually = size.truncate(val);
248 (t.name_str(), actually.to_string())
253 // If the value is negative,
254 // emits a note about the value itself, apart from the literal.
255 lint.note(fluent::negative_note);
256 lint.note(fluent::negative_becomes_note);
258 lint.note(fluent::positive_note);
260 if let Some(sugg_ty) =
261 get_type_suggestion(cx.typeck_results().node_type(expr.hir_id), val, negative)
263 lint.set_arg("suggestion_ty", sugg_ty);
264 if let Some(pos) = repr_str.chars().position(|c| c == 'i' || c == 'u') {
265 let (sans_suffix, _) = repr_str.split_at(pos);
266 lint.span_suggestion(
269 format!("{}{}", sans_suffix, sugg_ty),
270 Applicability::MachineApplicable,
273 lint.help(fluent::help);
276 lint.set_arg("ty", t)
277 .set_arg("lit", repr_str)
279 .set_arg("actually", actually);
286 // This function finds the next fitting type and generates a suggestion string.
287 // It searches for fitting types in the following way (`X < Y`):
288 // - `iX`: if literal fits in `uX` => `uX`, else => `iY`
292 // No suggestion for: `isize`, `usize`.
293 fn get_type_suggestion(t: Ty<'_>, val: u128, negative: bool) -> Option<&'static str> {
296 macro_rules! find_fit {
297 ($ty:expr, $val:expr, $negative:expr,
298 $($type:ident => [$($utypes:expr),*] => [$($itypes:expr),*]),+) => {
300 let _neg = if negative { 1 } else { 0 };
303 $(if !negative && val <= uint_ty_range($utypes).1 {
304 return Some($utypes.name_str())
306 $(if val <= int_ty_range($itypes).1 as u128 + _neg {
307 return Some($itypes.name_str())
317 ty::Int(i) => find_fit!(i, val, negative,
318 I8 => [U8] => [I16, I32, I64, I128],
319 I16 => [U16] => [I32, I64, I128],
320 I32 => [U32] => [I64, I128],
321 I64 => [U64] => [I128],
322 I128 => [U128] => []),
323 ty::Uint(u) => find_fit!(u, val, negative,
324 U8 => [U8, U16, U32, U64, U128] => [],
325 U16 => [U16, U32, U64, U128] => [],
326 U32 => [U32, U64, U128] => [],
327 U64 => [U64, U128] => [],
328 U128 => [U128] => []),
333 fn lint_int_literal<'tcx>(
334 cx: &LateContext<'tcx>,
335 type_limits: &TypeLimits,
336 e: &'tcx hir::Expr<'tcx>,
341 let int_type = t.normalize(cx.sess().target.pointer_width);
342 let (min, max) = int_ty_range(int_type);
343 let max = max as u128;
344 let negative = type_limits.negated_expr_id == Some(e.hir_id);
346 // Detect literal value out of range [min, max] inclusive
347 // avoiding use of -min to prevent overflow/panic
348 if (negative && v > max + 1) || (!negative && v > max) {
349 if let Some(repr_str) = get_bin_hex_repr(cx, lit) {
350 report_bin_hex_error(
353 attr::IntType::SignedInt(ty::ast_int_ty(t)),
354 Integer::from_int_ty(cx, t).size(),
362 if lint_overflowing_range_endpoint(cx, lit, v, max, e, t.name_str()) {
363 // The overflowing literal lint was emitted by `lint_overflowing_range_endpoint`.
367 cx.struct_span_lint(OVERFLOWING_LITERALS, e.span, fluent::lint_overflowing_int, |lint| {
368 lint.set_arg("ty", t.name_str())
373 .span_to_snippet(lit.span)
374 .expect("must get snippet from literal"),
380 if let Some(sugg_ty) =
381 get_type_suggestion(cx.typeck_results().node_type(e.hir_id), v, negative)
383 lint.set_arg("suggestion_ty", sugg_ty);
384 lint.help(fluent::help);
392 fn lint_uint_literal<'tcx>(
393 cx: &LateContext<'tcx>,
394 e: &'tcx hir::Expr<'tcx>,
398 let uint_type = t.normalize(cx.sess().target.pointer_width);
399 let (min, max) = uint_ty_range(uint_type);
400 let lit_val: u128 = match lit.node {
401 // _v is u8, within range by definition
402 ast::LitKind::Byte(_v) => return,
403 ast::LitKind::Int(v, _) => v,
406 if lit_val < min || lit_val > max {
407 let parent_id = cx.tcx.hir().get_parent_node(e.hir_id);
408 if let Node::Expr(par_e) = cx.tcx.hir().get(parent_id) {
410 hir::ExprKind::Cast(..) => {
411 if let ty::Char = cx.typeck_results().expr_ty(par_e).kind() {
413 OVERFLOWING_LITERALS,
415 fluent::lint_only_cast_u8_to_char,
417 lint.span_suggestion(
420 format!("'\\u{{{:X}}}'", lit_val),
421 Applicability::MachineApplicable,
431 if lint_overflowing_range_endpoint(cx, lit, lit_val, max, e, t.name_str()) {
432 // The overflowing literal lint was emitted by `lint_overflowing_range_endpoint`.
435 if let Some(repr_str) = get_bin_hex_repr(cx, lit) {
436 report_bin_hex_error(
439 attr::IntType::UnsignedInt(ty::ast_uint_ty(t)),
440 Integer::from_uint_ty(cx, t).size(),
447 cx.struct_span_lint(OVERFLOWING_LITERALS, e.span, fluent::lint_overflowing_uint, |lint| {
448 lint.set_arg("ty", t.name_str())
453 .span_to_snippet(lit.span)
454 .expect("must get snippet from literal"),
463 fn lint_literal<'tcx>(
464 cx: &LateContext<'tcx>,
465 type_limits: &TypeLimits,
466 e: &'tcx hir::Expr<'tcx>,
469 match *cx.typeck_results().node_type(e.hir_id).kind() {
472 ast::LitKind::Int(v, ast::LitIntType::Signed(_) | ast::LitIntType::Unsuffixed) => {
473 lint_int_literal(cx, type_limits, e, lit, t, v)
478 ty::Uint(t) => lint_uint_literal(cx, e, lit, t),
480 let is_infinite = match lit.node {
481 ast::LitKind::Float(v, _) => match t {
482 ty::FloatTy::F32 => v.as_str().parse().map(f32::is_infinite),
483 ty::FloatTy::F64 => v.as_str().parse().map(f64::is_infinite),
487 if is_infinite == Ok(true) {
489 OVERFLOWING_LITERALS,
491 fluent::lint_overflowing_literal,
493 lint.set_arg("ty", t.name_str())
498 .span_to_snippet(lit.span)
499 .expect("must get snippet from literal"),
510 impl<'tcx> LateLintPass<'tcx> for TypeLimits {
511 fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx hir::Expr<'tcx>) {
513 hir::ExprKind::Unary(hir::UnOp::Neg, ref expr) => {
514 // propagate negation, if the negation itself isn't negated
515 if self.negated_expr_id != Some(e.hir_id) {
516 self.negated_expr_id = Some(expr.hir_id);
519 hir::ExprKind::Binary(binop, ref l, ref r) => {
520 if is_comparison(binop) && !check_limits(cx, binop, &l, &r) {
524 fluent::lint_unused_comparisons,
529 hir::ExprKind::Lit(ref lit) => lint_literal(cx, self, e, lit),
533 fn is_valid<T: PartialOrd>(binop: hir::BinOp, v: T, min: T, max: T) -> bool {
535 hir::BinOpKind::Lt => v > min && v <= max,
536 hir::BinOpKind::Le => v >= min && v < max,
537 hir::BinOpKind::Gt => v >= min && v < max,
538 hir::BinOpKind::Ge => v > min && v <= max,
539 hir::BinOpKind::Eq | hir::BinOpKind::Ne => v >= min && v <= max,
544 fn rev_binop(binop: hir::BinOp) -> hir::BinOp {
548 hir::BinOpKind::Lt => hir::BinOpKind::Gt,
549 hir::BinOpKind::Le => hir::BinOpKind::Ge,
550 hir::BinOpKind::Gt => hir::BinOpKind::Lt,
551 hir::BinOpKind::Ge => hir::BinOpKind::Le,
558 cx: &LateContext<'_>,
563 let (lit, expr, swap) = match (&l.kind, &r.kind) {
564 (&hir::ExprKind::Lit(_), _) => (l, r, true),
565 (_, &hir::ExprKind::Lit(_)) => (r, l, false),
568 // Normalize the binop so that the literal is always on the RHS in
570 let norm_binop = if swap { rev_binop(binop) } else { binop };
571 match *cx.typeck_results().node_type(expr.hir_id).kind() {
573 let (min, max) = int_ty_range(int_ty);
574 let lit_val: i128 = match lit.kind {
575 hir::ExprKind::Lit(ref li) => match li.node {
578 ast::LitIntType::Signed(_) | ast::LitIntType::Unsuffixed,
584 is_valid(norm_binop, lit_val, min, max)
586 ty::Uint(uint_ty) => {
587 let (min, max): (u128, u128) = uint_ty_range(uint_ty);
588 let lit_val: u128 = match lit.kind {
589 hir::ExprKind::Lit(ref li) => match li.node {
590 ast::LitKind::Int(v, _) => v,
595 is_valid(norm_binop, lit_val, min, max)
601 fn is_comparison(binop: hir::BinOp) -> bool {
616 /// The `improper_ctypes` lint detects incorrect use of types in foreign
623 /// static STATIC: String;
631 /// The compiler has several checks to verify that types used in `extern`
632 /// blocks are safe and follow certain rules to ensure proper
633 /// compatibility with the foreign interfaces. This lint is issued when it
634 /// detects a probable mistake in a definition. The lint usually should
635 /// provide a description of the issue, along with possibly a hint on how
639 "proper use of libc types in foreign modules"
642 declare_lint_pass!(ImproperCTypesDeclarations => [IMPROPER_CTYPES]);
645 /// The `improper_ctypes_definitions` lint detects incorrect use of
646 /// [`extern` function] definitions.
648 /// [`extern` function]: https://doc.rust-lang.org/reference/items/functions.html#extern-function-qualifier
653 /// # #![allow(unused)]
654 /// pub extern "C" fn str_type(p: &str) { }
661 /// There are many parameter and return types that may be specified in an
662 /// `extern` function that are not compatible with the given ABI. This
663 /// lint is an alert that these types should not be used. The lint usually
664 /// should provide a description of the issue, along with possibly a hint
665 /// on how to resolve it.
666 IMPROPER_CTYPES_DEFINITIONS,
668 "proper use of libc types in foreign item definitions"
671 declare_lint_pass!(ImproperCTypesDefinitions => [IMPROPER_CTYPES_DEFINITIONS]);
673 #[derive(Clone, Copy)]
674 pub(crate) enum CItemKind {
679 struct ImproperCTypesVisitor<'a, 'tcx> {
680 cx: &'a LateContext<'tcx>,
684 enum FfiResult<'tcx> {
686 FfiPhantom(Ty<'tcx>),
687 FfiUnsafe { ty: Ty<'tcx>, reason: DiagnosticMessage, help: Option<DiagnosticMessage> },
690 pub(crate) fn nonnull_optimization_guaranteed<'tcx>(
692 def: ty::AdtDef<'tcx>,
694 tcx.has_attr(def.did(), sym::rustc_nonnull_optimization_guaranteed)
697 /// `repr(transparent)` structs can have a single non-ZST field, this function returns that
699 pub fn transparent_newtype_field<'a, 'tcx>(
701 variant: &'a ty::VariantDef,
702 ) -> Option<&'a ty::FieldDef> {
703 let param_env = tcx.param_env(variant.def_id);
704 variant.fields.iter().find(|field| {
705 let field_ty = tcx.type_of(field.did);
706 let is_zst = tcx.layout_of(param_env.and(field_ty)).map_or(false, |layout| layout.is_zst());
711 /// Is type known to be non-null?
712 fn ty_is_known_nonnull<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>, mode: CItemKind) -> bool {
715 ty::FnPtr(_) => true,
717 ty::Adt(def, _) if def.is_box() && matches!(mode, CItemKind::Definition) => true,
718 ty::Adt(def, substs) if def.repr().transparent() && !def.is_union() => {
719 let marked_non_null = nonnull_optimization_guaranteed(tcx, *def);
725 // `UnsafeCell` has its niche hidden.
726 if def.is_unsafe_cell() {
732 .filter_map(|variant| transparent_newtype_field(cx.tcx, variant))
733 .any(|field| ty_is_known_nonnull(cx, field.ty(tcx, substs), mode))
739 /// Given a non-null scalar (or transparent) type `ty`, return the nullable version of that type.
740 /// If the type passed in was not scalar, returns None.
741 fn get_nullable_type<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> Option<Ty<'tcx>> {
743 Some(match *ty.kind() {
744 ty::Adt(field_def, field_substs) => {
745 let inner_field_ty = {
746 let mut first_non_zst_ty = field_def
749 .filter_map(|v| transparent_newtype_field(cx.tcx, v));
751 first_non_zst_ty.clone().count(),
753 "Wrong number of fields for transparent type"
757 .expect("No non-zst fields in transparent type.")
758 .ty(tcx, field_substs)
760 return get_nullable_type(cx, inner_field_ty);
762 ty::Int(ty) => tcx.mk_mach_int(ty),
763 ty::Uint(ty) => tcx.mk_mach_uint(ty),
764 ty::RawPtr(ty_mut) => tcx.mk_ptr(ty_mut),
765 // As these types are always non-null, the nullable equivalent of
766 // Option<T> of these types are their raw pointer counterparts.
767 ty::Ref(_region, ty, mutbl) => tcx.mk_ptr(ty::TypeAndMut { ty, mutbl }),
769 // There is no nullable equivalent for Rust's function pointers -- you
770 // must use an Option<fn(..) -> _> to represent it.
774 // We should only ever reach this case if ty_is_known_nonnull is extended
778 "get_nullable_type: Unhandled scalar kind: {:?} while checking {:?}",
786 /// Check if this enum can be safely exported based on the "nullable pointer optimization". If it
787 /// can, return the type that `ty` can be safely converted to, otherwise return `None`.
788 /// Currently restricted to function pointers, boxes, references, `core::num::NonZero*`,
789 /// `core::ptr::NonNull`, and `#[repr(transparent)]` newtypes.
790 /// FIXME: This duplicates code in codegen.
791 pub(crate) fn repr_nullable_ptr<'tcx>(
792 cx: &LateContext<'tcx>,
795 ) -> Option<Ty<'tcx>> {
796 debug!("is_repr_nullable_ptr(cx, ty = {:?})", ty);
797 if let ty::Adt(ty_def, substs) = ty.kind() {
798 let field_ty = match &ty_def.variants().raw[..] {
799 [var_one, var_two] => match (&var_one.fields[..], &var_two.fields[..]) {
800 ([], [field]) | ([field], []) => field.ty(cx.tcx, substs),
806 if !ty_is_known_nonnull(cx, field_ty, ckind) {
810 // At this point, the field's type is known to be nonnull and the parent enum is Option-like.
811 // If the computed size for the field and the enum are different, the nonnull optimization isn't
812 // being applied (and we've got a problem somewhere).
813 let compute_size_skeleton = |t| SizeSkeleton::compute(t, cx.tcx, cx.param_env).unwrap();
814 if !compute_size_skeleton(ty).same_size(compute_size_skeleton(field_ty)) {
815 bug!("improper_ctypes: Option nonnull optimization not applied?");
818 // Return the nullable type this Option-like enum can be safely represented with.
819 let field_ty_abi = &cx.layout_of(field_ty).unwrap().abi;
820 if let Abi::Scalar(field_ty_scalar) = field_ty_abi {
821 match field_ty_scalar.valid_range(cx) {
822 WrappingRange { start: 0, end }
823 if end == field_ty_scalar.size(&cx.tcx).unsigned_int_max() - 1 =>
825 return Some(get_nullable_type(cx, field_ty).unwrap());
827 WrappingRange { start: 1, .. } => {
828 return Some(get_nullable_type(cx, field_ty).unwrap());
830 WrappingRange { start, end } => {
831 unreachable!("Unhandled start and end range: ({}, {})", start, end)
839 impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
840 /// Check if the type is array and emit an unsafe type lint.
841 fn check_for_array_ty(&mut self, sp: Span, ty: Ty<'tcx>) -> bool {
842 if let ty::Array(..) = ty.kind() {
843 self.emit_ffi_unsafe_type_lint(
846 fluent::lint_improper_ctypes_array_reason,
847 Some(fluent::lint_improper_ctypes_array_help),
855 /// Checks if the given field's type is "ffi-safe".
856 fn check_field_type_for_ffi(
858 cache: &mut FxHashSet<Ty<'tcx>>,
859 field: &ty::FieldDef,
860 substs: SubstsRef<'tcx>,
861 ) -> FfiResult<'tcx> {
862 let field_ty = field.ty(self.cx.tcx, substs);
863 if field_ty.has_opaque_types() {
864 self.check_type_for_ffi(cache, field_ty)
866 let field_ty = self.cx.tcx.normalize_erasing_regions(self.cx.param_env, field_ty);
867 self.check_type_for_ffi(cache, field_ty)
871 /// Checks if the given `VariantDef`'s field types are "ffi-safe".
872 fn check_variant_for_ffi(
874 cache: &mut FxHashSet<Ty<'tcx>>,
876 def: ty::AdtDef<'tcx>,
877 variant: &ty::VariantDef,
878 substs: SubstsRef<'tcx>,
879 ) -> FfiResult<'tcx> {
882 if def.repr().transparent() {
883 // Can assume that at most one field is not a ZST, so only check
884 // that field's type for FFI-safety.
885 if let Some(field) = transparent_newtype_field(self.cx.tcx, variant) {
886 self.check_field_type_for_ffi(cache, field, substs)
888 // All fields are ZSTs; this means that the type should behave
889 // like (), which is FFI-unsafe
890 FfiUnsafe { ty, reason: fluent::lint_improper_ctypes_struct_zst, help: None }
893 // We can't completely trust repr(C) markings; make sure the fields are
895 let mut all_phantom = !variant.fields.is_empty();
896 for field in &variant.fields {
897 match self.check_field_type_for_ffi(cache, &field, substs) {
901 FfiPhantom(..) if def.is_enum() => {
904 reason: fluent::lint_improper_ctypes_enum_phantomdata,
913 if all_phantom { FfiPhantom(ty) } else { FfiSafe }
917 /// Checks if the given type is "ffi-safe" (has a stable, well-defined
918 /// representation which can be exported to C code).
919 fn check_type_for_ffi(&self, cache: &mut FxHashSet<Ty<'tcx>>, ty: Ty<'tcx>) -> FfiResult<'tcx> {
922 let tcx = self.cx.tcx;
924 // Protect against infinite recursion, for example
925 // `struct S(*mut S);`.
926 // FIXME: A recursion limit is necessary as well, for irregular
928 if !cache.insert(ty) {
933 ty::Adt(def, substs) => {
934 if def.is_box() && matches!(self.mode, CItemKind::Definition) {
935 if ty.boxed_ty().is_sized(tcx, self.cx.param_env) {
940 reason: fluent::lint_improper_ctypes_box,
945 if def.is_phantom_data() {
946 return FfiPhantom(ty);
948 match def.adt_kind() {
949 AdtKind::Struct | AdtKind::Union => {
950 if !def.repr().c() && !def.repr().transparent() {
953 reason: if def.is_struct() {
954 fluent::lint_improper_ctypes_struct_layout_reason
956 fluent::lint_improper_ctypes_union_layout_reason
958 help: if def.is_struct() {
959 Some(fluent::lint_improper_ctypes_struct_layout_help)
961 Some(fluent::lint_improper_ctypes_union_layout_help)
966 let is_non_exhaustive =
967 def.non_enum_variant().is_field_list_non_exhaustive();
968 if is_non_exhaustive && !def.did().is_local() {
971 reason: if def.is_struct() {
972 fluent::lint_improper_ctypes_struct_non_exhaustive
974 fluent::lint_improper_ctypes_union_non_exhaustive
980 if def.non_enum_variant().fields.is_empty() {
983 reason: if def.is_struct() {
984 fluent::lint_improper_ctypes_struct_fieldless_reason
986 fluent::lint_improper_ctypes_union_fieldless_reason
988 help: if def.is_struct() {
989 Some(fluent::lint_improper_ctypes_struct_fieldless_help)
991 Some(fluent::lint_improper_ctypes_union_fieldless_help)
996 self.check_variant_for_ffi(cache, ty, def, def.non_enum_variant(), substs)
999 if def.variants().is_empty() {
1000 // Empty enums are okay... although sort of useless.
1004 // Check for a repr() attribute to specify the size of the
1006 if !def.repr().c() && !def.repr().transparent() && def.repr().int.is_none()
1008 // Special-case types like `Option<extern fn()>`.
1009 if repr_nullable_ptr(self.cx, ty, self.mode).is_none() {
1012 reason: fluent::lint_improper_ctypes_enum_repr_reason,
1013 help: Some(fluent::lint_improper_ctypes_enum_repr_help),
1018 if def.is_variant_list_non_exhaustive() && !def.did().is_local() {
1021 reason: fluent::lint_improper_ctypes_non_exhaustive,
1026 // Check the contained variants.
1027 for variant in def.variants() {
1028 let is_non_exhaustive = variant.is_field_list_non_exhaustive();
1029 if is_non_exhaustive && !variant.def_id.is_local() {
1032 reason: fluent::lint_improper_ctypes_non_exhaustive_variant,
1037 match self.check_variant_for_ffi(cache, ty, def, variant, substs) {
1048 ty::Char => FfiUnsafe {
1050 reason: fluent::lint_improper_ctypes_char_reason,
1051 help: Some(fluent::lint_improper_ctypes_char_help),
1054 ty::Int(ty::IntTy::I128) | ty::Uint(ty::UintTy::U128) => {
1055 FfiUnsafe { ty, reason: fluent::lint_improper_ctypes_128bit, help: None }
1058 // Primitive types with a stable representation.
1059 ty::Bool | ty::Int(..) | ty::Uint(..) | ty::Float(..) | ty::Never => FfiSafe,
1061 ty::Slice(_) => FfiUnsafe {
1063 reason: fluent::lint_improper_ctypes_slice_reason,
1064 help: Some(fluent::lint_improper_ctypes_slice_help),
1067 ty::Dynamic(..) => {
1068 FfiUnsafe { ty, reason: fluent::lint_improper_ctypes_dyn, help: None }
1071 ty::Str => FfiUnsafe {
1073 reason: fluent::lint_improper_ctypes_str_reason,
1074 help: Some(fluent::lint_improper_ctypes_str_help),
1077 ty::Tuple(..) => FfiUnsafe {
1079 reason: fluent::lint_improper_ctypes_tuple_reason,
1080 help: Some(fluent::lint_improper_ctypes_tuple_help),
1083 ty::RawPtr(ty::TypeAndMut { ty, .. }) | ty::Ref(_, ty, _)
1085 matches!(self.mode, CItemKind::Definition)
1086 && ty.is_sized(self.cx.tcx, self.cx.param_env)
1092 ty::RawPtr(ty::TypeAndMut { ty, .. })
1093 if match ty.kind() {
1094 ty::Tuple(tuple) => tuple.is_empty(),
1101 ty::RawPtr(ty::TypeAndMut { ty, .. }) | ty::Ref(_, ty, _) => {
1102 self.check_type_for_ffi(cache, ty)
1105 ty::Array(inner_ty, _) => self.check_type_for_ffi(cache, inner_ty),
1108 if self.is_internal_abi(sig.abi()) {
1111 reason: fluent::lint_improper_ctypes_fnptr_reason,
1112 help: Some(fluent::lint_improper_ctypes_fnptr_help),
1116 let sig = tcx.erase_late_bound_regions(sig);
1117 if !sig.output().is_unit() {
1118 let r = self.check_type_for_ffi(cache, sig.output());
1126 for arg in sig.inputs() {
1127 let r = self.check_type_for_ffi(cache, *arg);
1138 ty::Foreign(..) => FfiSafe,
1140 // While opaque types are checked for earlier, if a projection in a struct field
1141 // normalizes to an opaque type, then it will reach this branch.
1143 FfiUnsafe { ty, reason: fluent::lint_improper_ctypes_opaque, help: None }
1146 // `extern "C" fn` functions can have type parameters, which may or may not be FFI-safe,
1147 // so they are currently ignored for the purposes of this lint.
1148 ty::Param(..) | ty::Projection(..) if matches!(self.mode, CItemKind::Definition) => {
1153 | ty::Projection(..)
1159 | ty::GeneratorWitness(..)
1160 | ty::Placeholder(..)
1161 | ty::FnDef(..) => bug!("unexpected type in foreign function: {:?}", ty),
1165 fn emit_ffi_unsafe_type_lint(
1169 note: DiagnosticMessage,
1170 help: Option<DiagnosticMessage>,
1172 let lint = match self.mode {
1173 CItemKind::Declaration => IMPROPER_CTYPES,
1174 CItemKind::Definition => IMPROPER_CTYPES_DEFINITIONS,
1177 self.cx.struct_span_lint(lint, sp, fluent::lint_improper_ctypes, |lint| {
1178 let item_description = match self.mode {
1179 CItemKind::Declaration => "block",
1180 CItemKind::Definition => "fn",
1182 lint.set_arg("ty", ty);
1183 lint.set_arg("desc", item_description);
1184 lint.span_label(sp, fluent::label);
1185 if let Some(help) = help {
1189 if let ty::Adt(def, _) = ty.kind() {
1190 if let Some(sp) = self.cx.tcx.hir().span_if_local(def.did()) {
1191 lint.span_note(sp, fluent::note);
1198 fn check_for_opaque_ty(&mut self, sp: Span, ty: Ty<'tcx>) -> bool {
1199 struct ProhibitOpaqueTypes;
1200 impl<'tcx> ty::visit::TypeVisitor<'tcx> for ProhibitOpaqueTypes {
1201 type BreakTy = Ty<'tcx>;
1203 fn visit_ty(&mut self, ty: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
1204 if !ty.has_opaque_types() {
1205 return ControlFlow::CONTINUE;
1208 if let ty::Opaque(..) = ty.kind() {
1209 ControlFlow::Break(ty)
1211 ty.super_visit_with(self)
1216 if let Some(ty) = self
1219 .normalize_erasing_regions(self.cx.param_env, ty)
1220 .visit_with(&mut ProhibitOpaqueTypes)
1223 self.emit_ffi_unsafe_type_lint(ty, sp, fluent::lint_improper_ctypes_opaque, None);
1230 fn check_type_for_ffi_and_report_errors(
1235 is_return_type: bool,
1237 // We have to check for opaque types before `normalize_erasing_regions`,
1238 // which will replace opaque types with their underlying concrete type.
1239 if self.check_for_opaque_ty(sp, ty) {
1240 // We've already emitted an error due to an opaque type.
1244 // it is only OK to use this function because extern fns cannot have
1245 // any generic types right now:
1246 let ty = self.cx.tcx.normalize_erasing_regions(self.cx.param_env, ty);
1248 // C doesn't really support passing arrays by value - the only way to pass an array by value
1249 // is through a struct. So, first test that the top level isn't an array, and then
1250 // recursively check the types inside.
1251 if !is_static && self.check_for_array_ty(sp, ty) {
1255 // Don't report FFI errors for unit return types. This check exists here, and not in
1256 // `check_foreign_fn` (where it would make more sense) so that normalization has definitely
1258 if is_return_type && ty.is_unit() {
1262 match self.check_type_for_ffi(&mut FxHashSet::default(), ty) {
1263 FfiResult::FfiSafe => {}
1264 FfiResult::FfiPhantom(ty) => {
1265 self.emit_ffi_unsafe_type_lint(
1268 fluent::lint_improper_ctypes_only_phantomdata,
1272 // If `ty` is a `repr(transparent)` newtype, and the non-zero-sized type is a generic
1273 // argument, which after substitution, is `()`, then this branch can be hit.
1274 FfiResult::FfiUnsafe { ty, .. } if is_return_type && ty.is_unit() => {}
1275 FfiResult::FfiUnsafe { ty, reason, help } => {
1276 self.emit_ffi_unsafe_type_lint(ty, sp, reason, help);
1281 fn check_foreign_fn(&mut self, id: hir::HirId, decl: &hir::FnDecl<'_>) {
1282 let def_id = self.cx.tcx.hir().local_def_id(id);
1283 let sig = self.cx.tcx.fn_sig(def_id);
1284 let sig = self.cx.tcx.erase_late_bound_regions(sig);
1286 for (input_ty, input_hir) in iter::zip(sig.inputs(), decl.inputs) {
1287 self.check_type_for_ffi_and_report_errors(input_hir.span, *input_ty, false, false);
1290 if let hir::FnRetTy::Return(ref ret_hir) = decl.output {
1291 let ret_ty = sig.output();
1292 self.check_type_for_ffi_and_report_errors(ret_hir.span, ret_ty, false, true);
1296 fn check_foreign_static(&mut self, id: hir::HirId, span: Span) {
1297 let def_id = self.cx.tcx.hir().local_def_id(id);
1298 let ty = self.cx.tcx.type_of(def_id);
1299 self.check_type_for_ffi_and_report_errors(span, ty, true, false);
1302 fn is_internal_abi(&self, abi: SpecAbi) -> bool {
1305 SpecAbi::Rust | SpecAbi::RustCall | SpecAbi::RustIntrinsic | SpecAbi::PlatformIntrinsic
1310 impl<'tcx> LateLintPass<'tcx> for ImproperCTypesDeclarations {
1311 fn check_foreign_item(&mut self, cx: &LateContext<'_>, it: &hir::ForeignItem<'_>) {
1312 let mut vis = ImproperCTypesVisitor { cx, mode: CItemKind::Declaration };
1313 let abi = cx.tcx.hir().get_foreign_abi(it.hir_id());
1315 if !vis.is_internal_abi(abi) {
1317 hir::ForeignItemKind::Fn(ref decl, _, _) => {
1318 vis.check_foreign_fn(it.hir_id(), decl);
1320 hir::ForeignItemKind::Static(ref ty, _) => {
1321 vis.check_foreign_static(it.hir_id(), ty.span);
1323 hir::ForeignItemKind::Type => (),
1329 impl<'tcx> LateLintPass<'tcx> for ImproperCTypesDefinitions {
1332 cx: &LateContext<'tcx>,
1333 kind: hir::intravisit::FnKind<'tcx>,
1334 decl: &'tcx hir::FnDecl<'_>,
1335 _: &'tcx hir::Body<'_>,
1339 use hir::intravisit::FnKind;
1341 let abi = match kind {
1342 FnKind::ItemFn(_, _, header, ..) => header.abi,
1343 FnKind::Method(_, sig, ..) => sig.header.abi,
1347 let mut vis = ImproperCTypesVisitor { cx, mode: CItemKind::Definition };
1348 if !vis.is_internal_abi(abi) {
1349 vis.check_foreign_fn(hir_id, decl);
1354 declare_lint_pass!(VariantSizeDifferences => [VARIANT_SIZE_DIFFERENCES]);
1356 impl<'tcx> LateLintPass<'tcx> for VariantSizeDifferences {
1357 fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1358 if let hir::ItemKind::Enum(ref enum_definition, _) = it.kind {
1359 let t = cx.tcx.type_of(it.owner_id);
1360 let ty = cx.tcx.erase_regions(t);
1361 let Ok(layout) = cx.layout_of(ty) else { return };
1362 let Variants::Multiple {
1363 tag_encoding: TagEncoding::Direct, tag, ref variants, ..
1364 } = &layout.variants else {
1368 let tag_size = tag.size(&cx.tcx).bytes();
1371 "enum `{}` is {} bytes large with layout:\n{:#?}",
1373 layout.size.bytes(),
1377 let (largest, slargest, largest_index) = iter::zip(enum_definition.variants, variants)
1378 .map(|(variant, variant_layout)| {
1379 // Subtract the size of the enum tag.
1380 let bytes = variant_layout.size.bytes().saturating_sub(tag_size);
1382 debug!("- variant `{}` is {} bytes large", variant.ident, bytes);
1386 .fold((0, 0, 0), |(l, s, li), (idx, size)| {
1389 } else if size > s {
1396 // We only warn if the largest variant is at least thrice as large as
1397 // the second-largest.
1398 if largest > slargest * 3 && slargest > 0 {
1399 cx.struct_span_lint(
1400 VARIANT_SIZE_DIFFERENCES,
1401 enum_definition.variants[largest_index].span,
1402 fluent::lint_variant_size_differences,
1403 |lint| lint.set_arg("largest", largest),
1411 /// The `invalid_atomic_ordering` lint detects passing an `Ordering`
1412 /// to an atomic operation that does not support that ordering.
1416 /// ```rust,compile_fail
1417 /// # use core::sync::atomic::{AtomicU8, Ordering};
1418 /// let atom = AtomicU8::new(0);
1419 /// let value = atom.load(Ordering::Release);
1420 /// # let _ = value;
1427 /// Some atomic operations are only supported for a subset of the
1428 /// `atomic::Ordering` variants. Passing an unsupported variant will cause
1429 /// an unconditional panic at runtime, which is detected by this lint.
1431 /// This lint will trigger in the following cases: (where `AtomicType` is an
1432 /// atomic type from `core::sync::atomic`, such as `AtomicBool`,
1433 /// `AtomicPtr`, `AtomicUsize`, or any of the other integer atomics).
1435 /// - Passing `Ordering::Acquire` or `Ordering::AcqRel` to
1436 /// `AtomicType::store`.
1438 /// - Passing `Ordering::Release` or `Ordering::AcqRel` to
1439 /// `AtomicType::load`.
1441 /// - Passing `Ordering::Relaxed` to `core::sync::atomic::fence` or
1442 /// `core::sync::atomic::compiler_fence`.
1444 /// - Passing `Ordering::Release` or `Ordering::AcqRel` as the failure
1445 /// ordering for any of `AtomicType::compare_exchange`,
1446 /// `AtomicType::compare_exchange_weak`, or `AtomicType::fetch_update`.
1447 INVALID_ATOMIC_ORDERING,
1449 "usage of invalid atomic ordering in atomic operations and memory fences"
1452 declare_lint_pass!(InvalidAtomicOrdering => [INVALID_ATOMIC_ORDERING]);
1454 impl InvalidAtomicOrdering {
1455 fn inherent_atomic_method_call<'hir>(
1456 cx: &LateContext<'_>,
1458 recognized_names: &[Symbol], // used for fast path calculation
1459 ) -> Option<(Symbol, &'hir [Expr<'hir>])> {
1460 const ATOMIC_TYPES: &[Symbol] = &[
1476 if let ExprKind::MethodCall(ref method_path, _, args, _) = &expr.kind
1477 && recognized_names.contains(&method_path.ident.name)
1478 && let Some(m_def_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id)
1479 && let Some(impl_did) = cx.tcx.impl_of_method(m_def_id)
1480 && let Some(adt) = cx.tcx.type_of(impl_did).ty_adt_def()
1481 // skip extension traits, only lint functions from the standard library
1482 && cx.tcx.trait_id_of_impl(impl_did).is_none()
1483 && let parent = cx.tcx.parent(adt.did())
1484 && cx.tcx.is_diagnostic_item(sym::atomic_mod, parent)
1485 && ATOMIC_TYPES.contains(&cx.tcx.item_name(adt.did()))
1487 return Some((method_path.ident.name, args));
1492 fn match_ordering(cx: &LateContext<'_>, ord_arg: &Expr<'_>) -> Option<Symbol> {
1493 let ExprKind::Path(ref ord_qpath) = ord_arg.kind else { return None };
1494 let did = cx.qpath_res(ord_qpath, ord_arg.hir_id).opt_def_id()?;
1496 let atomic_ordering = tcx.get_diagnostic_item(sym::Ordering);
1497 let name = tcx.item_name(did);
1498 let parent = tcx.parent(did);
1499 [sym::Relaxed, sym::Release, sym::Acquire, sym::AcqRel, sym::SeqCst].into_iter().find(
1502 && (Some(parent) == atomic_ordering
1503 // needed in case this is a ctor, not a variant
1504 || tcx.opt_parent(parent) == atomic_ordering)
1509 fn check_atomic_load_store(cx: &LateContext<'_>, expr: &Expr<'_>) {
1510 if let Some((method, args)) = Self::inherent_atomic_method_call(cx, expr, &[sym::load, sym::store])
1511 && let Some((ordering_arg, invalid_ordering, msg)) = match method {
1512 sym::load => Some((&args[0], sym::Release, fluent::lint_atomic_ordering_load)),
1513 sym::store => Some((&args[1], sym::Acquire, fluent::lint_atomic_ordering_store)),
1516 && let Some(ordering) = Self::match_ordering(cx, ordering_arg)
1517 && (ordering == invalid_ordering || ordering == sym::AcqRel)
1519 cx.struct_span_lint(INVALID_ATOMIC_ORDERING, ordering_arg.span, msg, |lint| {
1520 lint.help(fluent::help)
1525 fn check_memory_fence(cx: &LateContext<'_>, expr: &Expr<'_>) {
1526 if let ExprKind::Call(ref func, ref args) = expr.kind
1527 && let ExprKind::Path(ref func_qpath) = func.kind
1528 && let Some(def_id) = cx.qpath_res(func_qpath, func.hir_id).opt_def_id()
1529 && matches!(cx.tcx.get_diagnostic_name(def_id), Some(sym::fence | sym::compiler_fence))
1530 && Self::match_ordering(cx, &args[0]) == Some(sym::Relaxed)
1532 cx.struct_span_lint(INVALID_ATOMIC_ORDERING, args[0].span, fluent::lint_atomic_ordering_fence, |lint| {
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[1],
1545 sym::compare_exchange | sym::compare_exchange_weak => &args[3],
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 #[diag(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);