1 #![allow(non_snake_case)]
3 use crate::hir::def_id::DefId;
4 use lint::{LateContext, LintArray, LintContext};
5 use lint::{LateLintPass, LintPass};
7 use rustc::mir::interpret::{sign_extend, truncate};
8 use rustc::ty::layout::{self, IntegerExt, LayoutOf, SizeSkeleton, VariantIdx};
9 use rustc::ty::subst::SubstsRef;
10 use rustc::ty::{self, AdtKind, ParamEnv, Ty, TyCtxt};
11 use rustc_data_structures::fx::FxHashSet;
12 use rustc_errors::Applicability;
14 use rustc_hir::{is_range_literal, ExprKind, Node};
15 use rustc_index::vec::Idx;
16 use rustc_span::source_map;
17 use rustc_span::symbol::sym;
19 use rustc_target::spec::abi::Abi;
20 use syntax::{ast, attr};
24 use std::{f32, f64, i16, i32, i64, i8, u16, u32, u64, u8};
29 "comparisons made useless by limits of the types involved"
35 "literal out of range for its type"
39 VARIANT_SIZE_DIFFERENCES,
41 "detects enums with widely varying variant sizes"
44 #[derive(Copy, Clone)]
45 pub struct TypeLimits {
46 /// Id of the last visited negated expression
47 negated_expr_id: hir::HirId,
50 impl_lint_pass!(TypeLimits => [UNUSED_COMPARISONS, OVERFLOWING_LITERALS]);
53 pub fn new() -> TypeLimits {
54 TypeLimits { negated_expr_id: hir::DUMMY_HIR_ID }
58 /// Attempts to special-case the overflowing literal lint when it occurs as a range endpoint.
59 /// Returns `true` iff the lint was overridden.
60 fn lint_overflowing_range_endpoint<'a, 'tcx>(
61 cx: &LateContext<'a, 'tcx>,
65 expr: &'tcx hir::Expr<'tcx>,
66 parent_expr: &'tcx hir::Expr<'tcx>,
69 // We only want to handle exclusive (`..`) ranges,
70 // which are represented as `ExprKind::Struct`.
71 if let ExprKind::Struct(_, eps, _) = &parent_expr.kind {
75 // We can suggest using an inclusive range
76 // (`..=`) instead only if it is the `end` that is
77 // overflowing and only by 1.
78 if eps[1].expr.hir_id == expr.hir_id && lit_val - 1 == max {
79 let mut err = cx.struct_span_lint(
82 &format!("range endpoint is out of range for `{}`", ty),
84 if let Ok(start) = cx.sess().source_map().span_to_snippet(eps[0].span) {
85 use ast::{LitIntType, LitKind};
86 // We need to preserve the literal's suffix,
87 // as it may determine typing information.
88 let suffix = match lit.node {
89 LitKind::Int(_, LitIntType::Signed(s)) => format!("{}", s.name_str()),
90 LitKind::Int(_, LitIntType::Unsigned(s)) => format!("{}", s.name_str()),
91 LitKind::Int(_, LitIntType::Unsuffixed) => "".to_owned(),
94 let suggestion = format!("{}..={}{}", start, lit_val - 1, suffix);
97 &"use an inclusive range instead",
99 Applicability::MachineApplicable,
110 // For `isize` & `usize`, be conservative with the warnings, so that the
111 // warnings are consistent between 32- and 64-bit platforms.
112 fn int_ty_range(int_ty: ast::IntTy) -> (i128, i128) {
114 ast::IntTy::Isize => (i64::min_value() as i128, i64::max_value() as i128),
115 ast::IntTy::I8 => (i8::min_value() as i64 as i128, i8::max_value() as i128),
116 ast::IntTy::I16 => (i16::min_value() as i64 as i128, i16::max_value() as i128),
117 ast::IntTy::I32 => (i32::min_value() as i64 as i128, i32::max_value() as i128),
118 ast::IntTy::I64 => (i64::min_value() as i128, i64::max_value() as i128),
119 ast::IntTy::I128 => (i128::min_value() as i128, i128::max_value()),
123 fn uint_ty_range(uint_ty: ast::UintTy) -> (u128, u128) {
125 ast::UintTy::Usize => (u64::min_value() as u128, u64::max_value() as u128),
126 ast::UintTy::U8 => (u8::min_value() as u128, u8::max_value() as u128),
127 ast::UintTy::U16 => (u16::min_value() as u128, u16::max_value() as u128),
128 ast::UintTy::U32 => (u32::min_value() as u128, u32::max_value() as u128),
129 ast::UintTy::U64 => (u64::min_value() as u128, u64::max_value() as u128),
130 ast::UintTy::U128 => (u128::min_value(), u128::max_value()),
134 fn get_bin_hex_repr(cx: &LateContext<'_, '_>, lit: &hir::Lit) -> Option<String> {
135 let src = cx.sess().source_map().span_to_snippet(lit.span).ok()?;
136 let firstch = src.chars().next()?;
139 match src.chars().nth(1) {
140 Some('x') | Some('b') => return Some(src),
148 fn report_bin_hex_error(
149 cx: &LateContext<'_, '_>,
150 expr: &hir::Expr<'_>,
156 let size = layout::Integer::from_attr(&cx.tcx, ty).size();
157 let (t, actually) = match ty {
158 attr::IntType::SignedInt(t) => {
159 let actually = sign_extend(val, size) as i128;
160 (t.name_str(), actually.to_string())
162 attr::IntType::UnsignedInt(t) => {
163 let actually = truncate(val, size);
164 (t.name_str(), actually.to_string())
167 let mut err = cx.struct_span_lint(
168 OVERFLOWING_LITERALS,
170 &format!("literal out of range for {}", t),
173 "the literal `{}` (decimal `{}`) does not fit into \
174 an `{}` and will become `{}{}`",
175 repr_str, val, t, actually, t
177 if let Some(sugg_ty) = get_type_suggestion(&cx.tables.node_type(expr.hir_id), val, negative) {
178 if let Some(pos) = repr_str.chars().position(|c| c == 'i' || c == 'u') {
179 let (sans_suffix, _) = repr_str.split_at(pos);
182 &format!("consider using `{}` instead", sugg_ty),
183 format!("{}{}", sans_suffix, sugg_ty),
184 Applicability::MachineApplicable,
187 err.help(&format!("consider using `{}` instead", sugg_ty));
194 // This function finds the next fitting type and generates a suggestion string.
195 // It searches for fitting types in the following way (`X < Y`):
196 // - `iX`: if literal fits in `uX` => `uX`, else => `iY`
200 // No suggestion for: `isize`, `usize`.
201 fn get_type_suggestion(t: Ty<'_>, val: u128, negative: bool) -> Option<&'static str> {
202 use syntax::ast::IntTy::*;
203 use syntax::ast::UintTy::*;
204 macro_rules! find_fit {
205 ($ty:expr, $val:expr, $negative:expr,
206 $($type:ident => [$($utypes:expr),*] => [$($itypes:expr),*]),+) => {
208 let _neg = if negative { 1 } else { 0 };
211 $(if !negative && val <= uint_ty_range($utypes).1 {
212 return Some($utypes.name_str())
214 $(if val <= int_ty_range($itypes).1 as u128 + _neg {
215 return Some($itypes.name_str())
225 ty::Int(i) => find_fit!(i, val, negative,
226 I8 => [U8] => [I16, I32, I64, I128],
227 I16 => [U16] => [I32, I64, I128],
228 I32 => [U32] => [I64, I128],
229 I64 => [U64] => [I128],
230 I128 => [U128] => []),
231 ty::Uint(u) => find_fit!(u, val, negative,
232 U8 => [U8, U16, U32, U64, U128] => [],
233 U16 => [U16, U32, U64, U128] => [],
234 U32 => [U32, U64, U128] => [],
235 U64 => [U64, U128] => [],
236 U128 => [U128] => []),
241 fn lint_int_literal<'a, 'tcx>(
242 cx: &LateContext<'a, 'tcx>,
243 type_limits: &TypeLimits,
244 e: &'tcx hir::Expr<'tcx>,
249 let int_type = t.normalize(cx.sess().target.ptr_width);
250 let (_, max) = int_ty_range(int_type);
251 let max = max as u128;
252 let negative = type_limits.negated_expr_id == e.hir_id;
254 // Detect literal value out of range [min, max] inclusive
255 // avoiding use of -min to prevent overflow/panic
256 if (negative && v > max + 1) || (!negative && v > max) {
257 if let Some(repr_str) = get_bin_hex_repr(cx, lit) {
258 report_bin_hex_error(cx, e, attr::IntType::SignedInt(t), repr_str, v, negative);
262 let par_id = cx.tcx.hir().get_parent_node(e.hir_id);
263 if let Node::Expr(par_e) = cx.tcx.hir().get(par_id) {
264 if let hir::ExprKind::Struct(..) = par_e.kind {
265 if is_range_literal(cx.sess().source_map(), par_e)
266 && lint_overflowing_range_endpoint(cx, lit, v, max, e, par_e, t.name_str())
268 // The overflowing literal lint was overridden.
275 OVERFLOWING_LITERALS,
277 &format!("literal out of range for `{}`", t.name_str()),
282 fn lint_uint_literal<'a, 'tcx>(
283 cx: &LateContext<'a, 'tcx>,
284 e: &'tcx hir::Expr<'tcx>,
288 let uint_type = t.normalize(cx.sess().target.ptr_width);
289 let (min, max) = uint_ty_range(uint_type);
290 let lit_val: u128 = match lit.node {
291 // _v is u8, within range by definition
292 ast::LitKind::Byte(_v) => return,
293 ast::LitKind::Int(v, _) => v,
296 if lit_val < min || lit_val > max {
297 let parent_id = cx.tcx.hir().get_parent_node(e.hir_id);
298 if let Node::Expr(par_e) = cx.tcx.hir().get(parent_id) {
300 hir::ExprKind::Cast(..) => {
301 if let ty::Char = cx.tables.expr_ty(par_e).kind {
302 let mut err = cx.struct_span_lint(
303 OVERFLOWING_LITERALS,
305 "only `u8` can be cast into `char`",
309 &"use a `char` literal instead",
310 format!("'\\u{{{:X}}}'", lit_val),
311 Applicability::MachineApplicable,
317 hir::ExprKind::Struct(..) if is_range_literal(cx.sess().source_map(), par_e) => {
318 let t = t.name_str();
319 if lint_overflowing_range_endpoint(cx, lit, lit_val, max, e, par_e, t) {
320 // The overflowing literal lint was overridden.
327 if let Some(repr_str) = get_bin_hex_repr(cx, lit) {
328 report_bin_hex_error(cx, e, attr::IntType::UnsignedInt(t), repr_str, lit_val, false);
332 OVERFLOWING_LITERALS,
334 &format!("literal out of range for `{}`", t.name_str()),
339 fn lint_literal<'a, 'tcx>(
340 cx: &LateContext<'a, 'tcx>,
341 type_limits: &TypeLimits,
342 e: &'tcx hir::Expr<'tcx>,
345 match cx.tables.node_type(e.hir_id).kind {
348 ast::LitKind::Int(v, ast::LitIntType::Signed(_))
349 | ast::LitKind::Int(v, ast::LitIntType::Unsuffixed) => {
350 lint_int_literal(cx, type_limits, e, lit, t, v)
355 ty::Uint(t) => lint_uint_literal(cx, e, lit, t),
357 let is_infinite = match lit.node {
358 ast::LitKind::Float(v, _) => match t {
359 ast::FloatTy::F32 => v.as_str().parse().map(f32::is_infinite),
360 ast::FloatTy::F64 => v.as_str().parse().map(f64::is_infinite),
364 if is_infinite == Ok(true) {
366 OVERFLOWING_LITERALS,
368 &format!("literal out of range for `{}`", t.name_str()),
376 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TypeLimits {
377 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx hir::Expr<'tcx>) {
379 hir::ExprKind::Unary(hir::UnOp::UnNeg, ref expr) => {
380 // propagate negation, if the negation itself isn't negated
381 if self.negated_expr_id != e.hir_id {
382 self.negated_expr_id = expr.hir_id;
385 hir::ExprKind::Binary(binop, ref l, ref r) => {
386 if is_comparison(binop) && !check_limits(cx, binop, &l, &r) {
390 "comparison is useless due to type limits",
394 hir::ExprKind::Lit(ref lit) => lint_literal(cx, self, e, lit),
398 fn is_valid<T: cmp::PartialOrd>(binop: hir::BinOp, v: T, min: T, max: T) -> bool {
400 hir::BinOpKind::Lt => v > min && v <= max,
401 hir::BinOpKind::Le => v >= min && v < max,
402 hir::BinOpKind::Gt => v >= min && v < max,
403 hir::BinOpKind::Ge => v > min && v <= max,
404 hir::BinOpKind::Eq | hir::BinOpKind::Ne => v >= min && v <= max,
409 fn rev_binop(binop: hir::BinOp) -> hir::BinOp {
413 hir::BinOpKind::Lt => hir::BinOpKind::Gt,
414 hir::BinOpKind::Le => hir::BinOpKind::Ge,
415 hir::BinOpKind::Gt => hir::BinOpKind::Lt,
416 hir::BinOpKind::Ge => hir::BinOpKind::Le,
423 cx: &LateContext<'_, '_>,
428 let (lit, expr, swap) = match (&l.kind, &r.kind) {
429 (&hir::ExprKind::Lit(_), _) => (l, r, true),
430 (_, &hir::ExprKind::Lit(_)) => (r, l, false),
433 // Normalize the binop so that the literal is always on the RHS in
435 let norm_binop = if swap { rev_binop(binop) } else { binop };
436 match cx.tables.node_type(expr.hir_id).kind {
438 let (min, max) = int_ty_range(int_ty);
439 let lit_val: i128 = match lit.kind {
440 hir::ExprKind::Lit(ref li) => match li.node {
441 ast::LitKind::Int(v, ast::LitIntType::Signed(_))
442 | ast::LitKind::Int(v, ast::LitIntType::Unsuffixed) => v as i128,
447 is_valid(norm_binop, lit_val, min, max)
449 ty::Uint(uint_ty) => {
450 let (min, max): (u128, u128) = uint_ty_range(uint_ty);
451 let lit_val: u128 = match lit.kind {
452 hir::ExprKind::Lit(ref li) => match li.node {
453 ast::LitKind::Int(v, _) => v,
458 is_valid(norm_binop, lit_val, min, max)
464 fn is_comparison(binop: hir::BinOp) -> bool {
471 | hir::BinOpKind::Gt => true,
481 "proper use of libc types in foreign modules"
484 declare_lint_pass!(ImproperCTypes => [IMPROPER_CTYPES]);
486 struct ImproperCTypesVisitor<'a, 'tcx> {
487 cx: &'a LateContext<'a, 'tcx>,
490 enum FfiResult<'tcx> {
492 FfiPhantom(Ty<'tcx>),
493 FfiUnsafe { ty: Ty<'tcx>, reason: &'static str, help: Option<&'static str> },
496 fn is_zst<'tcx>(tcx: TyCtxt<'tcx>, did: DefId, ty: Ty<'tcx>) -> bool {
497 tcx.layout_of(tcx.param_env(did).and(ty)).map(|layout| layout.is_zst()).unwrap_or(false)
500 fn ty_is_known_nonnull<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> bool {
502 ty::FnPtr(_) => true,
504 ty::Adt(field_def, substs) if field_def.repr.transparent() && !field_def.is_union() => {
505 for field in field_def.all_fields() {
507 tcx.normalize_erasing_regions(ParamEnv::reveal_all(), field.ty(tcx, substs));
508 if is_zst(tcx, field.did, field_ty) {
512 let attrs = tcx.get_attrs(field_def.did);
513 if attrs.iter().any(|a| a.check_name(sym::rustc_nonnull_optimization_guaranteed))
514 || ty_is_known_nonnull(tcx, field_ty)
526 /// Check if this enum can be safely exported based on the
527 /// "nullable pointer optimization". Currently restricted
528 /// to function pointers, references, core::num::NonZero*,
529 /// core::ptr::NonNull, and #[repr(transparent)] newtypes.
530 /// FIXME: This duplicates code in codegen.
531 fn is_repr_nullable_ptr<'tcx>(
534 ty_def: &'tcx ty::AdtDef,
535 substs: SubstsRef<'tcx>,
537 if ty_def.variants.len() != 2 {
541 let get_variant_fields = |index| &ty_def.variants[VariantIdx::new(index)].fields;
542 let variant_fields = [get_variant_fields(0), get_variant_fields(1)];
543 let fields = if variant_fields[0].is_empty() {
545 } else if variant_fields[1].is_empty() {
551 if fields.len() != 1 {
555 let field_ty = fields[0].ty(tcx, substs);
556 if !ty_is_known_nonnull(tcx, field_ty) {
560 // At this point, the field's type is known to be nonnull and the parent enum is Option-like.
561 // If the computed size for the field and the enum are different, the nonnull optimization isn't
562 // being applied (and we've got a problem somewhere).
563 let compute_size_skeleton = |t| SizeSkeleton::compute(t, tcx, ParamEnv::reveal_all()).unwrap();
564 if !compute_size_skeleton(ty).same_size(compute_size_skeleton(field_ty)) {
565 bug!("improper_ctypes: Option nonnull optimization not applied?");
571 impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
572 /// Check if the type is array and emit an unsafe type lint.
573 fn check_for_array_ty(&mut self, sp: Span, ty: Ty<'tcx>) -> bool {
574 if let ty::Array(..) = ty.kind {
575 self.emit_ffi_unsafe_type_lint(
578 "passing raw arrays by value is not FFI-safe",
579 Some("consider passing a pointer to the array"),
587 /// Checks if the given type is "ffi-safe" (has a stable, well-defined
588 /// representation which can be exported to C code).
589 fn check_type_for_ffi(&self, cache: &mut FxHashSet<Ty<'tcx>>, ty: Ty<'tcx>) -> FfiResult<'tcx> {
592 let cx = self.cx.tcx;
594 // Protect against infinite recursion, for example
595 // `struct S(*mut S);`.
596 // FIXME: A recursion limit is necessary as well, for irregular
598 if !cache.insert(ty) {
603 ty::Adt(def, substs) => {
604 if def.is_phantom_data() {
605 return FfiPhantom(ty);
607 match def.adt_kind() {
609 if !def.repr.c() && !def.repr.transparent() {
612 reason: "this struct has unspecified layout",
614 "consider adding a `#[repr(C)]` or \
615 `#[repr(transparent)]` attribute to this struct",
620 let is_non_exhaustive =
621 def.non_enum_variant().is_field_list_non_exhaustive();
622 if is_non_exhaustive && !def.did.is_local() {
625 reason: "this struct is non-exhaustive",
630 if def.non_enum_variant().fields.is_empty() {
633 reason: "this struct has no fields",
634 help: Some("consider adding a member to this struct"),
638 // We can't completely trust repr(C) and repr(transparent) markings;
639 // make sure the fields are actually safe.
640 let mut all_phantom = true;
641 for field in &def.non_enum_variant().fields {
642 let field_ty = cx.normalize_erasing_regions(
643 ParamEnv::reveal_all(),
644 field.ty(cx, substs),
646 // repr(transparent) types are allowed to have arbitrary ZSTs, not just
647 // PhantomData -- skip checking all ZST fields
648 if def.repr.transparent() && is_zst(cx, field.did, field_ty) {
651 let r = self.check_type_for_ffi(cache, field_ty);
657 FfiUnsafe { .. } => {
663 if all_phantom { FfiPhantom(ty) } else { FfiSafe }
666 if !def.repr.c() && !def.repr.transparent() {
669 reason: "this union has unspecified layout",
671 "consider adding a `#[repr(C)]` or \
672 `#[repr(transparent)]` attribute to this union",
677 if def.non_enum_variant().fields.is_empty() {
680 reason: "this union has no fields",
681 help: Some("consider adding a field to this union"),
685 let mut all_phantom = true;
686 for field in &def.non_enum_variant().fields {
687 let field_ty = cx.normalize_erasing_regions(
688 ParamEnv::reveal_all(),
689 field.ty(cx, substs),
691 // repr(transparent) types are allowed to have arbitrary ZSTs, not just
692 // PhantomData -- skip checking all ZST fields.
693 if def.repr.transparent() && is_zst(cx, field.did, field_ty) {
696 let r = self.check_type_for_ffi(cache, field_ty);
702 FfiUnsafe { .. } => {
708 if all_phantom { FfiPhantom(ty) } else { FfiSafe }
711 if def.variants.is_empty() {
712 // Empty enums are okay... although sort of useless.
716 // Check for a repr() attribute to specify the size of the
718 if !def.repr.c() && !def.repr.transparent() && def.repr.int.is_none() {
719 // Special-case types like `Option<extern fn()>`.
720 if !is_repr_nullable_ptr(cx, ty, def, substs) {
723 reason: "enum has no representation hint",
725 "consider adding a `#[repr(C)]`, \
726 `#[repr(transparent)]`, or integer `#[repr(...)]` \
727 attribute to this enum",
733 if def.is_variant_list_non_exhaustive() && !def.did.is_local() {
736 reason: "this enum is non-exhaustive",
741 // Check the contained variants.
742 for variant in &def.variants {
743 let is_non_exhaustive = variant.is_field_list_non_exhaustive();
744 if is_non_exhaustive && !variant.def_id.is_local() {
747 reason: "this enum has non-exhaustive variants",
752 for field in &variant.fields {
753 let field_ty = cx.normalize_erasing_regions(
754 ParamEnv::reveal_all(),
755 field.ty(cx, substs),
757 // repr(transparent) types are allowed to have arbitrary ZSTs, not
758 // just PhantomData -- skip checking all ZST fields.
759 if def.repr.transparent() && is_zst(cx, field.did, field_ty) {
762 let r = self.check_type_for_ffi(cache, field_ty);
765 FfiUnsafe { .. } => {
771 reason: "this enum contains a PhantomData field",
783 ty::Char => FfiUnsafe {
785 reason: "the `char` type has no C equivalent",
786 help: Some("consider using `u32` or `libc::wchar_t` instead"),
789 ty::Int(ast::IntTy::I128) | ty::Uint(ast::UintTy::U128) => FfiUnsafe {
791 reason: "128-bit integers don't currently have a known stable ABI",
795 // Primitive types with a stable representation.
796 ty::Bool | ty::Int(..) | ty::Uint(..) | ty::Float(..) | ty::Never => FfiSafe,
798 ty::Slice(_) => FfiUnsafe {
800 reason: "slices have no C equivalent",
801 help: Some("consider using a raw pointer instead"),
805 FfiUnsafe { ty, reason: "trait objects have no C equivalent", help: None }
808 ty::Str => FfiUnsafe {
810 reason: "string slices have no C equivalent",
811 help: Some("consider using `*const u8` and a length instead"),
814 ty::Tuple(..) => FfiUnsafe {
816 reason: "tuples have unspecified layout",
817 help: Some("consider using a struct instead"),
820 ty::RawPtr(ty::TypeAndMut { ty, .. }) | ty::Ref(_, ty, _) => {
821 self.check_type_for_ffi(cache, ty)
824 ty::Array(inner_ty, _) => self.check_type_for_ffi(cache, inner_ty),
828 Abi::Rust | Abi::RustIntrinsic | Abi::PlatformIntrinsic | Abi::RustCall => {
831 reason: "this function pointer has Rust-specific calling convention",
833 "consider using an `extern fn(...) -> ...` \
834 function pointer instead",
841 let sig = cx.erase_late_bound_regions(&sig);
842 if !sig.output().is_unit() {
843 let r = self.check_type_for_ffi(cache, sig.output());
851 for arg in sig.inputs() {
852 let r = self.check_type_for_ffi(cache, arg);
863 ty::Foreign(..) => FfiSafe,
871 | ty::GeneratorWitness(..)
872 | ty::Placeholder(..)
873 | ty::UnnormalizedProjection(..)
876 | ty::FnDef(..) => bug!("unexpected type in foreign function: {:?}", ty),
880 fn emit_ffi_unsafe_type_lint(
887 let mut diag = self.cx.struct_span_lint(
890 &format!("`extern` block uses type `{}`, which is not FFI-safe", ty),
892 diag.span_label(sp, "not FFI-safe");
893 if let Some(help) = help {
897 if let ty::Adt(def, _) = ty.kind {
898 if let Some(sp) = self.cx.tcx.hir().span_if_local(def.did) {
899 diag.span_note(sp, "type defined here");
905 fn check_for_opaque_ty(&mut self, sp: Span, ty: Ty<'tcx>) -> bool {
906 use crate::rustc::ty::TypeFoldable;
908 struct ProhibitOpaqueTypes<'tcx> {
909 ty: Option<Ty<'tcx>>,
912 impl<'tcx> ty::fold::TypeVisitor<'tcx> for ProhibitOpaqueTypes<'tcx> {
913 fn visit_ty(&mut self, ty: Ty<'tcx>) -> bool {
914 if let ty::Opaque(..) = ty.kind {
918 ty.super_visit_with(self)
923 let mut visitor = ProhibitOpaqueTypes { ty: None };
924 ty.visit_with(&mut visitor);
925 if let Some(ty) = visitor.ty {
926 self.emit_ffi_unsafe_type_lint(ty, sp, "opaque types have no C equivalent", None);
933 fn check_type_for_ffi_and_report_errors(&mut self, sp: Span, ty: Ty<'tcx>, is_static: bool) {
934 // We have to check for opaque types before `normalize_erasing_regions`,
935 // which will replace opaque types with their underlying concrete type.
936 if self.check_for_opaque_ty(sp, ty) {
937 // We've already emitted an error due to an opaque type.
941 // it is only OK to use this function because extern fns cannot have
942 // any generic types right now:
943 let ty = self.cx.tcx.normalize_erasing_regions(ParamEnv::reveal_all(), ty);
944 // C doesn't really support passing arrays by value.
945 // The only way to pass an array by value is through a struct.
946 // So we first test that the top level isn't an array,
947 // and then recursively check the types inside.
948 if !is_static && self.check_for_array_ty(sp, ty) {
952 match self.check_type_for_ffi(&mut FxHashSet::default(), ty) {
953 FfiResult::FfiSafe => {}
954 FfiResult::FfiPhantom(ty) => {
955 self.emit_ffi_unsafe_type_lint(ty, sp, "composed only of `PhantomData`", None);
957 FfiResult::FfiUnsafe { ty, reason, help } => {
958 self.emit_ffi_unsafe_type_lint(ty, sp, reason, help);
963 fn check_foreign_fn(&mut self, id: hir::HirId, decl: &hir::FnDecl<'_>) {
964 let def_id = self.cx.tcx.hir().local_def_id(id);
965 let sig = self.cx.tcx.fn_sig(def_id);
966 let sig = self.cx.tcx.erase_late_bound_regions(&sig);
968 for (input_ty, input_hir) in sig.inputs().iter().zip(decl.inputs) {
969 self.check_type_for_ffi_and_report_errors(input_hir.span, input_ty, false);
972 if let hir::FunctionRetTy::Return(ref ret_hir) = decl.output {
973 let ret_ty = sig.output();
974 if !ret_ty.is_unit() {
975 self.check_type_for_ffi_and_report_errors(ret_hir.span, ret_ty, false);
980 fn check_foreign_static(&mut self, id: hir::HirId, span: Span) {
981 let def_id = self.cx.tcx.hir().local_def_id(id);
982 let ty = self.cx.tcx.type_of(def_id);
983 self.check_type_for_ffi_and_report_errors(span, ty, true);
987 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ImproperCTypes {
988 fn check_foreign_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::ForeignItem<'_>) {
989 let mut vis = ImproperCTypesVisitor { cx };
990 let abi = cx.tcx.hir().get_foreign_abi(it.hir_id);
991 if let Abi::Rust | Abi::RustCall | Abi::RustIntrinsic | Abi::PlatformIntrinsic = abi {
992 // Don't worry about types in internal ABIs.
995 hir::ForeignItemKind::Fn(ref decl, _, _) => {
996 vis.check_foreign_fn(it.hir_id, decl);
998 hir::ForeignItemKind::Static(ref ty, _) => {
999 vis.check_foreign_static(it.hir_id, ty.span);
1001 hir::ForeignItemKind::Type => (),
1007 declare_lint_pass!(VariantSizeDifferences => [VARIANT_SIZE_DIFFERENCES]);
1009 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for VariantSizeDifferences {
1010 fn check_item(&mut self, cx: &LateContext<'_, '_>, it: &hir::Item<'_>) {
1011 if let hir::ItemKind::Enum(ref enum_definition, _) = it.kind {
1012 let item_def_id = cx.tcx.hir().local_def_id(it.hir_id);
1013 let t = cx.tcx.type_of(item_def_id);
1014 let ty = cx.tcx.erase_regions(&t);
1015 let layout = match cx.layout_of(ty) {
1016 Ok(layout) => layout,
1017 Err(ty::layout::LayoutError::Unknown(_)) => return,
1018 Err(err @ ty::layout::LayoutError::SizeOverflow(_)) => {
1019 bug!("failed to get layout for `{}`: {}", t, err);
1022 let (variants, tag) = match layout.variants {
1023 layout::Variants::Multiple {
1024 discr_kind: layout::DiscriminantKind::Tag,
1028 } => (variants, discr),
1032 let discr_size = tag.value.size(&cx.tcx).bytes();
1035 "enum `{}` is {} bytes large with layout:\n{:#?}",
1037 layout.size.bytes(),
1041 let (largest, slargest, largest_index) = enum_definition
1045 .map(|(variant, variant_layout)| {
1046 // Subtract the size of the enum discriminant.
1047 let bytes = variant_layout.size.bytes().saturating_sub(discr_size);
1049 debug!("- variant `{}` is {} bytes large", variant.ident, bytes);
1053 .fold((0, 0, 0), |(l, s, li), (idx, size)| {
1056 } else if size > s {
1063 // We only warn if the largest variant is at least thrice as large as
1064 // the second-largest.
1065 if largest > slargest * 3 && slargest > 0 {
1067 VARIANT_SIZE_DIFFERENCES,
1068 enum_definition.variants[largest_index].span,
1070 "enum variant is more than three times \
1071 larger ({} bytes) than the next largest",