compiler/rustc_lint/src/types.rs

   1 #![deny(rustc::untranslatable_diagnostic)]
   2 #![deny(rustc::diagnostic_outside_of_impl)]
   3 use crate::lints::{
   4     AtomicOrderingFence, AtomicOrderingLoad, AtomicOrderingStore, InvalidAtomicOrderingDiag,
   5     OnlyCastu8ToChar, OverflowingBinHex, OverflowingBinHexSign, OverflowingBinHexSub,
   6     OverflowingInt, OverflowingLiteral, OverflowingUInt, RangeEndpointOutOfRange,
   7     UnusedComparisons, VariantSizeDifferencesDiag,
   8 };
   9 use crate::{LateContext, LateLintPass, LintContext};
  10 use rustc_ast as ast;
  11 use rustc_attr as attr;
  12 use rustc_data_structures::fx::FxHashSet;
  13 use rustc_errors::{fluent, DiagnosticMessage};
  14 use rustc_hir as hir;
  15 use rustc_hir::{is_range_literal, Expr, ExprKind, Node};
  16 use rustc_middle::ty::layout::{IntegerExt, LayoutOf, SizeSkeleton};
  17 use rustc_middle::ty::subst::SubstsRef;
  18 use rustc_middle::ty::{self, AdtKind, DefIdTree, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable};
  19 use rustc_span::source_map;
  20 use rustc_span::symbol::sym;
  21 use rustc_span::{Span, Symbol};
  22 use rustc_target::abi::{Abi, Size, WrappingRange};
  23 use rustc_target::abi::{Integer, TagEncoding, Variants};
  24 use rustc_target::spec::abi::Abi as SpecAbi;
  25
  26 use std::iter;
  27 use std::ops::ControlFlow;
  28
  29 declare_lint! {
  30     /// The `unused_comparisons` lint detects comparisons made useless by
  31     /// limits of the types involved.
  32     ///
  33     /// ### Example
  34     ///
  35     /// ```rust
  36     /// fn foo(x: u8) {
  37     ///     x >= 0;
  38     /// }
  39     /// ```
  40     ///
  41     /// {{produces}}
  42     ///
  43     /// ### Explanation
  44     ///
  45     /// A useless comparison may indicate a mistake, and should be fixed or
  46     /// removed.
  47     UNUSED_COMPARISONS,
  48     Warn,
  49     "comparisons made useless by limits of the types involved"
  50 }
  51
  52 declare_lint! {
  53     /// The `overflowing_literals` lint detects literal out of range for its
  54     /// type.
  55     ///
  56     /// ### Example
  57     ///
  58     /// ```rust,compile_fail
  59     /// let x: u8 = 1000;
  60     /// ```
  61     ///
  62     /// {{produces}}
  63     ///
  64     /// ### Explanation
  65     ///
  66     /// It is usually a mistake to use a literal that overflows the type where
  67     /// it is used. Either use a literal that is within range, or change the
  68     /// type to be within the range of the literal.
  69     OVERFLOWING_LITERALS,
  70     Deny,
  71     "literal out of range for its type"
  72 }
  73
  74 declare_lint! {
  75     /// The `variant_size_differences` lint detects enums with widely varying
  76     /// variant sizes.
  77     ///
  78     /// ### Example
  79     ///
  80     /// ```rust,compile_fail
  81     /// #![deny(variant_size_differences)]
  82     /// enum En {
  83     ///     V0(u8),
  84     ///     VBig([u8; 1024]),
  85     /// }
  86     /// ```
  87     ///
  88     /// {{produces}}
  89     ///
  90     /// ### Explanation
  91     ///
  92     /// It can be a mistake to add a variant to an enum that is much larger
  93     /// than the other variants, bloating the overall size required for all
  94     /// variants. This can impact performance and memory usage. This is
  95     /// triggered if one variant is more than 3 times larger than the
  96     /// second-largest variant.
  97     ///
  98     /// Consider placing the large variant's contents on the heap (for example
  99     /// via [`Box`]) to keep the overall size of the enum itself down.
 100     ///
 101     /// This lint is "allow" by default because it can be noisy, and may not be
 102     /// an actual problem. Decisions about this should be guided with
 103     /// profiling and benchmarking.
 104     ///
 105     /// [`Box`]: https://doc.rust-lang.org/std/boxed/index.html
 106     VARIANT_SIZE_DIFFERENCES,
 107     Allow,
 108     "detects enums with widely varying variant sizes"
 109 }
 110
 111 #[derive(Copy, Clone)]
 112 pub struct TypeLimits {
 113     /// Id of the last visited negated expression
 114     negated_expr_id: Option<hir::HirId>,
 115 }
 116
 117 impl_lint_pass!(TypeLimits => [UNUSED_COMPARISONS, OVERFLOWING_LITERALS]);
 118
 119 impl TypeLimits {
 120     pub fn new() -> TypeLimits {
 121         TypeLimits { negated_expr_id: None }
 122     }
 123 }
 124
 125 /// Attempts to special-case the overflowing literal lint when it occurs as a range endpoint (`expr..MAX+1`).
 126 /// Returns `true` iff the lint was emitted.
 127 fn lint_overflowing_range_endpoint<'tcx>(
 128     cx: &LateContext<'tcx>,
 129     lit: &hir::Lit,
 130     lit_val: u128,
 131     max: u128,
 132     expr: &'tcx hir::Expr<'tcx>,
 133     ty: &str,
 134 ) -> bool {
 135     // We only want to handle exclusive (`..`) ranges,
 136     // which are represented as `ExprKind::Struct`.
 137     let par_id = cx.tcx.hir().parent_id(expr.hir_id);
 138     let Node::ExprField(field) = cx.tcx.hir().get(par_id) else { return false };
 139     let Node::Expr(struct_expr) = cx.tcx.hir().get_parent(field.hir_id) else { return false };
 140     if !is_range_literal(struct_expr) {
 141         return false;
 142     };
 143     let ExprKind::Struct(_, eps, _) = &struct_expr.kind else { return false };
 144     if eps.len() != 2 {
 145         return false;
 146     }
 147
 148     // We can suggest using an inclusive range
 149     // (`..=`) instead only if it is the `end` that is
 150     // overflowing and only by 1.
 151     if !(eps[1].expr.hir_id == expr.hir_id && lit_val - 1 == max) {
 152         return false;
 153     };
 154     let Ok(start) = cx.sess().source_map().span_to_snippet(eps[0].span) else { return false };
 155
 156     use rustc_ast::{LitIntType, LitKind};
 157     let suffix = match lit.node {
 158         LitKind::Int(_, LitIntType::Signed(s)) => s.name_str(),
 159         LitKind::Int(_, LitIntType::Unsigned(s)) => s.name_str(),
 160         LitKind::Int(_, LitIntType::Unsuffixed) => "",
 161         _ => bug!(),
 162     };
 163     cx.emit_spanned_lint(
 164         OVERFLOWING_LITERALS,
 165         struct_expr.span,
 166         RangeEndpointOutOfRange {
 167             ty,
 168             suggestion: struct_expr.span,
 169             start,
 170             literal: lit_val - 1,
 171             suffix,
 172         },
 173     );
 174
 175     // We've just emitted a lint, special cased for `(...)..MAX+1` ranges,
 176     // return `true` so the callers don't also emit a lint
 177     true
 178 }
 179
 180 // For `isize` & `usize`, be conservative with the warnings, so that the
 181 // warnings are consistent between 32- and 64-bit platforms.
 182 fn int_ty_range(int_ty: ty::IntTy) -> (i128, i128) {
 183     match int_ty {
 184         ty::IntTy::Isize => (i64::MIN.into(), i64::MAX.into()),
 185         ty::IntTy::I8 => (i8::MIN.into(), i8::MAX.into()),
 186         ty::IntTy::I16 => (i16::MIN.into(), i16::MAX.into()),
 187         ty::IntTy::I32 => (i32::MIN.into(), i32::MAX.into()),
 188         ty::IntTy::I64 => (i64::MIN.into(), i64::MAX.into()),
 189         ty::IntTy::I128 => (i128::MIN, i128::MAX),
 190     }
 191 }
 192
 193 fn uint_ty_range(uint_ty: ty::UintTy) -> (u128, u128) {
 194     let max = match uint_ty {
 195         ty::UintTy::Usize => u64::MAX.into(),
 196         ty::UintTy::U8 => u8::MAX.into(),
 197         ty::UintTy::U16 => u16::MAX.into(),
 198         ty::UintTy::U32 => u32::MAX.into(),
 199         ty::UintTy::U64 => u64::MAX.into(),
 200         ty::UintTy::U128 => u128::MAX,
 201     };
 202     (0, max)
 203 }
 204
 205 fn get_bin_hex_repr(cx: &LateContext<'_>, lit: &hir::Lit) -> Option<String> {
 206     let src = cx.sess().source_map().span_to_snippet(lit.span).ok()?;
 207     let firstch = src.chars().next()?;
 208
 209     if firstch == '0' {
 210         match src.chars().nth(1) {
 211             Some('x' | 'b') => return Some(src),
 212             _ => return None,
 213         }
 214     }
 215
 216     None
 217 }
 218
 219 fn report_bin_hex_error(
 220     cx: &LateContext<'_>,
 221     expr: &hir::Expr<'_>,
 222     ty: attr::IntType,
 223     size: Size,
 224     repr_str: String,
 225     val: u128,
 226     negative: bool,
 227 ) {
 228     let (t, actually) = match ty {
 229         attr::IntType::SignedInt(t) => {
 230             let actually = if negative {
 231                 -(size.sign_extend(val) as i128)
 232             } else {
 233                 size.sign_extend(val) as i128
 234             };
 235             (t.name_str(), actually.to_string())
 236         }
 237         attr::IntType::UnsignedInt(t) => {
 238             let actually = size.truncate(val);
 239             (t.name_str(), actually.to_string())
 240         }
 241     };
 242     let sign =
 243         if negative { OverflowingBinHexSign::Negative } else { OverflowingBinHexSign::Positive };
 244     let sub = get_type_suggestion(cx.typeck_results().node_type(expr.hir_id), val, negative).map(
 245         |suggestion_ty| {
 246             if let Some(pos) = repr_str.chars().position(|c| c == 'i' || c == 'u') {
 247                 let (sans_suffix, _) = repr_str.split_at(pos);
 248                 OverflowingBinHexSub::Suggestion { span: expr.span, suggestion_ty, sans_suffix }
 249             } else {
 250                 OverflowingBinHexSub::Help { suggestion_ty }
 251             }
 252         },
 253     );
 254     cx.emit_spanned_lint(
 255         OVERFLOWING_LITERALS,
 256         expr.span,
 257         OverflowingBinHex { ty: t, lit: repr_str.clone(), dec: val, actually, sign, sub },
 258     )
 259 }
 260
 261 // This function finds the next fitting type and generates a suggestion string.
 262 // It searches for fitting types in the following way (`X < Y`):
 263 //  - `iX`: if literal fits in `uX` => `uX`, else => `iY`
 264 //  - `-iX` => `iY`
 265 //  - `uX` => `uY`
 266 //
 267 // No suggestion for: `isize`, `usize`.
 268 fn get_type_suggestion(t: Ty<'_>, val: u128, negative: bool) -> Option<&'static str> {
 269     use ty::IntTy::*;
 270     use ty::UintTy::*;
 271     macro_rules! find_fit {
 272         ($ty:expr, $val:expr, $negative:expr,
 273          $($type:ident => [$($utypes:expr),*] => [$($itypes:expr),*]),+) => {
 274             {
 275                 let _neg = if negative { 1 } else { 0 };
 276                 match $ty {
 277                     $($type => {
 278                         $(if !negative && val <= uint_ty_range($utypes).1 {
 279                             return Some($utypes.name_str())
 280                         })*
 281                         $(if val <= int_ty_range($itypes).1 as u128 + _neg {
 282                             return Some($itypes.name_str())
 283                         })*
 284                         None
 285                     },)+
 286                     _ => None
 287                 }
 288             }
 289         }
 290     }
 291     match t.kind() {
 292         ty::Int(i) => find_fit!(i, val, negative,
 293                       I8 => [U8] => [I16, I32, I64, I128],
 294                       I16 => [U16] => [I32, I64, I128],
 295                       I32 => [U32] => [I64, I128],
 296                       I64 => [U64] => [I128],
 297                       I128 => [U128] => []),
 298         ty::Uint(u) => find_fit!(u, val, negative,
 299                       U8 => [U8, U16, U32, U64, U128] => [],
 300                       U16 => [U16, U32, U64, U128] => [],
 301                       U32 => [U32, U64, U128] => [],
 302                       U64 => [U64, U128] => [],
 303                       U128 => [U128] => []),
 304         _ => None,
 305     }
 306 }
 307
 308 fn lint_int_literal<'tcx>(
 309     cx: &LateContext<'tcx>,
 310     type_limits: &TypeLimits,
 311     e: &'tcx hir::Expr<'tcx>,
 312     lit: &hir::Lit,
 313     t: ty::IntTy,
 314     v: u128,
 315 ) {
 316     let int_type = t.normalize(cx.sess().target.pointer_width);
 317     let (min, max) = int_ty_range(int_type);
 318     let max = max as u128;
 319     let negative = type_limits.negated_expr_id == Some(e.hir_id);
 320
 321     // Detect literal value out of range [min, max] inclusive
 322     // avoiding use of -min to prevent overflow/panic
 323     if (negative && v > max + 1) || (!negative && v > max) {
 324         if let Some(repr_str) = get_bin_hex_repr(cx, lit) {
 325             report_bin_hex_error(
 326                 cx,
 327                 e,
 328                 attr::IntType::SignedInt(ty::ast_int_ty(t)),
 329                 Integer::from_int_ty(cx, t).size(),
 330                 repr_str,
 331                 v,
 332                 negative,
 333             );
 334             return;
 335         }
 336
 337         if lint_overflowing_range_endpoint(cx, lit, v, max, e, t.name_str()) {
 338             // The overflowing literal lint was emitted by `lint_overflowing_range_endpoint`.
 339             return;
 340         }
 341
 342         cx.emit_spanned_lint(
 343             OVERFLOWING_LITERALS,
 344             e.span,
 345             OverflowingInt {
 346                 ty: t.name_str(),
 347                 lit: cx
 348                     .sess()
 349                     .source_map()
 350                     .span_to_snippet(lit.span)
 351                     .expect("must get snippet from literal"),
 352                 min,
 353                 max,
 354                 suggestion_ty: get_type_suggestion(
 355                     cx.typeck_results().node_type(e.hir_id),
 356                     v,
 357                     negative,
 358                 ),
 359             },
 360         );
 361     }
 362 }
 363
 364 fn lint_uint_literal<'tcx>(
 365     cx: &LateContext<'tcx>,
 366     e: &'tcx hir::Expr<'tcx>,
 367     lit: &hir::Lit,
 368     t: ty::UintTy,
 369 ) {
 370     let uint_type = t.normalize(cx.sess().target.pointer_width);
 371     let (min, max) = uint_ty_range(uint_type);
 372     let lit_val: u128 = match lit.node {
 373         // _v is u8, within range by definition
 374         ast::LitKind::Byte(_v) => return,
 375         ast::LitKind::Int(v, _) => v,
 376         _ => bug!(),
 377     };
 378     if lit_val < min || lit_val > max {
 379         let parent_id = cx.tcx.hir().parent_id(e.hir_id);
 380         if let Node::Expr(par_e) = cx.tcx.hir().get(parent_id) {
 381             match par_e.kind {
 382                 hir::ExprKind::Cast(..) => {
 383                     if let ty::Char = cx.typeck_results().expr_ty(par_e).kind() {
 384                         cx.emit_spanned_lint(
 385                             OVERFLOWING_LITERALS,
 386                             par_e.span,
 387                             OnlyCastu8ToChar { span: par_e.span, literal: lit_val },
 388                         );
 389                         return;
 390                     }
 391                 }
 392                 _ => {}
 393             }
 394         }
 395         if lint_overflowing_range_endpoint(cx, lit, lit_val, max, e, t.name_str()) {
 396             // The overflowing literal lint was emitted by `lint_overflowing_range_endpoint`.
 397             return;
 398         }
 399         if let Some(repr_str) = get_bin_hex_repr(cx, lit) {
 400             report_bin_hex_error(
 401                 cx,
 402                 e,
 403                 attr::IntType::UnsignedInt(ty::ast_uint_ty(t)),
 404                 Integer::from_uint_ty(cx, t).size(),
 405                 repr_str,
 406                 lit_val,
 407                 false,
 408             );
 409             return;
 410         }
 411         cx.emit_spanned_lint(
 412             OVERFLOWING_LITERALS,
 413             e.span,
 414             OverflowingUInt {
 415                 ty: t.name_str(),
 416                 lit: cx
 417                     .sess()
 418                     .source_map()
 419                     .span_to_snippet(lit.span)
 420                     .expect("must get snippet from literal"),
 421                 min,
 422                 max,
 423             },
 424         );
 425     }
 426 }
 427
 428 fn lint_literal<'tcx>(
 429     cx: &LateContext<'tcx>,
 430     type_limits: &TypeLimits,
 431     e: &'tcx hir::Expr<'tcx>,
 432     lit: &hir::Lit,
 433 ) {
 434     match *cx.typeck_results().node_type(e.hir_id).kind() {
 435         ty::Int(t) => {
 436             match lit.node {
 437                 ast::LitKind::Int(v, ast::LitIntType::Signed(_) | ast::LitIntType::Unsuffixed) => {
 438                     lint_int_literal(cx, type_limits, e, lit, t, v)
 439                 }
 440                 _ => bug!(),
 441             };
 442         }
 443         ty::Uint(t) => lint_uint_literal(cx, e, lit, t),
 444         ty::Float(t) => {
 445             let is_infinite = match lit.node {
 446                 ast::LitKind::Float(v, _) => match t {
 447                     ty::FloatTy::F32 => v.as_str().parse().map(f32::is_infinite),
 448                     ty::FloatTy::F64 => v.as_str().parse().map(f64::is_infinite),
 449                 },
 450                 _ => bug!(),
 451             };
 452             if is_infinite == Ok(true) {
 453                 cx.emit_spanned_lint(
 454                     OVERFLOWING_LITERALS,
 455                     e.span,
 456                     OverflowingLiteral {
 457                         ty: t.name_str(),
 458                         lit: cx
 459                             .sess()
 460                             .source_map()
 461                             .span_to_snippet(lit.span)
 462                             .expect("must get snippet from literal"),
 463                     },
 464                 );
 465             }
 466         }
 467         _ => {}
 468     }
 469 }
 470
 471 impl<'tcx> LateLintPass<'tcx> for TypeLimits {
 472     fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx hir::Expr<'tcx>) {
 473         match e.kind {
 474             hir::ExprKind::Unary(hir::UnOp::Neg, ref expr) => {
 475                 // propagate negation, if the negation itself isn't negated
 476                 if self.negated_expr_id != Some(e.hir_id) {
 477                     self.negated_expr_id = Some(expr.hir_id);
 478                 }
 479             }
 480             hir::ExprKind::Binary(binop, ref l, ref r) => {
 481                 if is_comparison(binop) && !check_limits(cx, binop, &l, &r) {
 482                     cx.emit_spanned_lint(UNUSED_COMPARISONS, e.span, UnusedComparisons);
 483                 }
 484             }
 485             hir::ExprKind::Lit(ref lit) => lint_literal(cx, self, e, lit),
 486             _ => {}
 487         };
 488
 489         fn is_valid<T: PartialOrd>(binop: hir::BinOp, v: T, min: T, max: T) -> bool {
 490             match binop.node {
 491                 hir::BinOpKind::Lt => v > min && v <= max,
 492                 hir::BinOpKind::Le => v >= min && v < max,
 493                 hir::BinOpKind::Gt => v >= min && v < max,
 494                 hir::BinOpKind::Ge => v > min && v <= max,
 495                 hir::BinOpKind::Eq | hir::BinOpKind::Ne => v >= min && v <= max,
 496                 _ => bug!(),
 497             }
 498         }
 499
 500         fn rev_binop(binop: hir::BinOp) -> hir::BinOp {
 501             source_map::respan(
 502                 binop.span,
 503                 match binop.node {
 504                     hir::BinOpKind::Lt => hir::BinOpKind::Gt,
 505                     hir::BinOpKind::Le => hir::BinOpKind::Ge,
 506                     hir::BinOpKind::Gt => hir::BinOpKind::Lt,
 507                     hir::BinOpKind::Ge => hir::BinOpKind::Le,
 508                     _ => return binop,
 509                 },
 510             )
 511         }
 512
 513         fn check_limits(
 514             cx: &LateContext<'_>,
 515             binop: hir::BinOp,
 516             l: &hir::Expr<'_>,
 517             r: &hir::Expr<'_>,
 518         ) -> bool {
 519             let (lit, expr, swap) = match (&l.kind, &r.kind) {
 520                 (&hir::ExprKind::Lit(_), _) => (l, r, true),
 521                 (_, &hir::ExprKind::Lit(_)) => (r, l, false),
 522                 _ => return true,
 523             };
 524             // Normalize the binop so that the literal is always on the RHS in
 525             // the comparison
 526             let norm_binop = if swap { rev_binop(binop) } else { binop };
 527             match *cx.typeck_results().node_type(expr.hir_id).kind() {
 528                 ty::Int(int_ty) => {
 529                     let (min, max) = int_ty_range(int_ty);
 530                     let lit_val: i128 = match lit.kind {
 531                         hir::ExprKind::Lit(ref li) => match li.node {
 532                             ast::LitKind::Int(
 533                                 v,
 534                                 ast::LitIntType::Signed(_) | ast::LitIntType::Unsuffixed,
 535                             ) => v as i128,
 536                             _ => return true,
 537                         },
 538                         _ => bug!(),
 539                     };
 540                     is_valid(norm_binop, lit_val, min, max)
 541                 }
 542                 ty::Uint(uint_ty) => {
 543                     let (min, max): (u128, u128) = uint_ty_range(uint_ty);
 544                     let lit_val: u128 = match lit.kind {
 545                         hir::ExprKind::Lit(ref li) => match li.node {
 546                             ast::LitKind::Int(v, _) => v,
 547                             _ => return true,
 548                         },
 549                         _ => bug!(),
 550                     };
 551                     is_valid(norm_binop, lit_val, min, max)
 552                 }
 553                 _ => true,
 554             }
 555         }
 556
 557         fn is_comparison(binop: hir::BinOp) -> bool {
 558             matches!(
 559                 binop.node,
 560                 hir::BinOpKind::Eq
 561                     | hir::BinOpKind::Lt
 562                     | hir::BinOpKind::Le
 563                     | hir::BinOpKind::Ne
 564                     | hir::BinOpKind::Ge
 565                     | hir::BinOpKind::Gt
 566             )
 567         }
 568     }
 569 }
 570
 571 declare_lint! {
 572     /// The `improper_ctypes` lint detects incorrect use of types in foreign
 573     /// modules.
 574     ///
 575     /// ### Example
 576     ///
 577     /// ```rust
 578     /// extern "C" {
 579     ///     static STATIC: String;
 580     /// }
 581     /// ```
 582     ///
 583     /// {{produces}}
 584     ///
 585     /// ### Explanation
 586     ///
 587     /// The compiler has several checks to verify that types used in `extern`
 588     /// blocks are safe and follow certain rules to ensure proper
 589     /// compatibility with the foreign interfaces. This lint is issued when it
 590     /// detects a probable mistake in a definition. The lint usually should
 591     /// provide a description of the issue, along with possibly a hint on how
 592     /// to resolve it.
 593     IMPROPER_CTYPES,
 594     Warn,
 595     "proper use of libc types in foreign modules"
 596 }
 597
 598 declare_lint_pass!(ImproperCTypesDeclarations => [IMPROPER_CTYPES]);
 599
 600 declare_lint! {
 601     /// The `improper_ctypes_definitions` lint detects incorrect use of
 602     /// [`extern` function] definitions.
 603     ///
 604     /// [`extern` function]: https://doc.rust-lang.org/reference/items/functions.html#extern-function-qualifier
 605     ///
 606     /// ### Example
 607     ///
 608     /// ```rust
 609     /// # #![allow(unused)]
 610     /// pub extern "C" fn str_type(p: &str) { }
 611     /// ```
 612     ///
 613     /// {{produces}}
 614     ///
 615     /// ### Explanation
 616     ///
 617     /// There are many parameter and return types that may be specified in an
 618     /// `extern` function that are not compatible with the given ABI. This
 619     /// lint is an alert that these types should not be used. The lint usually
 620     /// should provide a description of the issue, along with possibly a hint
 621     /// on how to resolve it.
 622     IMPROPER_CTYPES_DEFINITIONS,
 623     Warn,
 624     "proper use of libc types in foreign item definitions"
 625 }
 626
 627 declare_lint_pass!(ImproperCTypesDefinitions => [IMPROPER_CTYPES_DEFINITIONS]);
 628
 629 #[derive(Clone, Copy)]
 630 pub(crate) enum CItemKind {
 631     Declaration,
 632     Definition,
 633 }
 634
 635 struct ImproperCTypesVisitor<'a, 'tcx> {
 636     cx: &'a LateContext<'tcx>,
 637     mode: CItemKind,
 638 }
 639
 640 enum FfiResult<'tcx> {
 641     FfiSafe,
 642     FfiPhantom(Ty<'tcx>),
 643     FfiUnsafe { ty: Ty<'tcx>, reason: DiagnosticMessage, help: Option<DiagnosticMessage> },
 644 }
 645
 646 pub(crate) fn nonnull_optimization_guaranteed<'tcx>(
 647     tcx: TyCtxt<'tcx>,
 648     def: ty::AdtDef<'tcx>,
 649 ) -> bool {
 650     tcx.has_attr(def.did(), sym::rustc_nonnull_optimization_guaranteed)
 651 }
 652
 653 /// `repr(transparent)` structs can have a single non-ZST field, this function returns that
 654 /// field.
 655 pub fn transparent_newtype_field<'a, 'tcx>(
 656     tcx: TyCtxt<'tcx>,
 657     variant: &'a ty::VariantDef,
 658 ) -> Option<&'a ty::FieldDef> {
 659     let param_env = tcx.param_env(variant.def_id);
 660     variant.fields.iter().find(|field| {
 661         let field_ty = tcx.type_of(field.did);
 662         let is_zst = tcx.layout_of(param_env.and(field_ty)).map_or(false, |layout| layout.is_zst());
 663         !is_zst
 664     })
 665 }
 666
 667 /// Is type known to be non-null?
 668 fn ty_is_known_nonnull<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>, mode: CItemKind) -> bool {
 669     let tcx = cx.tcx;
 670     match ty.kind() {
 671         ty::FnPtr(_) => true,
 672         ty::Ref(..) => true,
 673         ty::Adt(def, _) if def.is_box() && matches!(mode, CItemKind::Definition) => true,
 674         ty::Adt(def, substs) if def.repr().transparent() && !def.is_union() => {
 675             let marked_non_null = nonnull_optimization_guaranteed(tcx, *def);
 676
 677             if marked_non_null {
 678                 return true;
 679             }
 680
 681             // `UnsafeCell` has its niche hidden.
 682             if def.is_unsafe_cell() {
 683                 return false;
 684             }
 685
 686             def.variants()
 687                 .iter()
 688                 .filter_map(|variant| transparent_newtype_field(cx.tcx, variant))
 689                 .any(|field| ty_is_known_nonnull(cx, field.ty(tcx, substs), mode))
 690         }
 691         _ => false,
 692     }
 693 }
 694
 695 /// Given a non-null scalar (or transparent) type `ty`, return the nullable version of that type.
 696 /// If the type passed in was not scalar, returns None.
 697 fn get_nullable_type<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> Option<Ty<'tcx>> {
 698     let tcx = cx.tcx;
 699     Some(match *ty.kind() {
 700         ty::Adt(field_def, field_substs) => {
 701             let inner_field_ty = {
 702                 let mut first_non_zst_ty = field_def
 703                     .variants()
 704                     .iter()
 705                     .filter_map(|v| transparent_newtype_field(cx.tcx, v));
 706                 debug_assert_eq!(
 707                     first_non_zst_ty.clone().count(),
 708                     1,
 709                     "Wrong number of fields for transparent type"
 710                 );
 711                 first_non_zst_ty
 712                     .next_back()
 713                     .expect("No non-zst fields in transparent type.")
 714                     .ty(tcx, field_substs)
 715             };
 716             return get_nullable_type(cx, inner_field_ty);
 717         }
 718         ty::Int(ty) => tcx.mk_mach_int(ty),
 719         ty::Uint(ty) => tcx.mk_mach_uint(ty),
 720         ty::RawPtr(ty_mut) => tcx.mk_ptr(ty_mut),
 721         // As these types are always non-null, the nullable equivalent of
 722         // Option<T> of these types are their raw pointer counterparts.
 723         ty::Ref(_region, ty, mutbl) => tcx.mk_ptr(ty::TypeAndMut { ty, mutbl }),
 724         ty::FnPtr(..) => {
 725             // There is no nullable equivalent for Rust's function pointers -- you
 726             // must use an Option<fn(..) -> _> to represent it.
 727             ty
 728         }
 729
 730         // We should only ever reach this case if ty_is_known_nonnull is extended
 731         // to other types.
 732         ref unhandled => {
 733             debug!(
 734                 "get_nullable_type: Unhandled scalar kind: {:?} while checking {:?}",
 735                 unhandled, ty
 736             );
 737             return None;
 738         }
 739     })
 740 }
 741
 742 /// Check if this enum can be safely exported based on the "nullable pointer optimization". If it
 743 /// can, return the type that `ty` can be safely converted to, otherwise return `None`.
 744 /// Currently restricted to function pointers, boxes, references, `core::num::NonZero*`,
 745 /// `core::ptr::NonNull`, and `#[repr(transparent)]` newtypes.
 746 /// FIXME: This duplicates code in codegen.
 747 pub(crate) fn repr_nullable_ptr<'tcx>(
 748     cx: &LateContext<'tcx>,
 749     ty: Ty<'tcx>,
 750     ckind: CItemKind,
 751 ) -> Option<Ty<'tcx>> {
 752     debug!("is_repr_nullable_ptr(cx, ty = {:?})", ty);
 753     if let ty::Adt(ty_def, substs) = ty.kind() {
 754         let field_ty = match &ty_def.variants().raw[..] {
 755             [var_one, var_two] => match (&var_one.fields[..], &var_two.fields[..]) {
 756                 ([], [field]) | ([field], []) => field.ty(cx.tcx, substs),
 757                 _ => return None,
 758             },
 759             _ => return None,
 760         };
 761
 762         if !ty_is_known_nonnull(cx, field_ty, ckind) {
 763             return None;
 764         }
 765
 766         // At this point, the field's type is known to be nonnull and the parent enum is Option-like.
 767         // If the computed size for the field and the enum are different, the nonnull optimization isn't
 768         // being applied (and we've got a problem somewhere).
 769         let compute_size_skeleton = |t| SizeSkeleton::compute(t, cx.tcx, cx.param_env).unwrap();
 770         if !compute_size_skeleton(ty).same_size(compute_size_skeleton(field_ty)) {
 771             bug!("improper_ctypes: Option nonnull optimization not applied?");
 772         }
 773
 774         // Return the nullable type this Option-like enum can be safely represented with.
 775         let field_ty_abi = &cx.layout_of(field_ty).unwrap().abi;
 776         if let Abi::Scalar(field_ty_scalar) = field_ty_abi {
 777             match field_ty_scalar.valid_range(cx) {
 778                 WrappingRange { start: 0, end }
 779                     if end == field_ty_scalar.size(&cx.tcx).unsigned_int_max() - 1 =>
 780                 {
 781                     return Some(get_nullable_type(cx, field_ty).unwrap());
 782                 }
 783                 WrappingRange { start: 1, .. } => {
 784                     return Some(get_nullable_type(cx, field_ty).unwrap());
 785                 }
 786                 WrappingRange { start, end } => {
 787                     unreachable!("Unhandled start and end range: ({}, {})", start, end)
 788                 }
 789             };
 790         }
 791     }
 792     None
 793 }
 794
 795 impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
 796     /// Check if the type is array and emit an unsafe type lint.
 797     fn check_for_array_ty(&mut self, sp: Span, ty: Ty<'tcx>) -> bool {
 798         if let ty::Array(..) = ty.kind() {
 799             self.emit_ffi_unsafe_type_lint(
 800                 ty,
 801                 sp,
 802                 fluent::lint_improper_ctypes_array_reason,
 803                 Some(fluent::lint_improper_ctypes_array_help),
 804             );
 805             true
 806         } else {
 807             false
 808         }
 809     }
 810
 811     /// Checks if the given field's type is "ffi-safe".
 812     fn check_field_type_for_ffi(
 813         &self,
 814         cache: &mut FxHashSet<Ty<'tcx>>,
 815         field: &ty::FieldDef,
 816         substs: SubstsRef<'tcx>,
 817     ) -> FfiResult<'tcx> {
 818         let field_ty = field.ty(self.cx.tcx, substs);
 819         if field_ty.has_opaque_types() {
 820             self.check_type_for_ffi(cache, field_ty)
 821         } else {
 822             let field_ty = self.cx.tcx.normalize_erasing_regions(self.cx.param_env, field_ty);
 823             self.check_type_for_ffi(cache, field_ty)
 824         }
 825     }
 826
 827     /// Checks if the given `VariantDef`'s field types are "ffi-safe".
 828     fn check_variant_for_ffi(
 829         &self,
 830         cache: &mut FxHashSet<Ty<'tcx>>,
 831         ty: Ty<'tcx>,
 832         def: ty::AdtDef<'tcx>,
 833         variant: &ty::VariantDef,
 834         substs: SubstsRef<'tcx>,
 835     ) -> FfiResult<'tcx> {
 836         use FfiResult::*;
 837
 838         if def.repr().transparent() {
 839             // Can assume that at most one field is not a ZST, so only check
 840             // that field's type for FFI-safety.
 841             if let Some(field) = transparent_newtype_field(self.cx.tcx, variant) {
 842                 self.check_field_type_for_ffi(cache, field, substs)
 843             } else {
 844                 // All fields are ZSTs; this means that the type should behave
 845                 // like (), which is FFI-unsafe
 846                 FfiUnsafe { ty, reason: fluent::lint_improper_ctypes_struct_zst, help: None }
 847             }
 848         } else {
 849             // We can't completely trust repr(C) markings; make sure the fields are
 850             // actually safe.
 851             let mut all_phantom = !variant.fields.is_empty();
 852             for field in &variant.fields {
 853                 match self.check_field_type_for_ffi(cache, &field, substs) {
 854                     FfiSafe => {
 855                         all_phantom = false;
 856                     }
 857                     FfiPhantom(..) if def.is_enum() => {
 858                         return FfiUnsafe {
 859                             ty,
 860                             reason: fluent::lint_improper_ctypes_enum_phantomdata,
 861                             help: None,
 862                         };
 863                     }
 864                     FfiPhantom(..) => {}
 865                     r => return r,
 866                 }
 867             }
 868
 869             if all_phantom { FfiPhantom(ty) } else { FfiSafe }
 870         }
 871     }
 872
 873     /// Checks if the given type is "ffi-safe" (has a stable, well-defined
 874     /// representation which can be exported to C code).
 875     fn check_type_for_ffi(&self, cache: &mut FxHashSet<Ty<'tcx>>, ty: Ty<'tcx>) -> FfiResult<'tcx> {
 876         use FfiResult::*;
 877
 878         let tcx = self.cx.tcx;
 879
 880         // Protect against infinite recursion, for example
 881         // `struct S(*mut S);`.
 882         // FIXME: A recursion limit is necessary as well, for irregular
 883         // recursive types.
 884         if !cache.insert(ty) {
 885             return FfiSafe;
 886         }
 887
 888         match *ty.kind() {
 889             ty::Adt(def, substs) => {
 890                 if def.is_box() && matches!(self.mode, CItemKind::Definition) {
 891                     if ty.boxed_ty().is_sized(tcx, self.cx.param_env) {
 892                         return FfiSafe;
 893                     } else {
 894                         return FfiUnsafe {
 895                             ty,
 896                             reason: fluent::lint_improper_ctypes_box,
 897                             help: None,
 898                         };
 899                     }
 900                 }
 901                 if def.is_phantom_data() {
 902                     return FfiPhantom(ty);
 903                 }
 904                 match def.adt_kind() {
 905                     AdtKind::Struct | AdtKind::Union => {
 906                         if !def.repr().c() && !def.repr().transparent() {
 907                             return FfiUnsafe {
 908                                 ty,
 909                                 reason: if def.is_struct() {
 910                                     fluent::lint_improper_ctypes_struct_layout_reason
 911                                 } else {
 912                                     fluent::lint_improper_ctypes_union_layout_reason
 913                                 },
 914                                 help: if def.is_struct() {
 915                                     Some(fluent::lint_improper_ctypes_struct_layout_help)
 916                                 } else {
 917                                     Some(fluent::lint_improper_ctypes_union_layout_help)
 918                                 },
 919                             };
 920                         }
 921
 922                         let is_non_exhaustive =
 923                             def.non_enum_variant().is_field_list_non_exhaustive();
 924                         if is_non_exhaustive && !def.did().is_local() {
 925                             return FfiUnsafe {
 926                                 ty,
 927                                 reason: if def.is_struct() {
 928                                     fluent::lint_improper_ctypes_struct_non_exhaustive
 929                                 } else {
 930                                     fluent::lint_improper_ctypes_union_non_exhaustive
 931                                 },
 932                                 help: None,
 933                             };
 934                         }
 935
 936                         if def.non_enum_variant().fields.is_empty() {
 937                             return FfiUnsafe {
 938                                 ty,
 939                                 reason: if def.is_struct() {
 940                                     fluent::lint_improper_ctypes_struct_fieldless_reason
 941                                 } else {
 942                                     fluent::lint_improper_ctypes_union_fieldless_reason
 943                                 },
 944                                 help: if def.is_struct() {
 945                                     Some(fluent::lint_improper_ctypes_struct_fieldless_help)
 946                                 } else {
 947                                     Some(fluent::lint_improper_ctypes_union_fieldless_help)
 948                                 },
 949                             };
 950                         }
 951
 952                         self.check_variant_for_ffi(cache, ty, def, def.non_enum_variant(), substs)
 953                     }
 954                     AdtKind::Enum => {
 955                         if def.variants().is_empty() {
 956                             // Empty enums are okay... although sort of useless.
 957                             return FfiSafe;
 958                         }
 959
 960                         // Check for a repr() attribute to specify the size of the
 961                         // discriminant.
 962                         if !def.repr().c() && !def.repr().transparent() && def.repr().int.is_none()
 963                         {
 964                             // Special-case types like `Option<extern fn()>`.
 965                             if repr_nullable_ptr(self.cx, ty, self.mode).is_none() {
 966                                 return FfiUnsafe {
 967                                     ty,
 968                                     reason: fluent::lint_improper_ctypes_enum_repr_reason,
 969                                     help: Some(fluent::lint_improper_ctypes_enum_repr_help),
 970                                 };
 971                             }
 972                         }
 973
 974                         if def.is_variant_list_non_exhaustive() && !def.did().is_local() {
 975                             return FfiUnsafe {
 976                                 ty,
 977                                 reason: fluent::lint_improper_ctypes_non_exhaustive,
 978                                 help: None,
 979                             };
 980                         }
 981
 982                         // Check the contained variants.
 983                         for variant in def.variants() {
 984                             let is_non_exhaustive = variant.is_field_list_non_exhaustive();
 985                             if is_non_exhaustive && !variant.def_id.is_local() {
 986                                 return FfiUnsafe {
 987                                     ty,
 988                                     reason: fluent::lint_improper_ctypes_non_exhaustive_variant,
 989                                     help: None,
 990                                 };
 991                             }
 992
 993                             match self.check_variant_for_ffi(cache, ty, def, variant, substs) {
 994                                 FfiSafe => (),
 995                                 r => return r,
 996                             }
 997                         }
 998
 999                         FfiSafe
1000                     }
1001                 }
1002             }
1003
1004             ty::Char => FfiUnsafe {
1005                 ty,
1006                 reason: fluent::lint_improper_ctypes_char_reason,
1007                 help: Some(fluent::lint_improper_ctypes_char_help),
1008             },
1009
1010             ty::Int(ty::IntTy::I128) | ty::Uint(ty::UintTy::U128) => {
1011                 FfiUnsafe { ty, reason: fluent::lint_improper_ctypes_128bit, help: None }
1012             }
1013
1014             // Primitive types with a stable representation.
1015             ty::Bool | ty::Int(..) | ty::Uint(..) | ty::Float(..) | ty::Never => FfiSafe,
1016
1017             ty::Slice(_) => FfiUnsafe {
1018                 ty,
1019                 reason: fluent::lint_improper_ctypes_slice_reason,
1020                 help: Some(fluent::lint_improper_ctypes_slice_help),
1021             },
1022
1023             ty::Dynamic(..) => {
1024                 FfiUnsafe { ty, reason: fluent::lint_improper_ctypes_dyn, help: None }
1025             }
1026
1027             ty::Str => FfiUnsafe {
1028                 ty,
1029                 reason: fluent::lint_improper_ctypes_str_reason,
1030                 help: Some(fluent::lint_improper_ctypes_str_help),
1031             },
1032
1033             ty::Tuple(..) => FfiUnsafe {
1034                 ty,
1035                 reason: fluent::lint_improper_ctypes_tuple_reason,
1036                 help: Some(fluent::lint_improper_ctypes_tuple_help),
1037             },
1038
1039             ty::RawPtr(ty::TypeAndMut { ty, .. }) | ty::Ref(_, ty, _)
1040                 if {
1041                     matches!(self.mode, CItemKind::Definition)
1042                         && ty.is_sized(self.cx.tcx, self.cx.param_env)
1043                 } =>
1044             {
1045                 FfiSafe
1046             }
1047
1048             ty::RawPtr(ty::TypeAndMut { ty, .. })
1049                 if match ty.kind() {
1050                     ty::Tuple(tuple) => tuple.is_empty(),
1051                     _ => false,
1052                 } =>
1053             {
1054                 FfiSafe
1055             }
1056
1057             ty::RawPtr(ty::TypeAndMut { ty, .. }) | ty::Ref(_, ty, _) => {
1058                 self.check_type_for_ffi(cache, ty)
1059             }
1060
1061             ty::Array(inner_ty, _) => self.check_type_for_ffi(cache, inner_ty),
1062
1063             ty::FnPtr(sig) => {
1064                 if self.is_internal_abi(sig.abi()) {
1065                     return FfiUnsafe {
1066                         ty,
1067                         reason: fluent::lint_improper_ctypes_fnptr_reason,
1068                         help: Some(fluent::lint_improper_ctypes_fnptr_help),
1069                     };
1070                 }
1071
1072                 let sig = tcx.erase_late_bound_regions(sig);
1073                 if !sig.output().is_unit() {
1074                     let r = self.check_type_for_ffi(cache, sig.output());
1075                     match r {
1076                         FfiSafe => {}
1077                         _ => {
1078                             return r;
1079                         }
1080                     }
1081                 }
1082                 for arg in sig.inputs() {
1083                     let r = self.check_type_for_ffi(cache, *arg);
1084                     match r {
1085                         FfiSafe => {}
1086                         _ => {
1087                             return r;
1088                         }
1089                     }
1090                 }
1091                 FfiSafe
1092             }
1093
1094             ty::Foreign(..) => FfiSafe,
1095
1096             // While opaque types are checked for earlier, if a projection in a struct field
1097             // normalizes to an opaque type, then it will reach this branch.
1098             ty::Alias(ty::Opaque, ..) => {
1099                 FfiUnsafe { ty, reason: fluent::lint_improper_ctypes_opaque, help: None }
1100             }
1101
1102             // `extern "C" fn` functions can have type parameters, which may or may not be FFI-safe,
1103             //  so they are currently ignored for the purposes of this lint.
1104             ty::Param(..) | ty::Alias(ty::Projection, ..)
1105                 if matches!(self.mode, CItemKind::Definition) =>
1106             {
1107                 FfiSafe
1108             }
1109
1110             ty::Param(..)
1111             | ty::Alias(ty::Projection, ..)
1112             | ty::Infer(..)
1113             | ty::Bound(..)
1114             | ty::Error(_)
1115             | ty::Closure(..)
1116             | ty::Generator(..)
1117             | ty::GeneratorWitness(..)
1118             | ty::Placeholder(..)
1119             | ty::FnDef(..) => bug!("unexpected type in foreign function: {:?}", ty),
1120         }
1121     }
1122
1123     fn emit_ffi_unsafe_type_lint(
1124         &mut self,
1125         ty: Ty<'tcx>,
1126         sp: Span,
1127         note: DiagnosticMessage,
1128         help: Option<DiagnosticMessage>,
1129     ) {
1130         let lint = match self.mode {
1131             CItemKind::Declaration => IMPROPER_CTYPES,
1132             CItemKind::Definition => IMPROPER_CTYPES_DEFINITIONS,
1133         };
1134
1135         self.cx.struct_span_lint(lint, sp, fluent::lint_improper_ctypes, |lint| {
1136             let item_description = match self.mode {
1137                 CItemKind::Declaration => "block",
1138                 CItemKind::Definition => "fn",
1139             };
1140             #[allow(rustc::diagnostic_outside_of_impl)]
1141             let mut diag = lint.build(fluent::lint_improper_ctypes);
1142             diag.set_arg("ty", ty);
1143             diag.set_arg("desc", item_description);
1144             diag.span_label(sp, fluent::label);
1145             if let Some(help) = help {
1146                 lint.help(help);
1147             }
1148             lint.note(note);
1149             if let ty::Adt(def, _) = ty.kind() {
1150                 if let Some(sp) = self.cx.tcx.hir().span_if_local(def.did()) {
1151                     lint.span_note(sp, fluent::note);
1152                 }
1153             }
1154             lint
1155         });
1156     }
1157
1158     fn check_for_opaque_ty(&mut self, sp: Span, ty: Ty<'tcx>) -> bool {
1159         struct ProhibitOpaqueTypes;
1160         impl<'tcx> ty::visit::TypeVisitor<'tcx> for ProhibitOpaqueTypes {
1161             type BreakTy = Ty<'tcx>;
1162
1163             fn visit_ty(&mut self, ty: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
1164                 if !ty.has_opaque_types() {
1165                     return ControlFlow::CONTINUE;
1166                 }
1167
1168                 if let ty::Alias(ty::Opaque, ..) = ty.kind() {
1169                     ControlFlow::Break(ty)
1170                 } else {
1171                     ty.super_visit_with(self)
1172                 }
1173             }
1174         }
1175
1176         if let Some(ty) = self
1177             .cx
1178             .tcx
1179             .normalize_erasing_regions(self.cx.param_env, ty)
1180             .visit_with(&mut ProhibitOpaqueTypes)
1181             .break_value()
1182         {
1183             self.emit_ffi_unsafe_type_lint(ty, sp, fluent::lint_improper_ctypes_opaque, None);
1184             true
1185         } else {
1186             false
1187         }
1188     }
1189
1190     fn check_type_for_ffi_and_report_errors(
1191         &mut self,
1192         sp: Span,
1193         ty: Ty<'tcx>,
1194         is_static: bool,
1195         is_return_type: bool,
1196     ) {
1197         // We have to check for opaque types before `normalize_erasing_regions`,
1198         // which will replace opaque types with their underlying concrete type.
1199         if self.check_for_opaque_ty(sp, ty) {
1200             // We've already emitted an error due to an opaque type.
1201             return;
1202         }
1203
1204         // it is only OK to use this function because extern fns cannot have
1205         // any generic types right now:
1206         let ty = self.cx.tcx.normalize_erasing_regions(self.cx.param_env, ty);
1207
1208         // C doesn't really support passing arrays by value - the only way to pass an array by value
1209         // is through a struct. So, first test that the top level isn't an array, and then
1210         // recursively check the types inside.
1211         if !is_static && self.check_for_array_ty(sp, ty) {
1212             return;
1213         }
1214
1215         // Don't report FFI errors for unit return types. This check exists here, and not in
1216         // `check_foreign_fn` (where it would make more sense) so that normalization has definitely
1217         // happened.
1218         if is_return_type && ty.is_unit() {
1219             return;
1220         }
1221
1222         match self.check_type_for_ffi(&mut FxHashSet::default(), ty) {
1223             FfiResult::FfiSafe => {}
1224             FfiResult::FfiPhantom(ty) => {
1225                 self.emit_ffi_unsafe_type_lint(
1226                     ty,
1227                     sp,
1228                     fluent::lint_improper_ctypes_only_phantomdata,
1229                     None,
1230                 );
1231             }
1232             // If `ty` is a `repr(transparent)` newtype, and the non-zero-sized type is a generic
1233             // argument, which after substitution, is `()`, then this branch can be hit.
1234             FfiResult::FfiUnsafe { ty, .. } if is_return_type && ty.is_unit() => {}
1235             FfiResult::FfiUnsafe { ty, reason, help } => {
1236                 self.emit_ffi_unsafe_type_lint(ty, sp, reason, help);
1237             }
1238         }
1239     }
1240
1241     fn check_foreign_fn(&mut self, id: hir::HirId, decl: &hir::FnDecl<'_>) {
1242         let def_id = self.cx.tcx.hir().local_def_id(id);
1243         let sig = self.cx.tcx.fn_sig(def_id);
1244         let sig = self.cx.tcx.erase_late_bound_regions(sig);
1245
1246         for (input_ty, input_hir) in iter::zip(sig.inputs(), decl.inputs) {
1247             self.check_type_for_ffi_and_report_errors(input_hir.span, *input_ty, false, false);
1248         }
1249
1250         if let hir::FnRetTy::Return(ref ret_hir) = decl.output {
1251             let ret_ty = sig.output();
1252             self.check_type_for_ffi_and_report_errors(ret_hir.span, ret_ty, false, true);
1253         }
1254     }
1255
1256     fn check_foreign_static(&mut self, id: hir::HirId, span: Span) {
1257         let def_id = self.cx.tcx.hir().local_def_id(id);
1258         let ty = self.cx.tcx.type_of(def_id);
1259         self.check_type_for_ffi_and_report_errors(span, ty, true, false);
1260     }
1261
1262     fn is_internal_abi(&self, abi: SpecAbi) -> bool {
1263         matches!(
1264             abi,
1265             SpecAbi::Rust | SpecAbi::RustCall | SpecAbi::RustIntrinsic | SpecAbi::PlatformIntrinsic
1266         )
1267     }
1268 }
1269
1270 impl<'tcx> LateLintPass<'tcx> for ImproperCTypesDeclarations {
1271     fn check_foreign_item(&mut self, cx: &LateContext<'_>, it: &hir::ForeignItem<'_>) {
1272         let mut vis = ImproperCTypesVisitor { cx, mode: CItemKind::Declaration };
1273         let abi = cx.tcx.hir().get_foreign_abi(it.hir_id());
1274
1275         if !vis.is_internal_abi(abi) {
1276             match it.kind {
1277                 hir::ForeignItemKind::Fn(ref decl, _, _) => {
1278                     vis.check_foreign_fn(it.hir_id(), decl);
1279                 }
1280                 hir::ForeignItemKind::Static(ref ty, _) => {
1281                     vis.check_foreign_static(it.hir_id(), ty.span);
1282                 }
1283                 hir::ForeignItemKind::Type => (),
1284             }
1285         }
1286     }
1287 }
1288
1289 impl<'tcx> LateLintPass<'tcx> for ImproperCTypesDefinitions {
1290     fn check_fn(
1291         &mut self,
1292         cx: &LateContext<'tcx>,
1293         kind: hir::intravisit::FnKind<'tcx>,
1294         decl: &'tcx hir::FnDecl<'_>,
1295         _: &'tcx hir::Body<'_>,
1296         _: Span,
1297         hir_id: hir::HirId,
1298     ) {
1299         use hir::intravisit::FnKind;
1300
1301         let abi = match kind {
1302             FnKind::ItemFn(_, _, header, ..) => header.abi,
1303             FnKind::Method(_, sig, ..) => sig.header.abi,
1304             _ => return,
1305         };
1306
1307         let mut vis = ImproperCTypesVisitor { cx, mode: CItemKind::Definition };
1308         if !vis.is_internal_abi(abi) {
1309             vis.check_foreign_fn(hir_id, decl);
1310         }
1311     }
1312 }
1313
1314 declare_lint_pass!(VariantSizeDifferences => [VARIANT_SIZE_DIFFERENCES]);
1315
1316 impl<'tcx> LateLintPass<'tcx> for VariantSizeDifferences {
1317     fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1318         if let hir::ItemKind::Enum(ref enum_definition, _) = it.kind {
1319             let t = cx.tcx.type_of(it.owner_id);
1320             let ty = cx.tcx.erase_regions(t);
1321             let Ok(layout) = cx.layout_of(ty) else { return };
1322             let Variants::Multiple {
1323                     tag_encoding: TagEncoding::Direct, tag, ref variants, ..
1324                 } = &layout.variants else {
1325                 return
1326             };
1327
1328             let tag_size = tag.size(&cx.tcx).bytes();
1329
1330             debug!(
1331                 "enum `{}` is {} bytes large with layout:\n{:#?}",
1332                 t,
1333                 layout.size.bytes(),
1334                 layout
1335             );
1336
1337             let (largest, slargest, largest_index) = iter::zip(enum_definition.variants, variants)
1338                 .map(|(variant, variant_layout)| {
1339                     // Subtract the size of the enum tag.
1340                     let bytes = variant_layout.size.bytes().saturating_sub(tag_size);
1341
1342                     debug!("- variant `{}` is {} bytes large", variant.ident, bytes);
1343                     bytes
1344                 })
1345                 .enumerate()
1346                 .fold((0, 0, 0), |(l, s, li), (idx, size)| {
1347                     if size > l {
1348                         (size, l, idx)
1349                     } else if size > s {
1350                         (l, size, li)
1351                     } else {
1352                         (l, s, li)
1353                     }
1354                 });
1355
1356             // We only warn if the largest variant is at least thrice as large as
1357             // the second-largest.
1358             if largest > slargest * 3 && slargest > 0 {
1359                 cx.emit_spanned_lint(
1360                     VARIANT_SIZE_DIFFERENCES,
1361                     enum_definition.variants[largest_index].span,
1362                     VariantSizeDifferencesDiag { largest },
1363                 );
1364             }
1365         }
1366     }
1367 }
1368
1369 declare_lint! {
1370     /// The `invalid_atomic_ordering` lint detects passing an `Ordering`
1371     /// to an atomic operation that does not support that ordering.
1372     ///
1373     /// ### Example
1374     ///
1375     /// ```rust,compile_fail
1376     /// # use core::sync::atomic::{AtomicU8, Ordering};
1377     /// let atom = AtomicU8::new(0);
1378     /// let value = atom.load(Ordering::Release);
1379     /// # let _ = value;
1380     /// ```
1381     ///
1382     /// {{produces}}
1383     ///
1384     /// ### Explanation
1385     ///
1386     /// Some atomic operations are only supported for a subset of the
1387     /// `atomic::Ordering` variants. Passing an unsupported variant will cause
1388     /// an unconditional panic at runtime, which is detected by this lint.
1389     ///
1390     /// This lint will trigger in the following cases: (where `AtomicType` is an
1391     /// atomic type from `core::sync::atomic`, such as `AtomicBool`,
1392     /// `AtomicPtr`, `AtomicUsize`, or any of the other integer atomics).
1393     ///
1394     /// - Passing `Ordering::Acquire` or `Ordering::AcqRel` to
1395     ///   `AtomicType::store`.
1396     ///
1397     /// - Passing `Ordering::Release` or `Ordering::AcqRel` to
1398     ///   `AtomicType::load`.
1399     ///
1400     /// - Passing `Ordering::Relaxed` to `core::sync::atomic::fence` or
1401     ///   `core::sync::atomic::compiler_fence`.
1402     ///
1403     /// - Passing `Ordering::Release` or `Ordering::AcqRel` as the failure
1404     ///   ordering for any of `AtomicType::compare_exchange`,
1405     ///   `AtomicType::compare_exchange_weak`, or `AtomicType::fetch_update`.
1406     INVALID_ATOMIC_ORDERING,
1407     Deny,
1408     "usage of invalid atomic ordering in atomic operations and memory fences"
1409 }
1410
1411 declare_lint_pass!(InvalidAtomicOrdering => [INVALID_ATOMIC_ORDERING]);
1412
1413 impl InvalidAtomicOrdering {
1414     fn inherent_atomic_method_call<'hir>(
1415         cx: &LateContext<'_>,
1416         expr: &Expr<'hir>,
1417         recognized_names: &[Symbol], // used for fast path calculation
1418     ) -> Option<(Symbol, &'hir [Expr<'hir>])> {
1419         const ATOMIC_TYPES: &[Symbol] = &[
1420             sym::AtomicBool,
1421             sym::AtomicPtr,
1422             sym::AtomicUsize,
1423             sym::AtomicU8,
1424             sym::AtomicU16,
1425             sym::AtomicU32,
1426             sym::AtomicU64,
1427             sym::AtomicU128,
1428             sym::AtomicIsize,
1429             sym::AtomicI8,
1430             sym::AtomicI16,
1431             sym::AtomicI32,
1432             sym::AtomicI64,
1433             sym::AtomicI128,
1434         ];
1435         if let ExprKind::MethodCall(ref method_path, _, args, _) = &expr.kind
1436             && recognized_names.contains(&method_path.ident.name)
1437             && let Some(m_def_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id)
1438             && let Some(impl_did) = cx.tcx.impl_of_method(m_def_id)
1439             && let Some(adt) = cx.tcx.type_of(impl_did).ty_adt_def()
1440             // skip extension traits, only lint functions from the standard library
1441             && cx.tcx.trait_id_of_impl(impl_did).is_none()
1442             && let parent = cx.tcx.parent(adt.did())
1443             && cx.tcx.is_diagnostic_item(sym::atomic_mod, parent)
1444             && ATOMIC_TYPES.contains(&cx.tcx.item_name(adt.did()))
1445         {
1446             return Some((method_path.ident.name, args));
1447         }
1448         None
1449     }
1450
1451     fn match_ordering(cx: &LateContext<'_>, ord_arg: &Expr<'_>) -> Option<Symbol> {
1452         let ExprKind::Path(ref ord_qpath) = ord_arg.kind else { return None };
1453         let did = cx.qpath_res(ord_qpath, ord_arg.hir_id).opt_def_id()?;
1454         let tcx = cx.tcx;
1455         let atomic_ordering = tcx.get_diagnostic_item(sym::Ordering);
1456         let name = tcx.item_name(did);
1457         let parent = tcx.parent(did);
1458         [sym::Relaxed, sym::Release, sym::Acquire, sym::AcqRel, sym::SeqCst].into_iter().find(
1459             |&ordering| {
1460                 name == ordering
1461                     && (Some(parent) == atomic_ordering
1462                             // needed in case this is a ctor, not a variant
1463                             || tcx.opt_parent(parent) == atomic_ordering)
1464             },
1465         )
1466     }
1467
1468     fn check_atomic_load_store(cx: &LateContext<'_>, expr: &Expr<'_>) {
1469         if let Some((method, args)) = Self::inherent_atomic_method_call(cx, expr, &[sym::load, sym::store])
1470             && let Some((ordering_arg, invalid_ordering)) = match method {
1471                 sym::load => Some((&args[0], sym::Release)),
1472                 sym::store => Some((&args[1], sym::Acquire)),
1473                 _ => None,
1474             }
1475             && let Some(ordering) = Self::match_ordering(cx, ordering_arg)
1476             && (ordering == invalid_ordering || ordering == sym::AcqRel)
1477         {
1478             if method == sym::load {
1479                 cx.emit_spanned_lint(INVALID_ATOMIC_ORDERING, ordering_arg.span, AtomicOrderingLoad);
1480             } else {
1481                 cx.emit_spanned_lint(INVALID_ATOMIC_ORDERING, ordering_arg.span, AtomicOrderingStore);
1482             };
1483         }
1484     }
1485
1486     fn check_memory_fence(cx: &LateContext<'_>, expr: &Expr<'_>) {
1487         if let ExprKind::Call(ref func, ref args) = expr.kind
1488             && let ExprKind::Path(ref func_qpath) = func.kind
1489             && let Some(def_id) = cx.qpath_res(func_qpath, func.hir_id).opt_def_id()
1490             && matches!(cx.tcx.get_diagnostic_name(def_id), Some(sym::fence | sym::compiler_fence))
1491             && Self::match_ordering(cx, &args[0]) == Some(sym::Relaxed)
1492         {
1493             cx.emit_spanned_lint(INVALID_ATOMIC_ORDERING, args[0].span, AtomicOrderingFence);
1494         }
1495     }
1496
1497     fn check_atomic_compare_exchange(cx: &LateContext<'_>, expr: &Expr<'_>) {
1498         let Some((method, args)) = Self::inherent_atomic_method_call(cx, expr, &[sym::fetch_update, sym::compare_exchange, sym::compare_exchange_weak])
1499             else {return };
1500
1501         let fail_order_arg = match method {
1502             sym::fetch_update => &args[1],
1503             sym::compare_exchange | sym::compare_exchange_weak => &args[3],
1504             _ => return,
1505         };
1506
1507         let Some(fail_ordering) = Self::match_ordering(cx, fail_order_arg) else { return };
1508
1509         if matches!(fail_ordering, sym::Release | sym::AcqRel) {
1510             cx.emit_spanned_lint(
1511                 INVALID_ATOMIC_ORDERING,
1512                 fail_order_arg.span,
1513                 InvalidAtomicOrderingDiag { method, fail_order_arg_span: fail_order_arg.span },
1514             );
1515         }
1516     }
1517 }
1518
1519 impl<'tcx> LateLintPass<'tcx> for InvalidAtomicOrdering {
1520     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
1521         Self::check_atomic_load_store(cx, expr);
1522         Self::check_memory_fence(cx, expr);
1523         Self::check_atomic_compare_exchange(cx, expr);
1524     }
1525 }