compiler/rustc_lint/src/types.rs

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