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, ImproperCTypes,
   5     InvalidAtomicOrderingDiag, OnlyCastu8ToChar, OverflowingBinHex, OverflowingBinHexSign,
   6     OverflowingBinHexSub, OverflowingInt, OverflowingIntHelp, OverflowingLiteral, OverflowingUInt,
   7     RangeEndpointOutOfRange, 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         let lit = cx
 343             .sess()
 344             .source_map()
 345             .span_to_snippet(lit.span)
 346             .expect("must get snippet from literal");
 347         let help = get_type_suggestion(cx.typeck_results().node_type(e.hir_id), v, negative)
 348             .map(|suggestion_ty| OverflowingIntHelp { suggestion_ty });
 349
 350         cx.emit_spanned_lint(
 351             OVERFLOWING_LITERALS,
 352             e.span,
 353             OverflowingInt { ty: t.name_str(), lit, min, max, help },
 354         );
 355     }
 356 }
 357
 358 fn lint_uint_literal<'tcx>(
 359     cx: &LateContext<'tcx>,
 360     e: &'tcx hir::Expr<'tcx>,
 361     lit: &hir::Lit,
 362     t: ty::UintTy,
 363 ) {
 364     let uint_type = t.normalize(cx.sess().target.pointer_width);
 365     let (min, max) = uint_ty_range(uint_type);
 366     let lit_val: u128 = match lit.node {
 367         // _v is u8, within range by definition
 368         ast::LitKind::Byte(_v) => return,
 369         ast::LitKind::Int(v, _) => v,
 370         _ => bug!(),
 371     };
 372     if lit_val < min || lit_val > max {
 373         let parent_id = cx.tcx.hir().parent_id(e.hir_id);
 374         if let Node::Expr(par_e) = cx.tcx.hir().get(parent_id) {
 375             match par_e.kind {
 376                 hir::ExprKind::Cast(..) => {
 377                     if let ty::Char = cx.typeck_results().expr_ty(par_e).kind() {
 378                         cx.emit_spanned_lint(
 379                             OVERFLOWING_LITERALS,
 380                             par_e.span,
 381                             OnlyCastu8ToChar { span: par_e.span, literal: lit_val },
 382                         );
 383                         return;
 384                     }
 385                 }
 386                 _ => {}
 387             }
 388         }
 389         if lint_overflowing_range_endpoint(cx, lit, lit_val, max, e, t.name_str()) {
 390             // The overflowing literal lint was emitted by `lint_overflowing_range_endpoint`.
 391             return;
 392         }
 393         if let Some(repr_str) = get_bin_hex_repr(cx, lit) {
 394             report_bin_hex_error(
 395                 cx,
 396                 e,
 397                 attr::IntType::UnsignedInt(ty::ast_uint_ty(t)),
 398                 Integer::from_uint_ty(cx, t).size(),
 399                 repr_str,
 400                 lit_val,
 401                 false,
 402             );
 403             return;
 404         }
 405         cx.emit_spanned_lint(
 406             OVERFLOWING_LITERALS,
 407             e.span,
 408             OverflowingUInt {
 409                 ty: t.name_str(),
 410                 lit: cx
 411                     .sess()
 412                     .source_map()
 413                     .span_to_snippet(lit.span)
 414                     .expect("must get snippet from literal"),
 415                 min,
 416                 max,
 417             },
 418         );
 419     }
 420 }
 421
 422 fn lint_literal<'tcx>(
 423     cx: &LateContext<'tcx>,
 424     type_limits: &TypeLimits,
 425     e: &'tcx hir::Expr<'tcx>,
 426     lit: &hir::Lit,
 427 ) {
 428     match *cx.typeck_results().node_type(e.hir_id).kind() {
 429         ty::Int(t) => {
 430             match lit.node {
 431                 ast::LitKind::Int(v, ast::LitIntType::Signed(_) | ast::LitIntType::Unsuffixed) => {
 432                     lint_int_literal(cx, type_limits, e, lit, t, v)
 433                 }
 434                 _ => bug!(),
 435             };
 436         }
 437         ty::Uint(t) => lint_uint_literal(cx, e, lit, t),
 438         ty::Float(t) => {
 439             let is_infinite = match lit.node {
 440                 ast::LitKind::Float(v, _) => match t {
 441                     ty::FloatTy::F32 => v.as_str().parse().map(f32::is_infinite),
 442                     ty::FloatTy::F64 => v.as_str().parse().map(f64::is_infinite),
 443                 },
 444                 _ => bug!(),
 445             };
 446             if is_infinite == Ok(true) {
 447                 cx.emit_spanned_lint(
 448                     OVERFLOWING_LITERALS,
 449                     e.span,
 450                     OverflowingLiteral {
 451                         ty: t.name_str(),
 452                         lit: cx
 453                             .sess()
 454                             .source_map()
 455                             .span_to_snippet(lit.span)
 456                             .expect("must get snippet from literal"),
 457                     },
 458                 );
 459             }
 460         }
 461         _ => {}
 462     }
 463 }
 464
 465 impl<'tcx> LateLintPass<'tcx> for TypeLimits {
 466     fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx hir::Expr<'tcx>) {
 467         match e.kind {
 468             hir::ExprKind::Unary(hir::UnOp::Neg, ref expr) => {
 469                 // propagate negation, if the negation itself isn't negated
 470                 if self.negated_expr_id != Some(e.hir_id) {
 471                     self.negated_expr_id = Some(expr.hir_id);
 472                 }
 473             }
 474             hir::ExprKind::Binary(binop, ref l, ref r) => {
 475                 if is_comparison(binop) && !check_limits(cx, binop, &l, &r) {
 476                     cx.emit_spanned_lint(UNUSED_COMPARISONS, e.span, UnusedComparisons);
 477                 }
 478             }
 479             hir::ExprKind::Lit(ref lit) => lint_literal(cx, self, e, lit),
 480             _ => {}
 481         };
 482
 483         fn is_valid<T: PartialOrd>(binop: hir::BinOp, v: T, min: T, max: T) -> bool {
 484             match binop.node {
 485                 hir::BinOpKind::Lt => v > min && v <= max,
 486                 hir::BinOpKind::Le => v >= min && v < max,
 487                 hir::BinOpKind::Gt => v >= min && v < max,
 488                 hir::BinOpKind::Ge => v > min && v <= max,
 489                 hir::BinOpKind::Eq | hir::BinOpKind::Ne => v >= min && v <= max,
 490                 _ => bug!(),
 491             }
 492         }
 493
 494         fn rev_binop(binop: hir::BinOp) -> hir::BinOp {
 495             source_map::respan(
 496                 binop.span,
 497                 match binop.node {
 498                     hir::BinOpKind::Lt => hir::BinOpKind::Gt,
 499                     hir::BinOpKind::Le => hir::BinOpKind::Ge,
 500                     hir::BinOpKind::Gt => hir::BinOpKind::Lt,
 501                     hir::BinOpKind::Ge => hir::BinOpKind::Le,
 502                     _ => return binop,
 503                 },
 504             )
 505         }
 506
 507         fn check_limits(
 508             cx: &LateContext<'_>,
 509             binop: hir::BinOp,
 510             l: &hir::Expr<'_>,
 511             r: &hir::Expr<'_>,
 512         ) -> bool {
 513             let (lit, expr, swap) = match (&l.kind, &r.kind) {
 514                 (&hir::ExprKind::Lit(_), _) => (l, r, true),
 515                 (_, &hir::ExprKind::Lit(_)) => (r, l, false),
 516                 _ => return true,
 517             };
 518             // Normalize the binop so that the literal is always on the RHS in
 519             // the comparison
 520             let norm_binop = if swap { rev_binop(binop) } else { binop };
 521             match *cx.typeck_results().node_type(expr.hir_id).kind() {
 522                 ty::Int(int_ty) => {
 523                     let (min, max) = int_ty_range(int_ty);
 524                     let lit_val: i128 = match lit.kind {
 525                         hir::ExprKind::Lit(ref li) => match li.node {
 526                             ast::LitKind::Int(
 527                                 v,
 528                                 ast::LitIntType::Signed(_) | ast::LitIntType::Unsuffixed,
 529                             ) => v as i128,
 530                             _ => return true,
 531                         },
 532                         _ => bug!(),
 533                     };
 534                     is_valid(norm_binop, lit_val, min, max)
 535                 }
 536                 ty::Uint(uint_ty) => {
 537                     let (min, max): (u128, u128) = uint_ty_range(uint_ty);
 538                     let lit_val: u128 = match lit.kind {
 539                         hir::ExprKind::Lit(ref li) => match li.node {
 540                             ast::LitKind::Int(v, _) => v,
 541                             _ => return true,
 542                         },
 543                         _ => bug!(),
 544                     };
 545                     is_valid(norm_binop, lit_val, min, max)
 546                 }
 547                 _ => true,
 548             }
 549         }
 550
 551         fn is_comparison(binop: hir::BinOp) -> bool {
 552             matches!(
 553                 binop.node,
 554                 hir::BinOpKind::Eq
 555                     | hir::BinOpKind::Lt
 556                     | hir::BinOpKind::Le
 557                     | hir::BinOpKind::Ne
 558                     | hir::BinOpKind::Ge
 559                     | hir::BinOpKind::Gt
 560             )
 561         }
 562     }
 563 }
 564
 565 declare_lint! {
 566     /// The `improper_ctypes` lint detects incorrect use of types in foreign
 567     /// modules.
 568     ///
 569     /// ### Example
 570     ///
 571     /// ```rust
 572     /// extern "C" {
 573     ///     static STATIC: String;
 574     /// }
 575     /// ```
 576     ///
 577     /// {{produces}}
 578     ///
 579     /// ### Explanation
 580     ///
 581     /// The compiler has several checks to verify that types used in `extern`
 582     /// blocks are safe and follow certain rules to ensure proper
 583     /// compatibility with the foreign interfaces. This lint is issued when it
 584     /// detects a probable mistake in a definition. The lint usually should
 585     /// provide a description of the issue, along with possibly a hint on how
 586     /// to resolve it.
 587     IMPROPER_CTYPES,
 588     Warn,
 589     "proper use of libc types in foreign modules"
 590 }
 591
 592 declare_lint_pass!(ImproperCTypesDeclarations => [IMPROPER_CTYPES]);
 593
 594 declare_lint! {
 595     /// The `improper_ctypes_definitions` lint detects incorrect use of
 596     /// [`extern` function] definitions.
 597     ///
 598     /// [`extern` function]: https://doc.rust-lang.org/reference/items/functions.html#extern-function-qualifier
 599     ///
 600     /// ### Example
 601     ///
 602     /// ```rust
 603     /// # #![allow(unused)]
 604     /// pub extern "C" fn str_type(p: &str) { }
 605     /// ```
 606     ///
 607     /// {{produces}}
 608     ///
 609     /// ### Explanation
 610     ///
 611     /// There are many parameter and return types that may be specified in an
 612     /// `extern` function that are not compatible with the given ABI. This
 613     /// lint is an alert that these types should not be used. The lint usually
 614     /// should provide a description of the issue, along with possibly a hint
 615     /// on how to resolve it.
 616     IMPROPER_CTYPES_DEFINITIONS,
 617     Warn,
 618     "proper use of libc types in foreign item definitions"
 619 }
 620
 621 declare_lint_pass!(ImproperCTypesDefinitions => [IMPROPER_CTYPES_DEFINITIONS]);
 622
 623 #[derive(Clone, Copy)]
 624 pub(crate) enum CItemKind {
 625     Declaration,
 626     Definition,
 627 }
 628
 629 struct ImproperCTypesVisitor<'a, 'tcx> {
 630     cx: &'a LateContext<'tcx>,
 631     mode: CItemKind,
 632 }
 633
 634 enum FfiResult<'tcx> {
 635     FfiSafe,
 636     FfiPhantom(Ty<'tcx>),
 637     FfiUnsafe { ty: Ty<'tcx>, reason: DiagnosticMessage, help: Option<DiagnosticMessage> },
 638 }
 639
 640 pub(crate) fn nonnull_optimization_guaranteed<'tcx>(
 641     tcx: TyCtxt<'tcx>,
 642     def: ty::AdtDef<'tcx>,
 643 ) -> bool {
 644     tcx.has_attr(def.did(), sym::rustc_nonnull_optimization_guaranteed)
 645 }
 646
 647 /// `repr(transparent)` structs can have a single non-ZST field, this function returns that
 648 /// field.
 649 pub fn transparent_newtype_field<'a, 'tcx>(
 650     tcx: TyCtxt<'tcx>,
 651     variant: &'a ty::VariantDef,
 652 ) -> Option<&'a ty::FieldDef> {
 653     let param_env = tcx.param_env(variant.def_id);
 654     variant.fields.iter().find(|field| {
 655         let field_ty = tcx.type_of(field.did);
 656         let is_zst = tcx.layout_of(param_env.and(field_ty)).map_or(false, |layout| layout.is_zst());
 657         !is_zst
 658     })
 659 }
 660
 661 /// Is type known to be non-null?
 662 fn ty_is_known_nonnull<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>, mode: CItemKind) -> bool {
 663     let tcx = cx.tcx;
 664     match ty.kind() {
 665         ty::FnPtr(_) => true,
 666         ty::Ref(..) => true,
 667         ty::Adt(def, _) if def.is_box() && matches!(mode, CItemKind::Definition) => true,
 668         ty::Adt(def, substs) if def.repr().transparent() && !def.is_union() => {
 669             let marked_non_null = nonnull_optimization_guaranteed(tcx, *def);
 670
 671             if marked_non_null {
 672                 return true;
 673             }
 674
 675             // `UnsafeCell` has its niche hidden.
 676             if def.is_unsafe_cell() {
 677                 return false;
 678             }
 679
 680             def.variants()
 681                 .iter()
 682                 .filter_map(|variant| transparent_newtype_field(cx.tcx, variant))
 683                 .any(|field| ty_is_known_nonnull(cx, field.ty(tcx, substs), mode))
 684         }
 685         _ => false,
 686     }
 687 }
 688
 689 /// Given a non-null scalar (or transparent) type `ty`, return the nullable version of that type.
 690 /// If the type passed in was not scalar, returns None.
 691 fn get_nullable_type<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> Option<Ty<'tcx>> {
 692     let tcx = cx.tcx;
 693     Some(match *ty.kind() {
 694         ty::Adt(field_def, field_substs) => {
 695             let inner_field_ty = {
 696                 let mut first_non_zst_ty = field_def
 697                     .variants()
 698                     .iter()
 699                     .filter_map(|v| transparent_newtype_field(cx.tcx, v));
 700                 debug_assert_eq!(
 701                     first_non_zst_ty.clone().count(),
 702                     1,
 703                     "Wrong number of fields for transparent type"
 704                 );
 705                 first_non_zst_ty
 706                     .next_back()
 707                     .expect("No non-zst fields in transparent type.")
 708                     .ty(tcx, field_substs)
 709             };
 710             return get_nullable_type(cx, inner_field_ty);
 711         }
 712         ty::Int(ty) => tcx.mk_mach_int(ty),
 713         ty::Uint(ty) => tcx.mk_mach_uint(ty),
 714         ty::RawPtr(ty_mut) => tcx.mk_ptr(ty_mut),
 715         // As these types are always non-null, the nullable equivalent of
 716         // Option<T> of these types are their raw pointer counterparts.
 717         ty::Ref(_region, ty, mutbl) => tcx.mk_ptr(ty::TypeAndMut { ty, mutbl }),
 718         ty::FnPtr(..) => {
 719             // There is no nullable equivalent for Rust's function pointers -- you
 720             // must use an Option<fn(..) -> _> to represent it.
 721             ty
 722         }
 723
 724         // We should only ever reach this case if ty_is_known_nonnull is extended
 725         // to other types.
 726         ref unhandled => {
 727             debug!(
 728                 "get_nullable_type: Unhandled scalar kind: {:?} while checking {:?}",
 729                 unhandled, ty
 730             );
 731             return None;
 732         }
 733     })
 734 }
 735
 736 /// Check if this enum can be safely exported based on the "nullable pointer optimization". If it
 737 /// can, return the type that `ty` can be safely converted to, otherwise return `None`.
 738 /// Currently restricted to function pointers, boxes, references, `core::num::NonZero*`,
 739 /// `core::ptr::NonNull`, and `#[repr(transparent)]` newtypes.
 740 /// FIXME: This duplicates code in codegen.
 741 pub(crate) fn repr_nullable_ptr<'tcx>(
 742     cx: &LateContext<'tcx>,
 743     ty: Ty<'tcx>,
 744     ckind: CItemKind,
 745 ) -> Option<Ty<'tcx>> {
 746     debug!("is_repr_nullable_ptr(cx, ty = {:?})", ty);
 747     if let ty::Adt(ty_def, substs) = ty.kind() {
 748         let field_ty = match &ty_def.variants().raw[..] {
 749             [var_one, var_two] => match (&var_one.fields[..], &var_two.fields[..]) {
 750                 ([], [field]) | ([field], []) => field.ty(cx.tcx, substs),
 751                 _ => return None,
 752             },
 753             _ => return None,
 754         };
 755
 756         if !ty_is_known_nonnull(cx, field_ty, ckind) {
 757             return None;
 758         }
 759
 760         // At this point, the field's type is known to be nonnull and the parent enum is Option-like.
 761         // If the computed size for the field and the enum are different, the nonnull optimization isn't
 762         // being applied (and we've got a problem somewhere).
 763         let compute_size_skeleton = |t| SizeSkeleton::compute(t, cx.tcx, cx.param_env).unwrap();
 764         if !compute_size_skeleton(ty).same_size(compute_size_skeleton(field_ty)) {
 765             bug!("improper_ctypes: Option nonnull optimization not applied?");
 766         }
 767
 768         // Return the nullable type this Option-like enum can be safely represented with.
 769         let field_ty_abi = &cx.layout_of(field_ty).unwrap().abi;
 770         if let Abi::Scalar(field_ty_scalar) = field_ty_abi {
 771             match field_ty_scalar.valid_range(cx) {
 772                 WrappingRange { start: 0, end }
 773                     if end == field_ty_scalar.size(&cx.tcx).unsigned_int_max() - 1 =>
 774                 {
 775                     return Some(get_nullable_type(cx, field_ty).unwrap());
 776                 }
 777                 WrappingRange { start: 1, .. } => {
 778                     return Some(get_nullable_type(cx, field_ty).unwrap());
 779                 }
 780                 WrappingRange { start, end } => {
 781                     unreachable!("Unhandled start and end range: ({}, {})", start, end)
 782                 }
 783             };
 784         }
 785     }
 786     None
 787 }
 788
 789 impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
 790     /// Check if the type is array and emit an unsafe type lint.
 791     fn check_for_array_ty(&mut self, sp: Span, ty: Ty<'tcx>) -> bool {
 792         if let ty::Array(..) = ty.kind() {
 793             self.emit_ffi_unsafe_type_lint(
 794                 ty,
 795                 sp,
 796                 fluent::lint_improper_ctypes_array_reason,
 797                 Some(fluent::lint_improper_ctypes_array_help),
 798             );
 799             true
 800         } else {
 801             false
 802         }
 803     }
 804
 805     /// Checks if the given field's type is "ffi-safe".
 806     fn check_field_type_for_ffi(
 807         &self,
 808         cache: &mut FxHashSet<Ty<'tcx>>,
 809         field: &ty::FieldDef,
 810         substs: SubstsRef<'tcx>,
 811     ) -> FfiResult<'tcx> {
 812         let field_ty = field.ty(self.cx.tcx, substs);
 813         if field_ty.has_opaque_types() {
 814             self.check_type_for_ffi(cache, field_ty)
 815         } else {
 816             let field_ty = self.cx.tcx.normalize_erasing_regions(self.cx.param_env, field_ty);
 817             self.check_type_for_ffi(cache, field_ty)
 818         }
 819     }
 820
 821     /// Checks if the given `VariantDef`'s field types are "ffi-safe".
 822     fn check_variant_for_ffi(
 823         &self,
 824         cache: &mut FxHashSet<Ty<'tcx>>,
 825         ty: Ty<'tcx>,
 826         def: ty::AdtDef<'tcx>,
 827         variant: &ty::VariantDef,
 828         substs: SubstsRef<'tcx>,
 829     ) -> FfiResult<'tcx> {
 830         use FfiResult::*;
 831
 832         if def.repr().transparent() {
 833             // Can assume that at most one field is not a ZST, so only check
 834             // that field's type for FFI-safety.
 835             if let Some(field) = transparent_newtype_field(self.cx.tcx, variant) {
 836                 self.check_field_type_for_ffi(cache, field, substs)
 837             } else {
 838                 // All fields are ZSTs; this means that the type should behave
 839                 // like (), which is FFI-unsafe
 840                 FfiUnsafe { ty, reason: fluent::lint_improper_ctypes_struct_zst, help: None }
 841             }
 842         } else {
 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.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 r,
 860                 }
 861             }
 862
 863             if all_phantom { FfiPhantom(ty) } else { FfiSafe }
 864         }
 865     }
 866
 867     /// Checks if the given type is "ffi-safe" (has a stable, well-defined
 868     /// representation which can be exported to C code).
 869     fn check_type_for_ffi(&self, cache: &mut FxHashSet<Ty<'tcx>>, ty: Ty<'tcx>) -> FfiResult<'tcx> {
 870         use FfiResult::*;
 871
 872         let tcx = self.cx.tcx;
 873
 874         // Protect against infinite recursion, for example
 875         // `struct S(*mut S);`.
 876         // FIXME: A recursion limit is necessary as well, for irregular
 877         // recursive types.
 878         if !cache.insert(ty) {
 879             return FfiSafe;
 880         }
 881
 882         match *ty.kind() {
 883             ty::Adt(def, substs) => {
 884                 if def.is_box() && matches!(self.mode, CItemKind::Definition) {
 885                     if ty.boxed_ty().is_sized(tcx, self.cx.param_env) {
 886                         return FfiSafe;
 887                     } else {
 888                         return FfiUnsafe {
 889                             ty,
 890                             reason: fluent::lint_improper_ctypes_box,
 891                             help: None,
 892                         };
 893                     }
 894                 }
 895                 if def.is_phantom_data() {
 896                     return FfiPhantom(ty);
 897                 }
 898                 match def.adt_kind() {
 899                     AdtKind::Struct | AdtKind::Union => {
 900                         if !def.repr().c() && !def.repr().transparent() {
 901                             return FfiUnsafe {
 902                                 ty,
 903                                 reason: if def.is_struct() {
 904                                     fluent::lint_improper_ctypes_struct_layout_reason
 905                                 } else {
 906                                     fluent::lint_improper_ctypes_union_layout_reason
 907                                 },
 908                                 help: if def.is_struct() {
 909                                     Some(fluent::lint_improper_ctypes_struct_layout_help)
 910                                 } else {
 911                                     Some(fluent::lint_improper_ctypes_union_layout_help)
 912                                 },
 913                             };
 914                         }
 915
 916                         let is_non_exhaustive =
 917                             def.non_enum_variant().is_field_list_non_exhaustive();
 918                         if is_non_exhaustive && !def.did().is_local() {
 919                             return FfiUnsafe {
 920                                 ty,
 921                                 reason: if def.is_struct() {
 922                                     fluent::lint_improper_ctypes_struct_non_exhaustive
 923                                 } else {
 924                                     fluent::lint_improper_ctypes_union_non_exhaustive
 925                                 },
 926                                 help: None,
 927                             };
 928                         }
 929
 930                         if def.non_enum_variant().fields.is_empty() {
 931                             return FfiUnsafe {
 932                                 ty,
 933                                 reason: if def.is_struct() {
 934                                     fluent::lint_improper_ctypes_struct_fieldless_reason
 935                                 } else {
 936                                     fluent::lint_improper_ctypes_union_fieldless_reason
 937                                 },
 938                                 help: if def.is_struct() {
 939                                     Some(fluent::lint_improper_ctypes_struct_fieldless_help)
 940                                 } else {
 941                                     Some(fluent::lint_improper_ctypes_union_fieldless_help)
 942                                 },
 943                             };
 944                         }
 945
 946                         self.check_variant_for_ffi(cache, ty, def, def.non_enum_variant(), substs)
 947                     }
 948                     AdtKind::Enum => {
 949                         if def.variants().is_empty() {
 950                             // Empty enums are okay... although sort of useless.
 951                             return FfiSafe;
 952                         }
 953
 954                         // Check for a repr() attribute to specify the size of the
 955                         // discriminant.
 956                         if !def.repr().c() && !def.repr().transparent() && def.repr().int.is_none()
 957                         {
 958                             // Special-case types like `Option<extern fn()>`.
 959                             if repr_nullable_ptr(self.cx, ty, self.mode).is_none() {
 960                                 return FfiUnsafe {
 961                                     ty,
 962                                     reason: fluent::lint_improper_ctypes_enum_repr_reason,
 963                                     help: Some(fluent::lint_improper_ctypes_enum_repr_help),
 964                                 };
 965                             }
 966                         }
 967
 968                         if def.is_variant_list_non_exhaustive() && !def.did().is_local() {
 969                             return FfiUnsafe {
 970                                 ty,
 971                                 reason: fluent::lint_improper_ctypes_non_exhaustive,
 972                                 help: None,
 973                             };
 974                         }
 975
 976                         // Check the contained variants.
 977                         for variant in def.variants() {
 978                             let is_non_exhaustive = variant.is_field_list_non_exhaustive();
 979                             if is_non_exhaustive && !variant.def_id.is_local() {
 980                                 return FfiUnsafe {
 981                                     ty,
 982                                     reason: fluent::lint_improper_ctypes_non_exhaustive_variant,
 983                                     help: None,
 984                                 };
 985                             }
 986
 987                             match self.check_variant_for_ffi(cache, ty, def, variant, substs) {
 988                                 FfiSafe => (),
 989                                 r => return r,
 990                             }
 991                         }
 992
 993                         FfiSafe
 994                     }
 995                 }
 996             }
 997
 998             ty::Char => FfiUnsafe {
 999                 ty,
1000                 reason: fluent::lint_improper_ctypes_char_reason,
1001                 help: Some(fluent::lint_improper_ctypes_char_help),
1002             },
1003
1004             ty::Int(ty::IntTy::I128) | ty::Uint(ty::UintTy::U128) => {
1005                 FfiUnsafe { ty, reason: fluent::lint_improper_ctypes_128bit, help: None }
1006             }
1007
1008             // Primitive types with a stable representation.
1009             ty::Bool | ty::Int(..) | ty::Uint(..) | ty::Float(..) | ty::Never => FfiSafe,
1010
1011             ty::Slice(_) => FfiUnsafe {
1012                 ty,
1013                 reason: fluent::lint_improper_ctypes_slice_reason,
1014                 help: Some(fluent::lint_improper_ctypes_slice_help),
1015             },
1016
1017             ty::Dynamic(..) => {
1018                 FfiUnsafe { ty, reason: fluent::lint_improper_ctypes_dyn, help: None }
1019             }
1020
1021             ty::Str => FfiUnsafe {
1022                 ty,
1023                 reason: fluent::lint_improper_ctypes_str_reason,
1024                 help: Some(fluent::lint_improper_ctypes_str_help),
1025             },
1026
1027             ty::Tuple(..) => FfiUnsafe {
1028                 ty,
1029                 reason: fluent::lint_improper_ctypes_tuple_reason,
1030                 help: Some(fluent::lint_improper_ctypes_tuple_help),
1031             },
1032
1033             ty::RawPtr(ty::TypeAndMut { ty, .. }) | ty::Ref(_, ty, _)
1034                 if {
1035                     matches!(self.mode, CItemKind::Definition)
1036                         && ty.is_sized(self.cx.tcx, self.cx.param_env)
1037                 } =>
1038             {
1039                 FfiSafe
1040             }
1041
1042             ty::RawPtr(ty::TypeAndMut { ty, .. })
1043                 if match ty.kind() {
1044                     ty::Tuple(tuple) => tuple.is_empty(),
1045                     _ => false,
1046                 } =>
1047             {
1048                 FfiSafe
1049             }
1050
1051             ty::RawPtr(ty::TypeAndMut { ty, .. }) | ty::Ref(_, ty, _) => {
1052                 self.check_type_for_ffi(cache, ty)
1053             }
1054
1055             ty::Array(inner_ty, _) => self.check_type_for_ffi(cache, inner_ty),
1056
1057             ty::FnPtr(sig) => {
1058                 if self.is_internal_abi(sig.abi()) {
1059                     return FfiUnsafe {
1060                         ty,
1061                         reason: fluent::lint_improper_ctypes_fnptr_reason,
1062                         help: Some(fluent::lint_improper_ctypes_fnptr_help),
1063                     };
1064                 }
1065
1066                 let sig = tcx.erase_late_bound_regions(sig);
1067                 if !sig.output().is_unit() {
1068                     let r = self.check_type_for_ffi(cache, sig.output());
1069                     match r {
1070                         FfiSafe => {}
1071                         _ => {
1072                             return r;
1073                         }
1074                     }
1075                 }
1076                 for arg in sig.inputs() {
1077                     let r = self.check_type_for_ffi(cache, *arg);
1078                     match r {
1079                         FfiSafe => {}
1080                         _ => {
1081                             return r;
1082                         }
1083                     }
1084                 }
1085                 FfiSafe
1086             }
1087
1088             ty::Foreign(..) => FfiSafe,
1089
1090             // While opaque types are checked for earlier, if a projection in a struct field
1091             // normalizes to an opaque type, then it will reach this branch.
1092             ty::Alias(ty::Opaque, ..) => {
1093                 FfiUnsafe { ty, reason: fluent::lint_improper_ctypes_opaque, help: None }
1094             }
1095
1096             // `extern "C" fn` functions can have type parameters, which may or may not be FFI-safe,
1097             //  so they are currently ignored for the purposes of this lint.
1098             ty::Param(..) | ty::Alias(ty::Projection, ..)
1099                 if matches!(self.mode, CItemKind::Definition) =>
1100             {
1101                 FfiSafe
1102             }
1103
1104             ty::Param(..)
1105             | ty::Alias(ty::Projection, ..)
1106             | ty::Infer(..)
1107             | ty::Bound(..)
1108             | ty::Error(_)
1109             | ty::Closure(..)
1110             | ty::Generator(..)
1111             | ty::GeneratorWitness(..)
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, id: hir::HirId, decl: &hir::FnDecl<'_>) {
1229         let def_id = self.cx.tcx.hir().local_def_id(id);
1230         let sig = self.cx.tcx.fn_sig(def_id);
1231         let sig = self.cx.tcx.erase_late_bound_regions(sig);
1232
1233         for (input_ty, input_hir) in iter::zip(sig.inputs(), decl.inputs) {
1234             self.check_type_for_ffi_and_report_errors(input_hir.span, *input_ty, false, false);
1235         }
1236
1237         if let hir::FnRetTy::Return(ref ret_hir) = decl.output {
1238             let ret_ty = sig.output();
1239             self.check_type_for_ffi_and_report_errors(ret_hir.span, ret_ty, false, true);
1240         }
1241     }
1242
1243     fn check_foreign_static(&mut self, id: hir::HirId, span: Span) {
1244         let def_id = self.cx.tcx.hir().local_def_id(id);
1245         let ty = self.cx.tcx.type_of(def_id);
1246         self.check_type_for_ffi_and_report_errors(span, ty, true, false);
1247     }
1248
1249     fn is_internal_abi(&self, abi: SpecAbi) -> bool {
1250         matches!(
1251             abi,
1252             SpecAbi::Rust | SpecAbi::RustCall | SpecAbi::RustIntrinsic | SpecAbi::PlatformIntrinsic
1253         )
1254     }
1255 }
1256
1257 impl<'tcx> LateLintPass<'tcx> for ImproperCTypesDeclarations {
1258     fn check_foreign_item(&mut self, cx: &LateContext<'_>, it: &hir::ForeignItem<'_>) {
1259         let mut vis = ImproperCTypesVisitor { cx, mode: CItemKind::Declaration };
1260         let abi = cx.tcx.hir().get_foreign_abi(it.hir_id());
1261
1262         if !vis.is_internal_abi(abi) {
1263             match it.kind {
1264                 hir::ForeignItemKind::Fn(ref decl, _, _) => {
1265                     vis.check_foreign_fn(it.hir_id(), decl);
1266                 }
1267                 hir::ForeignItemKind::Static(ref ty, _) => {
1268                     vis.check_foreign_static(it.hir_id(), ty.span);
1269                 }
1270                 hir::ForeignItemKind::Type => (),
1271             }
1272         }
1273     }
1274 }
1275
1276 impl<'tcx> LateLintPass<'tcx> for ImproperCTypesDefinitions {
1277     fn check_fn(
1278         &mut self,
1279         cx: &LateContext<'tcx>,
1280         kind: hir::intravisit::FnKind<'tcx>,
1281         decl: &'tcx hir::FnDecl<'_>,
1282         _: &'tcx hir::Body<'_>,
1283         _: Span,
1284         hir_id: hir::HirId,
1285     ) {
1286         use hir::intravisit::FnKind;
1287
1288         let abi = match kind {
1289             FnKind::ItemFn(_, _, header, ..) => header.abi,
1290             FnKind::Method(_, sig, ..) => sig.header.abi,
1291             _ => return,
1292         };
1293
1294         let mut vis = ImproperCTypesVisitor { cx, mode: CItemKind::Definition };
1295         if !vis.is_internal_abi(abi) {
1296             vis.check_foreign_fn(hir_id, decl);
1297         }
1298     }
1299 }
1300
1301 declare_lint_pass!(VariantSizeDifferences => [VARIANT_SIZE_DIFFERENCES]);
1302
1303 impl<'tcx> LateLintPass<'tcx> for VariantSizeDifferences {
1304     fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
1305         if let hir::ItemKind::Enum(ref enum_definition, _) = it.kind {
1306             let t = cx.tcx.type_of(it.owner_id);
1307             let ty = cx.tcx.erase_regions(t);
1308             let Ok(layout) = cx.layout_of(ty) else { return };
1309             let Variants::Multiple {
1310                     tag_encoding: TagEncoding::Direct, tag, ref variants, ..
1311                 } = &layout.variants else {
1312                 return
1313             };
1314
1315             let tag_size = tag.size(&cx.tcx).bytes();
1316
1317             debug!(
1318                 "enum `{}` is {} bytes large with layout:\n{:#?}",
1319                 t,
1320                 layout.size.bytes(),
1321                 layout
1322             );
1323
1324             let (largest, slargest, largest_index) = iter::zip(enum_definition.variants, variants)
1325                 .map(|(variant, variant_layout)| {
1326                     // Subtract the size of the enum tag.
1327                     let bytes = variant_layout.size.bytes().saturating_sub(tag_size);
1328
1329                     debug!("- variant `{}` is {} bytes large", variant.ident, bytes);
1330                     bytes
1331                 })
1332                 .enumerate()
1333                 .fold((0, 0, 0), |(l, s, li), (idx, size)| {
1334                     if size > l {
1335                         (size, l, idx)
1336                     } else if size > s {
1337                         (l, size, li)
1338                     } else {
1339                         (l, s, li)
1340                     }
1341                 });
1342
1343             // We only warn if the largest variant is at least thrice as large as
1344             // the second-largest.
1345             if largest > slargest * 3 && slargest > 0 {
1346                 cx.emit_spanned_lint(
1347                     VARIANT_SIZE_DIFFERENCES,
1348                     enum_definition.variants[largest_index].span,
1349                     VariantSizeDifferencesDiag { largest },
1350                 );
1351             }
1352         }
1353     }
1354 }
1355
1356 declare_lint! {
1357     /// The `invalid_atomic_ordering` lint detects passing an `Ordering`
1358     /// to an atomic operation that does not support that ordering.
1359     ///
1360     /// ### Example
1361     ///
1362     /// ```rust,compile_fail
1363     /// # use core::sync::atomic::{AtomicU8, Ordering};
1364     /// let atom = AtomicU8::new(0);
1365     /// let value = atom.load(Ordering::Release);
1366     /// # let _ = value;
1367     /// ```
1368     ///
1369     /// {{produces}}
1370     ///
1371     /// ### Explanation
1372     ///
1373     /// Some atomic operations are only supported for a subset of the
1374     /// `atomic::Ordering` variants. Passing an unsupported variant will cause
1375     /// an unconditional panic at runtime, which is detected by this lint.
1376     ///
1377     /// This lint will trigger in the following cases: (where `AtomicType` is an
1378     /// atomic type from `core::sync::atomic`, such as `AtomicBool`,
1379     /// `AtomicPtr`, `AtomicUsize`, or any of the other integer atomics).
1380     ///
1381     /// - Passing `Ordering::Acquire` or `Ordering::AcqRel` to
1382     ///   `AtomicType::store`.
1383     ///
1384     /// - Passing `Ordering::Release` or `Ordering::AcqRel` to
1385     ///   `AtomicType::load`.
1386     ///
1387     /// - Passing `Ordering::Relaxed` to `core::sync::atomic::fence` or
1388     ///   `core::sync::atomic::compiler_fence`.
1389     ///
1390     /// - Passing `Ordering::Release` or `Ordering::AcqRel` as the failure
1391     ///   ordering for any of `AtomicType::compare_exchange`,
1392     ///   `AtomicType::compare_exchange_weak`, or `AtomicType::fetch_update`.
1393     INVALID_ATOMIC_ORDERING,
1394     Deny,
1395     "usage of invalid atomic ordering in atomic operations and memory fences"
1396 }
1397
1398 declare_lint_pass!(InvalidAtomicOrdering => [INVALID_ATOMIC_ORDERING]);
1399
1400 impl InvalidAtomicOrdering {
1401     fn inherent_atomic_method_call<'hir>(
1402         cx: &LateContext<'_>,
1403         expr: &Expr<'hir>,
1404         recognized_names: &[Symbol], // used for fast path calculation
1405     ) -> Option<(Symbol, &'hir [Expr<'hir>])> {
1406         const ATOMIC_TYPES: &[Symbol] = &[
1407             sym::AtomicBool,
1408             sym::AtomicPtr,
1409             sym::AtomicUsize,
1410             sym::AtomicU8,
1411             sym::AtomicU16,
1412             sym::AtomicU32,
1413             sym::AtomicU64,
1414             sym::AtomicU128,
1415             sym::AtomicIsize,
1416             sym::AtomicI8,
1417             sym::AtomicI16,
1418             sym::AtomicI32,
1419             sym::AtomicI64,
1420             sym::AtomicI128,
1421         ];
1422         if let ExprKind::MethodCall(ref method_path, _, args, _) = &expr.kind
1423             && recognized_names.contains(&method_path.ident.name)
1424             && let Some(m_def_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id)
1425             && let Some(impl_did) = cx.tcx.impl_of_method(m_def_id)
1426             && let Some(adt) = cx.tcx.type_of(impl_did).ty_adt_def()
1427             // skip extension traits, only lint functions from the standard library
1428             && cx.tcx.trait_id_of_impl(impl_did).is_none()
1429             && let parent = cx.tcx.parent(adt.did())
1430             && cx.tcx.is_diagnostic_item(sym::atomic_mod, parent)
1431             && ATOMIC_TYPES.contains(&cx.tcx.item_name(adt.did()))
1432         {
1433             return Some((method_path.ident.name, args));
1434         }
1435         None
1436     }
1437
1438     fn match_ordering(cx: &LateContext<'_>, ord_arg: &Expr<'_>) -> Option<Symbol> {
1439         let ExprKind::Path(ref ord_qpath) = ord_arg.kind else { return None };
1440         let did = cx.qpath_res(ord_qpath, ord_arg.hir_id).opt_def_id()?;
1441         let tcx = cx.tcx;
1442         let atomic_ordering = tcx.get_diagnostic_item(sym::Ordering);
1443         let name = tcx.item_name(did);
1444         let parent = tcx.parent(did);
1445         [sym::Relaxed, sym::Release, sym::Acquire, sym::AcqRel, sym::SeqCst].into_iter().find(
1446             |&ordering| {
1447                 name == ordering
1448                     && (Some(parent) == atomic_ordering
1449                             // needed in case this is a ctor, not a variant
1450                             || tcx.opt_parent(parent) == atomic_ordering)
1451             },
1452         )
1453     }
1454
1455     fn check_atomic_load_store(cx: &LateContext<'_>, expr: &Expr<'_>) {
1456         if let Some((method, args)) = Self::inherent_atomic_method_call(cx, expr, &[sym::load, sym::store])
1457             && let Some((ordering_arg, invalid_ordering)) = match method {
1458                 sym::load => Some((&args[0], sym::Release)),
1459                 sym::store => Some((&args[1], sym::Acquire)),
1460                 _ => None,
1461             }
1462             && let Some(ordering) = Self::match_ordering(cx, ordering_arg)
1463             && (ordering == invalid_ordering || ordering == sym::AcqRel)
1464         {
1465             if method == sym::load {
1466                 cx.emit_spanned_lint(INVALID_ATOMIC_ORDERING, ordering_arg.span, AtomicOrderingLoad);
1467             } else {
1468                 cx.emit_spanned_lint(INVALID_ATOMIC_ORDERING, ordering_arg.span, AtomicOrderingStore);
1469             };
1470         }
1471     }
1472
1473     fn check_memory_fence(cx: &LateContext<'_>, expr: &Expr<'_>) {
1474         if let ExprKind::Call(ref func, ref args) = expr.kind
1475             && let ExprKind::Path(ref func_qpath) = func.kind
1476             && let Some(def_id) = cx.qpath_res(func_qpath, func.hir_id).opt_def_id()
1477             && matches!(cx.tcx.get_diagnostic_name(def_id), Some(sym::fence | sym::compiler_fence))
1478             && Self::match_ordering(cx, &args[0]) == Some(sym::Relaxed)
1479         {
1480             cx.emit_spanned_lint(INVALID_ATOMIC_ORDERING, args[0].span, AtomicOrderingFence);
1481         }
1482     }
1483
1484     fn check_atomic_compare_exchange(cx: &LateContext<'_>, expr: &Expr<'_>) {
1485         let Some((method, args)) = Self::inherent_atomic_method_call(cx, expr, &[sym::fetch_update, sym::compare_exchange, sym::compare_exchange_weak])
1486             else {return };
1487
1488         let fail_order_arg = match method {
1489             sym::fetch_update => &args[1],
1490             sym::compare_exchange | sym::compare_exchange_weak => &args[3],
1491             _ => return,
1492         };
1493
1494         let Some(fail_ordering) = Self::match_ordering(cx, fail_order_arg) else { return };
1495
1496         if matches!(fail_ordering, sym::Release | sym::AcqRel) {
1497             cx.emit_spanned_lint(
1498                 INVALID_ATOMIC_ORDERING,
1499                 fail_order_arg.span,
1500                 InvalidAtomicOrderingDiag { method, fail_order_arg_span: fail_order_arg.span },
1501             );
1502         }
1503     }
1504 }
1505
1506 impl<'tcx> LateLintPass<'tcx> for InvalidAtomicOrdering {
1507     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
1508         Self::check_atomic_load_store(cx, expr);
1509         Self::check_memory_fence(cx, expr);
1510         Self::check_atomic_compare_exchange(cx, expr);
1511     }
1512 }