| // Copyright 2012-2015 The Rust Project Developers. See the COPYRIGHT |
| // file at the top-level directory of this distribution and at |
| // http://rust-lang.org/COPYRIGHT. |
| // |
| // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or |
| // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license |
| // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your |
| // option. This file may not be copied, modified, or distributed |
| // except according to those terms. |
| |
| #![allow(non_snake_case)] |
| |
| use rustc::hir::def_id::DefId; |
| use rustc::ty::subst::Substs; |
| use rustc::ty::{self, Ty, TyCtxt}; |
| use rustc::ty::layout::{Layout, Primitive}; |
| use rustc::traits::ProjectionMode; |
| use middle::const_val::ConstVal; |
| use rustc_const_eval::eval_const_expr_partial; |
| use rustc_const_eval::EvalHint::ExprTypeChecked; |
| use util::nodemap::{FnvHashSet}; |
| use lint::{LateContext, LintContext, LintArray}; |
| use lint::{LintPass, LateLintPass}; |
| |
| use std::cmp; |
| use std::{i8, i16, i32, i64, u8, u16, u32, u64, f32, f64}; |
| |
| use syntax::ast; |
| use syntax::abi::Abi; |
| use syntax::attr; |
| use syntax_pos::Span; |
| use syntax::codemap; |
| |
| use rustc::hir; |
| |
| register_long_diagnostics! { |
| E0519: r##" |
| It is not allowed to negate an unsigned integer. |
| You can negate a signed integer and cast it to an |
| unsigned integer or use the `!` operator. |
| |
| ``` |
| let x: usize = -1isize as usize; |
| let y: usize = !0; |
| assert_eq!(x, y); |
| ``` |
| |
| Alternatively you can use the `Wrapping` newtype |
| or the `wrapping_neg` operation that all |
| integral types support: |
| |
| ``` |
| use std::num::Wrapping; |
| let x: Wrapping<usize> = -Wrapping(1); |
| let Wrapping(x) = x; |
| let y: usize = 1.wrapping_neg(); |
| assert_eq!(x, y); |
| ``` |
| |
| "## |
| } |
| |
| declare_lint! { |
| UNUSED_COMPARISONS, |
| Warn, |
| "comparisons made useless by limits of the types involved" |
| } |
| |
| declare_lint! { |
| OVERFLOWING_LITERALS, |
| Warn, |
| "literal out of range for its type" |
| } |
| |
| declare_lint! { |
| EXCEEDING_BITSHIFTS, |
| Deny, |
| "shift exceeds the type's number of bits" |
| } |
| |
| declare_lint! { |
| VARIANT_SIZE_DIFFERENCES, |
| Allow, |
| "detects enums with widely varying variant sizes" |
| } |
| |
| #[derive(Copy, Clone)] |
| pub struct TypeLimits { |
| /// Id of the last visited negated expression |
| negated_expr_id: ast::NodeId, |
| } |
| |
| impl TypeLimits { |
| pub fn new() -> TypeLimits { |
| TypeLimits { |
| negated_expr_id: !0, |
| } |
| } |
| } |
| |
| impl LintPass for TypeLimits { |
| fn get_lints(&self) -> LintArray { |
| lint_array!(UNUSED_COMPARISONS, OVERFLOWING_LITERALS, EXCEEDING_BITSHIFTS) |
| } |
| } |
| |
| impl LateLintPass for TypeLimits { |
| fn check_expr(&mut self, cx: &LateContext, e: &hir::Expr) { |
| match e.node { |
| hir::ExprUnary(hir::UnNeg, ref expr) => { |
| if let hir::ExprLit(ref lit) = expr.node { |
| match lit.node { |
| ast::LitKind::Int(_, ast::LitIntType::Unsigned(_)) => { |
| forbid_unsigned_negation(cx, e.span); |
| }, |
| ast::LitKind::Int(_, ast::LitIntType::Unsuffixed) => { |
| if let ty::TyUint(_) = cx.tcx.node_id_to_type(e.id).sty { |
| forbid_unsigned_negation(cx, e.span); |
| } |
| }, |
| _ => () |
| } |
| } else { |
| let t = cx.tcx.node_id_to_type(expr.id); |
| if let ty::TyUint(_) = t.sty { |
| forbid_unsigned_negation(cx, e.span); |
| } |
| } |
| // propagate negation, if the negation itself isn't negated |
| if self.negated_expr_id != e.id { |
| self.negated_expr_id = expr.id; |
| } |
| }, |
| hir::ExprBinary(binop, ref l, ref r) => { |
| if is_comparison(binop) && !check_limits(cx.tcx, binop, &l, &r) { |
| cx.span_lint(UNUSED_COMPARISONS, e.span, |
| "comparison is useless due to type limits"); |
| } |
| |
| if binop.node.is_shift() { |
| let opt_ty_bits = match cx.tcx.node_id_to_type(l.id).sty { |
| ty::TyInt(t) => Some(int_ty_bits(t, cx.sess().target.int_type)), |
| ty::TyUint(t) => Some(uint_ty_bits(t, cx.sess().target.uint_type)), |
| _ => None |
| }; |
| |
| if let Some(bits) = opt_ty_bits { |
| let exceeding = if let hir::ExprLit(ref lit) = r.node { |
| if let ast::LitKind::Int(shift, _) = lit.node { shift >= bits } |
| else { false } |
| } else { |
| match eval_const_expr_partial(cx.tcx, &r, ExprTypeChecked, None) { |
| Ok(ConstVal::Integral(i)) => { |
| i.is_negative() || i.to_u64() |
| .map(|i| i >= bits) |
| .unwrap_or(true) |
| }, |
| _ => { false } |
| } |
| }; |
| if exceeding { |
| cx.span_lint(EXCEEDING_BITSHIFTS, e.span, |
| "bitshift exceeds the type's number of bits"); |
| } |
| }; |
| } |
| }, |
| hir::ExprLit(ref lit) => { |
| match cx.tcx.node_id_to_type(e.id).sty { |
| ty::TyInt(t) => { |
| match lit.node { |
| ast::LitKind::Int(v, ast::LitIntType::Signed(_)) | |
| ast::LitKind::Int(v, ast::LitIntType::Unsuffixed) => { |
| let int_type = if let ast::IntTy::Is = t { |
| cx.sess().target.int_type |
| } else { |
| t |
| }; |
| let (_, max) = int_ty_range(int_type); |
| let negative = self.negated_expr_id == e.id; |
| |
| // Detect literal value out of range [min, max] inclusive |
| // avoiding use of -min to prevent overflow/panic |
| if (negative && v > max as u64 + 1) || |
| (!negative && v > max as u64) { |
| cx.span_lint(OVERFLOWING_LITERALS, e.span, |
| &format!("literal out of range for {:?}", t)); |
| return; |
| } |
| } |
| _ => bug!() |
| }; |
| }, |
| ty::TyUint(t) => { |
| let uint_type = if let ast::UintTy::Us = t { |
| cx.sess().target.uint_type |
| } else { |
| t |
| }; |
| let (min, max) = uint_ty_range(uint_type); |
| let lit_val: u64 = match lit.node { |
| // _v is u8, within range by definition |
| ast::LitKind::Byte(_v) => return, |
| ast::LitKind::Int(v, _) => v, |
| _ => bug!() |
| }; |
| if lit_val < min || lit_val > max { |
| cx.span_lint(OVERFLOWING_LITERALS, e.span, |
| &format!("literal out of range for {:?}", t)); |
| } |
| }, |
| ty::TyFloat(t) => { |
| let (min, max) = float_ty_range(t); |
| let lit_val: f64 = match lit.node { |
| ast::LitKind::Float(ref v, _) | |
| ast::LitKind::FloatUnsuffixed(ref v) => { |
| match v.parse() { |
| Ok(f) => f, |
| Err(_) => return |
| } |
| } |
| _ => bug!() |
| }; |
| if lit_val < min || lit_val > max { |
| cx.span_lint(OVERFLOWING_LITERALS, e.span, |
| &format!("literal out of range for {:?}", t)); |
| } |
| }, |
| _ => () |
| }; |
| }, |
| _ => () |
| }; |
| |
| fn is_valid<T:cmp::PartialOrd>(binop: hir::BinOp, v: T, |
| min: T, max: T) -> bool { |
| match binop.node { |
| hir::BiLt => v > min && v <= max, |
| hir::BiLe => v >= min && v < max, |
| hir::BiGt => v >= min && v < max, |
| hir::BiGe => v > min && v <= max, |
| hir::BiEq | hir::BiNe => v >= min && v <= max, |
| _ => bug!() |
| } |
| } |
| |
| fn rev_binop(binop: hir::BinOp) -> hir::BinOp { |
| codemap::respan(binop.span, match binop.node { |
| hir::BiLt => hir::BiGt, |
| hir::BiLe => hir::BiGe, |
| hir::BiGt => hir::BiLt, |
| hir::BiGe => hir::BiLe, |
| _ => return binop |
| }) |
| } |
| |
| // for isize & usize, be conservative with the warnings, so that the |
| // warnings are consistent between 32- and 64-bit platforms |
| fn int_ty_range(int_ty: ast::IntTy) -> (i64, i64) { |
| match int_ty { |
| ast::IntTy::Is => (i64::MIN, i64::MAX), |
| ast::IntTy::I8 => (i8::MIN as i64, i8::MAX as i64), |
| ast::IntTy::I16 => (i16::MIN as i64, i16::MAX as i64), |
| ast::IntTy::I32 => (i32::MIN as i64, i32::MAX as i64), |
| ast::IntTy::I64 => (i64::MIN, i64::MAX) |
| } |
| } |
| |
| fn uint_ty_range(uint_ty: ast::UintTy) -> (u64, u64) { |
| match uint_ty { |
| ast::UintTy::Us => (u64::MIN, u64::MAX), |
| ast::UintTy::U8 => (u8::MIN as u64, u8::MAX as u64), |
| ast::UintTy::U16 => (u16::MIN as u64, u16::MAX as u64), |
| ast::UintTy::U32 => (u32::MIN as u64, u32::MAX as u64), |
| ast::UintTy::U64 => (u64::MIN, u64::MAX) |
| } |
| } |
| |
| fn float_ty_range(float_ty: ast::FloatTy) -> (f64, f64) { |
| match float_ty { |
| ast::FloatTy::F32 => (f32::MIN as f64, f32::MAX as f64), |
| ast::FloatTy::F64 => (f64::MIN, f64::MAX) |
| } |
| } |
| |
| fn int_ty_bits(int_ty: ast::IntTy, target_int_ty: ast::IntTy) -> u64 { |
| match int_ty { |
| ast::IntTy::Is => int_ty_bits(target_int_ty, target_int_ty), |
| ast::IntTy::I8 => 8, |
| ast::IntTy::I16 => 16 as u64, |
| ast::IntTy::I32 => 32, |
| ast::IntTy::I64 => 64, |
| } |
| } |
| |
| fn uint_ty_bits(uint_ty: ast::UintTy, target_uint_ty: ast::UintTy) -> u64 { |
| match uint_ty { |
| ast::UintTy::Us => uint_ty_bits(target_uint_ty, target_uint_ty), |
| ast::UintTy::U8 => 8, |
| ast::UintTy::U16 => 16, |
| ast::UintTy::U32 => 32, |
| ast::UintTy::U64 => 64, |
| } |
| } |
| |
| fn check_limits<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, |
| binop: hir::BinOp, |
| l: &hir::Expr, |
| r: &hir::Expr) -> bool { |
| let (lit, expr, swap) = match (&l.node, &r.node) { |
| (&hir::ExprLit(_), _) => (l, r, true), |
| (_, &hir::ExprLit(_)) => (r, l, false), |
| _ => return true |
| }; |
| // Normalize the binop so that the literal is always on the RHS in |
| // the comparison |
| let norm_binop = if swap { |
| rev_binop(binop) |
| } else { |
| binop |
| }; |
| match tcx.node_id_to_type(expr.id).sty { |
| ty::TyInt(int_ty) => { |
| let (min, max) = int_ty_range(int_ty); |
| let lit_val: i64 = match lit.node { |
| hir::ExprLit(ref li) => match li.node { |
| ast::LitKind::Int(v, ast::LitIntType::Signed(_)) | |
| ast::LitKind::Int(v, ast::LitIntType::Unsuffixed) => v as i64, |
| _ => return true |
| }, |
| _ => bug!() |
| }; |
| is_valid(norm_binop, lit_val, min, max) |
| } |
| ty::TyUint(uint_ty) => { |
| let (min, max): (u64, u64) = uint_ty_range(uint_ty); |
| let lit_val: u64 = match lit.node { |
| hir::ExprLit(ref li) => match li.node { |
| ast::LitKind::Int(v, _) => v, |
| _ => return true |
| }, |
| _ => bug!() |
| }; |
| is_valid(norm_binop, lit_val, min, max) |
| } |
| _ => true |
| } |
| } |
| |
| fn is_comparison(binop: hir::BinOp) -> bool { |
| match binop.node { |
| hir::BiEq | hir::BiLt | hir::BiLe | |
| hir::BiNe | hir::BiGe | hir::BiGt => true, |
| _ => false |
| } |
| } |
| |
| fn forbid_unsigned_negation(cx: &LateContext, span: Span) { |
| cx.sess() |
| .struct_span_err_with_code(span, "unary negation of unsigned integer", "E0519") |
| .span_help(span, "use a cast or the `!` operator") |
| .emit(); |
| } |
| } |
| } |
| |
| declare_lint! { |
| IMPROPER_CTYPES, |
| Warn, |
| "proper use of libc types in foreign modules" |
| } |
| |
| struct ImproperCTypesVisitor<'a, 'tcx: 'a> { |
| cx: &'a LateContext<'a, 'tcx> |
| } |
| |
| enum FfiResult { |
| FfiSafe, |
| FfiUnsafe(&'static str), |
| FfiBadStruct(DefId, &'static str), |
| FfiBadEnum(DefId, &'static str) |
| } |
| |
| /// Check if this enum can be safely exported based on the |
| /// "nullable pointer optimization". Currently restricted |
| /// to function pointers and references, but could be |
| /// expanded to cover NonZero raw pointers and newtypes. |
| /// FIXME: This duplicates code in trans. |
| fn is_repr_nullable_ptr<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, |
| def: ty::AdtDef<'tcx>, |
| substs: &Substs<'tcx>) |
| -> bool { |
| if def.variants.len() == 2 { |
| let data_idx; |
| |
| if def.variants[0].fields.is_empty() { |
| data_idx = 1; |
| } else if def.variants[1].fields.is_empty() { |
| data_idx = 0; |
| } else { |
| return false; |
| } |
| |
| if def.variants[data_idx].fields.len() == 1 { |
| match def.variants[data_idx].fields[0].ty(tcx, substs).sty { |
| ty::TyFnPtr(_) => { return true; } |
| ty::TyRef(..) => { return true; } |
| _ => { } |
| } |
| } |
| } |
| false |
| } |
| |
| impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> { |
| /// Check if the given type is "ffi-safe" (has a stable, well-defined |
| /// representation which can be exported to C code). |
| fn check_type_for_ffi(&self, |
| cache: &mut FnvHashSet<Ty<'tcx>>, |
| ty: Ty<'tcx>) |
| -> FfiResult { |
| use self::FfiResult::*; |
| let cx = self.cx.tcx; |
| |
| // Protect against infinite recursion, for example |
| // `struct S(*mut S);`. |
| // FIXME: A recursion limit is necessary as well, for irregular |
| // recusive types. |
| if !cache.insert(ty) { |
| return FfiSafe; |
| } |
| |
| match ty.sty { |
| ty::TyStruct(def, substs) => { |
| if !cx.lookup_repr_hints(def.did).contains(&attr::ReprExtern) { |
| return FfiUnsafe( |
| "found struct without foreign-function-safe \ |
| representation annotation in foreign module, \ |
| consider adding a #[repr(C)] attribute to \ |
| the type"); |
| } |
| |
| // We can't completely trust repr(C) markings; make sure the |
| // fields are actually safe. |
| if def.struct_variant().fields.is_empty() { |
| return FfiUnsafe( |
| "found zero-size struct in foreign module, consider \ |
| adding a member to this struct"); |
| } |
| |
| for field in &def.struct_variant().fields { |
| let field_ty = cx.normalize_associated_type(&field.ty(cx, substs)); |
| let r = self.check_type_for_ffi(cache, field_ty); |
| match r { |
| FfiSafe => {} |
| FfiBadStruct(..) | FfiBadEnum(..) => { return r; } |
| FfiUnsafe(s) => { return FfiBadStruct(def.did, s); } |
| } |
| } |
| FfiSafe |
| } |
| ty::TyEnum(def, substs) => { |
| if def.variants.is_empty() { |
| // Empty enums are okay... although sort of useless. |
| return FfiSafe |
| } |
| |
| // Check for a repr() attribute to specify the size of the |
| // discriminant. |
| let repr_hints = cx.lookup_repr_hints(def.did); |
| match &repr_hints[..] { |
| &[] => { |
| // Special-case types like `Option<extern fn()>`. |
| if !is_repr_nullable_ptr(cx, def, substs) { |
| return FfiUnsafe( |
| "found enum without foreign-function-safe \ |
| representation annotation in foreign module, \ |
| consider adding a #[repr(...)] attribute to \ |
| the type") |
| } |
| } |
| &[ref hint] => { |
| if !hint.is_ffi_safe() { |
| // FIXME: This shouldn't be reachable: we should check |
| // this earlier. |
| return FfiUnsafe( |
| "enum has unexpected #[repr(...)] attribute") |
| } |
| |
| // Enum with an explicitly sized discriminant; either |
| // a C-style enum or a discriminated union. |
| |
| // The layout of enum variants is implicitly repr(C). |
| // FIXME: Is that correct? |
| } |
| _ => { |
| // FIXME: This shouldn't be reachable: we should check |
| // this earlier. |
| return FfiUnsafe( |
| "enum has too many #[repr(...)] attributes"); |
| } |
| } |
| |
| // Check the contained variants. |
| for variant in &def.variants { |
| for field in &variant.fields { |
| let arg = cx.normalize_associated_type(&field.ty(cx, substs)); |
| let r = self.check_type_for_ffi(cache, arg); |
| match r { |
| FfiSafe => {} |
| FfiBadStruct(..) | FfiBadEnum(..) => { return r; } |
| FfiUnsafe(s) => { return FfiBadEnum(def.did, s); } |
| } |
| } |
| } |
| FfiSafe |
| } |
| |
| ty::TyChar => { |
| FfiUnsafe("found Rust type `char` in foreign module, while \ |
| `u32` or `libc::wchar_t` should be used") |
| } |
| |
| // Primitive types with a stable representation. |
| ty::TyBool | ty::TyInt(..) | ty::TyUint(..) | |
| ty::TyFloat(..) => FfiSafe, |
| |
| ty::TyBox(..) => { |
| FfiUnsafe("found Rust type Box<_> in foreign module, \ |
| consider using a raw pointer instead") |
| } |
| |
| ty::TySlice(_) => { |
| FfiUnsafe("found Rust slice type in foreign module, \ |
| consider using a raw pointer instead") |
| } |
| |
| ty::TyTrait(..) => { |
| FfiUnsafe("found Rust trait type in foreign module, \ |
| consider using a raw pointer instead") |
| } |
| |
| ty::TyStr => { |
| FfiUnsafe("found Rust type `str` in foreign module; \ |
| consider using a `*const libc::c_char`") |
| } |
| |
| ty::TyTuple(_) => { |
| FfiUnsafe("found Rust tuple type in foreign module; \ |
| consider using a struct instead`") |
| } |
| |
| ty::TyRawPtr(ref m) | ty::TyRef(_, ref m) => { |
| self.check_type_for_ffi(cache, m.ty) |
| } |
| |
| ty::TyArray(ty, _) => { |
| self.check_type_for_ffi(cache, ty) |
| } |
| |
| ty::TyFnPtr(bare_fn) => { |
| match bare_fn.abi { |
| Abi::Rust | |
| Abi::RustIntrinsic | |
| Abi::PlatformIntrinsic | |
| Abi::RustCall => { |
| return FfiUnsafe( |
| "found function pointer with Rust calling \ |
| convention in foreign module; consider using an \ |
| `extern` function pointer") |
| } |
| _ => {} |
| } |
| |
| let sig = cx.erase_late_bound_regions(&bare_fn.sig); |
| match sig.output { |
| ty::FnDiverging => {} |
| ty::FnConverging(output) => { |
| if !output.is_nil() { |
| let r = self.check_type_for_ffi(cache, output); |
| match r { |
| FfiSafe => {} |
| _ => { return r; } |
| } |
| } |
| } |
| } |
| for arg in sig.inputs { |
| let r = self.check_type_for_ffi(cache, arg); |
| match r { |
| FfiSafe => {} |
| _ => { return r; } |
| } |
| } |
| FfiSafe |
| } |
| |
| ty::TyParam(..) | ty::TyInfer(..) | ty::TyError | |
| ty::TyClosure(..) | ty::TyProjection(..) | |
| ty::TyFnDef(..) => { |
| bug!("Unexpected type in foreign function") |
| } |
| } |
| } |
| |
| fn check_type_for_ffi_and_report_errors(&mut self, sp: Span, ty: Ty<'tcx>) { |
| // it is only OK to use this function because extern fns cannot have |
| // any generic types right now: |
| let ty = self.cx.tcx.normalize_associated_type(&ty); |
| |
| match self.check_type_for_ffi(&mut FnvHashSet(), ty) { |
| FfiResult::FfiSafe => {} |
| FfiResult::FfiUnsafe(s) => { |
| self.cx.span_lint(IMPROPER_CTYPES, sp, s); |
| } |
| FfiResult::FfiBadStruct(_, s) => { |
| // FIXME: This diagnostic is difficult to read, and doesn't |
| // point at the relevant field. |
| self.cx.span_lint(IMPROPER_CTYPES, sp, |
| &format!("found non-foreign-function-safe member in \ |
| struct marked #[repr(C)]: {}", s)); |
| } |
| FfiResult::FfiBadEnum(_, s) => { |
| // FIXME: This diagnostic is difficult to read, and doesn't |
| // point at the relevant variant. |
| self.cx.span_lint(IMPROPER_CTYPES, sp, |
| &format!("found non-foreign-function-safe member in \ |
| enum: {}", s)); |
| } |
| } |
| } |
| |
| fn check_foreign_fn(&mut self, id: ast::NodeId, decl: &hir::FnDecl) { |
| let def_id = self.cx.tcx.map.local_def_id(id); |
| let scheme = self.cx.tcx.lookup_item_type(def_id); |
| let sig = scheme.ty.fn_sig(); |
| let sig = self.cx.tcx.erase_late_bound_regions(&sig); |
| |
| for (&input_ty, input_hir) in sig.inputs.iter().zip(&decl.inputs) { |
| self.check_type_for_ffi_and_report_errors(input_hir.ty.span, &input_ty); |
| } |
| |
| if let hir::Return(ref ret_hir) = decl.output { |
| let ret_ty = sig.output.unwrap(); |
| if !ret_ty.is_nil() { |
| self.check_type_for_ffi_and_report_errors(ret_hir.span, ret_ty); |
| } |
| } |
| } |
| |
| fn check_foreign_static(&mut self, id: ast::NodeId, span: Span) { |
| let def_id = self.cx.tcx.map.local_def_id(id); |
| let scheme = self.cx.tcx.lookup_item_type(def_id); |
| self.check_type_for_ffi_and_report_errors(span, scheme.ty); |
| } |
| } |
| |
| #[derive(Copy, Clone)] |
| pub struct ImproperCTypes; |
| |
| impl LintPass for ImproperCTypes { |
| fn get_lints(&self) -> LintArray { |
| lint_array!(IMPROPER_CTYPES) |
| } |
| } |
| |
| impl LateLintPass for ImproperCTypes { |
| fn check_item(&mut self, cx: &LateContext, it: &hir::Item) { |
| let mut vis = ImproperCTypesVisitor { cx: cx }; |
| if let hir::ItemForeignMod(ref nmod) = it.node { |
| if nmod.abi != Abi::RustIntrinsic && nmod.abi != Abi::PlatformIntrinsic { |
| for ni in &nmod.items { |
| match ni.node { |
| hir::ForeignItemFn(ref decl, _) => { |
| vis.check_foreign_fn(ni.id, decl); |
| } |
| hir::ForeignItemStatic(ref ty, _) => { |
| vis.check_foreign_static(ni.id, ty.span); |
| } |
| } |
| } |
| } |
| } |
| } |
| } |
| |
| pub struct VariantSizeDifferences; |
| |
| impl LintPass for VariantSizeDifferences { |
| fn get_lints(&self) -> LintArray { |
| lint_array!(VARIANT_SIZE_DIFFERENCES) |
| } |
| } |
| |
| impl LateLintPass for VariantSizeDifferences { |
| fn check_item(&mut self, cx: &LateContext, it: &hir::Item) { |
| if let hir::ItemEnum(ref enum_definition, ref gens) = it.node { |
| if gens.ty_params.is_empty() { // sizes only make sense for non-generic types |
| let t = cx.tcx.node_id_to_type(it.id); |
| let layout = cx.tcx.normalizing_infer_ctxt(ProjectionMode::Any).enter(|infcx| { |
| let ty = cx.tcx.erase_regions(&t); |
| ty.layout(&infcx).unwrap_or_else(|e| { |
| bug!("failed to get layout for `{}`: {}", t, e) |
| }) |
| }); |
| |
| if let Layout::General { ref variants, ref size, discr, .. } = *layout { |
| let discr_size = Primitive::Int(discr).size(&cx.tcx.data_layout).bytes(); |
| |
| debug!("enum `{}` is {} bytes large", t, size.bytes()); |
| |
| let (largest, slargest, largest_index) = enum_definition.variants |
| .iter() |
| .zip(variants) |
| .map(|(variant, variant_layout)| { |
| // Subtract the size of the enum discriminant |
| let bytes = variant_layout.min_size().bytes() |
| .saturating_sub(discr_size); |
| |
| debug!("- variant `{}` is {} bytes large", variant.node.name, bytes); |
| bytes |
| }) |
| .enumerate() |
| .fold((0, 0, 0), |
| |(l, s, li), (idx, size)| |
| if size > l { |
| (size, l, idx) |
| } else if size > s { |
| (l, size, li) |
| } else { |
| (l, s, li) |
| } |
| ); |
| |
| // we only warn if the largest variant is at least thrice as large as |
| // the second-largest. |
| if largest > slargest * 3 && slargest > 0 { |
| cx.span_lint(VARIANT_SIZE_DIFFERENCES, |
| enum_definition.variants[largest_index].span, |
| &format!("enum variant is more than three times larger \ |
| ({} bytes) than the next largest", largest)); |
| } |
| } |
| } |
| } |
| } |
| } |
