| use crate::utils::{last_path_segment, match_def_path, paths, snippet, span_lint, span_lint_and_then, sugg}; |
| use if_chain::if_chain; |
| use rustc::hir::*; |
| use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass}; |
| use rustc::ty::{self, Ty}; |
| use rustc::{declare_lint_pass, declare_tool_lint}; |
| use rustc_errors::Applicability; |
| use std::borrow::Cow; |
| use syntax::ast; |
| |
| declare_clippy_lint! { |
| /// **What it does:** Checks for transmutes that can't ever be correct on any |
| /// architecture. |
| /// |
| /// **Why is this bad?** It's basically guaranteed to be undefined behaviour. |
| /// |
| /// **Known problems:** When accessing C, users might want to store pointer |
| /// sized objects in `extradata` arguments to save an allocation. |
| /// |
| /// **Example:** |
| /// ```ignore |
| /// let ptr: *const T = core::intrinsics::transmute('x') |
| /// ``` |
| pub WRONG_TRANSMUTE, |
| correctness, |
| "transmutes that are confusing at best, undefined behaviour at worst and always useless" |
| } |
| |
| declare_clippy_lint! { |
| /// **What it does:** Checks for transmutes to the original type of the object |
| /// and transmutes that could be a cast. |
| /// |
| /// **Why is this bad?** Readability. The code tricks people into thinking that |
| /// something complex is going on. |
| /// |
| /// **Known problems:** None. |
| /// |
| /// **Example:** |
| /// ```rust,ignore |
| /// core::intrinsics::transmute(t); // where the result type is the same as `t`'s |
| /// ``` |
| pub USELESS_TRANSMUTE, |
| complexity, |
| "transmutes that have the same to and from types or could be a cast/coercion" |
| } |
| |
| declare_clippy_lint! { |
| /// **What it does:** Checks for transmutes between a type `T` and `*T`. |
| /// |
| /// **Why is this bad?** It's easy to mistakenly transmute between a type and a |
| /// pointer to that type. |
| /// |
| /// **Known problems:** None. |
| /// |
| /// **Example:** |
| /// ```rust,ignore |
| /// core::intrinsics::transmute(t) // where the result type is the same as |
| /// // `*t` or `&t`'s |
| /// ``` |
| pub CROSSPOINTER_TRANSMUTE, |
| complexity, |
| "transmutes that have to or from types that are a pointer to the other" |
| } |
| |
| declare_clippy_lint! { |
| /// **What it does:** Checks for transmutes from a pointer to a reference. |
| /// |
| /// **Why is this bad?** This can always be rewritten with `&` and `*`. |
| /// |
| /// **Known problems:** None. |
| /// |
| /// **Example:** |
| /// ```rust,ignore |
| /// unsafe { |
| /// let _: &T = std::mem::transmute(p); // where p: *const T |
| /// } |
| /// |
| /// // can be written: |
| /// let _: &T = &*p; |
| /// ``` |
| pub TRANSMUTE_PTR_TO_REF, |
| complexity, |
| "transmutes from a pointer to a reference type" |
| } |
| |
| declare_clippy_lint! { |
| /// **What it does:** Checks for transmutes from an integer to a `char`. |
| /// |
| /// **Why is this bad?** Not every integer is a Unicode scalar value. |
| /// |
| /// **Known problems:** |
| /// - [`from_u32`] which this lint suggests using is slower than `transmute` |
| /// as it needs to validate the input. |
| /// If you are certain that the input is always a valid Unicode scalar value, |
| /// use [`from_u32_unchecked`] which is as fast as `transmute` |
| /// but has a semantically meaningful name. |
| /// - You might want to handle `None` returned from [`from_u32`] instead of calling `unwrap`. |
| /// |
| /// [`from_u32`]: https://doc.rust-lang.org/std/char/fn.from_u32.html |
| /// [`from_u32_unchecked`]: https://doc.rust-lang.org/std/char/fn.from_u32_unchecked.html |
| /// |
| /// **Example:** |
| /// ```rust |
| /// let x = 1_u32; |
| /// unsafe { |
| /// let _: char = std::mem::transmute(x); // where x: u32 |
| /// } |
| /// |
| /// // should be: |
| /// let _ = std::char::from_u32(x).unwrap(); |
| /// ``` |
| pub TRANSMUTE_INT_TO_CHAR, |
| complexity, |
| "transmutes from an integer to a `char`" |
| } |
| |
| declare_clippy_lint! { |
| /// **What it does:** Checks for transmutes from a `&[u8]` to a `&str`. |
| /// |
| /// **Why is this bad?** Not every byte slice is a valid UTF-8 string. |
| /// |
| /// **Known problems:** |
| /// - [`from_utf8`] which this lint suggests using is slower than `transmute` |
| /// as it needs to validate the input. |
| /// If you are certain that the input is always a valid UTF-8, |
| /// use [`from_utf8_unchecked`] which is as fast as `transmute` |
| /// but has a semantically meaningful name. |
| /// - You might want to handle errors returned from [`from_utf8`] instead of calling `unwrap`. |
| /// |
| /// [`from_utf8`]: https://doc.rust-lang.org/std/str/fn.from_utf8.html |
| /// [`from_utf8_unchecked`]: https://doc.rust-lang.org/std/str/fn.from_utf8_unchecked.html |
| /// |
| /// **Example:** |
| /// ```rust |
| /// let b: &[u8] = &[1_u8, 2_u8]; |
| /// unsafe { |
| /// let _: &str = std::mem::transmute(b); // where b: &[u8] |
| /// } |
| /// |
| /// // should be: |
| /// let _ = std::str::from_utf8(b).unwrap(); |
| /// ``` |
| pub TRANSMUTE_BYTES_TO_STR, |
| complexity, |
| "transmutes from a `&[u8]` to a `&str`" |
| } |
| |
| declare_clippy_lint! { |
| /// **What it does:** Checks for transmutes from an integer to a `bool`. |
| /// |
| /// **Why is this bad?** This might result in an invalid in-memory representation of a `bool`. |
| /// |
| /// **Known problems:** None. |
| /// |
| /// **Example:** |
| /// ```rust |
| /// let x = 1_u8; |
| /// unsafe { |
| /// let _: bool = std::mem::transmute(x); // where x: u8 |
| /// } |
| /// |
| /// // should be: |
| /// let _: bool = x != 0; |
| /// ``` |
| pub TRANSMUTE_INT_TO_BOOL, |
| complexity, |
| "transmutes from an integer to a `bool`" |
| } |
| |
| declare_clippy_lint! { |
| /// **What it does:** Checks for transmutes from an integer to a float. |
| /// |
| /// **Why is this bad?** Transmutes are dangerous and error-prone, whereas `from_bits` is intuitive |
| /// and safe. |
| /// |
| /// **Known problems:** None. |
| /// |
| /// **Example:** |
| /// ```rust |
| /// unsafe { |
| /// let _: f32 = std::mem::transmute(1_u32); // where x: u32 |
| /// } |
| /// |
| /// // should be: |
| /// let _: f32 = f32::from_bits(1_u32); |
| /// ``` |
| pub TRANSMUTE_INT_TO_FLOAT, |
| complexity, |
| "transmutes from an integer to a float" |
| } |
| |
| declare_clippy_lint! { |
| /// **What it does:** Checks for transmutes from a pointer to a pointer, or |
| /// from a reference to a reference. |
| /// |
| /// **Why is this bad?** Transmutes are dangerous, and these can instead be |
| /// written as casts. |
| /// |
| /// **Known problems:** None. |
| /// |
| /// **Example:** |
| /// ```rust |
| /// let ptr = &1u32 as *const u32; |
| /// unsafe { |
| /// // pointer-to-pointer transmute |
| /// let _: *const f32 = std::mem::transmute(ptr); |
| /// // ref-ref transmute |
| /// let _: &f32 = std::mem::transmute(&1u32); |
| /// } |
| /// // These can be respectively written: |
| /// let _ = ptr as *const f32; |
| /// let _ = unsafe{ &*(&1u32 as *const u32 as *const f32) }; |
| /// ``` |
| pub TRANSMUTE_PTR_TO_PTR, |
| complexity, |
| "transmutes from a pointer to a pointer / a reference to a reference" |
| } |
| |
| declare_clippy_lint! { |
| /// **What it does:** Checks for transmutes between collections whose |
| /// types have different ABI, size or alignment. |
| /// |
| /// **Why is this bad?** This is undefined behavior. |
| /// |
| /// **Known problems:** Currently, we cannot know whether a type is a |
| /// collection, so we just lint the ones that come with `std`. |
| /// |
| /// **Example:** |
| /// ```rust |
| /// // different size, therefore likely out-of-bounds memory access |
| /// // You absolutely do not want this in your code! |
| /// unsafe { |
| /// std::mem::transmute::<_, Vec<u32>>(vec![2_u16]) |
| /// }; |
| /// ``` |
| /// |
| /// You must always iterate, map and collect the values: |
| /// |
| /// ```rust |
| /// vec![2_u16].into_iter().map(u32::from).collect::<Vec<_>>(); |
| /// ``` |
| pub UNSOUND_COLLECTION_TRANSMUTE, |
| correctness, |
| "transmute between collections of layout-incompatible types" |
| } |
| declare_lint_pass!(Transmute => [ |
| CROSSPOINTER_TRANSMUTE, |
| TRANSMUTE_PTR_TO_REF, |
| TRANSMUTE_PTR_TO_PTR, |
| USELESS_TRANSMUTE, |
| WRONG_TRANSMUTE, |
| TRANSMUTE_INT_TO_CHAR, |
| TRANSMUTE_BYTES_TO_STR, |
| TRANSMUTE_INT_TO_BOOL, |
| TRANSMUTE_INT_TO_FLOAT, |
| UNSOUND_COLLECTION_TRANSMUTE, |
| ]); |
| |
| // used to check for UNSOUND_COLLECTION_TRANSMUTE |
| static COLLECTIONS: &[&[&str]] = &[ |
| &paths::VEC, |
| &paths::VEC_DEQUE, |
| &paths::BINARY_HEAP, |
| &paths::BTREESET, |
| &paths::BTREEMAP, |
| &paths::HASHSET, |
| &paths::HASHMAP, |
| ]; |
| impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Transmute { |
| #[allow(clippy::similar_names, clippy::too_many_lines)] |
| fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) { |
| if_chain! { |
| if let ExprKind::Call(ref path_expr, ref args) = e.kind; |
| if let ExprKind::Path(ref qpath) = path_expr.kind; |
| if let Some(def_id) = cx.tables.qpath_res(qpath, path_expr.hir_id).opt_def_id(); |
| if match_def_path(cx, def_id, &paths::TRANSMUTE); |
| then { |
| let from_ty = cx.tables.expr_ty(&args[0]); |
| let to_ty = cx.tables.expr_ty(e); |
| |
| match (&from_ty.kind, &to_ty.kind) { |
| _ if from_ty == to_ty => span_lint( |
| cx, |
| USELESS_TRANSMUTE, |
| e.span, |
| &format!("transmute from a type (`{}`) to itself", from_ty), |
| ), |
| (&ty::Ref(_, rty, rty_mutbl), &ty::RawPtr(ptr_ty)) => span_lint_and_then( |
| cx, |
| USELESS_TRANSMUTE, |
| e.span, |
| "transmute from a reference to a pointer", |
| |db| { |
| if let Some(arg) = sugg::Sugg::hir_opt(cx, &args[0]) { |
| let rty_and_mut = ty::TypeAndMut { |
| ty: rty, |
| mutbl: rty_mutbl, |
| }; |
| |
| let sugg = if ptr_ty == rty_and_mut { |
| arg.as_ty(to_ty) |
| } else { |
| arg.as_ty(cx.tcx.mk_ptr(rty_and_mut)).as_ty(to_ty) |
| }; |
| |
| db.span_suggestion(e.span, "try", sugg.to_string(), Applicability::Unspecified); |
| } |
| }, |
| ), |
| (&ty::Int(_), &ty::RawPtr(_)) | (&ty::Uint(_), &ty::RawPtr(_)) => span_lint_and_then( |
| cx, |
| USELESS_TRANSMUTE, |
| e.span, |
| "transmute from an integer to a pointer", |
| |db| { |
| if let Some(arg) = sugg::Sugg::hir_opt(cx, &args[0]) { |
| db.span_suggestion( |
| e.span, |
| "try", |
| arg.as_ty(&to_ty.to_string()).to_string(), |
| Applicability::Unspecified, |
| ); |
| } |
| }, |
| ), |
| (&ty::Float(_), &ty::Ref(..)) |
| | (&ty::Float(_), &ty::RawPtr(_)) |
| | (&ty::Char, &ty::Ref(..)) |
| | (&ty::Char, &ty::RawPtr(_)) => span_lint( |
| cx, |
| WRONG_TRANSMUTE, |
| e.span, |
| &format!("transmute from a `{}` to a pointer", from_ty), |
| ), |
| (&ty::RawPtr(from_ptr), _) if from_ptr.ty == to_ty => span_lint( |
| cx, |
| CROSSPOINTER_TRANSMUTE, |
| e.span, |
| &format!( |
| "transmute from a type (`{}`) to the type that it points to (`{}`)", |
| from_ty, to_ty |
| ), |
| ), |
| (_, &ty::RawPtr(to_ptr)) if to_ptr.ty == from_ty => span_lint( |
| cx, |
| CROSSPOINTER_TRANSMUTE, |
| e.span, |
| &format!( |
| "transmute from a type (`{}`) to a pointer to that type (`{}`)", |
| from_ty, to_ty |
| ), |
| ), |
| (&ty::RawPtr(from_pty), &ty::Ref(_, to_ref_ty, mutbl)) => span_lint_and_then( |
| cx, |
| TRANSMUTE_PTR_TO_REF, |
| e.span, |
| &format!( |
| "transmute from a pointer type (`{}`) to a reference type \ |
| (`{}`)", |
| from_ty, to_ty |
| ), |
| |db| { |
| let arg = sugg::Sugg::hir(cx, &args[0], ".."); |
| let (deref, cast) = if mutbl == Mutability::MutMutable { |
| ("&mut *", "*mut") |
| } else { |
| ("&*", "*const") |
| }; |
| |
| let arg = if from_pty.ty == to_ref_ty { |
| arg |
| } else { |
| arg.as_ty(&format!("{} {}", cast, get_type_snippet(cx, qpath, to_ref_ty))) |
| }; |
| |
| db.span_suggestion( |
| e.span, |
| "try", |
| sugg::make_unop(deref, arg).to_string(), |
| Applicability::Unspecified, |
| ); |
| }, |
| ), |
| (&ty::Int(ast::IntTy::I32), &ty::Char) | (&ty::Uint(ast::UintTy::U32), &ty::Char) => { |
| span_lint_and_then( |
| cx, |
| TRANSMUTE_INT_TO_CHAR, |
| e.span, |
| &format!("transmute from a `{}` to a `char`", from_ty), |
| |db| { |
| let arg = sugg::Sugg::hir(cx, &args[0], ".."); |
| let arg = if let ty::Int(_) = from_ty.kind { |
| arg.as_ty(ast::UintTy::U32) |
| } else { |
| arg |
| }; |
| db.span_suggestion( |
| e.span, |
| "consider using", |
| format!("std::char::from_u32({}).unwrap()", arg.to_string()), |
| Applicability::Unspecified, |
| ); |
| }, |
| ) |
| }, |
| (&ty::Ref(_, ty_from, from_mutbl), &ty::Ref(_, ty_to, to_mutbl)) => { |
| if_chain! { |
| if let (&ty::Slice(slice_ty), &ty::Str) = (&ty_from.kind, &ty_to.kind); |
| if let ty::Uint(ast::UintTy::U8) = slice_ty.kind; |
| if from_mutbl == to_mutbl; |
| then { |
| let postfix = if from_mutbl == Mutability::MutMutable { |
| "_mut" |
| } else { |
| "" |
| }; |
| |
| span_lint_and_then( |
| cx, |
| TRANSMUTE_BYTES_TO_STR, |
| e.span, |
| &format!("transmute from a `{}` to a `{}`", from_ty, to_ty), |
| |db| { |
| db.span_suggestion( |
| e.span, |
| "consider using", |
| format!( |
| "std::str::from_utf8{}({}).unwrap()", |
| postfix, |
| snippet(cx, args[0].span, ".."), |
| ), |
| Applicability::Unspecified, |
| ); |
| } |
| ) |
| } else { |
| if cx.tcx.erase_regions(&from_ty) != cx.tcx.erase_regions(&to_ty) { |
| span_lint_and_then( |
| cx, |
| TRANSMUTE_PTR_TO_PTR, |
| e.span, |
| "transmute from a reference to a reference", |
| |db| if let Some(arg) = sugg::Sugg::hir_opt(cx, &args[0]) { |
| let ty_from_and_mut = ty::TypeAndMut { |
| ty: ty_from, |
| mutbl: from_mutbl |
| }; |
| let ty_to_and_mut = ty::TypeAndMut { ty: ty_to, mutbl: to_mutbl }; |
| let sugg_paren = arg |
| .as_ty(cx.tcx.mk_ptr(ty_from_and_mut)) |
| .as_ty(cx.tcx.mk_ptr(ty_to_and_mut)); |
| let sugg = if to_mutbl == Mutability::MutMutable { |
| sugg_paren.mut_addr_deref() |
| } else { |
| sugg_paren.addr_deref() |
| }; |
| db.span_suggestion( |
| e.span, |
| "try", |
| sugg.to_string(), |
| Applicability::Unspecified, |
| ); |
| }, |
| ) |
| } |
| } |
| } |
| }, |
| (&ty::RawPtr(_), &ty::RawPtr(to_ty)) => span_lint_and_then( |
| cx, |
| TRANSMUTE_PTR_TO_PTR, |
| e.span, |
| "transmute from a pointer to a pointer", |
| |db| { |
| if let Some(arg) = sugg::Sugg::hir_opt(cx, &args[0]) { |
| let sugg = arg.as_ty(cx.tcx.mk_ptr(to_ty)); |
| db.span_suggestion(e.span, "try", sugg.to_string(), Applicability::Unspecified); |
| } |
| }, |
| ), |
| (&ty::Int(ast::IntTy::I8), &ty::Bool) | (&ty::Uint(ast::UintTy::U8), &ty::Bool) => { |
| span_lint_and_then( |
| cx, |
| TRANSMUTE_INT_TO_BOOL, |
| e.span, |
| &format!("transmute from a `{}` to a `bool`", from_ty), |
| |db| { |
| let arg = sugg::Sugg::hir(cx, &args[0], ".."); |
| let zero = sugg::Sugg::NonParen(Cow::from("0")); |
| db.span_suggestion( |
| e.span, |
| "consider using", |
| sugg::make_binop(ast::BinOpKind::Ne, &arg, &zero).to_string(), |
| Applicability::Unspecified, |
| ); |
| }, |
| ) |
| }, |
| (&ty::Int(_), &ty::Float(_)) | (&ty::Uint(_), &ty::Float(_)) => span_lint_and_then( |
| cx, |
| TRANSMUTE_INT_TO_FLOAT, |
| e.span, |
| &format!("transmute from a `{}` to a `{}`", from_ty, to_ty), |
| |db| { |
| let arg = sugg::Sugg::hir(cx, &args[0], ".."); |
| let arg = if let ty::Int(int_ty) = from_ty.kind { |
| arg.as_ty(format!( |
| "u{}", |
| int_ty.bit_width().map_or_else(|| "size".to_string(), |v| v.to_string()) |
| )) |
| } else { |
| arg |
| }; |
| db.span_suggestion( |
| e.span, |
| "consider using", |
| format!("{}::from_bits({})", to_ty, arg.to_string()), |
| Applicability::Unspecified, |
| ); |
| }, |
| ), |
| (&ty::Adt(ref from_adt, ref from_substs), &ty::Adt(ref to_adt, ref to_substs)) => { |
| if from_adt.did != to_adt.did || |
| !COLLECTIONS.iter().any(|path| match_def_path(cx, to_adt.did, path)) { |
| return; |
| } |
| if from_substs.types().zip(to_substs.types()) |
| .any(|(from_ty, to_ty)| is_layout_incompatible(cx, from_ty, to_ty)) { |
| span_lint( |
| cx, |
| UNSOUND_COLLECTION_TRANSMUTE, |
| e.span, |
| &format!( |
| "transmute from `{}` to `{}` with mismatched layout is unsound", |
| from_ty, |
| to_ty |
| ) |
| ); |
| } |
| }, |
| _ => return, |
| } |
| } |
| } |
| } |
| } |
| |
| /// Gets the snippet of `Bar` in `…::transmute<Foo, &Bar>`. If that snippet is |
| /// not available , use |
| /// the type's `ToString` implementation. In weird cases it could lead to types |
| /// with invalid `'_` |
| /// lifetime, but it should be rare. |
| fn get_type_snippet(cx: &LateContext<'_, '_>, path: &QPath, to_ref_ty: Ty<'_>) -> String { |
| let seg = last_path_segment(path); |
| if_chain! { |
| if let Some(ref params) = seg.args; |
| if !params.parenthesized; |
| if let Some(to_ty) = params.args.iter().filter_map(|arg| match arg { |
| GenericArg::Type(ty) => Some(ty), |
| _ => None, |
| }).nth(1); |
| if let TyKind::Rptr(_, ref to_ty) = to_ty.kind; |
| then { |
| return snippet(cx, to_ty.ty.span, &to_ref_ty.to_string()).to_string(); |
| } |
| } |
| |
| to_ref_ty.to_string() |
| } |
| |
| // check if the component types of the transmuted collection and the result have different ABI, |
| // size or alignment |
| fn is_layout_incompatible<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, from: Ty<'tcx>, to: Ty<'tcx>) -> bool { |
| let from_ty_layout = cx.tcx.layout_of(ty::ParamEnv::empty().and(from)); |
| let to_ty_layout = cx.tcx.layout_of(ty::ParamEnv::empty().and(to)); |
| if let (Ok(from_layout), Ok(to_layout)) = (from_ty_layout, to_ty_layout) { |
| from_layout.size != to_layout.size || from_layout.align != to_layout.align || from_layout.abi != to_layout.abi |
| } else { |
| // no idea about layout, so don't lint |
| false |
| } |
| } |