2 use rustc::ty::{self, Ty};
6 use utils::{last_path_segment, match_def_path, paths, snippet, span_lint, span_lint_and_then};
7 use utils::{opt_def_id, sugg};
9 /// **What it does:** Checks for transmutes that can't ever be correct on any
12 /// **Why is this bad?** It's basically guaranteed to be undefined behaviour.
14 /// **Known problems:** When accessing C, users might want to store pointer
15 /// sized objects in `extradata` arguments to save an allocation.
19 /// let ptr: *const T = core::intrinsics::transmute('x')
21 declare_clippy_lint! {
24 "transmutes that are confusing at best, undefined behaviour at worst and always useless"
27 /// **What it does:** Checks for transmutes to the original type of the object
28 /// and transmutes that could be a cast.
30 /// **Why is this bad?** Readability. The code tricks people into thinking that
31 /// something complex is going on.
33 /// **Known problems:** None.
37 /// core::intrinsics::transmute(t) // where the result type is the same as `t`'s
39 declare_clippy_lint! {
40 pub USELESS_TRANSMUTE,
42 "transmutes that have the same to and from types or could be a cast/coercion"
45 /// **What it does:** Checks for transmutes between a type `T` and `*T`.
47 /// **Why is this bad?** It's easy to mistakenly transmute between a type and a
48 /// pointer to that type.
50 /// **Known problems:** None.
54 /// core::intrinsics::transmute(t) // where the result type is the same as
57 declare_clippy_lint! {
58 pub CROSSPOINTER_TRANSMUTE,
60 "transmutes that have to or from types that are a pointer to the other"
63 /// **What it does:** Checks for transmutes from a pointer to a reference.
65 /// **Why is this bad?** This can always be rewritten with `&` and `*`.
67 /// **Known problems:** None.
71 /// let _: &T = std::mem::transmute(p); // where p: *const T
72 /// // can be written:
75 declare_clippy_lint! {
76 pub TRANSMUTE_PTR_TO_REF,
78 "transmutes from a pointer to a reference type"
81 /// **What it does:** Checks for transmutes from an integer to a `char`.
83 /// **Why is this bad?** Not every integer is a Unicode scalar value.
85 /// **Known problems:**
86 /// - [`from_u32`] which this lint suggests using is slower than `transmute`
87 /// as it needs to validate the input.
88 /// If you are certain that the input is always a valid Unicode scalar value,
89 /// use [`from_u32_unchecked`] which is as fast as `transmute`
90 /// but has a semantically meaningful name.
91 /// - You might want to handle `None` returned from [`from_u32`] instead of calling `unwrap`.
93 /// [`from_u32`]: https://doc.rust-lang.org/std/char/fn.from_u32.html
94 /// [`from_u32_unchecked`]: https://doc.rust-lang.org/std/char/fn.from_u32_unchecked.html
98 /// let _: char = std::mem::transmute(x); // where x: u32
100 /// let _ = std::char::from_u32(x).unwrap();
102 declare_clippy_lint! {
103 pub TRANSMUTE_INT_TO_CHAR,
105 "transmutes from an integer to a `char`"
108 /// **What it does:** Checks for transmutes from a `&[u8]` to a `&str`.
110 /// **Why is this bad?** Not every byte slice is a valid UTF-8 string.
112 /// **Known problems:**
113 /// - [`from_utf8`] which this lint suggests using is slower than `transmute`
114 /// as it needs to validate the input.
115 /// If you are certain that the input is always a valid UTF-8,
116 /// use [`from_utf8_unchecked`] which is as fast as `transmute`
117 /// but has a semantically meaningful name.
118 /// - You might want to handle errors returned from [`from_utf8`] instead of calling `unwrap`.
120 /// [`from_utf8`]: https://doc.rust-lang.org/std/str/fn.from_utf8.html
121 /// [`from_utf8_unchecked`]: https://doc.rust-lang.org/std/str/fn.from_utf8_unchecked.html
125 /// let _: &str = std::mem::transmute(b); // where b: &[u8]
127 /// let _ = std::str::from_utf8(b).unwrap();
129 declare_clippy_lint! {
130 pub TRANSMUTE_BYTES_TO_STR,
132 "transmutes from a `&[u8]` to a `&str`"
135 /// **What it does:** Checks for transmutes from an integer to a `bool`.
137 /// **Why is this bad?** This might result in an invalid in-memory representation of a `bool`.
139 /// **Known problems:** None.
143 /// let _: bool = std::mem::transmute(x); // where x: u8
145 /// let _: bool = x != 0;
147 declare_clippy_lint! {
148 pub TRANSMUTE_INT_TO_BOOL,
150 "transmutes from an integer to a `bool`"
153 /// **What it does:** Checks for transmutes from an integer to a float.
155 /// **Why is this bad?** This might result in an invalid in-memory representation of a float.
157 /// **Known problems:** None.
161 /// let _: f32 = std::mem::transmute(x); // where x: u32
163 /// let _: f32 = f32::from_bits(x);
165 declare_clippy_lint! {
166 pub TRANSMUTE_INT_TO_FLOAT,
168 "transmutes from an integer to a float"
171 /// **What it does:** Checks for transmutes from a pointer to a pointer, or
172 /// from a reference to a reference.
174 /// **Why is this bad?** Transmutes are dangerous, and these can instead be
175 /// written as casts.
177 /// **Known problems:** None.
181 /// let ptr = &1u32 as *const u32;
183 /// // pointer-to-pointer transmute
184 /// let _: *const f32 = std::mem::transmute(ptr);
185 /// // ref-ref transmute
186 /// let _: &f32 = std::mem::transmute(&1u32);
188 /// // These can be respectively written:
189 /// let _ = ptr as *const f32
190 /// let _ = unsafe{ &*(&1u32 as *const u32 as *const f32) };
192 declare_clippy_lint! {
193 pub TRANSMUTE_PTR_TO_PTR,
195 "transmutes from a pointer to a reference type"
198 pub struct Transmute;
200 impl LintPass for Transmute {
201 fn get_lints(&self) -> LintArray {
203 CROSSPOINTER_TRANSMUTE,
204 TRANSMUTE_PTR_TO_REF,
205 TRANSMUTE_PTR_TO_PTR,
208 TRANSMUTE_INT_TO_CHAR,
209 TRANSMUTE_BYTES_TO_STR,
210 TRANSMUTE_INT_TO_BOOL,
211 TRANSMUTE_INT_TO_FLOAT,
216 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Transmute {
217 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
218 if let ExprCall(ref path_expr, ref args) = e.node {
219 if let ExprPath(ref qpath) = path_expr.node {
220 if let Some(def_id) = opt_def_id(cx.tables.qpath_def(qpath, path_expr.hir_id)) {
221 if match_def_path(cx.tcx, def_id, &paths::TRANSMUTE) {
222 let from_ty = cx.tables.expr_ty(&args[0]);
223 let to_ty = cx.tables.expr_ty(e);
225 match (&from_ty.sty, &to_ty.sty) {
226 _ if from_ty == to_ty => span_lint(
230 &format!("transmute from a type (`{}`) to itself", from_ty),
232 (&ty::TyRef(_, rty, rty_mutbl), &ty::TyRawPtr(ptr_ty)) => span_lint_and_then(
236 "transmute from a reference to a pointer",
237 |db| if let Some(arg) = sugg::Sugg::hir_opt(cx, &args[0]) {
238 let rty_and_mut = ty::TypeAndMut { ty: rty, mutbl: rty_mutbl };
240 let sugg = if ptr_ty == rty_and_mut {
243 arg.as_ty(cx.tcx.mk_ptr(rty_and_mut)).as_ty(to_ty)
246 db.span_suggestion(e.span, "try", sugg.to_string());
249 (&ty::TyInt(_), &ty::TyRawPtr(_)) | (&ty::TyUint(_), &ty::TyRawPtr(_)) => {
254 "transmute from an integer to a pointer",
255 |db| if let Some(arg) = sugg::Sugg::hir_opt(cx, &args[0]) {
256 db.span_suggestion(e.span, "try", arg.as_ty(&to_ty.to_string()).to_string());
260 (&ty::TyFloat(_), &ty::TyRef(..)) |
261 (&ty::TyFloat(_), &ty::TyRawPtr(_)) |
262 (&ty::TyChar, &ty::TyRef(..)) |
263 (&ty::TyChar, &ty::TyRawPtr(_)) => span_lint(
267 &format!("transmute from a `{}` to a pointer", from_ty),
269 (&ty::TyRawPtr(from_ptr), _) if from_ptr.ty == to_ty => span_lint(
271 CROSSPOINTER_TRANSMUTE,
274 "transmute from a type (`{}`) to the type that it points to (`{}`)",
279 (_, &ty::TyRawPtr(to_ptr)) if to_ptr.ty == from_ty => span_lint(
281 CROSSPOINTER_TRANSMUTE,
284 "transmute from a type (`{}`) to a pointer to that type (`{}`)",
289 (&ty::TyRawPtr(from_pty), &ty::TyRef(_, to_ref_ty, mutbl)) => span_lint_and_then(
291 TRANSMUTE_PTR_TO_REF,
294 "transmute from a pointer type (`{}`) to a reference type \
300 let arg = sugg::Sugg::hir(cx, &args[0], "..");
301 let (deref, cast) = if mutbl == Mutability::MutMutable {
307 let arg = if from_pty.ty == to_ref_ty {
310 arg.as_ty(&format!("{} {}", cast, get_type_snippet(cx, qpath, to_ref_ty)))
313 db.span_suggestion(e.span, "try", sugg::make_unop(deref, arg).to_string());
316 (&ty::TyInt(ast::IntTy::I32), &ty::TyChar) |
317 (&ty::TyUint(ast::UintTy::U32), &ty::TyChar) => span_lint_and_then(
319 TRANSMUTE_INT_TO_CHAR,
321 &format!("transmute from a `{}` to a `char`", from_ty),
323 let arg = sugg::Sugg::hir(cx, &args[0], "..");
324 let arg = if let ty::TyInt(_) = from_ty.sty {
325 arg.as_ty(ty::TyUint(ast::UintTy::U32))
332 format!("std::char::from_u32({}).unwrap()", arg.to_string()),
336 (&ty::TyRef(_, ty_from, from_mutbl), &ty::TyRef(_, ty_to, to_mutbl)) => {
338 if let (&ty::TySlice(slice_ty), &ty::TyStr) = (&ty_from.sty, &ty_to.sty);
339 if let ty::TyUint(ast::UintTy::U8) = slice_ty.sty;
340 if from_mutbl == to_mutbl;
342 let postfix = if from_mutbl == Mutability::MutMutable {
350 TRANSMUTE_BYTES_TO_STR,
352 &format!("transmute from a `{}` to a `{}`", from_ty, to_ty),
358 "std::str::from_utf8{}({}).unwrap()",
360 snippet(cx, args[0].span, ".."),
368 TRANSMUTE_PTR_TO_PTR,
370 "transmute from a reference to a reference",
371 |db| if let Some(arg) = sugg::Sugg::hir_opt(cx, &args[0]) {
372 let ty_from_and_mut = ty::TypeAndMut { ty: ty_from, mutbl: from_mutbl };
373 let ty_to_and_mut = ty::TypeAndMut { ty: ty_to, mutbl: to_mutbl };
374 let sugg_paren = arg.as_ty(cx.tcx.mk_ptr(ty_from_and_mut)).as_ty(cx.tcx.mk_ptr(ty_to_and_mut));
375 let sugg = if to_mutbl == Mutability::MutMutable {
376 sugg_paren.mut_addr_deref()
378 sugg_paren.addr_deref()
380 db.span_suggestion(e.span, "try", sugg.to_string());
386 (&ty::TyRawPtr(_), &ty::TyRawPtr(to_ty)) => span_lint_and_then(
388 TRANSMUTE_PTR_TO_PTR,
390 "transmute from a pointer to a pointer",
391 |db| if let Some(arg) = sugg::Sugg::hir_opt(cx, &args[0]) {
392 let sugg = arg.as_ty(cx.tcx.mk_ptr(to_ty));
393 db.span_suggestion(e.span, "try", sugg.to_string());
396 (&ty::TyInt(ast::IntTy::I8), &ty::TyBool) | (&ty::TyUint(ast::UintTy::U8), &ty::TyBool) => {
399 TRANSMUTE_INT_TO_BOOL,
401 &format!("transmute from a `{}` to a `bool`", from_ty),
403 let arg = sugg::Sugg::hir(cx, &args[0], "..");
404 let zero = sugg::Sugg::NonParen(Cow::from("0"));
408 sugg::make_binop(ast::BinOpKind::Ne, &arg, &zero).to_string(),
413 (&ty::TyInt(_), &ty::TyFloat(_)) | (&ty::TyUint(_), &ty::TyFloat(_)) => {
416 TRANSMUTE_INT_TO_FLOAT,
418 &format!("transmute from a `{}` to a `{}`", from_ty, to_ty),
420 let arg = sugg::Sugg::hir(cx, &args[0], "..");
421 let arg = if let ty::TyInt(int_ty) = from_ty.sty {
426 .map_or_else(|| "size".to_string(), |v| v.to_string())
434 format!("{}::from_bits({})", to_ty, arg.to_string()),
448 /// Get the snippet of `Bar` in `…::transmute<Foo, &Bar>`. If that snippet is
449 /// not available , use
450 /// the type's `ToString` implementation. In weird cases it could lead to types
451 /// with invalid `'_`
452 /// lifetime, but it should be rare.
453 fn get_type_snippet(cx: &LateContext, path: &QPath, to_ref_ty: Ty) -> String {
454 let seg = last_path_segment(path);
456 if let Some(ref params) = seg.parameters;
457 if !params.parenthesized;
458 if let Some(to_ty) = params.types.get(1);
459 if let TyRptr(_, ref to_ty) = to_ty.node;
461 return snippet(cx, to_ty.ty.span, &to_ref_ty.to_string()).to_string();
465 to_ref_ty.to_string()