1 use crate::utils::{last_path_segment, match_def_path, paths, snippet, span_lint, span_lint_and_then};
2 use crate::utils::{opt_def_id, sugg};
3 use if_chain::if_chain;
5 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
6 use rustc::ty::{self, Ty};
7 use rustc::{declare_tool_lint, lint_array};
8 use rustc_errors::Applicability;
12 /// **What it does:** Checks for transmutes that can't ever be correct on any
15 /// **Why is this bad?** It's basically guaranteed to be undefined behaviour.
17 /// **Known problems:** When accessing C, users might want to store pointer
18 /// sized objects in `extradata` arguments to save an allocation.
22 /// let ptr: *const T = core::intrinsics::transmute('x')
24 declare_clippy_lint! {
27 "transmutes that are confusing at best, undefined behaviour at worst and always useless"
30 /// **What it does:** Checks for transmutes to the original type of the object
31 /// and transmutes that could be a cast.
33 /// **Why is this bad?** Readability. The code tricks people into thinking that
34 /// something complex is going on.
36 /// **Known problems:** None.
40 /// core::intrinsics::transmute(t) // where the result type is the same as `t`'s
42 declare_clippy_lint! {
43 pub USELESS_TRANSMUTE,
45 "transmutes that have the same to and from types or could be a cast/coercion"
48 /// **What it does:** Checks for transmutes between a type `T` and `*T`.
50 /// **Why is this bad?** It's easy to mistakenly transmute between a type and a
51 /// pointer to that type.
53 /// **Known problems:** None.
57 /// core::intrinsics::transmute(t) // where the result type is the same as
60 declare_clippy_lint! {
61 pub CROSSPOINTER_TRANSMUTE,
63 "transmutes that have to or from types that are a pointer to the other"
66 /// **What it does:** Checks for transmutes from a pointer to a reference.
68 /// **Why is this bad?** This can always be rewritten with `&` and `*`.
70 /// **Known problems:** None.
74 /// let _: &T = std::mem::transmute(p); // where p: *const T
76 /// // can be written:
79 declare_clippy_lint! {
80 pub TRANSMUTE_PTR_TO_REF,
82 "transmutes from a pointer to a reference type"
85 /// **What it does:** Checks for transmutes from an integer to a `char`.
87 /// **Why is this bad?** Not every integer is a Unicode scalar value.
89 /// **Known problems:**
90 /// - [`from_u32`] which this lint suggests using is slower than `transmute`
91 /// as it needs to validate the input.
92 /// If you are certain that the input is always a valid Unicode scalar value,
93 /// use [`from_u32_unchecked`] which is as fast as `transmute`
94 /// but has a semantically meaningful name.
95 /// - You might want to handle `None` returned from [`from_u32`] instead of calling `unwrap`.
97 /// [`from_u32`]: https://doc.rust-lang.org/std/char/fn.from_u32.html
98 /// [`from_u32_unchecked`]: https://doc.rust-lang.org/std/char/fn.from_u32_unchecked.html
102 /// let _: char = std::mem::transmute(x); // where x: u32
105 /// let _ = std::char::from_u32(x).unwrap();
107 declare_clippy_lint! {
108 pub TRANSMUTE_INT_TO_CHAR,
110 "transmutes from an integer to a `char`"
113 /// **What it does:** Checks for transmutes from a `&[u8]` to a `&str`.
115 /// **Why is this bad?** Not every byte slice is a valid UTF-8 string.
117 /// **Known problems:**
118 /// - [`from_utf8`] which this lint suggests using is slower than `transmute`
119 /// as it needs to validate the input.
120 /// If you are certain that the input is always a valid UTF-8,
121 /// use [`from_utf8_unchecked`] which is as fast as `transmute`
122 /// but has a semantically meaningful name.
123 /// - You might want to handle errors returned from [`from_utf8`] instead of calling `unwrap`.
125 /// [`from_utf8`]: https://doc.rust-lang.org/std/str/fn.from_utf8.html
126 /// [`from_utf8_unchecked`]: https://doc.rust-lang.org/std/str/fn.from_utf8_unchecked.html
130 /// let _: &str = std::mem::transmute(b); // where b: &[u8]
133 /// let _ = std::str::from_utf8(b).unwrap();
135 declare_clippy_lint! {
136 pub TRANSMUTE_BYTES_TO_STR,
138 "transmutes from a `&[u8]` to a `&str`"
141 /// **What it does:** Checks for transmutes from an integer to a `bool`.
143 /// **Why is this bad?** This might result in an invalid in-memory representation of a `bool`.
145 /// **Known problems:** None.
149 /// let _: bool = std::mem::transmute(x); // where x: u8
152 /// let _: bool = x != 0;
154 declare_clippy_lint! {
155 pub TRANSMUTE_INT_TO_BOOL,
157 "transmutes from an integer to a `bool`"
160 /// **What it does:** Checks for transmutes from an integer to a float.
162 /// **Why is this bad?** This might result in an invalid in-memory representation of a float.
164 /// **Known problems:** None.
168 /// let _: f32 = std::mem::transmute(x); // where x: u32
171 /// let _: f32 = f32::from_bits(x);
173 declare_clippy_lint! {
174 pub TRANSMUTE_INT_TO_FLOAT,
176 "transmutes from an integer to a float"
179 /// **What it does:** Checks for transmutes from a pointer to a pointer, or
180 /// from a reference to a reference.
182 /// **Why is this bad?** Transmutes are dangerous, and these can instead be
183 /// written as casts.
185 /// **Known problems:** None.
189 /// let ptr = &1u32 as *const u32;
191 /// // pointer-to-pointer transmute
192 /// let _: *const f32 = std::mem::transmute(ptr);
193 /// // ref-ref transmute
194 /// let _: &f32 = std::mem::transmute(&1u32);
196 /// // These can be respectively written:
197 /// let _ = ptr as *const f32
198 /// let _ = unsafe{ &*(&1u32 as *const u32 as *const f32) };
200 declare_clippy_lint! {
201 pub TRANSMUTE_PTR_TO_PTR,
203 "transmutes from a pointer to a pointer / a reference to a reference"
206 pub struct Transmute;
208 impl LintPass for Transmute {
209 fn get_lints(&self) -> LintArray {
211 CROSSPOINTER_TRANSMUTE,
212 TRANSMUTE_PTR_TO_REF,
213 TRANSMUTE_PTR_TO_PTR,
216 TRANSMUTE_INT_TO_CHAR,
217 TRANSMUTE_BYTES_TO_STR,
218 TRANSMUTE_INT_TO_BOOL,
219 TRANSMUTE_INT_TO_FLOAT,
223 fn name(&self) -> &'static str {
228 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Transmute {
229 #[allow(clippy::similar_names)]
230 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
231 if let ExprKind::Call(ref path_expr, ref args) = e.node {
232 if let ExprKind::Path(ref qpath) = path_expr.node {
233 if let Some(def_id) = opt_def_id(cx.tables.qpath_def(qpath, path_expr.hir_id)) {
234 if match_def_path(cx.tcx, def_id, &paths::TRANSMUTE) {
235 let from_ty = cx.tables.expr_ty(&args[0]);
236 let to_ty = cx.tables.expr_ty(e);
238 match (&from_ty.sty, &to_ty.sty) {
239 _ if from_ty == to_ty => span_lint(
243 &format!("transmute from a type (`{}`) to itself", from_ty),
245 (&ty::Ref(_, rty, rty_mutbl), &ty::RawPtr(ptr_ty)) => span_lint_and_then(
249 "transmute from a reference to a pointer",
251 if let Some(arg) = sugg::Sugg::hir_opt(cx, &args[0]) {
252 let rty_and_mut = ty::TypeAndMut {
257 let sugg = if ptr_ty == rty_and_mut {
260 arg.as_ty(cx.tcx.mk_ptr(rty_and_mut)).as_ty(to_ty)
263 db.span_suggestion(e.span, "try", sugg.to_string(), Applicability::Unspecified);
267 (&ty::Int(_), &ty::RawPtr(_)) | (&ty::Uint(_), &ty::RawPtr(_)) => span_lint_and_then(
271 "transmute from an integer to a pointer",
273 if let Some(arg) = sugg::Sugg::hir_opt(cx, &args[0]) {
277 arg.as_ty(&to_ty.to_string()).to_string(),
278 Applicability::Unspecified,
283 (&ty::Float(_), &ty::Ref(..))
284 | (&ty::Float(_), &ty::RawPtr(_))
285 | (&ty::Char, &ty::Ref(..))
286 | (&ty::Char, &ty::RawPtr(_)) => span_lint(
290 &format!("transmute from a `{}` to a pointer", from_ty),
292 (&ty::RawPtr(from_ptr), _) if from_ptr.ty == to_ty => span_lint(
294 CROSSPOINTER_TRANSMUTE,
297 "transmute from a type (`{}`) to the type that it points to (`{}`)",
301 (_, &ty::RawPtr(to_ptr)) if to_ptr.ty == from_ty => span_lint(
303 CROSSPOINTER_TRANSMUTE,
306 "transmute from a type (`{}`) to a pointer to that type (`{}`)",
310 (&ty::RawPtr(from_pty), &ty::Ref(_, to_ref_ty, mutbl)) => span_lint_and_then(
312 TRANSMUTE_PTR_TO_REF,
315 "transmute from a pointer type (`{}`) to a reference type \
320 let arg = sugg::Sugg::hir(cx, &args[0], "..");
321 let (deref, cast) = if mutbl == Mutability::MutMutable {
327 let arg = if from_pty.ty == to_ref_ty {
330 arg.as_ty(&format!("{} {}", cast, get_type_snippet(cx, qpath, to_ref_ty)))
336 sugg::make_unop(deref, arg).to_string(),
337 Applicability::Unspecified,
341 (&ty::Int(ast::IntTy::I32), &ty::Char) | (&ty::Uint(ast::UintTy::U32), &ty::Char) => {
344 TRANSMUTE_INT_TO_CHAR,
346 &format!("transmute from a `{}` to a `char`", from_ty),
348 let arg = sugg::Sugg::hir(cx, &args[0], "..");
349 let arg = if let ty::Int(_) = from_ty.sty {
350 arg.as_ty(ty::Uint(ast::UintTy::U32))
357 format!("std::char::from_u32({}).unwrap()", arg.to_string()),
358 Applicability::Unspecified,
363 (&ty::Ref(_, ty_from, from_mutbl), &ty::Ref(_, ty_to, to_mutbl)) => {
365 if let (&ty::Slice(slice_ty), &ty::Str) = (&ty_from.sty, &ty_to.sty);
366 if let ty::Uint(ast::UintTy::U8) = slice_ty.sty;
367 if from_mutbl == to_mutbl;
369 let postfix = if from_mutbl == Mutability::MutMutable {
377 TRANSMUTE_BYTES_TO_STR,
379 &format!("transmute from a `{}` to a `{}`", from_ty, to_ty),
385 "std::str::from_utf8{}({}).unwrap()",
387 snippet(cx, args[0].span, ".."),
389 Applicability::Unspecified,
394 if cx.tcx.erase_regions(&from_ty) != cx.tcx.erase_regions(&to_ty) {
397 TRANSMUTE_PTR_TO_PTR,
399 "transmute from a reference to a reference",
400 |db| if let Some(arg) = sugg::Sugg::hir_opt(cx, &args[0]) {
401 let ty_from_and_mut = ty::TypeAndMut {
405 let ty_to_and_mut = ty::TypeAndMut { ty: ty_to, mutbl: to_mutbl };
407 .as_ty(cx.tcx.mk_ptr(ty_from_and_mut))
408 .as_ty(cx.tcx.mk_ptr(ty_to_and_mut));
409 let sugg = if to_mutbl == Mutability::MutMutable {
410 sugg_paren.mut_addr_deref()
412 sugg_paren.addr_deref()
418 Applicability::Unspecified,
426 (&ty::RawPtr(_), &ty::RawPtr(to_ty)) => span_lint_and_then(
428 TRANSMUTE_PTR_TO_PTR,
430 "transmute from a pointer to a pointer",
432 if let Some(arg) = sugg::Sugg::hir_opt(cx, &args[0]) {
433 let sugg = arg.as_ty(cx.tcx.mk_ptr(to_ty));
434 db.span_suggestion(e.span, "try", sugg.to_string(), Applicability::Unspecified);
438 (&ty::Int(ast::IntTy::I8), &ty::Bool) | (&ty::Uint(ast::UintTy::U8), &ty::Bool) => {
441 TRANSMUTE_INT_TO_BOOL,
443 &format!("transmute from a `{}` to a `bool`", from_ty),
445 let arg = sugg::Sugg::hir(cx, &args[0], "..");
446 let zero = sugg::Sugg::NonParen(Cow::from("0"));
450 sugg::make_binop(ast::BinOpKind::Ne, &arg, &zero).to_string(),
451 Applicability::Unspecified,
456 (&ty::Int(_), &ty::Float(_)) | (&ty::Uint(_), &ty::Float(_)) => span_lint_and_then(
458 TRANSMUTE_INT_TO_FLOAT,
460 &format!("transmute from a `{}` to a `{}`", from_ty, to_ty),
462 let arg = sugg::Sugg::hir(cx, &args[0], "..");
463 let arg = if let ty::Int(int_ty) = from_ty.sty {
466 int_ty.bit_width().map_or_else(|| "size".to_string(), |v| v.to_string())
474 format!("{}::from_bits({})", to_ty, arg.to_string()),
475 Applicability::Unspecified,
488 /// Get the snippet of `Bar` in `…::transmute<Foo, &Bar>`. If that snippet is
489 /// not available , use
490 /// the type's `ToString` implementation. In weird cases it could lead to types
491 /// with invalid `'_`
492 /// lifetime, but it should be rare.
493 fn get_type_snippet(cx: &LateContext<'_, '_>, path: &QPath, to_ref_ty: Ty<'_>) -> String {
494 let seg = last_path_segment(path);
496 if let Some(ref params) = seg.args;
497 if !params.parenthesized;
498 if let Some(to_ty) = params.args.iter().filter_map(|arg| match arg {
499 GenericArg::Type(ty) => Some(ty),
500 GenericArg::Lifetime(_) => None,
502 if let TyKind::Rptr(_, ref to_ty) = to_ty.node;
504 return snippet(cx, to_ty.ty.span, &to_ref_ty.to_string()).to_string();
508 to_ref_ty.to_string()