| use clippy_utils::diagnostics::span_lint_and_help; |
| use clippy_utils::path_def_id; |
| use clippy_utils::ty::is_c_void; |
| use rustc_hir::def_id::DefId; |
| use rustc_hir::{Expr, ExprKind, QPath}; |
| use rustc_lint::{LateContext, LateLintPass}; |
| use rustc_middle::ty::{RawPtr, TypeAndMut}; |
| use rustc_session::{declare_lint_pass, declare_tool_lint}; |
| use rustc_span::sym; |
| |
| declare_clippy_lint! { |
| /// ### What it does |
| /// Checks if we're passing a `c_void` raw pointer to `{Box,Rc,Arc,Weak}::from_raw(_)` |
| /// |
| /// ### Why is this bad? |
| /// When dealing with `c_void` raw pointers in FFI, it is easy to run into the pitfall of calling `from_raw` with the `c_void` pointer. |
| /// The type signature of `Box::from_raw` is `fn from_raw(raw: *mut T) -> Box<T>`, so if you pass a `*mut c_void` you will get a `Box<c_void>` (and similarly for `Rc`, `Arc` and `Weak`). |
| /// For this to be safe, `c_void` would need to have the same memory layout as the original type, which is often not the case. |
| /// |
| /// ### Example |
| /// ```no_run |
| /// # use std::ffi::c_void; |
| /// let ptr = Box::into_raw(Box::new(42usize)) as *mut c_void; |
| /// let _ = unsafe { Box::from_raw(ptr) }; |
| /// ``` |
| /// Use instead: |
| /// ```no_run |
| /// # use std::ffi::c_void; |
| /// # let ptr = Box::into_raw(Box::new(42usize)) as *mut c_void; |
| /// let _ = unsafe { Box::from_raw(ptr as *mut usize) }; |
| /// ``` |
| /// |
| #[clippy::version = "1.67.0"] |
| pub FROM_RAW_WITH_VOID_PTR, |
| suspicious, |
| "creating a `Box` from a void raw pointer" |
| } |
| declare_lint_pass!(FromRawWithVoidPtr => [FROM_RAW_WITH_VOID_PTR]); |
| |
| impl LateLintPass<'_> for FromRawWithVoidPtr { |
| fn check_expr(&mut self, cx: &LateContext<'_>, expr: &Expr<'_>) { |
| if let ExprKind::Call(box_from_raw, [arg]) = expr.kind |
| && let ExprKind::Path(QPath::TypeRelative(ty, seg)) = box_from_raw.kind |
| && seg.ident.name == sym!(from_raw) |
| && let Some(type_str) = path_def_id(cx, ty).and_then(|id| def_id_matches_type(cx, id)) |
| && let arg_kind = cx.typeck_results().expr_ty(arg).kind() |
| && let RawPtr(TypeAndMut { ty, .. }) = arg_kind |
| && is_c_void(cx, *ty) |
| { |
| let msg = format!("creating a `{type_str}` from a void raw pointer"); |
| span_lint_and_help( |
| cx, |
| FROM_RAW_WITH_VOID_PTR, |
| expr.span, |
| &msg, |
| Some(arg.span), |
| "cast this to a pointer of the appropriate type", |
| ); |
| } |
| } |
| } |
| |
| /// Checks whether a `DefId` matches `Box`, `Rc`, `Arc`, or one of the `Weak` types. |
| /// Returns a static string slice with the name of the type, if one was found. |
| fn def_id_matches_type(cx: &LateContext<'_>, def_id: DefId) -> Option<&'static str> { |
| // Box |
| if Some(def_id) == cx.tcx.lang_items().owned_box() { |
| return Some("Box"); |
| } |
| |
| if let Some(symbol) = cx.tcx.get_diagnostic_name(def_id) { |
| if symbol == sym::Arc { |
| return Some("Arc"); |
| } else if symbol == sym::Rc { |
| return Some("Rc"); |
| } |
| } |
| |
| if matches!(cx.tcx.get_diagnostic_name(def_id), Some(sym::RcWeak | sym::ArcWeak)) { |
| Some("Weak") |
| } else { |
| None |
| } |
| } |