use clippy_utils::diagnostics::span_lint_and_help; use clippy_utils::ty::is_c_void; use clippy_utils::{match_def_path, path_def_id, paths}; use rustc_hir::def_id::DefId; use rustc_hir::{Expr, ExprKind, QPath}; use rustc_lint::{LateContext, LateLintPass}; use rustc_middle::ty::RawPtr; use rustc_middle::ty::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`, so if you pass a `*mut c_void` you will get a `Box` (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 /// ```rust /// # 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: /// ```rust /// # 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 match_def_path(cx, def_id, &paths::WEAK_RC) || match_def_path(cx, def_id, &paths::WEAK_ARC) { Some("Weak") } else { None } }