58 lines
2.4 KiB
Rust
58 lines
2.4 KiB
Rust
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use clippy_utils::diagnostics::span_lint_and_help;
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use clippy_utils::path_def_id;
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use clippy_utils::ty::is_c_void;
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use rustc_hir::{Expr, ExprKind, QPath};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_middle::ty::RawPtr;
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use rustc_middle::ty::TypeAndMut;
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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declare_clippy_lint! {
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/// ### What it does
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/// Checks if we're passing a `c_void` raw pointer to `Box::from_raw(_)`
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///
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/// ### Why is this bad?
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/// However, it is easy to run into the pitfall of calling from_raw with the c_void pointer.
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/// Note that the definition of, say, Box::from_raw is:
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///
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/// `pub unsafe fn from_raw(raw: *mut T) -> Box<T>`
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///
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/// meaning that if you pass a *mut c_void you will get a Box<c_void>.
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/// Per the safety requirements in the documentation, for this to be safe,
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/// c_void would need to have the same memory layout as the original type, which is often not the case.
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///
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/// ### Example
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/// ```rust
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/// # use std::ffi::c_void;
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/// let ptr = Box::into_raw(Box::new(42usize)) as *mut c_void;
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/// let _ = unsafe { Box::from_raw(ptr) };
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/// ```
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/// Use instead:
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/// ```rust
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/// # use std::ffi::c_void;
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/// # let ptr = Box::into_raw(Box::new(42usize)) as *mut c_void;
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/// let _ = unsafe { Box::from_raw(ptr as *mut usize) };
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/// ```
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///
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#[clippy::version = "1.66.0"]
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pub FROM_RAW_WITH_VOID_PTR,
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suspicious,
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"creating a `Box` from a raw void pointer"
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}
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declare_lint_pass!(FromRawWithVoidPtr => [FROM_RAW_WITH_VOID_PTR]);
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impl LateLintPass<'_> for FromRawWithVoidPtr {
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fn check_expr(&mut self, cx: &LateContext<'_>, expr: &Expr<'_>) {
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if let ExprKind::Call(box_from_raw, [arg]) = expr.kind
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&& let ExprKind::Path(QPath::TypeRelative(ty, seg)) = box_from_raw.kind
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&& seg.ident.name == sym!(from_raw)
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// FIXME: This lint is also applicable to other types, like `Rc`, `Arc` and `Weak`.
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&& path_def_id(cx, ty).map_or(false, |id| Some(id) == cx.tcx.lang_items().owned_box())
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&& let arg_kind = cx.typeck_results().expr_ty(arg).kind()
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&& let RawPtr(TypeAndMut { ty, .. }) = arg_kind
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&& is_c_void(cx, *ty) {
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span_lint_and_help(cx, FROM_RAW_WITH_VOID_PTR, expr.span, "creating a `Box` from a raw void pointer", Some(arg.span), "cast this to a pointer of the actual type");
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}
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}
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}
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