85 lines
3.1 KiB
Rust
85 lines
3.1 KiB
Rust
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::def_id::DefId;
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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;
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use rustc_session::declare_lint_pass;
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use rustc_span::sym;
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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,Rc,Arc,Weak}::from_raw(_)`
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///
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/// ### Why is this bad?
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/// 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.
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/// 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`).
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/// 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.
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///
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/// ### Example
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/// ```no_run
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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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/// ```no_run
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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 = "1.67.0"]
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pub FROM_RAW_WITH_VOID_PTR,
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suspicious,
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"creating a `Box` from a void raw 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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&& let Some(type_str) = path_def_id(cx, ty).and_then(|id| def_id_matches_type(cx, id))
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&& let arg_kind = cx.typeck_results().expr_ty(arg).kind()
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&& let ty::RawPtr(ty, _) = arg_kind
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&& is_c_void(cx, *ty)
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{
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let msg = format!("creating a `{type_str}` from a void raw pointer");
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span_lint_and_help(
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cx,
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FROM_RAW_WITH_VOID_PTR,
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expr.span,
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msg,
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Some(arg.span),
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"cast this to a pointer of the appropriate type",
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);
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}
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}
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}
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/// Checks whether a `DefId` matches `Box`, `Rc`, `Arc`, or one of the `Weak` types.
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/// Returns a static string slice with the name of the type, if one was found.
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fn def_id_matches_type(cx: &LateContext<'_>, def_id: DefId) -> Option<&'static str> {
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// Box
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if Some(def_id) == cx.tcx.lang_items().owned_box() {
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return Some("Box");
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}
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if let Some(symbol) = cx.tcx.get_diagnostic_name(def_id) {
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if symbol == sym::Arc {
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return Some("Arc");
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} else if symbol == sym::Rc {
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return Some("Rc");
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}
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}
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if matches!(cx.tcx.get_diagnostic_name(def_id), Some(sym::RcWeak | sym::ArcWeak)) {
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Some("Weak")
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} else {
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None
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}
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}
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