mirror of
https://github.com/rust-lang/rust-clippy
synced 2024-12-01 00:49:30 +00:00
4e5f69cc86
This PR has implemented improved representation. - Use "lib" instead of "lifb" - Use "triggered" instead of "triggere" - Use "blacklisted_name" instead of "blackisted_name" - Use "stabilization" instead of "stabilisation" - Use "behavior" instead of "behaviour" - Use "target" instead of "tartet" - Use "checked_add" instead of "chcked_add" - Use "anti-pattern" instead of "antipattern" - Use "suggestion" instead of "suggesttion" - Use "example" instead of "exampel" - Use "Cheat Sheet" instead of "Cheatsheet"
105 lines
3.4 KiB
Rust
105 lines
3.4 KiB
Rust
use clippy_utils::diagnostics::span_lint_and_help;
|
|
use rustc_hir::{self as hir, HirId, Item, ItemKind};
|
|
use rustc_lint::{LateContext, LateLintPass};
|
|
use rustc_middle::ty::layout::LayoutOf;
|
|
use rustc_session::{declare_lint_pass, declare_tool_lint};
|
|
use rustc_span::sym;
|
|
use rustc_typeck::hir_ty_to_ty;
|
|
|
|
declare_clippy_lint! {
|
|
/// ### What it does
|
|
/// Displays a warning when a union is declared with the default representation (without a `#[repr(C)]` attribute).
|
|
///
|
|
/// ### Why is this bad?
|
|
/// Unions in Rust have unspecified layout by default, despite many people thinking that they
|
|
/// lay out each field at the start of the union (like C does). That is, there are no guarantees
|
|
/// about the offset of the fields for unions with multiple non-ZST fields without an explicitly
|
|
/// specified layout. These cases may lead to undefined behavior in unsafe blocks.
|
|
///
|
|
/// ### Example
|
|
/// ```rust
|
|
/// union Foo {
|
|
/// a: i32,
|
|
/// b: u32,
|
|
/// }
|
|
///
|
|
/// fn main() {
|
|
/// let _x: u32 = unsafe {
|
|
/// Foo { a: 0_i32 }.b // Undefined behavior: `b` is allowed to be padding
|
|
/// };
|
|
/// }
|
|
/// ```
|
|
/// Use instead:
|
|
/// ```rust
|
|
/// #[repr(C)]
|
|
/// union Foo {
|
|
/// a: i32,
|
|
/// b: u32,
|
|
/// }
|
|
///
|
|
/// fn main() {
|
|
/// let _x: u32 = unsafe {
|
|
/// Foo { a: 0_i32 }.b // Now defined behavior, this is just an i32 -> u32 transmute
|
|
/// };
|
|
/// }
|
|
/// ```
|
|
#[clippy::version = "1.60.0"]
|
|
pub DEFAULT_UNION_REPRESENTATION,
|
|
restriction,
|
|
"unions without a `#[repr(C)]` attribute"
|
|
}
|
|
declare_lint_pass!(DefaultUnionRepresentation => [DEFAULT_UNION_REPRESENTATION]);
|
|
|
|
impl<'tcx> LateLintPass<'tcx> for DefaultUnionRepresentation {
|
|
fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'tcx>) {
|
|
if is_union_with_two_non_zst_fields(cx, item) && !has_c_repr_attr(cx, item.hir_id()) {
|
|
span_lint_and_help(
|
|
cx,
|
|
DEFAULT_UNION_REPRESENTATION,
|
|
item.span,
|
|
"this union has the default representation",
|
|
None,
|
|
&format!(
|
|
"consider annotating `{}` with `#[repr(C)]` to explicitly specify memory layout",
|
|
cx.tcx.def_path_str(item.def_id.to_def_id())
|
|
),
|
|
);
|
|
}
|
|
}
|
|
}
|
|
|
|
/// Returns true if the given item is a union with at least two non-ZST fields.
|
|
fn is_union_with_two_non_zst_fields(cx: &LateContext<'_>, item: &Item<'_>) -> bool {
|
|
if let ItemKind::Union(data, _) = &item.kind {
|
|
data.fields().iter().filter(|f| !is_zst(cx, f.ty)).count() >= 2
|
|
} else {
|
|
false
|
|
}
|
|
}
|
|
|
|
fn is_zst(cx: &LateContext<'_>, hir_ty: &hir::Ty<'_>) -> bool {
|
|
if hir_ty.span.from_expansion() {
|
|
return false;
|
|
}
|
|
let ty = hir_ty_to_ty(cx.tcx, hir_ty);
|
|
if let Ok(layout) = cx.layout_of(ty) {
|
|
layout.is_zst()
|
|
} else {
|
|
false
|
|
}
|
|
}
|
|
|
|
fn has_c_repr_attr(cx: &LateContext<'_>, hir_id: HirId) -> bool {
|
|
cx.tcx.hir().attrs(hir_id).iter().any(|attr| {
|
|
if attr.has_name(sym::repr) {
|
|
if let Some(items) = attr.meta_item_list() {
|
|
for item in items {
|
|
if item.is_word() && matches!(item.name_or_empty(), sym::C) {
|
|
return true;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
false
|
|
})
|
|
}
|