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|
use clippy_utils::diagnostics::span_lint;
use clippy_utils::is_hir_ty_cfg_dependant;
use if_chain::if_chain;
use rustc_hir::{Expr, ExprKind, GenericArg};
use rustc_lint::LateContext;
use rustc_middle::ty::layout::LayoutOf;
use rustc_middle::ty::{self, Ty};
use rustc_span::symbol::sym;
use super::CAST_PTR_ALIGNMENT;
pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>) {
if let ExprKind::Cast(cast_expr, cast_to) = expr.kind {
if is_hir_ty_cfg_dependant(cx, cast_to) {
return;
}
let (cast_from, cast_to) = (
cx.typeck_results().expr_ty(cast_expr),
cx.typeck_results().expr_ty(expr),
);
lint_cast_ptr_alignment(cx, expr, cast_from, cast_to);
} else if let ExprKind::MethodCall(method_path, _, [self_arg, ..], _) = &expr.kind {
if_chain! {
if method_path.ident.name == sym!(cast);
if let Some(generic_args) = method_path.args;
if let [GenericArg::Type(cast_to)] = generic_args.args;
// There probably is no obvious reason to do this, just to be consistent with `as` cases.
if !is_hir_ty_cfg_dependant(cx, cast_to);
then {
let (cast_from, cast_to) =
(cx.typeck_results().expr_ty(self_arg), cx.typeck_results().expr_ty(expr));
lint_cast_ptr_alignment(cx, expr, cast_from, cast_to);
}
}
}
}
fn lint_cast_ptr_alignment<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>, cast_from: Ty<'tcx>, cast_to: Ty<'tcx>) {
if_chain! {
if let ty::RawPtr(from_ptr_ty) = &cast_from.kind();
if let ty::RawPtr(to_ptr_ty) = &cast_to.kind();
if let Ok(from_layout) = cx.layout_of(from_ptr_ty.ty);
if let Ok(to_layout) = cx.layout_of(to_ptr_ty.ty);
if from_layout.align.abi < to_layout.align.abi;
// with c_void, we inherently need to trust the user
if !is_c_void(cx, from_ptr_ty.ty);
// when casting from a ZST, we don't know enough to properly lint
if !from_layout.is_zst();
then {
span_lint(
cx,
CAST_PTR_ALIGNMENT,
expr.span,
&format!(
"casting from `{}` to a more-strictly-aligned pointer (`{}`) ({} < {} bytes)",
cast_from,
cast_to,
from_layout.align.abi.bytes(),
to_layout.align.abi.bytes(),
),
);
}
}
}
/// Check if the given type is either `core::ffi::c_void` or
/// one of the platform specific `libc::<platform>::c_void` of libc.
fn is_c_void(cx: &LateContext<'_>, ty: Ty<'_>) -> bool {
if let ty::Adt(adt, _) = ty.kind() {
let names = cx.get_def_path(adt.did);
if names.is_empty() {
return false;
}
if names[0] == sym::libc || names[0] == sym::core && *names.last().unwrap() == sym!(c_void) {
return true;
}
}
false
}
|
