--- /dev/null
+use rustc_hir::{Expr, ExprKind, GenericArg};
+use rustc_lint::LateContext;
+use rustc_middle::ty::{self, Ty};
+use rustc_span::symbol::sym;
+use rustc_target::abi::LayoutOf;
+
+use if_chain::if_chain;
+
+use crate::utils::{is_hir_ty_cfg_dependant, span_lint};
+
+use super::CAST_PTR_ALIGNMENT;
+
+pub(super) fn check(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
+ if let ExprKind::Cast(ref 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, _, args, _) = 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(&args[0]), 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
+}