diff options
Diffstat (limited to 'src/tools/clippy/clippy_lints/src/casts/cast_ptr_alignment.rs')
-rw-r--r-- | src/tools/clippy/clippy_lints/src/casts/cast_ptr_alignment.rs | 96 |
1 files changed, 96 insertions, 0 deletions
diff --git a/src/tools/clippy/clippy_lints/src/casts/cast_ptr_alignment.rs b/src/tools/clippy/clippy_lints/src/casts/cast_ptr_alignment.rs new file mode 100644 index 000000000..d476a1a76 --- /dev/null +++ b/src/tools/clippy/clippy_lints/src/casts/cast_ptr_alignment.rs @@ -0,0 +1,96 @@ +use clippy_utils::diagnostics::span_lint; +use clippy_utils::ty::is_c_void; +use clippy_utils::{get_parent_expr, is_hir_ty_cfg_dependant, match_any_def_paths, paths}; +use rustc_hir::{Expr, ExprKind, GenericArg}; +use rustc_lint::LateContext; +use rustc_middle::ty::layout::LayoutOf; +use rustc_middle::ty::{self, Ty}; + +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 method_path.ident.name == sym!(cast) + && let Some(generic_args) = method_path.args + && let [GenericArg::Type(cast_to)] = generic_args.args + // There probably is no obvious reason to do this, just to be consistent with `as` cases. + && !is_hir_ty_cfg_dependant(cx, cast_to) + { + 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 let ty::RawPtr(from_ptr_ty) = &cast_from.kind() + && let ty::RawPtr(to_ptr_ty) = &cast_to.kind() + && let Ok(from_layout) = cx.layout_of(from_ptr_ty.ty) + && let Ok(to_layout) = cx.layout_of(to_ptr_ty.ty) + && from_layout.align.abi < to_layout.align.abi + // with c_void, we inherently need to trust the user + && !is_c_void(cx, from_ptr_ty.ty) + // when casting from a ZST, we don't know enough to properly lint + && !from_layout.is_zst() + && !is_used_as_unaligned(cx, expr) + { + 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(), + ), + ); + } +} + +fn is_used_as_unaligned(cx: &LateContext<'_>, e: &Expr<'_>) -> bool { + let Some(parent) = get_parent_expr(cx, e) else { + return false; + }; + match parent.kind { + ExprKind::MethodCall(name, [self_arg, ..], _) if self_arg.hir_id == e.hir_id => { + if matches!(name.ident.as_str(), "read_unaligned" | "write_unaligned") + && let Some(def_id) = cx.typeck_results().type_dependent_def_id(parent.hir_id) + && let Some(def_id) = cx.tcx.impl_of_method(def_id) + && cx.tcx.type_of(def_id).is_unsafe_ptr() + { + true + } else { + false + } + }, + ExprKind::Call(func, [arg, ..]) if arg.hir_id == e.hir_id => { + static PATHS: &[&[&str]] = &[ + paths::PTR_READ_UNALIGNED.as_slice(), + paths::PTR_WRITE_UNALIGNED.as_slice(), + paths::PTR_UNALIGNED_VOLATILE_LOAD.as_slice(), + paths::PTR_UNALIGNED_VOLATILE_STORE.as_slice(), + ]; + if let ExprKind::Path(path) = &func.kind + && let Some(def_id) = cx.qpath_res(path, func.hir_id).opt_def_id() + && match_any_def_paths(cx, def_id, PATHS).is_some() + { + true + } else { + false + } + }, + _ => false, + } +} |