diff --git a/clippy_lints/src/casts/cast_ptr_alignment.rs b/clippy_lints/src/casts/cast_ptr_alignment.rs index a4ef1344ab9..d476a1a7646 100644 --- a/clippy_lints/src/casts/cast_ptr_alignment.rs +++ b/clippy_lints/src/casts/cast_ptr_alignment.rs @@ -1,7 +1,6 @@ use clippy_utils::diagnostics::span_lint; -use clippy_utils::is_hir_ty_cfg_dependant; use clippy_utils::ty::is_c_void; -use if_chain::if_chain; +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; @@ -20,45 +19,78 @@ pub(super) fn check(cx: &LateContext<'_>, expr: &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; + 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. - 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); - } + && !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_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; + 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 - if !is_c_void(cx, from_ptr_ty.ty); + && !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(), - ), - ); - } + && !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, } } diff --git a/clippy_utils/src/paths.rs b/clippy_utils/src/paths.rs index 6f56f8d5136..79e6e92dc0a 100644 --- a/clippy_utils/src/paths.rs +++ b/clippy_utils/src/paths.rs @@ -105,6 +105,8 @@ pub const PTR_READ_VOLATILE: [&str; 3] = ["core", "ptr", "read_volatile"]; pub const PTR_REPLACE: [&str; 3] = ["core", "ptr", "replace"]; pub const PTR_SWAP: [&str; 3] = ["core", "ptr", "swap"]; +pub const PTR_UNALIGNED_VOLATILE_LOAD: [&str; 3] = ["core", "intrinsics", "unaligned_volatile_load"]; +pub const PTR_UNALIGNED_VOLATILE_STORE: [&str; 3] = ["core", "intrinsics", "unaligned_volatile_store"]; pub const PTR_WRITE: [&str; 3] = ["core", "ptr", "write"]; pub const PTR_WRITE_BYTES: [&str; 3] = ["core", "intrinsics", "write_bytes"]; pub const PTR_WRITE_UNALIGNED: [&str; 3] = ["core", "ptr", "write_unaligned"]; diff --git a/tests/ui/cast_alignment.rs b/tests/ui/cast_alignment.rs index 659591fffbe..e4e7290a30e 100644 --- a/tests/ui/cast_alignment.rs +++ b/tests/ui/cast_alignment.rs @@ -1,6 +1,7 @@ //! Test casts for alignment issues #![feature(rustc_private)] +#![feature(core_intrinsics)] extern crate libc; #[warn(clippy::cast_ptr_alignment)] @@ -34,4 +35,17 @@ fn main() { (&1u32 as *const u32 as *const libc::c_void) as *const u32; // For ZST, we should trust the user. See #4256 (&1u32 as *const u32 as *const ()) as *const u32; + + // Issue #2881 + let mut data = [0u8, 0u8]; + unsafe { + let ptr = &data as *const [u8; 2] as *const u8; + let _ = (ptr as *const u16).read_unaligned(); + let _ = core::ptr::read_unaligned(ptr as *const u16); + let _ = core::intrinsics::unaligned_volatile_load(ptr as *const u16); + let ptr = &mut data as *mut [u8; 2] as *mut u8; + let _ = (ptr as *mut u16).write_unaligned(0); + let _ = core::ptr::write_unaligned(ptr as *mut u16, 0); + let _ = core::intrinsics::unaligned_volatile_store(ptr as *mut u16, 0); + } } diff --git a/tests/ui/cast_alignment.stderr b/tests/ui/cast_alignment.stderr index aedd3684455..5df2b5b1094 100644 --- a/tests/ui/cast_alignment.stderr +++ b/tests/ui/cast_alignment.stderr @@ -1,5 +1,5 @@ error: casting from `*const u8` to a more-strictly-aligned pointer (`*const u16`) (1 < 2 bytes) - --> $DIR/cast_alignment.rs:18:5 + --> $DIR/cast_alignment.rs:19:5 | LL | (&1u8 as *const u8) as *const u16; | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ @@ -7,19 +7,19 @@ LL | (&1u8 as *const u8) as *const u16; = note: `-D clippy::cast-ptr-alignment` implied by `-D warnings` error: casting from `*mut u8` to a more-strictly-aligned pointer (`*mut u16`) (1 < 2 bytes) - --> $DIR/cast_alignment.rs:19:5 + --> $DIR/cast_alignment.rs:20:5 | LL | (&mut 1u8 as *mut u8) as *mut u16; | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ error: casting from `*const u8` to a more-strictly-aligned pointer (`*const u16`) (1 < 2 bytes) - --> $DIR/cast_alignment.rs:22:5 + --> $DIR/cast_alignment.rs:23:5 | LL | (&1u8 as *const u8).cast::(); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ error: casting from `*mut u8` to a more-strictly-aligned pointer (`*mut u16`) (1 < 2 bytes) - --> $DIR/cast_alignment.rs:23:5 + --> $DIR/cast_alignment.rs:24:5 | LL | (&mut 1u8 as *mut u8).cast::(); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^