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Auto merge of #8547 - Jarcho:transmute_8501, r=flip1995

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More `transmute_undefined_repr` fixes

fixes: #8498
fixes: #8501
fixes: #8503

changelog: Allow `transumte_undefined_repr` between fat pointers and `(usize, usize)`
changelog: Allow `transumte_undefined_repr` when one side is a union
changelog: Fix `transumte_undefined_repr` on tuples with one non-zero-sized type.
This commit is contained in:
bors 2022-03-16 09:39:22 +00:00
commit 2b0e730bf3
4 changed files with 49 additions and 15 deletions
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3
clippy_lints/src/transmute/mod.rs
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@ -415,7 +415,8 @@ impl<'tcx> LateLintPass<'tcx> for Transmute {
// And see https://github.com/rust-lang/rust/issues/51911 for dereferencing raw pointers.
let const_context = in_constant(cx, e.hir_id);
let from_ty = cx.typeck_results().expr_ty(arg);
let from_ty = cx.typeck_results().expr_ty_adjusted(arg);
// Adjustments for `to_ty` happen after the call to `transmute`, so don't use them.
let to_ty = cx.typeck_results().expr_ty(e);
// If useless_transmute is triggered, the other lints can be skipped.

34
clippy_lints/src/transmute/transmute_undefined_repr.rs
View File

@ -4,7 +4,7 @@ use clippy_utils::ty::is_c_void;
use rustc_hir::Expr;
use rustc_lint::LateContext;
use rustc_middle::ty::subst::Subst;
use rustc_middle::ty::{self, Ty, TypeAndMut};
use rustc_middle::ty::{self, IntTy, Ty, TypeAndMut, UintTy};
use rustc_span::Span;
#[allow(clippy::too_many_lines)]
@ -23,7 +23,8 @@ pub(super) fn check<'tcx>(
unsized_ty,
to_ty: to_sub_ty,
} => match reduce_ty(cx, to_sub_ty) {
ReducedTy::IntArray | ReducedTy::TypeErasure => break,
ReducedTy::TypeErasure => break,
ReducedTy::UnorderedFields(ty) if is_size_pair(ty) => break,
ReducedTy::Ref(to_sub_ty) => {
from_ty = unsized_ty;
to_ty = to_sub_ty;
@ -48,7 +49,8 @@ pub(super) fn check<'tcx>(
unsized_ty,
from_ty: from_sub_ty,
} => match reduce_ty(cx, from_sub_ty) {
ReducedTy::IntArray | ReducedTy::TypeErasure => break,
ReducedTy::TypeErasure => break,
ReducedTy::UnorderedFields(ty) if is_size_pair(ty) => break,
ReducedTy::Ref(from_sub_ty) => {
from_ty = from_sub_ty;
to_ty = unsized_ty;
@ -123,8 +125,7 @@ pub(super) fn check<'tcx>(
from_ty: from_sub_ty,
to_ty: to_sub_ty,
} => match (reduce_ty(cx, from_sub_ty), reduce_ty(cx, to_sub_ty)) {
(ReducedTy::IntArray | ReducedTy::TypeErasure, _)
| (_, ReducedTy::IntArray | ReducedTy::TypeErasure) => return false,
(ReducedTy::TypeErasure, _) | (_, ReducedTy::TypeErasure) => return false,
(ReducedTy::UnorderedFields(from_ty), ReducedTy::UnorderedFields(to_ty)) if from_ty != to_ty => {
span_lint_and_then(
cx,
@ -263,9 +264,6 @@ enum ReducedTy<'tcx> {
UnorderedFields(Ty<'tcx>),
/// The type is a reference to the contained type.
Ref(Ty<'tcx>),
/// The type is an array of a primitive integer type. These can be used as storage for a value
/// of another type.
IntArray,
/// Any other type.
Other(Ty<'tcx>),
}
@ -275,17 +273,18 @@ fn reduce_ty<'tcx>(cx: &LateContext<'tcx>, mut ty: Ty<'tcx>) -> ReducedTy<'tcx>
loop {
ty = cx.tcx.try_normalize_erasing_regions(cx.param_env, ty).unwrap_or(ty);
return match *ty.kind() {
ty::Array(sub_ty, _) if matches!(sub_ty.kind(), ty::Int(_) | ty::Uint(_)) => ReducedTy::IntArray,
ty::Array(sub_ty, _) if matches!(sub_ty.kind(), ty::Int(_) | ty::Uint(_)) => ReducedTy::TypeErasure,
ty::Array(sub_ty, _) | ty::Slice(sub_ty) => {
ty = sub_ty;
continue;
},
ty::Tuple(args) if args.is_empty() => ReducedTy::TypeErasure,
ty::Tuple(args) => {
let Some(sized_ty) = args.iter().find(|&ty| !is_zero_sized_ty(cx, ty)) else {
let mut iter = args.iter();
let Some(sized_ty) = iter.find(|&ty| !is_zero_sized_ty(cx, ty)) else {
return ReducedTy::OrderedFields(ty);
};
if args.iter().all(|ty| is_zero_sized_ty(cx, ty)) {
if iter.all(|ty| is_zero_sized_ty(cx, ty)) {
ty = sized_ty;
continue;
}
@ -313,6 +312,8 @@ fn reduce_ty<'tcx>(cx: &LateContext<'tcx>, mut ty: Ty<'tcx>) -> ReducedTy<'tcx>
ty::Adt(def, _) if def.is_enum() && (def.variants().is_empty() || is_c_void(cx, ty)) => {
ReducedTy::TypeErasure
},
// TODO: Check if the conversion to or from at least one of a union's fields is valid.
ty::Adt(def, _) if def.is_union() => ReducedTy::TypeErasure,
ty::Foreign(_) => ReducedTy::TypeErasure,
ty::Ref(_, ty, _) => ReducedTy::Ref(ty),
ty::RawPtr(ty) => ReducedTy::Ref(ty.ty),
@ -332,3 +333,14 @@ fn is_zero_sized_ty<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
}
}
}
fn is_size_pair(ty: Ty<'_>) -> bool {
if let ty::Tuple(tys) = *ty.kind()
&& let [ty1, ty2] = &**tys
{
matches!(ty1.kind(), ty::Int(IntTy::Isize) | ty::Uint(UintTy::Usize))
&& matches!(ty2.kind(), ty::Int(IntTy::Isize) | ty::Uint(UintTy::Usize))
} else {
false
}
}

23
tests/ui/transmute_undefined_repr.rs
View File

@ -2,7 +2,7 @@
#![allow(clippy::unit_arg, clippy::transmute_ptr_to_ref)]
use core::ffi::c_void;
use core::mem::{size_of, transmute};
use core::mem::{size_of, transmute, MaybeUninit};
fn value<T>() -> T {
unimplemented!()
@ -87,5 +87,26 @@ fn main() {
let _: *const [u8] = transmute(value::<Box<[u8]>>()); // Ok
let _: Box<[u8]> = transmute(value::<*mut [u8]>()); // Ok
let _: Ty2<u32, u32> = transmute(value::<(Ty2<u32, u32>,)>()); // Ok
let _: (Ty2<u32, u32>,) = transmute(value::<Ty2<u32, u32>>()); // Ok
let _: Ty2<u32, u32> = transmute(value::<(Ty2<u32, u32>, ())>()); // Ok
let _: (Ty2<u32, u32>, ()) = transmute(value::<Ty2<u32, u32>>()); // Ok
let _: Ty2<u32, u32> = transmute(value::<((), Ty2<u32, u32>)>()); // Ok
let _: ((), Ty2<u32, u32>) = transmute(value::<Ty2<u32, u32>>()); // Ok
let _: (usize, usize) = transmute(value::<&[u8]>()); // Ok
let _: &[u8] = transmute(value::<(usize, usize)>()); // Ok
trait Trait {}
let _: (isize, isize) = transmute(value::<&dyn Trait>()); // Ok
let _: &dyn Trait = transmute(value::<(isize, isize)>()); // Ok
let _: MaybeUninit<Ty2<u32, u32>> = transmute(value::<Ty2<u32, u32>>()); // Ok
let _: Ty2<u32, u32> = transmute(value::<MaybeUninit<Ty2<u32, u32>>>()); // Ok
let _: Ty<&[u32]> = transmute::<&[u32], _>(value::<&Vec<u32>>()); // Ok
}
}

4
tests/ui/transmutes_expressible_as_ptr_casts.stderr
View File

@ -34,13 +34,13 @@ error: transmute from a reference to a pointer
LL | let _array_ptr_transmute = unsafe { transmute::<&[i32; 4], *const [i32; 4]>(array_ref) };
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `array_ref as *const [i32; 4]`
error: transmute from `fn(usize) -> u8 {main::foo}` to `*const usize` which could be expressed as a pointer cast instead
error: transmute from `fn(usize) -> u8` to `*const usize` which could be expressed as a pointer cast instead
--> $DIR/transmutes_expressible_as_ptr_casts.rs:48:41
|
LL | let _usize_ptr_transmute = unsafe { transmute::<fn(usize) -> u8, *const usize>(foo) };
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `foo as *const usize`
error: transmute from `fn(usize) -> u8 {main::foo}` to `usize` which could be expressed as a pointer cast instead
error: transmute from `fn(usize) -> u8` to `usize` which could be expressed as a pointer cast instead
--> $DIR/transmutes_expressible_as_ptr_casts.rs:52:49
|
LL | let _usize_from_fn_ptr_transmute = unsafe { transmute::<fn(usize) -> u8, usize>(foo) };