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Allow transmuting fat pointers to some types in transmute_undefined_repr

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This commit is contained in:
Jason Newcomb 2022-02-16 10:45:49 -05:00
parent 447a24588a
commit 7c07022c98
2 changed files with 50 additions and 32 deletions
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66
clippy_lints/src/transmute/transmute_undefined_repr.rs
View file

@ -19,33 +19,39 @@ pub(super) fn check<'tcx>(
while from_ty != to_ty {
match reduce_refs(cx, e.span, from_ty, to_ty) {
ReducedTys::FromFatPtr { unsized_ty, .. } => {
span_lint_and_then(
cx,
TRANSMUTE_UNDEFINED_REPR,
e.span,
&format!("transmute from `{}` which has an undefined layout", from_ty_orig),
|diag| {
if from_ty_orig.peel_refs() != unsized_ty {
diag.note(&format!("the contained type `&{}` has an undefined layout", unsized_ty));
}
},
);
return true;
ReducedTys::FromFatPtr { unsized_ty, to_ty } => match reduce_ty(cx, to_ty) {
ReducedTy::IntArray | ReducedTy::TypeErasure => break,
_ => {
span_lint_and_then(
cx,
TRANSMUTE_UNDEFINED_REPR,
e.span,
&format!("transmute from `{}` which has an undefined layout", from_ty_orig),
|diag| {
if from_ty_orig.peel_refs() != unsized_ty {
diag.note(&format!("the contained type `&{}` has an undefined layout", unsized_ty));
}
},
);
return true;
},
},
ReducedTys::ToFatPtr { unsized_ty, .. } => {
span_lint_and_then(
cx,
TRANSMUTE_UNDEFINED_REPR,
e.span,
&format!("transmute to `{}` which has an undefined layout", to_ty_orig),
|diag| {
if to_ty_orig.peel_refs() != unsized_ty {
diag.note(&format!("the contained type `&{}` has an undefined layout", unsized_ty));
}
},
);
return true;
ReducedTys::ToFatPtr { unsized_ty, from_ty } => match reduce_ty(cx, from_ty) {
ReducedTy::IntArray | ReducedTy::TypeErasure => break,
_ => {
span_lint_and_then(
cx,
TRANSMUTE_UNDEFINED_REPR,
e.span,
&format!("transmute to `{}` which has an undefined layout", to_ty_orig),
|diag| {
if to_ty_orig.peel_refs() != unsized_ty {
diag.note(&format!("the contained type `&{}` has an undefined layout", unsized_ty));
}
},
);
return true;
},
},
ReducedTys::ToPtr {
from_ty: from_sub_ty,
@ -184,8 +190,8 @@ pub(super) fn check<'tcx>(
}
enum ReducedTys<'tcx> {
FromFatPtr { unsized_ty: Ty<'tcx> },
ToFatPtr { unsized_ty: Ty<'tcx> },
FromFatPtr { unsized_ty: Ty<'tcx>, to_ty: Ty<'tcx> },
ToFatPtr { unsized_ty: Ty<'tcx>, from_ty: Ty<'tcx> },
ToPtr { from_ty: Ty<'tcx>, to_ty: Ty<'tcx> },
FromPtr { from_ty: Ty<'tcx>, to_ty: Ty<'tcx> },
Other { from_ty: Ty<'tcx>, to_ty: Ty<'tcx> },
@ -211,12 +217,12 @@ fn reduce_refs<'tcx>(
(ty::Ref(_, unsized_ty, _) | ty::RawPtr(TypeAndMut { ty: unsized_ty, .. }), _)
if !unsized_ty.is_sized(cx.tcx.at(span), cx.param_env) =>
{
ReducedTys::FromFatPtr { unsized_ty }
ReducedTys::FromFatPtr { unsized_ty, to_ty }
},
(_, ty::Ref(_, unsized_ty, _) | ty::RawPtr(TypeAndMut { ty: unsized_ty, .. }))
if !unsized_ty.is_sized(cx.tcx.at(span), cx.param_env) =>
{
ReducedTys::ToFatPtr { unsized_ty }
ReducedTys::ToFatPtr { unsized_ty, from_ty }
},
(ty::Ref(_, from_ty, _) | ty::RawPtr(TypeAndMut { ty: from_ty, .. }), _) => {
ReducedTys::FromPtr { from_ty, to_ty }

16
tests/ui/transmute_undefined_repr.rs
View file

@ -1,8 +1,8 @@
#![warn(clippy::transmute_undefined_repr)]
#![allow(clippy::unit_arg)]
#![allow(clippy::unit_arg, clippy::transmute_ptr_to_ref)]
use core::ffi::c_void;
use core::mem::transmute;
use core::mem::{size_of, transmute};
fn value<T>() -> T {
unimplemented!()
@ -72,5 +72,17 @@ fn main() {
);
let _: *const Erase2 = transmute(value::<Ty<&Ty2<u32, f32>>>()); // Ok, type erasure
let _: Ty<&Ty2<u32, f32>> = transmute(value::<*const Erase2>()); // Ok, reverse type erasure
let _: *const () = transmute(value::<&&[u8]>()); // Ok, type erasure
let _: &&[u8] = transmute(value::<*const ()>()); // Ok, reverse type erasure
let _: *mut c_void = transmute(value::<&mut &[u8]>()); // Ok, type erasure
let _: &mut &[u8] = transmute(value::<*mut c_void>()); // Ok, reverse type erasure
let _: [u8; size_of::<&[u8]>()] = transmute(value::<&[u8]>()); // Ok, transmute to byte array
let _: &[u8] = transmute(value::<[u8; size_of::<&[u8]>()]>()); // Ok, transmute from byte array
let _: [usize; 2] = transmute(value::<&[u8]>()); // Ok, transmute to int array
let _: &[u8] = transmute(value::<[usize; 2]>()); // Ok, transmute from int array
}
}