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Clarify invalid_reference_casting lint around interior mutable types

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This commit is contained in:
Urgau 2023-10-04 16:03:39 +02:00
parent dd513e1150
commit e46236cceb
5 changed files with 68 additions and 32 deletions
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2
compiler/rustc_lint/messages.ftl
View File

@ -319,6 +319,8 @@ lint_invalid_reference_casting_borrow_as_mut = casting `&T` to `&mut T` is undef
lint_invalid_reference_casting_note_book = for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
lint_invalid_reference_casting_note_ty_has_interior_mutability = even for types with interior mutability, the only legal way to obtain a mutable pointer from a shared reference is through `UnsafeCell::get`
lint_lintpass_by_hand = implementing `LintPass` by hand
.help = try using `declare_lint_pass!` or `impl_lint_pass!` instead

4
compiler/rustc_lint/src/lints.rs
View File

@ -771,12 +771,16 @@ pub enum InvalidReferenceCastingDiag {
BorrowAsMut {
#[label]
orig_cast: Option<Span>,
#[note(lint_invalid_reference_casting_note_ty_has_interior_mutability)]
ty_has_interior_mutability: Option<()>,
},
#[diag(lint_invalid_reference_casting_assign_to_ref)]
#[note(lint_invalid_reference_casting_note_book)]
AssignToRef {
#[label]
orig_cast: Option<Span>,
#[note(lint_invalid_reference_casting_note_ty_has_interior_mutability)]
ty_has_interior_mutability: Option<()>,
},
}

26
compiler/rustc_lint/src/reference_casting.rs
View File

@ -43,19 +43,19 @@ impl<'tcx> LateLintPass<'tcx> for InvalidReferenceCasting {
let init = cx.expr_or_init(e);
let orig_cast = if is_cast_from_const_to_mut(cx, init) {
if init.span != e.span { Some(init.span) } else { None }
} else {
let Some(ty_has_interior_mutability) = is_cast_from_const_to_mut(cx, init) else {
return;
};
let orig_cast = if init.span != e.span { Some(init.span) } else { None };
let ty_has_interior_mutability = ty_has_interior_mutability.then_some(());
cx.emit_spanned_lint(
INVALID_REFERENCE_CASTING,
expr.span,
if is_assignment {
InvalidReferenceCastingDiag::AssignToRef { orig_cast }
InvalidReferenceCastingDiag::AssignToRef { orig_cast, ty_has_interior_mutability }
} else {
InvalidReferenceCastingDiag::BorrowAsMut { orig_cast }
InvalidReferenceCastingDiag::BorrowAsMut { orig_cast, ty_has_interior_mutability }
},
);
}
@ -104,7 +104,10 @@ fn is_operation_we_care_about<'tcx>(
deref_assign_or_addr_of(e).or_else(|| ptr_write(cx, e))
}
fn is_cast_from_const_to_mut<'tcx>(cx: &LateContext<'tcx>, orig_expr: &'tcx Expr<'tcx>) -> bool {
fn is_cast_from_const_to_mut<'tcx>(
cx: &LateContext<'tcx>,
orig_expr: &'tcx Expr<'tcx>,
) -> Option<bool> {
let mut need_check_freeze = false;
let mut e = orig_expr;
@ -112,7 +115,7 @@ fn is_cast_from_const_to_mut<'tcx>(cx: &LateContext<'tcx>, orig_expr: &'tcx Expr
// Bail out early if the end type is **not** a mutable pointer.
if !matches!(end_ty.kind(), ty::RawPtr(TypeAndMut { ty: _, mutbl: Mutability::Mut })) {
return false;
return None;
}
loop {
@ -155,10 +158,11 @@ fn is_cast_from_const_to_mut<'tcx>(cx: &LateContext<'tcx>, orig_expr: &'tcx Expr
//
// We also consider non concrete skeleton types (ie generics)
// to be an issue since there is no way to make it safe for abitrary types.
!need_check_freeze
|| inner_ty.is_freeze(cx.tcx, cx.param_env)
|| !inner_ty.has_concrete_skeleton()
let inner_ty_has_interior_mutability =
!inner_ty.is_freeze(cx.tcx, cx.param_env) && inner_ty.has_concrete_skeleton();
(!need_check_freeze || !inner_ty_has_interior_mutability)
.then_some(inner_ty_has_interior_mutability)
} else {
false
None
}
}

8
tests/ui/lint/reference_casting.rs
View File

@ -64,6 +64,10 @@ unsafe fn ref_to_mut() {
let _num = &mut *num;
//~^ ERROR casting `&T` to `&mut T` is undefined behavior
let cell = &std::cell::UnsafeCell::new(0);
let _num = &mut *(cell as *const _ as *mut i32);
//~^ ERROR casting `&T` to `&mut T` is undefined behavior
unsafe fn generic_ref_cast_mut<T>(this: &T) -> &mut T {
&mut *((this as *const _) as *mut _)
//~^ ERROR casting `&T` to `&mut T` is undefined behavior
@ -106,6 +110,8 @@ unsafe fn assign_to_ref() {
std::mem::transmute::<*const i32, *mut i32>(num),
-1i32,
);
*((&std::cell::UnsafeCell::new(0)) as *const _ as *mut i32) = 5;
//~^ ERROR assigning to `&T` is undefined behavior
let value = num as *const i32 as *mut i32;
*value = 1;
@ -148,6 +154,8 @@ unsafe fn no_warn() {
*RAW_PTR = 42; // RAW_PTR is defined outside the function body,
// make sure we don't ICE on it when trying to
// determine if we should lint on it or not.
let cell = &std::cell::UnsafeCell::new(0);
let _num = &mut *(cell.get() as *mut i32);
fn safe_as_mut<T>(x: &std::cell::UnsafeCell<T>) -> &mut T {
unsafe { &mut *std::cell::UnsafeCell::raw_get(x as *const _ as *const _) }

60
tests/ui/lint/reference_casting.stderr
View File

@ -158,7 +158,16 @@ LL | let _num = &mut *num;
= note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
error: casting `&T` to `&mut T` is undefined behavior, even if the reference is unused, consider instead using an `UnsafeCell`
--> $DIR/reference_casting.rs:68:9
--> $DIR/reference_casting.rs:68:16
|
LL | let _num = &mut *(cell as *const _ as *mut i32);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
= note: even for types with interior mutability, the only legal way to obtain a mutable pointer from a shared reference is through `UnsafeCell::get`
error: casting `&T` to `&mut T` is undefined behavior, even if the reference is unused, consider instead using an `UnsafeCell`
--> $DIR/reference_casting.rs:72:9
|
LL | &mut *((this as *const _) as *mut _)
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@ -166,7 +175,7 @@ LL | &mut *((this as *const _) as *mut _)
= note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
error: casting `&T` to `&mut T` is undefined behavior, even if the reference is unused, consider instead using an `UnsafeCell`
--> $DIR/reference_casting.rs:73:18
--> $DIR/reference_casting.rs:77:18
|
LL | unsafe { &mut *std::cell::UnsafeCell::raw_get(x as *const _ as *const _) }
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@ -174,7 +183,7 @@ LL | unsafe { &mut *std::cell::UnsafeCell::raw_get(x as *const _ as *con
= note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
error: casting `&T` to `&mut T` is undefined behavior, even if the reference is unused, consider instead using an `UnsafeCell`
--> $DIR/reference_casting.rs:78:18
--> $DIR/reference_casting.rs:82:18
|
LL | unsafe { &mut *std::cell::UnsafeCell::raw_get(x as *const _ as *const _) }
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@ -182,7 +191,7 @@ LL | unsafe { &mut *std::cell::UnsafeCell::raw_get(x as *const _ as *con
= note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
error: assigning to `&T` is undefined behavior, consider using an `UnsafeCell`
--> $DIR/reference_casting.rs:88:5
--> $DIR/reference_casting.rs:92:5
|
LL | *(a as *const _ as *mut _) = String::from("Replaced");
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@ -190,7 +199,7 @@ LL | *(a as *const _ as *mut _) = String::from("Replaced");
= note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
error: assigning to `&T` is undefined behavior, consider using an `UnsafeCell`
--> $DIR/reference_casting.rs:90:5
--> $DIR/reference_casting.rs:94:5
|
LL | *(a as *const _ as *mut String) += " world";
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@ -198,7 +207,7 @@ LL | *(a as *const _ as *mut String) += " world";
= note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
error: assigning to `&T` is undefined behavior, consider using an `UnsafeCell`
--> $DIR/reference_casting.rs:92:5
--> $DIR/reference_casting.rs:96:5
|
LL | *std::ptr::from_ref(num).cast_mut() += 1;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@ -206,7 +215,7 @@ LL | *std::ptr::from_ref(num).cast_mut() += 1;
= note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
error: assigning to `&T` is undefined behavior, consider using an `UnsafeCell`
--> $DIR/reference_casting.rs:94:5
--> $DIR/reference_casting.rs:98:5
|
LL | *std::ptr::from_ref({ num }).cast_mut() += 1;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@ -214,7 +223,7 @@ LL | *std::ptr::from_ref({ num }).cast_mut() += 1;
= note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
error: assigning to `&T` is undefined behavior, consider using an `UnsafeCell`
--> $DIR/reference_casting.rs:96:5
--> $DIR/reference_casting.rs:100:5
|
LL | *{ std::ptr::from_ref(num) }.cast_mut() += 1;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@ -222,7 +231,7 @@ LL | *{ std::ptr::from_ref(num) }.cast_mut() += 1;
= note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
error: assigning to `&T` is undefined behavior, consider using an `UnsafeCell`
--> $DIR/reference_casting.rs:98:5
--> $DIR/reference_casting.rs:102:5
|
LL | *(std::ptr::from_ref({ num }) as *mut i32) += 1;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@ -230,7 +239,7 @@ LL | *(std::ptr::from_ref({ num }) as *mut i32) += 1;
= note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
error: assigning to `&T` is undefined behavior, consider using an `UnsafeCell`
--> $DIR/reference_casting.rs:100:5
--> $DIR/reference_casting.rs:104:5
|
LL | *std::mem::transmute::<_, *mut i32>(num) += 1;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@ -238,7 +247,7 @@ LL | *std::mem::transmute::<_, *mut i32>(num) += 1;
= note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
error: assigning to `&T` is undefined behavior, consider using an `UnsafeCell`
--> $DIR/reference_casting.rs:102:5
--> $DIR/reference_casting.rs:106:5
|
LL | *(std::mem::transmute::<_, *mut i32>(num) as *mut i32) += 1;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@ -246,7 +255,7 @@ LL | *(std::mem::transmute::<_, *mut i32>(num) as *mut i32) += 1;
= note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
error: assigning to `&T` is undefined behavior, consider using an `UnsafeCell`
--> $DIR/reference_casting.rs:104:5
--> $DIR/reference_casting.rs:108:5
|
LL | / std::ptr::write(
LL | |
@ -258,7 +267,16 @@ LL | | );
= note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
error: assigning to `&T` is undefined behavior, consider using an `UnsafeCell`
--> $DIR/reference_casting.rs:111:5
--> $DIR/reference_casting.rs:113:5
|
LL | *((&std::cell::UnsafeCell::new(0)) as *const _ as *mut i32) = 5;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
= note: even for types with interior mutability, the only legal way to obtain a mutable pointer from a shared reference is through `UnsafeCell::get`
error: assigning to `&T` is undefined behavior, consider using an `UnsafeCell`
--> $DIR/reference_casting.rs:117:5
|
LL | let value = num as *const i32 as *mut i32;
| ----------------------------- casting happend here
@ -268,7 +286,7 @@ LL | *value = 1;
= note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
error: assigning to `&T` is undefined behavior, consider using an `UnsafeCell`
--> $DIR/reference_casting.rs:114:5
--> $DIR/reference_casting.rs:120:5
|
LL | let value = num as *const i32 as *mut i32;
| ----------------------------- casting happend here
@ -279,7 +297,7 @@ LL | *value_rebind = 1;
= note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
error: assigning to `&T` is undefined behavior, consider using an `UnsafeCell`
--> $DIR/reference_casting.rs:116:5
--> $DIR/reference_casting.rs:122:5
|
LL | *(num as *const i32).cast::<i32>().cast_mut() = 2;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@ -287,7 +305,7 @@ LL | *(num as *const i32).cast::<i32>().cast_mut() = 2;
= note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
error: assigning to `&T` is undefined behavior, consider using an `UnsafeCell`
--> $DIR/reference_casting.rs:118:5
--> $DIR/reference_casting.rs:124:5
|
LL | *(num as *const _ as usize as *mut i32) = 2;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@ -295,7 +313,7 @@ LL | *(num as *const _ as usize as *mut i32) = 2;
= note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
error: assigning to `&T` is undefined behavior, consider using an `UnsafeCell`
--> $DIR/reference_casting.rs:120:5
--> $DIR/reference_casting.rs:126:5
|
LL | let value = num as *const i32 as *mut i32;
| ----------------------------- casting happend here
@ -306,7 +324,7 @@ LL | std::ptr::write(value, 2);
= note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
error: assigning to `&T` is undefined behavior, consider using an `UnsafeCell`
--> $DIR/reference_casting.rs:122:5
--> $DIR/reference_casting.rs:128:5
|
LL | let value = num as *const i32 as *mut i32;
| ----------------------------- casting happend here
@ -317,7 +335,7 @@ LL | std::ptr::write_unaligned(value, 2);
= note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
error: assigning to `&T` is undefined behavior, consider using an `UnsafeCell`
--> $DIR/reference_casting.rs:124:5
--> $DIR/reference_casting.rs:130:5
|
LL | let value = num as *const i32 as *mut i32;
| ----------------------------- casting happend here
@ -328,12 +346,12 @@ LL | std::ptr::write_volatile(value, 2);
= note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
error: assigning to `&T` is undefined behavior, consider using an `UnsafeCell`
--> $DIR/reference_casting.rs:128:9
--> $DIR/reference_casting.rs:134:9
|
LL | *(this as *const _ as *mut _) = a;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
error: aborting due to 38 previous errors
error: aborting due to 40 previous errors