visit struct fields in uninit fallback check

This commit is contained in:
y21 2024-09-07 17:06:32 +02:00
parent a95afe2d0a
commit ae5326b967
3 changed files with 62 additions and 5 deletions

View file

@ -606,10 +606,13 @@ fn is_uninit_value_valid_for_ty_fallback<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'t
ty::Tuple(types) => types.iter().all(|ty| is_uninit_value_valid_for_ty(cx, ty)), ty::Tuple(types) => types.iter().all(|ty| is_uninit_value_valid_for_ty(cx, ty)),
// Unions are always fine right now. // Unions are always fine right now.
// This includes MaybeUninit, the main way people use uninitialized memory. // This includes MaybeUninit, the main way people use uninitialized memory.
// For ADTs, we could look at all fields just like for tuples, but that's potentially ty::Adt(adt, _) if adt.is_union() => true,
// exponential, so let's avoid doing that for now. Code doing that is sketchy enough to // Types (e.g. `UnsafeCell<MaybeUninit<T>>`) that recursively contain only types that can be uninit
// just use an `#[allow()]`. // can themselves be uninit too.
ty::Adt(adt, _) => adt.is_union(), // This purposefully ignores enums as they may have a discriminant that can't be uninit.
ty::Adt(adt, args) if adt.is_struct() => adt
.all_fields()
.all(|field| is_uninit_value_valid_for_ty(cx, field.ty(cx.tcx, args))),
// For the rest, conservatively assume that they cannot be uninit. // For the rest, conservatively assume that they cannot be uninit.
_ => false, _ => false,
} }

View file

@ -150,4 +150,36 @@ fn main() {
vec.set_len(10); vec.set_len(10);
} }
} }
fn nested_union<T>() {
let mut vec: Vec<UnsafeCell<MaybeUninit<T>>> = Vec::with_capacity(1);
unsafe {
vec.set_len(1);
}
}
struct Recursive<T>(*const Recursive<T>, MaybeUninit<T>);
fn recursive_union<T>() {
// Make sure we don't stack overflow on recursive types.
// The pointer acts as the base case because it can't be uninit regardless of its pointee.
let mut vec: Vec<Recursive<T>> = Vec::with_capacity(1);
//~^ uninit_vec
unsafe {
vec.set_len(1);
}
}
#[repr(u8)]
enum Enum<T> {
Variant(T),
}
fn union_in_enum<T>() {
// Enums can have a discriminant that can't be uninit, so this should still warn
let mut vec: Vec<Enum<T>> = Vec::with_capacity(1);
//~^ uninit_vec
unsafe {
vec.set_len(1);
}
}
} }

View file

@ -125,5 +125,27 @@ LL | vec.set_len(10);
| |
= help: initialize the buffer or wrap the content in `MaybeUninit` = help: initialize the buffer or wrap the content in `MaybeUninit`
error: aborting due to 12 previous errors error: calling `set_len()` immediately after reserving a buffer creates uninitialized values
--> tests/ui/uninit_vec.rs:166:9
|
LL | let mut vec: Vec<Recursive<T>> = Vec::with_capacity(1);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
...
LL | vec.set_len(1);
| ^^^^^^^^^^^^^^
|
= help: initialize the buffer or wrap the content in `MaybeUninit`
error: calling `set_len()` immediately after reserving a buffer creates uninitialized values
--> tests/ui/uninit_vec.rs:179:9
|
LL | let mut vec: Vec<Enum<T>> = Vec::with_capacity(1);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
...
LL | vec.set_len(1);
| ^^^^^^^^^^^^^^
|
= help: initialize the buffer or wrap the content in `MaybeUninit`
error: aborting due to 14 previous errors