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This commit is contained in:
Nathaniel Hamovitz 2021-10-16 02:26:08 -07:00
parent 4b4db59772
commit b9948c4be6
3 changed files with 147 additions and 41 deletions
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58
clippy_lints/src/trailing_zero_sized_array_without_repr_c.rs
View File

@ -26,7 +26,7 @@ declare_clippy_lint! {
/// Use instead:
/// ```rust
/// #[repr(C)]
/// struct MakesSense {
/// struct MoreOftenUseful {
/// some_field: usize,
/// last: [SomeType; 0],
/// }
@ -45,15 +45,13 @@ declare_lint_pass!(TrailingZeroSizedArrayWithoutReprC => [TRAILING_ZERO_SIZED_AR
impl<'tcx> LateLintPass<'tcx> for TrailingZeroSizedArrayWithoutReprC {
fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'tcx>) {
dbg!(item.ident);
if is_struct_with_trailing_zero_sized_array(cx, item) && !has_repr_c(cx, item.def_id) {
span_lint_and_sugg(
cx,
TRAILING_ZERO_SIZED_ARRAY_WITHOUT_REPR_C,
item.span,
"trailing zero-sized array in a struct which is not marked `#[repr(C)]`",
"try",
"try annotating the struct definition with `#[repr(C)]` (or another `repr` attribute):",
format!("#[repr(C)]\n{}", snippet(cx, item.span, "..")),
Applicability::MaybeIncorrect,
);
@ -62,46 +60,40 @@ impl<'tcx> LateLintPass<'tcx> for TrailingZeroSizedArrayWithoutReprC {
}
fn is_struct_with_trailing_zero_sized_array(cx: &LateContext<'tcx>, item: &'tcx Item<'tcx>) -> bool {
if let ItemKind::Struct(data, _generics) = &item.kind {
if let VariantData::Struct(field_defs, _) = data {
if let Some(last_field) = field_defs.last() {
if let TyKind::Array(_, aconst) = last_field.ty.kind {
let aconst_def_id = cx.tcx.hir().body_owner_def_id(aconst.body).to_def_id();
let ty = cx.tcx.type_of(aconst_def_id);
let constant = cx
.tcx
// NOTE: maybe const_eval_resolve? seems especially cursed to be using a const expr which
// resolves to 0 to create a zero-sized array, tho
.const_eval_poly(aconst_def_id)
.ok()
.map(|val| rustc_middle::ty::Const::from_value(cx.tcx, val, ty));
if let Some(Constant::Int(val)) = constant.and_then(miri_to_const) {
if val == 0 {
// eprintln!("trailing: true");
return true;
}
}
}
}
if_chain! {
if let ItemKind::Struct(data, _generics) = &item.kind;
if let VariantData::Struct(field_defs, _) = data;
if let Some(last_field) = field_defs.last();
if let TyKind::Array(_, aconst) = last_field.ty.kind;
let aconst_def_id = cx.tcx.hir().body_owner_def_id(aconst.body).to_def_id();
let ty = cx.tcx.type_of(aconst_def_id);
let constant = cx
.tcx
// NOTE: maybe const_eval_resolve?
.const_eval_poly(aconst_def_id)
.ok()
.map(|val| rustc_middle::ty::Const::from_value(cx.tcx, val, ty));
if let Some(Constant::Int(val)) = constant.and_then(miri_to_const);
if val == 0;
then {
true
} else {
false
}
}
// dbg!(aconst);
// eprintln!("trailing: false");
false
}
fn has_repr_c(cx: &LateContext<'tcx>, def_id: LocalDefId) -> bool {
let hir_id = cx.tcx.hir().local_def_id_to_hir_id(def_id);
let attrs = cx.tcx.hir().attrs(hir_id);
let hir_map = cx.tcx.hir();
let hir_id = hir_map.local_def_id_to_hir_id(def_id);
let attrs = hir_map.attrs(hir_id);
// NOTE: Can there ever be more than one `repr` attribute?
// other `repr` syms: repr, repr128, repr_align, repr_align_enum, repr_no_niche, repr_packed,
// repr_simd, repr_transparent
if let Some(_repr_attr) = attrs.iter().find(|attr| attr.has_name(sym::repr)) {
// eprintln!("repr: true");
if let Some(_attr) = attrs.iter().find(|attr| attr.has_name(sym::repr)) {
true
} else {
// eprintln!("repr: false");
false
}
}

17
tests/ui/trailing_zero_sized_array_without_repr_c.rs
View File

@ -1,6 +1,5 @@
#![warn(clippy::trailing_zero_sized_array_without_repr_c)]
// #![feature(const_generics_defaults)]
// #![feature(const_generics_defaults)] // see below
struct RarelyUseful {
field: i32,
@ -48,6 +47,9 @@ struct UsingFunction {
last: [usize; compute_zero()],
}
// NOTE: including these (along with the required feature) triggers an ICE. Should make sure the
// const generics people are aware of that if they weren't already.
// #[repr(C)]
// struct ConstParamOk<const N: usize = 0> {
// field: i32,
@ -59,8 +61,7 @@ struct UsingFunction {
// last: [usize; N]
// }
// TODO: actually, uh,,
// TODO: actually, uh,, no idea what behavior here would be
#[repr(packed)]
struct ReprPacked {
small: u8,
@ -68,20 +69,21 @@ struct ReprPacked {
weird: [u64; 0],
}
// same
// TODO: clarify expected behavior
#[repr(align(64))]
struct ReprAlign {
field: i32,
last: [usize; 0],
}
// same
// TODO: clarify expected behavior
#[repr(C, align(64))]
struct ReprCAlign {
field: i32,
last: [usize; 0],
}
// NOTE: because of https://doc.rust-lang.org/stable/reference/type-layout.html#primitive-representation-of-enums-with-fields and I'm not sure when in the compilation pipeline that would happen
#[repr(C)]
enum DontLintAnonymousStructsFromDesuraging {
A(u32),
@ -109,5 +111,4 @@ struct LotsOfFields {
last: [usize; 0],
}
fn main() {
}
fn main() {}

113
tests/ui/trailing_zero_sized_array_without_repr_c.stderr Normal file
View File

@ -0,0 +1,113 @@
error: trailing zero-sized array in a struct which is not marked `#[repr(C)]`
--> $DIR/trailing_zero_sized_array_without_repr_c.rs:4:1
|
LL | / struct RarelyUseful {
LL | | field: i32,
LL | | last: [usize; 0],
LL | | }
| |_^
|
= note: `-D clippy::trailing-zero-sized-array-without-repr-c` implied by `-D warnings`
help: try annotating the struct definition with `#[repr(C)]` (or another `repr` attribute):
|
LL + #[repr(C)]
LL + struct RarelyUseful {
LL + field: i32,
LL + last: [usize; 0],
LL + }
|
error: trailing zero-sized array in a struct which is not marked `#[repr(C)]`
--> $DIR/trailing_zero_sized_array_without_repr_c.rs:15:1
|
LL | / struct OnlyFieldIsZeroSizeArray {
LL | | first_and_last: [usize; 0],
LL | | }
| |_^
|
help: try annotating the struct definition with `#[repr(C)]` (or another `repr` attribute):
|
LL + #[repr(C)]
LL + struct OnlyFieldIsZeroSizeArray {
LL + first_and_last: [usize; 0],
LL + }
|
error: trailing zero-sized array in a struct which is not marked `#[repr(C)]`
--> $DIR/trailing_zero_sized_array_without_repr_c.rs:19:1
|
LL | / struct GenericArrayType<T> {
LL | | field: i32,
LL | | last: [T; 0],
LL | | }
| |_^
|
help: try annotating the struct definition with `#[repr(C)]` (or another `repr` attribute):
|
LL + #[repr(C)]
LL + struct GenericArrayType<T> {
LL + field: i32,
LL + last: [T; 0],
LL + }
|
error: trailing zero-sized array in a struct which is not marked `#[repr(C)]`
--> $DIR/trailing_zero_sized_array_without_repr_c.rs:30:1
|
LL | / struct ZeroSizedFromExternalConst {
LL | | field: i32,
LL | | last: [usize; ZERO],
LL | | }
| |_^
|
help: try annotating the struct definition with `#[repr(C)]` (or another `repr` attribute):
|
LL + #[repr(C)]
LL + struct ZeroSizedFromExternalConst {
LL + field: i32,
LL + last: [usize; ZERO],
LL + }
|
error: trailing zero-sized array in a struct which is not marked `#[repr(C)]`
--> $DIR/trailing_zero_sized_array_without_repr_c.rs:45:1
|
LL | / struct UsingFunction {
LL | | field: i32,
LL | | last: [usize; compute_zero()],
LL | | }
| |_^
|
help: try annotating the struct definition with `#[repr(C)]` (or another `repr` attribute):
|
LL + #[repr(C)]
LL + struct UsingFunction {
LL + field: i32,
LL + last: [usize; compute_zero()],
LL + }
|
error: trailing zero-sized array in a struct which is not marked `#[repr(C)]`
--> $DIR/trailing_zero_sized_array_without_repr_c.rs:94:1
|
LL | / struct LotsOfFields {
LL | | f1: u32,
LL | | f2: u32,
LL | | f3: u32,
... |
LL | | last: [usize; 0],
LL | | }
| |_^
|
help: try annotating the struct definition with `#[repr(C)]` (or another `repr` attribute):
|
LL + #[repr(C)]
LL + struct LotsOfFields {
LL + f1: u32,
LL + f2: u32,
LL + f3: u32,
LL + f4: u32,
...
error: aborting due to 6 previous errors