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[AIX] Ignore linting on repr(C) structs with repr(packed) or repr(align(n)) #138206

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Merged
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Mar 30, 2025
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[AIX] Ignore linting on repr(C) structs with repr(packed) or repr(align(n)) #138206

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6 changes: 6 additions & 0 deletions compiler/rustc_lint/src/types.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1638,6 +1638,9 @@ impl ImproperCTypesDefinitions {
return true;
} else if let Adt(adt_def, _) = ty.kind()
&& adt_def.is_struct()
&& adt_def.repr().c()
&& !adt_def.repr().packed()
&& adt_def.repr().align.is_none()
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Does this affect the strcuts without repr(C)? I guess this should be like this:

&& adt_def.is_struct()
&& (!adt_def.repr().c() || (!adt_def.repr().packed() && adt_def.repr().align.is_none()))

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@workingjubilee workingjubilee Mar 29, 2025 •
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That is incorrect, this should only matter for repr(C). The && means that repr(C) must be satisfied first before we concern ourselves with the rest, which is correct.

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@amy-kwan amy-kwan Mar 30, 2025 •
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Thanks @SparrowLii for the review and Thanks @workingjubilee for the reply - yes, this should only affect structures annotated with repr(C).

{
let struct_variant = adt_def.variant(VariantIdx::ZERO);
// Within a nested struct, all fields are examined to correctly
Expand All @@ -1659,8 +1662,11 @@ impl ImproperCTypesDefinitions {
item: &'tcx hir::Item<'tcx>,
) {
let adt_def = cx.tcx.adt_def(item.owner_id.to_def_id());
// repr(C) structs also with packed or aligned representation
// should be ignored.
if adt_def.repr().c()
&& !adt_def.repr().packed()
&& adt_def.repr().align.is_none()
&& cx.tcx.sess.target.os == "aix"
&& !adt_def.all_fields().next().is_none()
{
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26 changes: 25 additions & 1 deletion tests/ui/layout/reprc-power-alignment.rs
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Expand Up @@ -148,5 +148,29 @@ pub struct I {
d: f32,
e: f64,
}

#[repr(C)]
pub struct J {
a: u8,
b: I,
}
// The lint also ignores diagnosing #[repr(align(n))].
#[repr(C, align(8))]
pub struct K {
a: u8,
b: u8,
c: f64,
d: f32,
e: f64,
}
#[repr(C)]
pub struct L {
a: u8,
b: K,
}
#[repr(C, align(8))]
pub struct M {
a: u8,
b: K,
c: L,
}
fn main() { }
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