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RalfJungRalfJung
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fix the layout of repr(align) enums
1 parent 54f79ba commit cedc428

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4 files changed

+203
-4
lines changed

4 files changed

+203
-4
lines changed

‎compiler/rustc_middle/src/ty/layout.rs

+3-3
Original file line numberDiff line numberDiff line change
@@ -1418,9 +1418,9 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
14181418

14191419
if layout_variants.iter().all(|v| v.abi.is_uninhabited()) {
14201420
abi = Abi::Uninhabited;
1421-
} else if tag.size(dl) == size || variants.iter().all(|layout| layout.is_empty()) {
1422-
// Without latter check aligned enums with custom discriminant values
1423-
// Would result in ICE see the issue #92464 for more info
1421+
} else if tag.size(dl) == size {
1422+
// Make sure we only use scalar layout when the enum is entirely its
1423+
// own tag (i.e. it has no padding nor any non-ZST variant fields).
14241424
abi = Abi::Scalar(tag);
14251425
} else {
14261426
// Try to use a ScalarPair for all tagged enums.

‎src/test/ui/aligned_enum_cast.rs

+9-1
Original file line numberDiff line numberDiff line change
@@ -11,5 +11,13 @@ enum Aligned {
1111
fn main() {
1212
let aligned = Aligned::Zero;
1313
let fo = aligned as u8;
14-
println!("foo {}",fo);
14+
println!("foo {}", fo);
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println!("{}", tou8(Aligned::Zero));
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}
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#[inline(never)]
19+
fn tou8(al: Aligned) -> u8 {
20+
// Cast behind a function call so ConstProp does not see it
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// (so that we can test codegen).
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al as u8
1523
}

‎src/test/ui/layout/issue-96185-overaligned-enum.rs

+19
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,19 @@
1+
// normalize-stderr-test "pref: Align\([1-8] bytes\)" -> "pref: $$PREF_ALIGN"
2+
#![crate_type = "lib"]
3+
#![feature(rustc_attrs)]
4+
5+
// This cannot use `Scalar` abi since there is padding.
6+
#[rustc_layout(debug)]
7+
#[repr(align(8))]
8+
pub enum Aligned1 { //~ ERROR: layout_of
9+
Zero = 0,
10+
One = 1,
11+
}
12+
13+
// This should use `Scalar` abi.
14+
#[rustc_layout(debug)]
15+
#[repr(align(1))]
16+
pub enum Aligned2 { //~ ERROR: layout_of
17+
Zero = 0,
18+
One = 1,
19+
}

‎src/test/ui/layout/issue-96185-overaligned-enum.stderr

+172
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,172 @@
1+
error: layout_of(Aligned1) = Layout {
2+
fields: Arbitrary {
3+
offsets: [
4+
Size(0 bytes),
5+
],
6+
memory_index: [
7+
0,
8+
],
9+
},
10+
variants: Multiple {
11+
tag: Initialized {
12+
value: Int(
13+
I8,
14+
false,
15+
),
16+
valid_range: 0..=1,
17+
},
18+
tag_encoding: Direct,
19+
tag_field: 0,
20+
variants: [
21+
Layout {
22+
fields: Arbitrary {
23+
offsets: [],
24+
memory_index: [],
25+
},
26+
variants: Single {
27+
index: 0,
28+
},
29+
abi: Aggregate {
30+
sized: true,
31+
},
32+
largest_niche: None,
33+
align: AbiAndPrefAlign {
34+
abi: Align(8 bytes),
35+
pref: $PREF_ALIGN,
36+
},
37+
size: Size(8 bytes),
38+
},
39+
Layout {
40+
fields: Arbitrary {
41+
offsets: [],
42+
memory_index: [],
43+
},
44+
variants: Single {
45+
index: 1,
46+
},
47+
abi: Aggregate {
48+
sized: true,
49+
},
50+
largest_niche: None,
51+
align: AbiAndPrefAlign {
52+
abi: Align(8 bytes),
53+
pref: $PREF_ALIGN,
54+
},
55+
size: Size(8 bytes),
56+
},
57+
],
58+
},
59+
abi: Aggregate {
60+
sized: true,
61+
},
62+
largest_niche: Some(
63+
Niche {
64+
offset: Size(0 bytes),
65+
value: Int(
66+
I8,
67+
false,
68+
),
69+
valid_range: 0..=1,
70+
},
71+
),
72+
align: AbiAndPrefAlign {
73+
abi: Align(8 bytes),
74+
pref: $PREF_ALIGN,
75+
},
76+
size: Size(8 bytes),
77+
}
78+
--> $DIR/issue-96185-overaligned-enum.rs:8:1
79+
|
80+
LL | pub enum Aligned1 {
81+
| ^^^^^^^^^^^^^^^^^
82+
83+
error: layout_of(Aligned2) = Layout {
84+
fields: Arbitrary {
85+
offsets: [
86+
Size(0 bytes),
87+
],
88+
memory_index: [
89+
0,
90+
],
91+
},
92+
variants: Multiple {
93+
tag: Initialized {
94+
value: Int(
95+
I8,
96+
false,
97+
),
98+
valid_range: 0..=1,
99+
},
100+
tag_encoding: Direct,
101+
tag_field: 0,
102+
variants: [
103+
Layout {
104+
fields: Arbitrary {
105+
offsets: [],
106+
memory_index: [],
107+
},
108+
variants: Single {
109+
index: 0,
110+
},
111+
abi: Aggregate {
112+
sized: true,
113+
},
114+
largest_niche: None,
115+
align: AbiAndPrefAlign {
116+
abi: Align(1 bytes),
117+
pref: $PREF_ALIGN,
118+
},
119+
size: Size(1 bytes),
120+
},
121+
Layout {
122+
fields: Arbitrary {
123+
offsets: [],
124+
memory_index: [],
125+
},
126+
variants: Single {
127+
index: 1,
128+
},
129+
abi: Aggregate {
130+
sized: true,
131+
},
132+
largest_niche: None,
133+
align: AbiAndPrefAlign {
134+
abi: Align(1 bytes),
135+
pref: $PREF_ALIGN,
136+
},
137+
size: Size(1 bytes),
138+
},
139+
],
140+
},
141+
abi: Scalar(
142+
Initialized {
143+
value: Int(
144+
I8,
145+
false,
146+
),
147+
valid_range: 0..=1,
148+
},
149+
),
150+
largest_niche: Some(
151+
Niche {
152+
offset: Size(0 bytes),
153+
value: Int(
154+
I8,
155+
false,
156+
),
157+
valid_range: 0..=1,
158+
},
159+
),
160+
align: AbiAndPrefAlign {
161+
abi: Align(1 bytes),
162+
pref: $PREF_ALIGN,
163+
},
164+
size: Size(1 bytes),
165+
}
166+
--> $DIR/issue-96185-overaligned-enum.rs:16:1
167+
|
168+
LL | pub enum Aligned2 {
169+
| ^^^^^^^^^^^^^^^^^
170+
171+
error: aborting due to 2 previous errors
172+

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