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Rollup merge of #77360 - oli-obk:zst_const_pat_regression, r=RalfJung

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References to ZSTs may be at arbitrary aligned addresses

fixes #77320

r? @RalfJung
This commit is contained in:
Dylan DPC 2020-10-01 02:13:48 +02:00 committed by GitHub
parent ffb771bc79 ce6c25da58
commit cc1513b860
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2 changed files with 14 additions and 5 deletions
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10
compiler/rustc_mir/src/const_eval/eval_queries.rs
View file

@ -14,7 +14,7 @@ use rustc_middle::ty::print::with_no_trimmed_paths;
use rustc_middle::ty::{self, subst::Subst, TyCtxt};
use rustc_span::source_map::Span;
use rustc_target::abi::{Abi, LayoutOf};
use std::convert::TryInto;
use std::convert::{TryFrom, TryInto};
pub fn note_on_undefined_behavior_error() -> &'static str {
"The rules on what exactly is undefined behavior aren't clear, \
@ -148,10 +148,10 @@ pub(super) fn op_to_const<'tcx>(
Scalar::Raw { data, .. } => {
assert!(mplace.layout.is_zst());
assert_eq!(
data,
mplace.layout.align.abi.bytes().into(),
"this MPlaceTy must come from `try_as_mplace` being used on a zst, so we know what
value this integer address must have",
u64::try_from(data).unwrap() % mplace.layout.align.abi.bytes(),
0,
"this MPlaceTy must come from a validated constant, thus we can assume the \
alignment is correct",
);
ConstValue::Scalar(Scalar::zst())
}

9
src/test/ui/match/const_non_normal_zst_ref_pattern.rs Normal file
View file

@ -0,0 +1,9 @@
// check-pass
const FOO: isize = 10;
const ZST: &() = unsafe { std::mem::transmute(FOO) };
fn main() {
match &() {
ZST => 9,
};
}