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Rollup merge of #71280 - RalfJung:mplace-check-align, r=oli-obk

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Miri: mplace_access_checked: offer option to force different alignment on place

Required to solve https://github.com/rust-lang/miri/issues/1339 in https://github.com/rust-lang/miri/pull/1348.

r? @oli-obk
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Dylan DPC 2020-04-22 16:41:09 +02:00 committed by GitHub
commit e69141a52f
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1 changed files with 7 additions and 2 deletions
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9
src/librustc_mir/interpret/place.rs
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@ -333,7 +333,7 @@ where
let val = self.read_immediate(src)?;
trace!("deref to {} on {:?}", val.layout.ty, *val);
let place = self.ref_to_mplace(val)?;
self.mplace_access_checked(place)
self.mplace_access_checked(place, None)
}
/// Check if the given place is good for memory access with the given
@ -358,15 +358,20 @@ where
/// Return the "access-checked" version of this `MPlace`, where for non-ZST
/// this is definitely a `Pointer`.
///
/// `force_align` must only be used when correct alignment does not matter,
/// like in Stacked Borrows.
pub fn mplace_access_checked(
&self,
mut place: MPlaceTy<'tcx, M::PointerTag>,
force_align: Option<Align>,
) -> InterpResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
let (size, align) = self
.size_and_align_of_mplace(place)?
.unwrap_or((place.layout.size, place.layout.align.abi));
assert!(place.mplace.align <= align, "dynamic alignment less strict than static one?");
place.mplace.align = align; // maximally strict checking
// Check (stricter) dynamic alignment, unless forced otherwise.
place.mplace.align = force_align.unwrap_or(align);
// When dereferencing a pointer, it must be non-NULL, aligned, and live.
if let Some(ptr) = self.check_mplace_access(place, Some(size))? {
place.mplace.ptr = ptr.into();