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no barriers for boxes

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This commit is contained in:
Ralf Jung 2018-11-21 15:21:41 +01:00
parent 58309956c1
commit 194710e112
2 changed files with 23 additions and 18 deletions
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37
src/stacked_borrows.rs
View File

@ -673,19 +673,27 @@ impl<'a, 'mir, 'tcx> EvalContextExt<'tcx> for MiriEvalContext<'a, 'mir, 'tcx> {
fn_entry: bool,
place: PlaceTy<'tcx, Borrow>
) -> EvalResult<'tcx> {
// Determine mutability and whether to add a barrier.
// Cannot use `builtin_deref` because that reports *immutable* for `Box`,
// making it useless.
fn qualify(ty: ty::Ty<'_>, fn_entry: bool) -> Option<(Mutability, bool)> {
match ty.sty {
// References are simple
ty::Ref(_, _, mutbl) => Some((mutbl, fn_entry)),
// Boxes do not get a barrier: Barriers reflect that references outlive the call
// they were passed in to; that's just not the case for boxes.
ty::Adt(..) if ty.is_box() => Some((MutMutable, false)),
_ => None,
}
}
// We need a visitor to visit all references. However, that requires
// a `MemPlace`, so we have a fast path for reference types that
// avoids allocating.
// Cannot use `builtin_deref` because that reports *immutable* for `Box`,
// making it useless.
if let Some(mutbl) = match place.layout.ty.sty {
ty::Ref(_, _, mutbl) => Some(mutbl),
ty::Adt(..) if place.layout.ty.is_box() => Some(MutMutable),
_ => None, // handled with the general case below
} {
if let Some((mutbl, barrier)) = qualify(place.layout.ty, fn_entry) {
// fast path
let val = self.read_immediate(self.place_to_op(place)?)?;
let val = self.retag_reference(val, mutbl, fn_entry)?;
let val = self.retag_reference(val, mutbl, barrier)?;
self.write_immediate(val, place)?;
return Ok(());
}
@ -716,14 +724,11 @@ impl<'a, 'mir, 'tcx> EvalContextExt<'tcx> for MiriEvalContext<'a, 'mir, 'tcx> {
{
// Cannot use `builtin_deref` because that reports *immutable* for `Box`,
// making it useless.
let mutbl = match place.layout.ty.sty {
ty::Ref(_, _, mutbl) => mutbl,
ty::Adt(..) if place.layout.ty.is_box() => MutMutable,
_ => return Ok(()), // nothing to do
};
let val = self.ecx.read_immediate(place.into())?;
let val = self.ecx.retag_reference(val, mutbl, self.fn_entry)?;
self.ecx.write_immediate(val, place.into())?;
if let Some((mutbl, barrier)) = qualify(place.layout.ty, self.fn_entry) {
let val = self.ecx.read_immediate(place.into())?;
let val = self.ecx.retag_reference(val, mutbl, barrier)?;
self.ecx.write_immediate(val, place.into())?;
}
Ok(())
}
}

4
tests/compile-fail-fullmir/stacked_borrows/box_exclusive_violation1.rs
View File

@ -8,7 +8,7 @@ fn demo_mut_advanced_unique(mut our: Box<i32>) -> i32 {
unknown_code_2();
// We know this will return 5
*our
*our //~ ERROR does not exist on the stack
}
// Now comes the evil context
@ -21,7 +21,7 @@ fn unknown_code_1(x: &i32) { unsafe {
} }
fn unknown_code_2() { unsafe {
*LEAK = 7; //~ ERROR barrier
*LEAK = 7;
} }
fn main() {