bjoernager/rust
bjoernager/rust
1
Fork 0
Code Issues Pull requests Activity

refactor unsafety checking of places

Browse source
This commit is contained in:
Ralf Jung 2020-11-21 13:20:34 +01:00
parent df1c55a474
commit 571da2c62d
2 changed files with 87 additions and 76 deletions
Download patch file Download diff file Expand all files Collapse all files

4
compiler/rustc_middle/src/mir/mod.rs
View file

@ -1744,7 +1744,9 @@ impl<'tcx> Place<'tcx> {
/// Iterate over the projections in evaluation order, i.e., the first element is the base with
/// its projection and then subsequently more projections are added.
pub fn iter_projections(self) -> impl Iterator<Item=(PlaceRef<'tcx>, PlaceElem<'tcx>)> + DoubleEndedIterator {
pub fn iter_projections(
self,
) -> impl Iterator<Item = (PlaceRef<'tcx>, PlaceElem<'tcx>)> + DoubleEndedIterator {
self.projection.iter().enumerate().map(move |(i, proj)| {
let base = PlaceRef { local: self.local, projection: &self.projection[..i] };
(base, proj)

73
compiler/rustc_mir/src/transform/check_unsafety.rs
View file

@ -181,6 +181,9 @@ impl<'a, 'tcx> Visitor<'tcx> for UnsafetyChecker<'a, 'tcx> {
self.check_mut_borrowing_layout_constrained_field(*place, context.is_mutating_use());
}
// Check for borrows to packed fields.
// `is_disaligned` already traverses the place to consider all projections after the last
// `Deref`, so this only needs to be called once at the top level.
if context.is_borrow() {
if util::is_disaligned(self.tcx, self.body, self.param_env, *place) {
self.require_unsafe(
@ -190,20 +193,13 @@ impl<'a, 'tcx> Visitor<'tcx> for UnsafetyChecker<'a, 'tcx> {
}
}
for (i, _elem) in place.projection.iter().enumerate() {
let proj_base = &place.projection[..i];
if context.is_borrow() {
if util::is_disaligned(self.tcx, self.body, self.param_env, *place) {
self.require_unsafe(
UnsafetyViolationKind::BorrowPacked,
UnsafetyViolationDetails::BorrowOfPackedField,
);
}
}
let source_info = self.source_info;
if let [] = proj_base {
// Some checks below need the extra metainfo of the local declaration.
let decl = &self.body.local_decls[place.local];
if decl.internal {
// Check the base local: it might be an unsafe-to-access static. We only check derefs of the
// temporary holding the static pointer to avoid duplicate errors
// <https://github.com/rust-lang/rust/pull/78068#issuecomment-731753506>.
if decl.internal && place.projection.first() == Some(&ProjectionElem::Deref) {
// If the projection root is an artifical local that we introduced when
// desugaring `static`, give a more specific error message
// (avoid the general "raw pointer" clause below, that would only be confusing).
@ -221,22 +217,45 @@ impl<'a, 'tcx> Visitor<'tcx> for UnsafetyChecker<'a, 'tcx> {
);
return;
}
} else {
}
}
// Check for raw pointer `Deref`.
for (base, proj) in place.iter_projections() {
if proj == ProjectionElem::Deref {
let source_info = self.source_info; // Backup source_info so we can restore it later.
if base.projection.is_empty() && decl.internal {
// Internal locals are used in the `move_val_init` desugaring.
// We want to check unsafety against the source info of the
// desugaring, rather than the source info of the RHS.
self.source_info = self.body.local_decls[place.local].source_info;
}
}
}
let base_ty = Place::ty_from(place.local, proj_base, self.body, self.tcx).ty;
match base_ty.kind() {
ty::RawPtr(..) => self.require_unsafe(
let base_ty = base.ty(self.body, self.tcx).ty;
if base_ty.is_unsafe_ptr() {
self.require_unsafe(
UnsafetyViolationKind::GeneralAndConstFn,
UnsafetyViolationDetails::DerefOfRawPointer,
),
ty::Adt(adt, _) if adt.is_union() => {
let assign_to_field = matches!(
)
}
self.source_info = source_info; // Restore backed-up source_info.
}
}
// Check for union fields. For this we traverse right-to-left, as the last `Deref` changes
// whether we *read* the union field or potentially *write* to it (if this place is being assigned to).
let mut saw_deref = false;
for (base, proj) in place.iter_projections().rev() {
if proj == ProjectionElem::Deref {
saw_deref = true;
continue;
}
let base_ty = base.ty(self.body, self.tcx).ty;
if base_ty.ty_adt_def().map_or(false, |adt| adt.is_union()) {
// If we did not hit a `Deref` yet and the overall place use is an assignment, the
// rules are different.
let assign_to_field = !saw_deref
&& matches!(
context,
PlaceContext::MutatingUse(
MutatingUseContext::Store
@ -244,13 +263,6 @@ impl<'a, 'tcx> Visitor<'tcx> for UnsafetyChecker<'a, 'tcx> {
| MutatingUseContext::AsmOutput
)
);
// If there is a `Deref` further along the projection chain, this is *not* an
// assignment to a union field. In that case the union field is just read to
// obtain the pointer/reference.
let assign_to_field = assign_to_field
&& !place.projection[i..]
.iter()
.any(|elem| matches!(elem, ProjectionElem::Deref));
// If this is just an assignment, determine if the assigned type needs dropping.
if assign_to_field {
// We have to check the actual type of the assignment, as that determines if the
@ -280,9 +292,6 @@ impl<'a, 'tcx> Visitor<'tcx> for UnsafetyChecker<'a, 'tcx> {
)
}
}
_ => {}
}
self.source_info = source_info;
}
}
}