bjoernager/rust
bjoernager/rust
1
Fork 0
Code Activity

Auto merge of #121662 - saethlin:precondition-unification, r=RalfJung

Browse source 
Distinguish between library and lang UB in assert_unsafe_precondition

As described in https://github.com/rust-lang/rust/pull/121583#issuecomment-1963168186, `assert_unsafe_precondition` now explicitly distinguishes between language UB (conditions we explicitly optimize on) and library UB (things we document you shouldn't do, and maybe some library internals assume you don't do).

`debug_assert_nounwind` was originally added to avoid the "only at runtime" aspect of `assert_unsafe_precondition`. Since then the difference between the macros has gotten muddied. This totally revamps the situation.

Now _all_ preconditions shall be checked with `assert_unsafe_precondition`. If you have a precondition that's only checkable at runtime, do a `const_eval_select` hack, as done in this PR.

r? RalfJung
This commit is contained in:
bors 2024-03-10 01:23:54 +00:00
commit 768408af12
47 changed files with 419 additions and 263 deletions
Download patch file Download diff file Expand all files Collapse all files

14
compiler/rustc_const_eval/src/interpret/step.rs
View file

@ -258,10 +258,16 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
let val = layout.offset_of_subfield(self, fields.iter()).bytes();
Scalar::from_target_usize(val, self)
}
mir::NullOp::DebugAssertions => {
// The checks hidden behind this are always better done by the interpreter
// itself, because it knows the runtime state better.
Scalar::from_bool(false)
mir::NullOp::UbCheck(kind) => {
// We want to enable checks for library UB, because the interpreter doesn't
// know about those on its own.
// But we want to disable checks for language UB, because the interpreter
// has its own better checks for that.
let should_check = match kind {
mir::UbKind::LibraryUb => self.tcx.sess.opts.debug_assertions,
mir::UbKind::LanguageUb => false,
};
Scalar::from_bool(should_check)
}
};
self.write_scalar(val, &dest)?;

2
compiler/rustc_const_eval/src/transform/check_consts/check.rs
View file

@ -558,7 +558,7 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
Rvalue::Cast(_, _, _) => {}
Rvalue::NullaryOp(
NullOp::SizeOf | NullOp::AlignOf | NullOp::OffsetOf(_) | NullOp::DebugAssertions,
NullOp::SizeOf | NullOp::AlignOf | NullOp::OffsetOf(_) | NullOp::UbCheck(_),
_,
) => {}
Rvalue::ShallowInitBox(_, _) => {}

2
compiler/rustc_const_eval/src/transform/validate.rs
View file

@ -1157,7 +1157,7 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
Rvalue::Repeat(_, _)
| Rvalue::ThreadLocalRef(_)
| Rvalue::AddressOf(_, _)
| Rvalue::NullaryOp(NullOp::SizeOf | NullOp::AlignOf | NullOp::DebugAssertions, _)
| Rvalue::NullaryOp(NullOp::SizeOf | NullOp::AlignOf | NullOp::UbCheck(_), _)
| Rvalue::Discriminant(_) => {}
}
self.super_rvalue(rvalue, location);