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Rollup merge of #129199 - RalfJung:writes_through_immutable_pointer, r=compiler-errors

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make writes_through_immutable_pointer a hard error

This turns the lint added in https://github.com/rust-lang/rust/pull/118324 into a hard error. This has been reported in cargo's future-compat reports since Rust 1.76 (released in February). Given that const_mut_refs is still unstable, it should be impossible to even hit this error on stable: we did accidentally stabilize some functions that can cause this error, but that got reverted in https://github.com/rust-lang/rust/pull/117905. Still, let's do a crater run just to be sure.

Given that this should only affect unstable code, I don't think it needs an FCP, but let's Cc ``@rust-lang/lang`` anyway -- any objection to making this unambiguous UB into a hard error during const-eval? This can be viewed as part of https://github.com/rust-lang/rust/pull/129195 which is already nominated for discussion.
This commit is contained in:
Matthias Krüger
2024-08-24 22:14:12 +02:00
committed by GitHub
parent 0dfdea1c45 8b642a1883
commit 05b8bcc662
7 changed files with 23 additions and 102 deletions
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9
compiler/rustc_const_eval/src/const_eval/machine.rs
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@@ -12,7 +12,6 @@ use rustc_middle::query::TyCtxtAt;
use rustc_middle::ty::layout::{FnAbiOf, TyAndLayout};
use rustc_middle::ty::{self, TyCtxt};
use rustc_middle::{bug, mir};
use rustc_session::lint::builtin::WRITES_THROUGH_IMMUTABLE_POINTER;
use rustc_span::symbol::{sym, Symbol};
use rustc_span::Span;
use rustc_target::abi::{Align, Size};
@@ -732,8 +731,8 @@ impl<'tcx> interpret::Machine<'tcx> for CompileTimeMachine<'tcx> {
}
fn before_memory_write(
tcx: TyCtxtAt<'tcx>,
machine: &mut Self,
_tcx: TyCtxtAt<'tcx>,
_machine: &mut Self,
_alloc_extra: &mut Self::AllocExtra,
(_alloc_id, immutable): (AllocId, bool),
range: AllocRange,
@@ -744,9 +743,7 @@ impl<'tcx> interpret::Machine<'tcx> for CompileTimeMachine<'tcx> {
}
// Reject writes through immutable pointers.
if immutable {
super::lint(tcx, machine, WRITES_THROUGH_IMMUTABLE_POINTER, |frames| {
crate::errors::WriteThroughImmutablePointer { frames }
});
return Err(ConstEvalErrKind::WriteThroughImmutablePointer.into());
}
// Everything else is fine.
Ok(())