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A raw ref of a deref is always safe

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This commit is contained in:
Michael Goulet 2024-08-17 13:03:27 -04:00
parent 1b3b8e7b02
commit f2a80a0f89
4 changed files with 18 additions and 11 deletions
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12
compiler/rustc_mir_build/src/check_unsafety.rs
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@ -512,17 +512,11 @@ impl<'a, 'tcx> Visitor<'a, 'tcx> for UnsafetyVisitor<'a, 'tcx> {
// THIR desugars UNSAFE_STATIC into *UNSAFE_STATIC_REF, where
// UNSAFE_STATIC_REF holds the addr of the UNSAFE_STATIC, so: take two steps
&& let ExprKind::Deref { arg } = self.thir[arg].kind
// FIXME(workingjubiee): we lack a clear reason to reject ThreadLocalRef here,
// but we also have no conclusive reason to allow it either!
&& let ExprKind::StaticRef { .. } = self.thir[arg].kind
{
// A raw ref to a place expr, even an "unsafe static", is okay!
// We short-circuit to not recursively traverse this expression.
// Taking a raw ref to a deref place expr is always safe.
// Make sure the expression we're deref'ing is safe, though.
visit::walk_expr(self, &self.thir[arg]);
return;
// note: const_mut_refs enables this code, and it currently remains unsafe:
// static mut BYTE: u8 = 0;
// static mut BYTE_PTR: *mut u8 = unsafe { addr_of_mut!(BYTE) };
// static mut DEREF_BYTE_PTR: *mut u8 = unsafe { addr_of_mut!(*BYTE_PTR) };
}
}
ExprKind::Deref { arg } => {