From 218caa410aa38c29984be31a5229b9fa717560ee Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Wed, 17 Apr 2024 14:19:13 +0200 Subject: Merging upstream version 1.68.2+dfsg1. Signed-off-by: Daniel Baumann --- tests/ui/consts/invalid-union.rs | 44 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 44 insertions(+) create mode 100644 tests/ui/consts/invalid-union.rs (limited to 'tests/ui/consts/invalid-union.rs') diff --git a/tests/ui/consts/invalid-union.rs b/tests/ui/consts/invalid-union.rs new file mode 100644 index 000000000..28706b4a9 --- /dev/null +++ b/tests/ui/consts/invalid-union.rs @@ -0,0 +1,44 @@ +// Check that constants with interior mutability inside unions are rejected +// during validation. +// +// Note that this test case relies on undefined behaviour to construct a +// constant with interior mutability that is "invisible" to the static checks. +// If for some reason this approach no longer works, it is should be fine to +// remove the test case. +// +// build-fail +// stderr-per-bitwidth +#![feature(const_mut_refs)] + +use std::cell::Cell; +use std::mem::ManuallyDrop; + +#[repr(C)] +struct S { + x: u32, + y: E, +} + +#[repr(u32)] +enum E { + A, + B(U) +} + +union U { + cell: ManuallyDrop>, +} + +const C: S = { + let s = S { x: 0, y: E::A }; + // Go through an &u32 reference which is definitely not allowed to mutate anything. + let p = &s.x as *const u32 as *mut u32; + // Change enum tag to E::B. + unsafe { *p.add(1) = 1 }; + s +}; + +fn main() { //~ ERROR it is undefined behavior to use this value + // FIXME the span here is wrong, sould be pointing at the line below, not above. + let _: &'static _ = &C; +} -- cgit v1.2.3