error: Undefined Behavior: atomic operations cannot be performed on read-only memory
       many platforms require atomic read-modify-write instructions to be performed on writeable memory, even if the operation fails (and is hence nominally read-only)
       some platforms implement (some) atomic loads via compare-exchange, which means they do not work on read-only memory; it is possible that we could have an exception permitting this for specific kinds of loads
       please report an issue at <https://github.com/rust-lang/miri/issues> if this is a problem for you
  --> $DIR/read_only_atomic_cmpxchg.rs:LL:CC
   |
LL |     x.compare_exchange(1, 2, Ordering::Relaxed, Ordering::Relaxed).unwrap_err();
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ atomic operations cannot be performed on read-only memory
many platforms require atomic read-modify-write instructions to be performed on writeable memory, even if the operation fails (and is hence nominally read-only)
some platforms implement (some) atomic loads via compare-exchange, which means they do not work on read-only memory; it is possible that we could have an exception permitting this for specific kinds of loads
please report an issue at <https://github.com/rust-lang/miri/issues> if this is a problem for you
   |
   = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
   = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
   = note: BACKTRACE:
   = note: inside `main`

note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace

error: aborting due to previous error