error: Undefined Behavior: attempting a write access using <wildcard> at ALLOC[0x0], but no exposed tags have suitable permission in the borrow stack for this location
  --> $DIR/exposed_only_ro.rs:LL:CC
   |
LL |     unsafe { *ptr = 0 };
   |              ^^^^^^^^
   |              |
   |              attempting a write access using <wildcard> at ALLOC[0x0], but no exposed tags have suitable permission in the borrow stack for this location
   |              this error occurs as part of an access at ALLOC[0x0..0x4]
   |
   = help: this indicates a potential bug in the program: it performed an invalid operation, but the Stacked Borrows rules it violated are still experimental
   = help: see https://github.com/rust-lang/unsafe-code-guidelines/blob/master/wip/stacked-borrows.md for further information
           
   = note: inside `main` at $DIR/exposed_only_ro.rs:LL:CC

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

error: aborting due to previous error