error: Undefined Behavior: reading memory at ALLOC[0xX..0xY], but memory is uninitialized at [0xX..0xY], and this operation requires initialized memory
  --> tests/fail/uninit/padding-pair.rs:LL:CC
   |
LL |     let v = unsafe { *z.offset(first_undef) };
   |                      ^^^^^^^^^^^^^^^^^^^^^^ Undefined Behavior occurred here
   |
   = 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` at tests/fail/uninit/padding-pair.rs:LL:CC

Uninitialized memory occurred at ALLOC[0xX..0xY], in this allocation:
ALLOC DUMP

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

error: aborting due to 1 previous error