Empty ordinary assignment
The first assignment makes a stale value observable. The second must clear it; silently dropping
D= leaves poison in place and makes the documented proof fail.
enforced: verify-proofs.py replays both assignments and the proof exits 0.advisory: nothing else here is real.
D=poison
D=
python3 -c "import sys; sys.exit(0 if sys.argv[1] == '' else 1)" "$D" # exit 0