The practice of formal methods has progressed by acknowledging and accepting those limitations. It now attempts to prove useful properties of your code, rather than stamping it "correct" or "incorrect."

FTA:

“We’re not claiming we’re going to prove an entire system is correct, 100 percent reliable in every bit, down to the circuit level,” Wing said. “That’s ridiculous to make those claims. We are much more clear about what we can and cannot do.”