What's the difference between “dead code” and “unreachable code”?

Question

I thought those terms where synonymous, but a note in MISRA regarding dead code indicates this to be wrong? What\'s the difference? Is one a subset of the other?

Answer 1

unreachable code is something that would never be executed because there is no flow control to reach the code.

A dead code is something that gets (or might get) executed, but its results are never used.