On: Ratification of the RISC-V Base ISA and Privileged...

[dmitrygr]

Look at doom's source code for an idea of how often a bool is not just 0 or 1. I doubt doom is unique.

Spoiler: doom uses 2 values for bools: 0 for false, 1 for true, and -1 for not sure/unknown/error/something else