They were trying to build the entire OS using a 100% memory-safe language. At one point they could elide process boundaries and protected memory (and the associated context switch overhead) because the loader could statically verify your program didn&#x27;t do anything unsafe.<p>The ultimate answer to Singularity&#x2F;Midori&#x2F;etc is yes, you can have an OS (including drivers and interrupt handlers) that is 100% provably memory safe and thread safe and is performance-competitive with existing systems.<p>Unfortunately Microsoft basically sheleved most of the work and it doesn&#x27;t look like anyone else is going to pick up the slack. I predict more heartbleeds and zero-day RCEs in our future. At least we&#x27;ll all get 0wned with fast C code.