I actually once worked on a safety critical military application (though not DO-178b certified), and for a new version, we switched from C to real-time Java (RTSJ). RTSJ actually let's you avoid unpredictable GC altogether through what is called "scoped memory" in your critical threads, and provides real-time scheduling if run on a RTOS.
We switched because we wanted to reduce the risks of bugs, but you must remember that in most mission critical applications, one must consider failure not only in the software. You use redundancy - in the software, in the hardware, and in the network. We even used several separate power systems and several redundant generators.
Interesting, thanks! I didn't know about RTSJ and a cursory search in preparing my earlier comment only popped up links that looked bitrotted, so I assumed it wasn't a widespread technology.
It isn't widespread. Then again, hard real-time systems aren't widespread either. I think Boeing was (maybe still is) using RTSJ. The only downside it has is increased RAM footprint relative to C(which makes it unsuitable for very limited devices) and a small performance hit relative to regular Java because some classes need to be compiled to machine language ahead of time (the Hotspot JIT can do some very nifty optimization at runtime, but those come at a cost of non-determinism. Real-time systems always trade performance for determinism).
We switched because we wanted to reduce the risks of bugs, but you must remember that in most mission critical applications, one must consider failure not only in the software. You use redundancy - in the software, in the hardware, and in the network. We even used several separate power systems and several redundant generators.