You really can get quite far by having everything be statically allocated, placing reasonable constraints on input sizes/rates, and making use of ring buffers.

You really can get quite far by having everything be statically allocated, placing reasonable constraints on input sizes/rates, and making use of ring buffers. I've only worked on embedded development using C++, but I didn't really encounter any issues writing (admittedly, somewhat simple) device drivers with no heap whatsoever.