Not open source but mostly reverse engineered, and automotive: the PCM code for GM’s LT1 engines. The only thing that could be considered a bug is the behaviour

Not open source but mostly reverse engineered, and automotive: the PCM code for GM’s LT1 engines. The only thing that could be considered a bug is the behaviour of wide-open throttle fuelling, which was completely acceptable from the factory but made aftermarket tuning a bit tricky. Specifically, the fuel calculation routine would use the most recent BLM (short- and mid-term air-fuel ratio correction factory as measured by the O2 sensors) when calculating fuel delivery when wide-open, rather than locking it to a constant; the “most recent BLM” may be for a completely different area of the tune (like mid-RPM low throttle), where things like vacuum leaks or even just intake runner inefficiencies have a much greater affect on AFRs than when wide-open. This can result in either too much or too little fuel being injected, and under- or over-shooting the target AFR. The reason for this is a physical limitation: the cars weren’t shipped with wideband O2 sensors, so there’s no way to measure the AFR when wide-open (since it’s targeting a significantly richer mixture, and narrowband O2 sensors can only signal whether a the combustion is stoichiometric, or rich or lean relative to stoichiometric, with no further info). The implantation is probably not a bug but rather a compromise; in an ideal world, the “most recent” BLM will hopefully be from an “almost wide open” part of the map, and the general rich/lean characteristics will be close enough. And, the fuel table in the factory tune is quite safely rich when wide-open, so even with a leaking injector causing the idle BLMs to be way off, the fuel being pulled when wide open will still be completely safe. Aside from that, 128k of bug-free code.