Embedded developers often suffer under archaic toolchains. There's plenty of reasons for that, but one of them is UB: a newer version of the compiler can completely change an embedded program's behaviour.

Where I was it was quite the opposite. The bloody compiler guys kept on updating the compiler, and we were required to use the OS-delivered one. Since we were often using pre-release OS's, the toolchain could change every week.

It did make you write robust and defensive code, though...