Trying to build what little free firmware exists to use along with the kernel named Linux; finding some of these aren't even buildable at present and probably haven't been for a long time. For one of them, the assembler that it needs does build but immediately segfaults. In another case the carl9170 WiFi firmware has some problems building the cross-compiling toolchain, which is a prerequisite to building the actual firmware.

I'm guessing that people don't normally build these things from source and instead grab the binaries from linux-firmware.git and don't notice when there are problems.

In looking in to this problem where the toolchain for the carl9170 WiFi firmware wouldn't build, I found that Debian doesn't build it from source either: They just re-use the firmware file from linux-firmware.git and provide the same (broken) source.