FatalError add FatalError to output makes it simpler to find in core dumps
FatalError() is called from 366 different places, without any consistent prefix such as "FatalError"
A consistent prefix would allow users to use strings to search a core file for the cause of the error. It's a common issue that users don't have debug symbols, but do have a core file.
os/log.c contains the implementation of FatalError on line 983 The other way would be to add the "FatalError:" prefix there in the buffer, so visible in the core file. That would be the same as the way assert() macro messages are visible in core files then.