> If the list can change between reboots, this would be bad if
> precompiled or pre-expanded libraries are used.  A macro transformer
> that ran yesterday could have inserted the wrong code for today in its
> output.

In practice, new versions of software may add new codes but do not
change the meaning of existing codes. Our entire software stack would
fall down if e.g. a new Linux kernel randomly reassigned errno values,
or existing HTTP status codes started to mean something different.