Courtesy of @ogniK5377.
This also moves them into the cpp file and limits the visibility to
where they're directly used. It also gets rid of unused or duplicate
error codes.
The only reason this include was necessary, was because the constructor
wasn't defaulted in the cpp file and the compiler would inline it
wherever it was used. However, given Controller is forward declared, all
those inlined constructors would see an incomplete type, causing a
compilation failure. So, we just place the constructor in the cpp file,
where it can see the complete type definition, allowing us to remove
this include.
As means to pave the way for getting rid of global state within core,
This eliminates kernel global state by removing all globals. Instead
this introduces a KernelCore class which acts as a kernel instance. This
instance lives in the System class, which keeps its lifetime contained
to the lifetime of the System class.
This also forces the kernel types to actually interact with the main
kernel instance itself instead of having transient kernel state placed
all over several translation units, keeping everything together. It also
has a nice consequence of making dependencies much more explicit.
This also makes our initialization a tad bit more correct. Previously we
were creating a kernel process before the actual kernel was initialized,
which doesn't really make much sense.
The KernelCore class itself follows the PImpl idiom, which allows
keeping all the implementation details sealed away from everything else,
which forces the use of the exposed API and allows us to avoid any
unnecessary inclusions within the main kernel header.
This makes the formatting expectations more obvious (e.g. any zero padding specified
is padding that's entirely dedicated to the value being printed, not any pretty-printing
that also gets tacked on).
