Thanks :)

Hi all!

I've been working on this Uxntal operating system for the better part
of the past few days, and I started noticing that things were kind of
weird, and that building without tail-call optimisations resolved the
issue, the project is massive and I couldn't for the life of me,
figure out where the optimisation issue was occurring.

https://git.sr.ht/~rabbits/potato/commit/8323c42390821050418503bfd823aba17dd821b4

So yeah, be careful out there, I'll try to weed out the bug and figure
out which part fails. Just a head's up :)

Have a good rest of summer

This is specifically for Felix, but I'd like to make this conversation
available to all, in case anyone has ideas.

In UF, when uxncli under/overflows, it breaks the repl. It'd be nice
to agree on a way to handle this stuff by using this as a usecase.

The way I would handle this is to set a System/vector and clean up the
stack in that vector, and throw a custom error. Do you think that
would work for you? We could make that behaviour standard across
emulators if that would do it? What would be the ideal UX to handle
that?

I've implemented a simple check using a device support bitmask at the
emulator level, it'll catch 90% of the incompatibility issues which
will likely be folks trying to run graphical roms with uxncli.

The report came from someone using uxn11 on BSD, but this should
probably be added to uxnsdl as well.

https://git.sr.ht/~rabbits/uxn11/commit/5d837313e56d19cd6ecfa2ad9746edca20afb5f6

Found an exception.

The file device is a bit tricky I suppose, for example, noodle doesn't
assign a File/name until it tries to save, but the device does have a
vector, although it is unused.

Maybe applications should still test available devices on reset, I
could set a #0000 to File/vector on reset to make sure that it is
available.

If all else fails, a bit mask in a byte might work, but let's try to
see if we can do without first.

I've considered this but I couldn't find any example where the errors
didn't fire, for example, the moment you try to set a vector for mouse
or controller devices, the error fires.

The reset vector will invariably set some sort of vector or something
that will trigger the errors, there might be a way to skip the check
somehow that I haven't conceived of yet.

Someone asked me if we could add a way to detect if a device is a
missing, the usecase is like, trying to load noodle, with uxncli,
should say "Device is missing", something like this.

We could do it in emu-space, like: when a read/write happens on a
missing device, it prints a warning saying that the device is missing.

We could do it in uxn-space, maybe: if after setting a vector, the
vector is still #0000, then that means the device is missing? It would
work for most devices that disambiguates uxnemu/uxncli, but datetime
has no vector(yet).

Let me know what you think, in the meantime, I'll add warnings to
uxncli when a DEI/DEO occurs on a missing device.

Since, it turns there is an actual use to keep stacks across vectors
like you demonstrated, and also Claude contacted me about this
off-list to tell me they also used it, then forget about error4
altogether, there's nothing stopping you to just lead things in the
stacks :)

I found a way that I liked to work around this as well, the reason why
I was even considering error4 was that I tend to rely on this to tell
me if I have leaks.

Without having to change much at all, I figured that if I don't print
the stack content when they are empty, and leave a #01 .System/debug
DEO at the end of each vector in the programs I'm writing, the effect
is the same.

I've noodled around with this this afternoon and catching busy stacks
on break in userspace/per-application is pretty cumbersome and
invasive.

So what I did was this, a typical debug query:

#02 .System/debug DEO

And thereafter, the uxn11 emulator is printing a warning(not errorring),
when it is breaking on non-empty stack. It's non-intrusive,
varvara-space defined and straight-forward. I've grown used to this
little safeguard and I'd like to keep it in, this might be the way.

I'll spend a few more days with this to test it out :)

I've done a bit of a revamp to the Uxntal documentation based on some
feedback I've received today with the hopes of approaching something
like a freeze of the uxn core specs.

This doesn't cover anything Varvara related but I figured I should
probably say a few words about vectors and events.

This is aimed at someone who might be implementing an emulator, or
someone wanting to learn how to write uxntal programs, but it is not a
tutorial, just a reference of the behaviors of the uxn vm. I've tried
to have valuable examples to most opcodes.

I hope you like it! I'd love to know if you think, let me know if I've
missed something.