Show HN: Bedrock – An 8-bit computing system for running programs anywhere

> Locked and changed?

That could do with some better wording. Normally the user can freely drag-resize the window, but after the program sets the width or height then the user will be unable to resize that axis. This is for, say, a list program where the screen contents would have a fixed width but a dynamic height, so you'd want to keep the height resizable (unlocked).

> You also seem to be using double to refer to two bytes

Double does mean a 16-bit value, yeah, there's a list of definitions on the main page of the user manual and specification. Short tends to be the expected name for a 16-bit value (from C et al.), but it doesn't make much sense for a short to be the wider of two values. I briefly considered word, but the definition is too broad, with a byte also being a type of word. Double felt like the most intuitive name, because it's double the width of a byte. There weren't really any other decent candidates.

> a individual device for each permission that you wanted to supply and have the host environment optionally provide them

That's more or less the plan, only with a bit more granularity depending on the implementation, so that you can, say, allow reading files but forbid writing or deleting.

You've got it, yeah. It makes writing programs across different systems so much nicer, because you can just write your programs against a single tidy 'bedrock' abstraction of the file system, screen, networking, etc.

The source code for the microwave clock program is available on the 'Example: Microwave clock' subpage [0]. I hadn't put up code for any of the other programs yet, just because they currently use a lot of library code and idioms that I thought could be confusing to people. I'm intending to make them tidier and release them as proper examplars with commentary sometime. I'll also package up and release my library code at some point, it'd be helpful for people to be able to grab and use all kinds of pre-made functions, and there's a whole user interface framework in there too.

For the meantime though, I uploaded the source code for each of the snake [1], keyboard [2], and system information [3] programs for you or anyone else here to have a look at. Each one is a single source code file with library macros and functions baked in, so you can run `br asm snake-full.brc | br -z` to assemble and run them.

[0] https://benbridle.com/projects/bedrock/example-microwave-clo...

[1] https://benbridle.com/share/snake-full.brc

[2] https://benbridle.com/share/keyboard-full.brc

[3] https://benbridle.com/share/sysinfo-full.brc

The undefined behaviour is limited to only a couple of very edge-case situations that would cause issues for the program anyway, like overflowing the stacks. My thoughts were that a program would have to be broken in order to have triggered one of these situations in the first place.

All programs are broken. No program over 100 lines is bug-free, probably. Maybe seL4, but even seL4 had to be patched for Spectre.

In particular, you can be sure that if people build implementations that don't detect those situations, people who test their code on those implementations will ship code that triggers them. It's pretty easy to underflow a stack at startup if you don't use whatever you popped off of it for anything important, unless the thing you happen to be overwriting is important and/or gets written to later by another means. Limited stack overflow is less common but does occasionally happen.

What typically happens in situations like this is that new implementations have to copy the particular handling of supposedly undefined behavior that the most popular implementation of the platform happened to have. But because it isn't documented, or maybe even intentional, they have to reverse engineer it. It's often much more complex than anything that anyone would have come up with on purpose. This all strikes me as a massive waste of time, but maybe it's an acceptable tradeoff for squeezing that last 30% of performance out of your hardware, a consideration that isn't relevant here.

In the days before Valgrind we would often find new array bounds errors when we ported a C or C++ program to a new platform, and Tony Hoare tells us this sort of thing has been ubiquitous since the 60s. It's hard to avoid. Endianness used to be a pitfall, too, and Valgrind can't detect that, but then all the big-endian architectures died out. The C standards documents and good books were always clear on how to avoid the problems, but often people didn't understand, so they just did whatever seemed to work.

If you want write-once-run-anywhere instead of write-once-debug-everywhere you have to get rid of undefined behavior. That's why Uxn doesn't have any.