Zeropage persistance

[adiee5]

Hard to tell whether this belongs in this format, but there are some libraries, that only use zeropage when the code is actively running – The library doesn't store anything in zeropage and thus the space can be repurposed for other things, when the library code is not being ran. How to signify such thing and how should the loader or the library exactly behave is up to discussion

[fachat]

Interesting question. You could define a bit in the header, but the operating system would have to understand when exactly that library would be run so it could block anything else from using the zeropage locations. And if the operating system needs to / is able to monitor the library use, it should know what kind of library this is, and thus be able to map zeropage into a shared location anyway.

I had a similar idea about "init code" that could be thrown away and the memory freed after it had run for the "Next gen" draft. But those things I think are highly platform dependent and not ironed out so far.

In the end, in my experience, if you are not like Commodore BASIC, zeropage usage is actually not that heavy in most programs, or at least with considerate programming. So typically there is actually quite a lot of zeropage memory available, so that might not even be necessary.

Do you have a concrete use case for that?

[adiee5]

Famistudio engine is an example of a library, that uses zeropage only when it's running. Though ig the target platform (NES) is not a one suitable for dynamic linking.

Since it's been a while since I wrote that suggestion (and was instead very busy with stuff unrelated to 6502), I'm not sure if I had any specific linker implementation use case in mind while writing this. Since I've been working on a static o65 linker/converter for generating includables for 64tass/prog8, ig one of the use cases could be to inform in the output about such possibility.