Operating system

[robotman2412]

For the MCH2025 badge, we want to dynamically load apps so we can do things like exclude system libraries from their binaries, saving on flash memory space.
For all intents and purposes, this means making an Operating System of sorts which loads the apps and their libraries and serves their ABI calls.

This discussion is about requirements of the Operating System and eventually how to achieve them.
We need a list of (feature) requirements, I'll start:

• The operating system must be technically possible to port
  • Code shall be separated between hardware-specific and generic sections
  • It should be possible to port the operating system to another hardware platform
• Applications will be stored in ELF files
  • These ELF files will make use of the existing ELF standards for all functionality that exists in said standards
  • Dynamically linked libraries must also be supported
• Any given application must be fully portable
  • They shall not need recompilation on the same CPU architecture
  • A compliant C standard library needs to exist
  • Assuming an app only uses the C standard library, it shall be portable to Linux with no more than recompilation
  • The ABI provided shall not rely on anything other than CPU architecture
  • The ABI shall not provide implementation details to the app
• The app build system must be flexible
  • An app developer must be able to override any part of the build system they see fit
  • The default way to make apps should be easy to use
  • The app's minimum codebase should be only a handful of files

And for the wish list:

• Multiple applications loadable at once
• Support for the C++ standard library

[robotman2412]

We have made a document

You can see our design decisions and rationale here:
https://docs.google.com/document/d/1qgpeLhjLZvecd4yATPb-9B1IthdMw18idM6reSSEXS8/edit?usp=sharing