Environment variables could be injected into the main "service":

    CommandMain "my_app"

    inject Environment env

    entry main
    code
        String h = env.get "HOME"
    end

It would be nice to get all 3 of:

1. Efficient initialization
2. Efficient access
3. Thread-safety

Only 3 is a strict requirement.


Solutions:

* Copy the whole environment block at startup.
* At the first non-SLUL call, copy all env strings, and update
  the environment block.
    - But how to detect "non-SLUL calls"?
    - Maybe there could be some function qualifier?
      But it could be really hard to track.
* Redirect the "C-accessible" environment block to a separate page,
  which is handled by userfaultfd(?) and filled in as needed.
* Map separate copy-on-write pages of the environment block at startup,
  such that the SLUL "Environment" object does not see the changes
  (the "copy" could even be mapped without write permission).

On glibc/Linux there's ptrctl() PR_SET_MM_ENV_START/END.

Related:
Environment block access would probably require an initialized C
library anyway. So SLUL has to somehow be able to tell when the
C library needs to be initialized (or always initialize it).
Initializing lazilly in a multi-threaded program could be tricky.