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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.
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