The "principal" environment stack was the one that was associated with the
"principal" parser and would dispatch changes like to TZ, etc.
This was always very suspicious, as a global; now we can remove it.
The C++ version of this code simply copied the entire uvar table.
Today we take a reference. It's not clear which one is better.
Removal of locale variables like LC_ALL triggers variable change handlers
which call EnvStackImpl::get. This deadlocks because we still hold the lock
to protect the reference to all uvars. Work around this.
Closes#10513
We don't forward this variable for storage in any structs, so there's no reason
to go through an Arc instead of returning the `&'static EnvStack` directly.
NB: This particular change was safe, and passes all tests on its own.
We don't forward this variable for storage in any structs, so there's no reason
to go through an Arc instead of returning the `&'static EnvStack` directly.
These have clearer sync/unsync semantics and now ship with rust itself.
They don't paper over any possible cross-thread issues, and we can specifically
choose which we want for the purpose.
`Parser` is a single-threaded `!Send`, `!Sync` type and does not need to use
`Arc` for anything. We were using it because that's all we had for the parser's
`EnvStack`, but though that is *technically* protected internally by a mutex
(shared with global EnvStack), there's nothing to say that other parsers with a
narrower scope/lifetime on other threads will be necessarily using the same
backing mutex.
We can safely marshal the existing `Arc<EnvStack>` we get from
`environment::principal()` into an `Rc<EnvStack>` since the underlying reference
is always valid. To prove this point, we could have PRINCIPAL_STACK be a static
`EnvStack` and have `environment::principal()` use `Arc::from_raw()` to turn
that into an `Arc<EnvStack>`, but there's no need to factorize this process.
I think commit 8386088b3 (Update commandline state changes eagerly as well,
2024-04-11) broke the alt-s binding.
This is because we update the commandline state snapshot (which is consumed
by builtin commandline and others) only at key points. This seems like a
dubious optimization. With the new streamlined bind execution semantics,
this doesn't really work anymore; any shell command can run any number of
commands like "commandline -i foo" which should synchronize.
Do the simple thing of calculating the snapshot whenever needed.
