654e953fbf
* Revamp memory management of `InstanceHandle` This commit fixes a known but in Wasmtime where an instance could still be used after it was freed. Unfortunately the fix here is a bit of a hammer, but it's the best that we can do for now. The changes made in this commit are: * A `Store` now stores all `InstanceHandle` objects it ever creates. This keeps all instances alive unconditionally (along with all host functions and such) until the `Store` is itself dropped. Note that a `Store` is reference counted so basically everything has to be dropped to drop anything, there's no longer any partial deallocation of instances. * The `InstanceHandle` type's own reference counting has been removed. This is largely redundant with what's already happening in `Store`, so there's no need to manage two reference counts. * Each `InstanceHandle` no longer tracks its dependencies in terms of instance handles. This set was actually inaccurate due to dynamic updates to tables and such, so we needed to revamp it anyway. * Initialization of an `InstanceHandle` is now deferred until after `InstanceHandle::new`. This allows storing the `InstanceHandle` before side-effectful initialization, such as copying element segments or running the start function, to ensure that regardless of the result of instantiation the underlying `InstanceHandle` is still available to persist in storage. Overall this should fix a known possible way to safely segfault Wasmtime today (yay!) and it should also fix some flaikness I've seen on CI. Turns out one of the spec tests (bulk-memory-operations/partial-init-table-segment.wast) exercises this functionality and we were hitting sporating use-after-free, but only on Windows. * Shuffle some APIs around * Comment weak cycle
Wasmtime Embedding API
The wasmtime crate is an embedding API of the wasmtime WebAssembly runtime.
This is intended to be used in Rust projects and provides a high-level API of
working with WebAssembly modules.
If you're interested in embedding wasmtime in other languages, you may wish to
take a look a the C embedding API instead!