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Enable the new preview1 implementation by default #7365

Merged
merged 1 commit into from
Oct 27, 2023
Merged

Enable the new preview1 implementation by default #7365

merged 1 commit into from
Oct 27, 2023

Commits on Oct 25, 2023

  1. Enable the new preview1 implementation by default 

    Currently Wasmtime has two implementations of the `wasi_snapshot_preview1` set
of APIs. The now-historical implementation lives in the `wasi-common`
crate and the more recent implementation lives in the `wasmtime-wasi`
crate. The main difference is that the `wasmtime-wasi` implementation is
based on the implementation of preview2, meaning that the preview1
implementation is a shim in that direction. Additionally currently the
preview2 implementation of preview1 is accessible via the `-Spreview2`
flag on the CLI.

This commit updates the interpretation of the `-Spreview2` flag and the
defaults around which implementation to choose. By default the
preview1-built-on-preview2 implementation (the new `wasmtime-wasi`
implementation) is selected now. This means that the `wasi-common`
implementation is disabled by default. There are still two use cases to
keep running the `wasi-common` implementation, however:

* When running modules that import from `wasi_unstable`, the "snapshot"
  before `wasi_snapshot_preview1`, currently `wasi-common` is required.
  The shims to implement `wasi_unstable` have not yet been implemented
  in the `wasmtime-wasi` crate.

* When running with WASI threads (`-Sthreads`) the preview2
  implementation does not work. This is because the preview2
  implementation expects mutable access to the table which is not
  granted when threads are enabled.

Tests using `wasi_unstable` now pass `-Spreview2=n` to explicitly
request the old `wasi-common` implementation. Additionally the
`wasi-common` implementation is still selected by default when
`-Sthreads` is passed (enabling the WASI threads proposal).
    @alexcrichton
    alexcrichton committed Oct 25, 2023
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