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Remove the borrow checking from wiggle entirely #8702

Merged
merged 4 commits into from
May 31, 2024
Merged

Remove the borrow checking from wiggle entirely #8702

merged 4 commits into from
May 31, 2024

Commits on May 31, 2024

  1. Remove the borrow checking from wiggle entirely 

    This commit is a refactoring of the `wiggle` crate which powers the
`*.witx`-based bindings generation of Wasmtime for wasip1 support.
Originally `wiggle` had a full-blown runtime borrow checker which
verified that borrows were disjoint when appropriate. In bytecodealliance#8277 this was
removed in favor of a more coarse "either all shared or all mutable"
guarantee. It turns out that this exactly matches what the Rust type
system guarantees at compile time as well.

This commit removes all runtime borrow checking in favor of compile-time
borrow checking instead. This means that there is no longer the
possibility of a runtime error arising from borrowing errors. Current
bindings in Wasmtime needed no restructuring to work with this new API.

The source of the refactors here are all in the `wiggle` crate. Changes
include:

* The `GuestPtr` type lost its type parameter. Additionally it only
  contains a `u32` pointer now instead.
* The `GuestMemory` trait is replaced with a simple `enum` of
  possibilities.
* Helper methods on `GuestPtr` are all moved to `GuestMemory`.
* A number of abstractions were simplified now that borrow checking is
  no longer necessary.
* Generated trait methods now all take `&mut GuestMemory<'_>` as an
  argument.

These changes were then propagated to the `wasmtime-wasi` and
`wasi-common` crates in their preview0 and preview1 implementations of
WASI. All changes are just general refactors, no functional change is
intended here.
    @alexcrichton
    alexcrichton committed May 31, 2024
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  2. Review comments

    @alexcrichton
    alexcrichton committed May 31, 2024
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  3. Fix publishing of wiggle-macro crate

    @alexcrichton
    alexcrichton committed May 31, 2024
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  4. Fix wiggle docs

    @alexcrichton
    alexcrichton committed May 31, 2024
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