wit-dylib: Initial skeleton of async support #2317
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This commit starts to fill out the support for async in `wit-dylib`. In doing so this has filled out a number of pieces of functionality elsewhere and implemented more thorough testing. As a result of this some issues were discovered which are also fixed in this PR. Notable changes are: * Naming of the `task-return` intrinsic is now in a helper in `wit-parser` to avoid needing to duplicate that elsewhere. * A new `roundtrip` test was added to `wit-dylib` which generates arbitrary WITs and arbitrary values for the WIT and ensures that the values are communicated successfully. * Composition code shared between the `all` and `roundtrip` tests was moved to the `artifacts` crate as a shared dependency of the two. * In-memory data structures for `wit_func_t` are updated to reflect async support. * Deferred deallocation of bytes is pushed as a responsibility to the embedder. Storing values on the stack was getting too tricky and felt like a too-clever-by-half implementation. To simplify the generated code the responsibility is now on the `wit_dylib_*` implementor to deallocate bytes in a deferred fashion. * The `wit-bindgen` crate is a dependency of `wit-dylib-ffi`, the guest bindings of `wit_dylib.h`, for async support. * The `wasm-tools wit-dylib` subcommand now has configuration, in the same manner as `wit-bindgen` for which functions should be async and which should be sync. * The `with_temp_stack` helper was removed as that was also getting too tricky to manage and instead functions just always allocate some temporary space. * Existing bindings were updated for async functions when that ABI is selected, and new bindings were added for various intrinsics related to the lifecycle of async imports/exports. Perhaps the biggest feature in this commit is the addition of the `roundtrip` test which is hoped to provide a much more thorough implementation of testing this crate. Notably it generates an arbitrary WIT structure *and additionally* generates arbitrary values of this structure. This has weeded out a number of bugs in the bindings generator and necessitated various refactorings here. This is intended to be a crucial part of making this a solid dependency to build on.
alexcrichton
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Draft for now until bytecodealliance/wit-bindgen#1390 is merged |
dicej
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Sep 29, 2025
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Once again, I've only skimmed this, but looks reasonable to me.
Co-authored-by: Joel Dice <joel.dice@fermyon.com>
Co-authored-by: Joel Dice <joel.dice@fermyon.com>
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This commit starts to fill out the support for async in
wit-dylib. In doing so this has filled out a number of pieces of functionality elsewhere and implemented more thorough testing. As a result of this some issues were discovered which are also fixed in this PR. Notable changes are:task-returnintrinsic is now in a helper inwit-parserto avoid needing to duplicate that elsewhere.roundtriptest was added towit-dylibwhich generates arbitrary WITs and arbitrary values for the WIT and ensures that the values are communicated successfully.allandroundtriptests was moved to theartifactscrate as a shared dependency of the two.wit_func_tare updated to reflect async support.wit_dylib_*implementor to deallocate bytes in a deferred fashion.wit-bindgencrate is a dependency ofwit-dylib-ffi, the guest bindings ofwit_dylib.h, for async support.wasm-tools wit-dylibsubcommand now has configuration, in the same manner aswit-bindgenfor which functions should be async and which should be sync.with_temp_stackhelper was removed as that was also getting too tricky to manage and instead functions just always allocate some temporary space.Perhaps the biggest feature in this commit is the addition of the
roundtriptest which is hoped to provide a much more thorough implementation of testing this crate. Notably it generates an arbitrary WIT structure and additionally generates arbitrary values of this structure. This has weeded out a number of bugs in the bindings generator and necessitated various refactorings here. This is intended to be a crucial part of making this a solid dependency to build on.