[38.0.0] Fix externref/anyref ownership in C/C++ API#11803
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alexcrichton merged 1 commit intobytecodealliance:release-38.0.0from Oct 7, 2025
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[38.0.0] Fix externref/anyref ownership in C/C++ API#11803alexcrichton merged 1 commit intobytecodealliance:release-38.0.0from
alexcrichton merged 1 commit intobytecodealliance:release-38.0.0from
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* Fix externref/anyref ownership in C/C++ API This commit is a follow-up to bytecodealliance#11514 which was discovered through failing tests in the wasmtime-py repository when updating to Wasmtime 37.0.0. Effectively a combination of bugs in the Rust API meant that it wasn't possible to use `externref` or `anyref` bindings correctly. The Rust changes in this commit are: * `wasmtime_val_unroot` correctly drops the value now as opposed to effectively being a noop from before (typo of using `as_externref` vs `from_externref`). * `wasmtime_{anyref,externref,val}_t` now have a `Drop` implementation in Rust to correctly drop them if a value in Rust is dropped. This is required to correctly manage memory in the `wasmtime_func_{call,new}` implementations, for example. * `wasmtime_{anyref,externref,val}_clone` no longer have an unnecessary context parameter. * `wasmtime_{anyref,externref,val}_unroot` no longer have an unnecessary context parameter. Changes in the C/C++ APIs are: * `Result::{ok,err}_ref` APIs were added in addition to the preexisting rvalue accessors. * Loading/storing typed arguments now has an overload for `const T&` and `T&&` which behaves differently. Notably transferring ownership for `T&&` and not for `const T&`. This means that passing parameters when calling a wasm function uses `const T&`, but passing results from a host import uses `T&&`. * `TypedFunc::call` now uses `const Params&` instead of `Params` to explicitly specify it doesn't modify the parameters and forces using the `const T&` store method. * `Store::gc` is now a convenience method for `store.context().gc()` * `ExternRef`, `AnyRef`, and `Val` now have ownership semantics and destructors. This matches the spirit of bytecodealliance#11514 for Rust but models it in C++ as well. This required filling out move/copy constructors/assignments. * The explicit `ExternRef` now takes `std::any` instead of `T`. * Minor issues related to ownership are fixed in `Val` bindings. Valgrind was used to ensure that there were no leaks for the test suite which additionally resulted in a number of `*_delete` calls being added to tests using the C API (accidental omissions). The original goal of this change was to be a patch release for 37.0.1 to enable updating wasmtime-py to the 37.0.x releases of Wasmtime. In the end though the changes here were broad enough that I no longer feel that this is a good idea, so wasmtime-py will be skipping the 37 version of Wasmtime. * Run `clang-format` prtest:full
alexcrichton
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Backport of #11799