Wasmtime Files

33.0.0

Released 2025-05-20.

Added

• Cranelift now has initial support for try_call and try_call_indirect instructions, to be used in the future for the WebAssembly exception-handling proposal. Wasmtime does not yet implement this proposal yet. #10510 #10557 #10593

• Cranelift can now optimize some simple possibly-side-effectful instructions, such as division. #10524

• Wasmtime now supports --invoke for components using the WAVE format. #10054

• Initial support for the Component Model has landed in Wasmtime's C API. Note that the API is not yet feature-complete, however. #10566 #10598 #10651 #10675

• Wasmtime's C++ API is now available from this repository and the bytecodealliance/wasmtime-cpp repository has been archived. Additionally the monolithic wasmtime.hh header file has been split into separate header files. #10582 #10600

• Wasmtime's cookbook-style documentation has been expanded. #10630

• Wasmtime's now supports custom yield behavior when using epoch interrupts. #10671

Changed

• Wasmtime's bindgen now type-checks export functions in the constructor of the generated {Worldname}Pre or {Worldname} structs, rather than at the call of the export function. #10610

• Wasmtime's component::Component and component::Instance now have consistient get_export and get_export_index methods, which return (ComponentItem, ComponentExportIndex) and ComponentExportIndex, respectively. #10597

• On failure, wasmtime serve gives an internal server error response, rather than closing the connection. #10645

• Cranelift's single-pass allocator has been disabled due to being unable to support internal refactorings in preparation for the WebAssembly exceptions proposal. Re-enabling this allocator is tracked at regalloc2#217 for those interested. #10554

• Wasmtime's {Array,Extern,Struct}Ref functions will now automatically trigger a GC. #10560

• Wasmtime's GC heaps now use the same translation techniques as linear memories meaning they have far fewer bounds-checks than before. #10503

• Wasmtime's implementation of WASIp2 has moved to wasmtime_wasi::p2 from the root of the crate. #10073

• Wasmtime will no longer emit calls to Cranelift-defined "libcalls" and instead everything goes through Wasmtime's libcall mechanism instead, paving the way for a future change for more efficient stack limit checking in wasm. This can also improve deserialize-from-disk times and improve page cache usage for modules that use libcalls as relocations are no longer necessary. #10657

• Configuration of caching can now be done through an API instead of exclusively through a configuration file. Additionally cache-related APIs in Config have changed. #10665

• Resources in the Component Model are now stored in a single table per-instance instead of per-type tables. Guests will see a different pattern of index allocation but this is not expected to cause any issues at runtime. #10701

Fixed

• Some math intrinsics have been fixed when compiled by Rust 1.87+. #10534

• Component model libcalls correctly handle platform-specific argument extension in ABIs. #10540

• An off-by-one issue with DWARF debuginfo has been fixed. #10570

• The Config::target method is no longer gated by a #[cfg] for an enabled compiler, it can be used when only the runtime feature is available. #10618

• An issue with "simulated" DWARF has been fixed. #10681

• C/C++ headers are now tested that they can be included in isolation, and a number of issues have been fixed. #10694