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19.0.0

Unreleased.

Added

Changed

18.0.0

Unreleased.

Added

Changed

17.0.0

Released 2024-01-25

The major feature of this release is that the WASI support in Wasmtime is now considered stable and flagged at an 0.2.0 version approved by the WASI subgroup. The release was delayed a few days to hold off until the WASI subgroup voted to approve the CLI and HTTP worlds and they're now on-by-default! Additionally the component model is now enabled by default in Wasmtime, for example an opt-in flag is no longer required on the CLI. Note that embeddings still must opt-in to using the component model by using the wasmtime::component module.

Added

  • Cranelift optimizations have been added for "3-way comparisons", or Ord::cmp in Rust or <=> in C++. #7636 #7702

  • Components now use Wasmtime's compilation cache used for core wasm modules by default. #7649

  • The Resource<T> and ResourceAny types can now be converted between each other. #7649 #7712

Changed

  • Minor changes have been made to a number of WITs as they progressed to their official 0.2.0 status. #7625 #7640 #7690 #7781 #7817

  • The component model is now enabled by default. #7821

  • The implementation of memory.atomic.{wait,notify} has been rewritten. #7629

  • The wasmtime_wasi::preview2::Table type has been moved to wasmtime::component::ResourceTable. #7655

  • Creating a UDP stream now validates the address being sent to. #7648

  • Defining resource types in Linker<T> now takes the type to define as a runtime parameter. #7680

  • Socket address checks can now be performed dynamically at runtime. #7662

  • Wasmtime and Cranelift's MSRV is now 1.73.0. #7739

Fixed

  • Bindings for WIT APIs where interfaces have multiple versions are now fixed by putting the version in the generated binding names. #7656

  • The preview1 fd_{read,write} APIs are now fixed when a shared memory is used. #7755

  • The preview1 fd_{read,write} APIs no longer leak an intermediate stream created. #7819

16.0.0

Released 2023-12-20

Added

  • Add yielding support in wasmtime_store_epoch_deadline_callback in the C API. #7476

  • Support for the wasi_unstable module ("wasi preview0" canonically) has been added to the -Spreview2 support in the CLI. #7548

  • The original module can now be obtained from an "instance pre" in the C API. #7572

  • Usage of Mach ports on macOS can now be disabled in the C API. #7595

Changed

  • The preview1-to-preview2 component adapters now import a smaller number of interfaces by default. #7543 #7544

  • Wasmtime and Cranelift now require Rust 1.72.0 to build. #7554

  • The default world supported by wasmtime serve has been slimmed down to exactly what wasi:http/proxy specifies by default. Support for other WASI APIs can be included with the -S common command-line flag. #7597

  • The wasmtime --version CLI output will now include date/commit information when Wasmtime is built from a git checkout. #7610

  • Debug intrinsic symbols required by LLDB and GDB have been moved behind a debug-builtins feature of the wasmtime crate which is enabled by default. #7626

Fixed

  • MPK support is now explicitly disabled on AMD-based CPUs since the implementation does not currently support it. #7513

  • Initialization of a WebAssembly data segment with a negative offset is fixed to zero-extend the offset instead of sign-extend. #7559

  • The reported offset of O_APPEND files in preview1 has been fixed. #7586

  • MPK support does a better job of compacting memories to minimize virtual memory used. #7622

Cranelift

  • Union node bitpacking has been fixed with egraph optimizations to ensure the minimal cost node is selected. #7465

  • Equivalent-cost expressions now have ties broken with expression depth in egraphs to prefer "shallow" expression trees. #7456

  • Long-and-narrow chains of expressions are now optimized into shallow-and-wide trees. #7466

15.0.1

Released 2023-12-01.

Fixed

  • The wasi:random/insecure{,_seed} interfaces are now available through the CLI. #7614

  • A stray debugging println! was removed. #7618

15.0.0

Released 2023-11-20

Added

  • Multiple versions of interfaces are now supported in bindgen!. #7172

  • UDP has been implemented in wasi:sockets. #7148 #7243

  • Support for custom stack memory allocation has been added. #7209

  • The memory_init_cow setting can now be configured in the C API. #7227

  • The splice method of WASI streams has been implemented. #7234

  • Wasmtime binary releases now have a wasmtime-min executable in addition to libwasmtime-min.* libraries for the C API. These showcase a minimal build of Wasmtime for comparison. #7282 #7315 #7350

Changed

  • Many changes to wasi:http WITs have happened to keep up with the proposal as it prepares to reach a more stable status. #7161 #7406 #7383 #7417 #7451

  • Add an error resource to WASI streams. #7152

  • Syntax in bindgen!'s trappable_error_type configuration has changed. #7170

  • TCP errors in wasi:sockets have been simplified and clarified. #7120

  • Wasmtime/Cranelift now require Rust 1.71.0 to compile. #7206

  • Logging in Wasmtime is now configured with WASMTIME_LOG instead of RUST_LOG. #7239

  • Fuel-related APIs on Store have been refactored and reimplemented with two new methods set_fuel and reset_fuel. Previous methods have been removed. #7240 #7298

  • The forward method of WASI streams has been removed. #7234

  • The WebAssembly threads, multi-memory, and relaxed-simd proposals are now enabled by default. #7285

  • Logging is now implemented for wasmtime serve. #7366

  • Filesystem locking has been temporarily removed from WASI. #7355

  • Wasmtime's implementation of WASI preview1 built on top of preview2 (-Spreview2) has been enabled by default. #7365

  • The wasi:clocks interface now has two subscribe functions and a duration type. #7358

  • The wasi:io/poll interface has seen some refactoring. #7427

Fixed

  • Profiling the first function in a module now works. #7254

  • Consecutive writes to files in preview2 have been fixed. #7394

  • Copy-on-write initialization of linear memories has been fixed for components. #7459

Cranelift

  • Support for proof-carrying code has been added to Cranelift to assist with an extra layer of validation about properties such as WebAssembly memory accesses in the future. #7165 #7180 #7219 #7231 #7262 #7263 #7274 #7280 #7281 #7352 #7389 #7468

  • Rematerialization of values no longer accidentally overrides LICM. #7306

  • Inline stack probes no longer make Valgrind unhappy. #7470

14.0.4

Released 2023-11-01

Fixed

  • Using the --dir argument combined with a ::-remapped path no longer prints a warning about compatibility with the old CLI and works with remapping. #7416

  • Consecutive file writes in preview2 have been fixed. #7394

14.0.3

Released 2023-10-29

Fixed

  • The wasmtime executable will now attempt to more gracefully handle the transition from the 13.0.0 CLI arguments and parsing to the changes in 14.0.0. CLI commands should now warn if they no longer work with the new parser, but still execute as they previously did. This behavior can be controlled via a new WASMTIME_NEW_CLI environment variable if necessary. #7385

  • The serve subcommand of the wasmtime CLI is now enabled by default for the wasmtime executable. #7392

14.0.2

Released 2023-10-26

Fixed

  • Make the wasmtime::unix module accessible on macOS again. #7360

  • Inter-crate dependencies between cranelift-* crates now disable the default feature meaning that it's possible for embedders to depend on cranelift-codegen as well without the default feature. #7369

14.0.1

Released 2023-10-23

Fixed

  • Cranelift: preserve uext and sext flags for parameters on x86_64 and apple aarch64. Note that this does not affect Wasmtime and is only intended for Cranelift embedders such as rustc_codegen_cranelift. #7333

14.0.0

Released 2023-10-20

One of the larger changes in this release is a redesign of Wasmtime's CLI arguments and where arguments are passed. This means that previous invocations of the wasmtime CLI executable will need to be updated. No functionality was removed but most of it is behind new flags. One major change is that Wasmtime CLI flags are now grouped behind short options like -O. For example

wasmtime run --opt-level 2 foo.wasm

is now:

wasmtime run -O opt-level=2 foo.wasm

Additionally options prefixed with --enable-* or --disable-* now consistently are considered boolean setters. For example:

wasmtime run --disable-cache foo.wasm

is now:

wasmtime run -C cache=n foo.wasm

Options can be explored with wasmtime -C help for example, and wasmtime -h will show all option groups that can be expanded.

Another major change in the CLI is that any CLI argument which positionally comes after the wasm file specified will be passed as an argument to the guest module. For example this invocations

wasmtime run foo.wasm --epoch-interruption

was previously accepted as enabling epoch interruption for the foo.wasm file. This is now interpreted as if it were ./foo.wasm --epoch-interruption, however, passing the flag to the wasm file itself. Flags to Wasmtime must now come after Wasmtime's subcommand (in this case run) and before the wasm file that's being run, for example:

wasmtime run -W epoch-interruption foo.wasm

More information about this change can be found on #6925 and #6946.

Added

  • Added the wasmtime::FrameInfo::module method, which returns the wasmtime::Module associated with the stack frame.

  • The wasmtime::component::Linker type now implements Clone. #7032

  • Wasmtime's TypedFunc API now supports the v128 WebAssembly type on x86_64 and aarch64. #7010

  • Support for resources exported from a WebAssembly guest has been added to the component bindgen! macro. #7050

  • The C API now supports learning about a module's image_range. #7064

  • Passing values between components is now possible with a more complete implementation of type-checking of values. #7065

  • Types representing resources can now be customized with bindgen!. #7069

  • Wasm-defined globals and memories are now included in core dumps, and the wasmtime::WasmCoreDump type is now serializable. #6935 #7078

  • Initial experimental support for Intel MPK has been added to support running more instances concurrently. #7072

  • The implementation of wasi:http now supports inbound requests in addition to outbound requests. A new wasmtime serve command is an example way of handling http requests with wasm files. #7091

  • The C API now supports Wasmtime's "host memory creation" API to customize the allocation of linear memories. #7115

  • The C API now supports asynchronous invocation of WebAssembly programs. #7106

  • The C API now supports Wasmtime's InstancePre<T> type. #7140

  • The wasi:sockets/ip-name-lookup interface is now implemented by Wasmtime. #7109

Changed

  • Wasmtime's CLI has been significantly overhauled. See the note above. #6925 #6946

  • The wasmtime::FrameInfo::module_name has been removed, however you can now get identical results by chaining wasmtime::FrameInfo::module and wasmtime::Module::name: my_frame.module().name().

  • WASI interfaces have seen significant work since the previous release. Streams for example have a new backpressure and flushing design. Additionally WIT resources are now used ubiquitously throughout the specification and implementation. #6877 #7029 #7090

  • The implementation of wasi:http now uses {input,output}-stream from the wasi:io/streams interface. #7056

  • Lifting and lowering of the list<u8> component values has been significantly optimized. #6971

  • The wasmtime-c-api crate is now additionally built as an rlib as well as the previous cdylib/staticlib combo. #6765

Fixed

  • Support referencing stack slots in the DWARF debug info. #6960

  • Printing unicode to stdio on Windows has been fixed. #6825

  • Building for x86_64-linux-android has been fixed. #7055

  • Fixed stdout/stderr becoming nonblocking by accident with WASI preview2 on macOS. #7058

  • Fixed some character boundary-related panics in the preview2 implementation of preview1. #7011

  • Fixed an issue of guests sleeping for an incorrect amount of time with preview2. #6993

  • Cranelift will now return an error when running out of temporaries in a very large function instead of panicking. #7114

13.0.1

Released 2023-10-26

Fixed

  • Make the wasmtime::unix module accessible on macOS again. #7360

13.0.0

Released 2023-09-20

Added

  • Configuration of mach ports vs signals on macOS is now done through a Config instead of at compile time. #6807

  • Engine::detect_precompiled{,_file} can be used to to determine whether some bytes or a file look like a precompiled module or a component. #6832 #6937

  • A new feature "wmemcheck" has been added to enable Valgrind-like detection of use-after-free within a WebAssembly guest module. #6820 #6856

  • The wasmtime CLI now supports executing components. #6836

  • Support for WASI preview2's TCP sockets interface has been added. #6837

  • Wasmtime's implementation of the wasi-nn proposal now supports named models. #6854

  • The C API now supports configuring native_unwind_info, dynamic_memory_reserved_for_growth, target, and Cranelift settings. #6896 #6934

  • The wasmtime crate now has initial support for component model bindings generation for the WIT resource type. #6886

  • Cranelift's RISC-V backend now has a complete implementation of the WebAssembly SIMD proposal. Many thanks to Afonso Bordado for all their contributions! #6920 #6924

  • The bindgen! macro in the wasmtime crate now supports conditional configuration for which imports should be async and which should be synchronous. #6942

Changed

  • The pooling allocator was significantly refactored and the PoolingAllocationConfig has some minor breaking API changes that reflect those changes.

    Previously, the pooling allocator had count slots, and each slot had N memories and M tables. Every allocated instance would reserve those N memories and M tables regardless whether it actually needed them all or not. This could lead to some waste and over-allocation when a module used less memories and tables than the pooling allocator's configured maximums.

    After the refactors in this release, the pooling allocator doesn't have one-size-fits-all slots anymore. Instead, memories and tables are in separate pools that can be allocated from independently, and we allocate exactly as many memories and tables as are necessary for the instance being allocated.

    To preserve your old configuration with the new methods you can do the following:

    let mut config = PoolingAllocationConfig::default();

// If you used to have this old, no-longer-compiling configuration:
config.count(count);
config.instance_memories(n);
config.instance_tables(m);

// You can use these equivalent settings for the new config methods:
config.total_core_instances(count);
config.total_stacks(count); // If using the `async` feature.
config.total_memories(count * n);
config.max_memories_per_module(n);
config.total_tables(count * m);
config.max_tables_per_module(m);

    There are additionally a variety of methods to limit the maximum amount of resources a single core Wasm or component instance can take from the pool:

    • PoolingAllocationConfig::max_memories_per_module
    • PoolingAllocationConfig::max_tables_per_module
    • PoolingAllocationConfig::max_memories_per_component
    • PoolingAllocationConfig::max_tables_per_component
    • PoolingAllocationConfig::max_core_instances_per_component

    These methods do not affect the size of the pre-allocated pool. #6835

  • Builder methods for WASI contexts now use &mut self instead of self. #6770

  • Native unwinding information is now properly disabled when it is configured to be turned off. #6547

  • Wasmtime's minimum supported Rust version (MSRV) is now 1.70.0. Wasmtime's MSRV policy of supporting the last three releases of Rust (N-2) is now additionally documented. More discussion can additionally be found on the PR itself. #6900

  • Wasmtime's support for DWARF debugging information has seen some fixes for previously reported crashes. #6931

Removed

  • Wasmtime's experimental implementation of wasi-crypto has been removed. More discussion of this change can be found on #6732 and #6816

  • Support for union types in the component model has been removed. #6913

12.0.2

Released 2023-09-14.

Fixed

  • CVE-2023-41880 - Miscompilation of wasm i64x2.shr_s instruction with constant input on x86_64

12.0.1

Released 2023-08-24

Fixed

  • Optimized the cranelift compilation on aarch64 for large wasm modules. #6804

12.0.0

Released 2023-08-21

Added

  • Wasmtime now supports having multiple different versions of itself being linked into the same final executable by mangling some C symbols used by Wasmtime. #6673

  • The perfmap profiling option is now supported on any Unix platform instead of just Linux. #6701

  • The wasmtime CLI now supports --env FOO to inherit the value of the environment variable FOO which avoids needing to do --env FOO=$FOO for example. #6746

  • Wasmtime now supports component model resources, although support has not yet been added to bindgen!. #6691

  • Wasmtime now supports configuration to enable the tail calls proposal. Platform support now also includes AArch64 and RISC-V in addition to the previous x86_64 support. #6723 #6749 #6774

  • Wasmtime's implementation of WASI Preview 2 now supports streams/pollables with host objects that are all backed by Rust async. #6556

  • Support for core dumps has now been added to the wasmtime crate. #6513

  • New {Module,Component}::resources_required APIs allow inspecting what will be required when instantiating the module or component. #6789

Fixed

  • Functions on instances defined through component::Linker::func_new are now defined correctly. #6637

  • The async_stack_size configuration option is no longer inspected when async_support is disabled at runtime. #6771

  • WASI Preview 1 APIs will now trap on misaligned or out-of-bounds pointers instead of returning an error. #6776

Changed

  • Empty types are no longer allowed in the component model. #6777

11.0.2

Released 2023-09-14.

Fixed

  • CVE-2023-41880 - Miscompilation of wasm i64x2.shr_s instruction with constant input on x86_64

11.0.1

Released 2023-07-24.

Fixed

  • Update some minimum version requirements for Wasmtime's dependencies to fix building Wasmtime with historical versions of these dependencies. #6758

11.0.0

Released 2023-07-20

Changed

  • The WASI Preview 2 WasiCtxBuilder type has been refactored, and WasiCtx now has private fields. #6652

  • Component bindgen! now generates owned types by default instead of based on how they're used #6648

  • Wasmtime/Cranelift on x86-64 can now execute Wasm-SIMD on baseline SSE2, which all x86-64 processors support (as part of the base x86-64 spec). Previously, SSE4.2 extensions were required. This new work allows Wasm with SIMD extensions to execute on processors produced back to 2003. #6625

Fixed

  • Only export the top-level preview2 module from wasmtime-wasi when the preview2 feature is enabled. #6615

Cranelift changes

10.0.2

Released 2023-09-14.

Fixed

  • CVE-2023-41880 - Miscompilation of wasm i64x2.shr_s instruction with constant input on x86_64

10.0.1

Released 2023-06-21

Fixed

  • Only export the top-level preview2 module from wasmtime-wasi when the preview2 feature is enabled. #6615

10.0.0

Released 2023-06-20

Added

  • Expose the Config::static_memory_forced option through the C api #6413

  • Basic guest-profiler documentation for the book #6394

  • Merge the initial wasi-preview2 implementation #6391

  • The wasi-preview2 component adapter has been pulled into the main wasmtime repository. It is available for the first time as part of this release, but should be treated as as a beta at this time. Patch releases will not be made for bug fixes. #6374

  • A callback invoked when an epoch deadline is reached can now be configured via the C API. #6359

  • PR auto-assignment policies have been documented, to clarify the expectations of reviewers. #6346

  • Support for the function references has been added #5288

Changed

  • An epoch_deadline_callback now returns an UpdateDeadline enum to allow optionally yielding to the async executor after the callback runs. #6464

  • The --profile-guest flag has now been folded into --profile=guest #6352

  • Initializers are no longer tracked in the type information for globals, and instead are provided when creating the global. #6349

  • The "raw" representation of funcref and externref in the embedding API has been updated from a usize to a *mut u8 to be compatible with Rust's proposed strict provenance rules. This change is additionally reflected into the C API as well. #6338

Fixed

  • Fixed a soundness issue with the component model and async #6509

  • Opening directories with WASI on Windows with NONBLOCK in flags has been fixed. #6348

Cranelift changes

9.0.3

Released 2023-05-31.

Fixed

  • Fix Wasi rights system to work with wasi-testsuite, which exposed a corner case that was missed by the fixes in the 9.0.2 release. #6479

9.0.2

Released 2023-05-26.

Fixed

  • Fix Wasi rights system to work with wasi-libc. This regression was introduced in the 9.0.0 release. #6462 #6471

9.0.1

Released 2023-05-22.

Fixed

  • A panic which happened when enabling support for native platform profilers was fixed. #6435

9.0.0

Released 2023-05-22.

Added

  • Initial integration of the Winch baseline compiler into Wasmtime is implemented. Note that Winch still does not support much of WebAssembly, but intrepid explorers may have an easier time playing around with it now. #6119

  • The wasmtime CLI now has flags to limit memory, instances, and tables. For example --max-memory-size or --max-tables. Additionally it has a new --trap-on-grow-failure option to force a trap whenever a memory.grow would otherwise fail which can be useful for debugging modules which may be encountering OOM. #6149

  • An initial implementation of the wasi-http proposal was added to Wasmtime in the shape of a new wasmtime-wasi-http crate and a --wasi-modules=experimental-wasi-http CLI flag. Note that this is not on-by-default and still in an experimental status at this time. #5929

  • Wasmtime's bindgen! macro for components now has interfaces and with options to configure use of interfaces defined externally in separate crates. #6160 #6210

  • Wasmtime's bindgen! macro emits trace events for arguments and results when enabled. #6209

  • A new Engine::precompile_compatibility_hash method has been added to assist with hashing artifacts to be compatible with versions of Wasmtime. #5826

  • Wasmtime's C API now has functions for enabling the WebAssembly relaxed-simd proposal. #6292

  • A new --emit-clif flag has been added to wasmtime compile to see the CLIF corresponding to a WebAssembly module to be used for debugging. #6307

  • Support for an in-process sampling-based profiler has been added to Wasmtime. This is intended to be used in conjunction with epochs to enable relatively simple implementations of profiling a guest module. #6282

Changed

  • Overhauled the way that Wasmtime calls into Wasm and Wasm calls back out to the host. Instead of chaining together trampolines to convert between calling conventions, we now represent funcrefs with multiple function pointers, one per calling convention. This paves the way for supporting Wasm tail calls and also results in ~10% speed ups to a variety of function call benchmarks, however there are some slight compiled Wasm module code size regressions (which can be alleviated by disabling optional .eh_frame generation). Additionally, in the C API the wasmtime_func_call_unchecked function gained one more parameter, which is the capacity of the args-and-results buffer. #6262

  • The wasmtime compile command will now default to producing executables for the native host and its CPU features instead of the baseline feature set of the host's architecture. #6152

  • The ResourceLimiter trait and its async equivalent now support returning errors from growth to force a trap in the wasm module rather than reporting -1 to the wasm module. Note that this is primarily intended for debugging. #6149

  • The non-egraph-based optimization pipeline has been removed from Cranelift, and the corresponding Config::use_egraphs option is also removed. #6167

  • Generated types for WIT files now always generates owned types by default. #6189

  • Wasmtime's baseline x86_64 CPU features required for SIMD support has been lowered from SSE 4.2 to SSE 4.1. #6206

  • The fd_allocate implementation in Wasmtime will now always fail with ENOTSUP. #6217

  • The "rights" system in WASI has been removed and rights are no longer inspected in the implementation of any WASI functions. #6265

Fixed

  • WASI can now open directories without O_DIRECTORY. #6163

  • The poll_oneoff function has been fixed when handling non-regular files. #6258

  • The behavior of path_readlink on too-small buffers has been fixed to truncate. #6225

Cranelift changes

Note: this section documents changes to Cranelift, a code generator backend that Wasmtime uses. These changes are not always applicable to Wasmtime as a WebAssembly runtime but may be interesting to other projects which embed or use Cranelift.

  • New {u,s}{add,sub,mul}_overflow instructions have been added. #5784

  • The iadd_cout and isub_bout instructions have been removed. #6198

  • ISLE now supports binary and octal integer literals. #6234

  • An implementation of SIMD for RISC-V has started. #6240 #6266 #6268

8.0.1

Released 2023-04-27.

Changed

  • Breaking: Files opened using Wasmtime's implementation of WASI on Windows now cannot be deleted until the file handle is closed. This was already true for open directories. The change was necessary for the bug fix in #6163.

Fixed

  • Fixed wasi-common's implementation of the O_DIRECTORY flag to match POSIX. #6163

  • Undefined Behavior in Rust runtime functions GHSA-ch89-5g45-qwc7

8.0.0

Released 2023-04-20

Added

  • Allow the MPL-2.0 and OpenSSL licenses in dependencies of wasmtime. #6136

  • Add a bounds-checking optimization for dynamic memories and guard pages. #6031

  • Add support for generating perf maps for simple perf profiling. Additionally, the --jitdump and --vtune flags have been replaced with a single --profile flags that accepts perfmap, jitdump, and vtune arguments. #6030

  • Validate faulting addresses are valid to fault on. As a mitigation to CVEs like GHSA-ff4p-7xrq-q5r8, check that the address involved in a fault is one that could be contained in a Store, or print a scary message and abort immediately. #6028

  • Add the --default-values-unknown-imports option to define unknown function imports as functions that return the default value for their result type. #6010

  • Add Clone for component::InstancePre. #5996

  • Add --dynamic-memory-reserved-for-growth cli flag. #5980

  • Introduce the wasmtime-explorer crate for investigating the compilation of wasm modules. This functionality is also exposed via the wasmtime explore command. #5975

  • Added support for the Relaxed SIMD proposal. #5892

  • Cranelift gained many new machine-independent optimizations. #5909 #6032 #6033 #6034 #6037 #6052 #6053 #6072 #6095 #6130

Changed

Fixed

7.0.1

Released 2023-04-27.

Fixed

7.0.0

Released 2023-03-20

Added

  • An initial implementation of the wasi-threads proposal has been implemented and landed in the Wasmtime CLI. This is available behind a --wasi-modules experimental-wasi-threads flag. #5484

  • Support for WASI sockets has been added to the C API. #5624

  • Support for limiting Store-based resource usage, such as memory, tables, etc, has been added to the C API. #5761

  • A top level alias of anyhow::Result as wasmtime::Result has been added to avoid the need to explicitly depend on anyhow. #5853

  • Initial support for the WebAssembly core dump format has been added to the CLI with a --coredump-on-trap flag. #5868

Changed

  • The S type parameter on component-related methods has been removed. #5722

  • Selection of a world to bindgen has been updated to select any default world in a WIT package if there is only one. #5779

  • WASI preopened file descriptors can now be closed. #5828

  • The host traits generated by the bindgen! macro are now always named Host, but are still scoped to each individual module. #5890

Fixed

  • Components which have type imports are now supported better and error/panic in fewer cases. #5777

  • Types referred to by wasmtime::component::Val are now reexported under wasmtime::component. #5790

  • A panic due to a race between memory.atomic.{wait32,wait64,notify} instructions has been fixed. #5871

  • Guest-controlled out-of-bounds read/write on x86_64 GHSA-ff4p-7xrq-q5r8

  • Miscompilation of i8x16.select with the same inputs on x86_64 GHSA-xm67-587q-r2vw

6.0.2

Released 2023-04-27.

Fixed

6.0.1

Released 2023-03-08.

Fixed

6.0.0

Released 2023-02-20

Added

  • Wasmtime's built-in cache can now be disabled after being enabled previously. #5542

  • Older x86_64 CPUs, without SSE4.1 for example, are now supported when the wasm SIMD proposal is disabled. #5567

  • The Wasmtime C API now has WASMTIME_VERSION_* macros defined in its header files. #5651

  • The wasmtime CLI executable as part of Wasmtime's precompiled release artifacts now has the all-arch feature enabled. #5657

Changed

  • Equality of wasmtime::component::Val::Float{32,64} now considers NaNs as equal for assistance when fuzzing. #5535

  • WIT syntax supported by wasmtime::component::bindgen! has been updated in addition to the generated code being updated. #5565 #5692 #5694

  • Cranelift's egraph-based optimization framework is now enabled by default. #5587

  • The old PoolingAllocationStrategy type has been removed in favor of a more flexible configuration via a new option PoolingAllocationConfig::max_unused_warm_slots which is more flexible and subsumes the previous use cases for each strategy. #5661

  • Creation of InstancePre through Linker::instantiate_pre no longer requires a Store to be provided. Instead a Store-related argument is now required on Linker::define-style APIs instead. #5683

Fixed

  • Compilation for FreeBSD on x86_64 and AArch64 has been fixed. #5606

5.0.1

Released 2023-03-08.

Fixed

5.0.0

Released 2023-01-20

Added

  • A wasmtime::component::bingen! macro has been added for generating bindings from *.wit files. Note that WIT is still heavily in development so this is more of a preview of what will be as opposed to a finished feature. #5317 #5397

  • The wasmtime settings CLI command now has a --json option for machine-readable output. #5411

  • Wiggle-generated bindings can now generate the trait for either &mut self or &self. #5428

  • The wiggle crate has more convenience APIs for working with guest data that resides in shared memory. #5471 #5475

Changed

  • Cranelift's egraph support has been rewritten and updated. This functionality is still gated behind a flag and may become the default in the next release. #5382

  • The implementation of codegen for WebAssembly linear memory has changed significantly internally in Cranelift, moving more responsibility to the Wasmtime embedding rather than Cranelift itself. This should have no user-visible change, however. #5386

  • The Val::Float32 and Val::Float64 variants for components now store f32 and f64 instead of the bit representation. #5510

Fixed

  • Handling of DWARF debugging information in components with multiple modules has been fixed to ensure the right info is used for each module. #5358

4.0.1

Released 2023-03-08.

Fixed

4.0.0

Released 2022-12-20

Added

  • Dynamic memories are now supported with the pooling instance allocator which can possibly reduce the number of page faults throughout execution at the cost of slower to run code. Page faults are primarily reduced by avoiding releasing memory back to the system, relying on bounds checks to keep the memory inaccessible. #5208

  • The wiggle generator now supports function-level control over tracing calls. #5194

  • Support has been added to wiggle to be compatible with shared memories. #5225 #5229 #5264 #5268 #5054

  • The wiggle generator now supports a "trappable error" configuration to improve error conversions to guest errors and ensure that no host errors are forgotten or accidentally become traps. The wasi-common crate has been updated to use this. #5276 #5279

  • The memory.atomic.{notify,wait32,wait64} instructions are now all implemented in Wasmtime. #5255 #5311

  • A wasm_config_parallel_compilation_set configuration function has been added to the C API. #5298

  • The wasmtime CLI can have its input module piped into it from stdin now. #5342

  • WasmBacktrace::{capture,force_capture} methods have been added to programmatically capture a backtrace outside of a trapping context. #5341

Changed

  • The S type parameter on Func::typed and Instance::get_typed_func has been removed and no longer needs to be specified. #5275

  • The SharedMemory::data method now returns &[UnsafeCell<u8>] instead of the prior raw slice return. #5240

  • Creation of a WasiCtx will no longer unconditionally acquire randomness from the OS, instead using the rand::thread_rng() function in Rust which is only periodically reseeded with randomness from the OS. #5244

  • Codegen of dynamically-bounds-checked wasm memory accesses has been improved. #5190

  • Wasmtime will now emit inline stack probes in generated functions for x86_64, aarch64, and riscv64 architectures. This guarantees a process abort if an engine was misconfigured to give wasm too much stack instead of optionally allowing wasm to skip the guard page. #5350 #5353

Fixed

  • Dropping a Module will now release kernel resources in-use by the pooling allocator when enabled instead of waiting for a new instance to be re-instantiated into prior slots. #5321

3.0.1

Released 2022-12-01.

Fixed

  • The instruction cache is now flushed for AArch64 Android. #5331

  • Building for FreeBSD and Android has been fixed. #5323

3.0.0

Released 2022-11-21

Added

  • New WasiCtx::{push_file, push_dir} methods exist for embedders to add their own objects. #5027

  • Wasmtime's component-model support now supports async host functions and embedding in the same manner as core wasm. #5055

  • The wasmtime CLI executable now supports a --max-wasm-stack flag. #5156

  • AOT compilation support has been implemented for components (aka the component-model feature of the Wasmtime crate). #5160

  • A new wasi_config_set_stdin_bytes function is available in the C API to set the stdin of a WASI-using module from an in-memory slice. #5179

  • When using the pooling allocator there are now options to reset memory with memset instead of madvisev on Linux to keep pages resident in memory to reduce page faults when reusing linear memory slots. #5207

Changed

  • Consuming 0 fuel with 0 fuel left is now considered to succeed. Additionally a store may not consume its last unit of fuel. #5013

  • A number of variants in the wasi_common::ErrorKind enum have been removed. #5015

  • Methods on WasiDir now error-by-default instead of requiring a definition by default. #5019

  • Bindings generated by the wiggle crate now always depend on the wasmtime crate meaning crates like wasi-common no longer compile for platforms such as wasm32-unknown-emscripten. #5137

  • Error handling in the wasmtime crate's API has been changed to primarily work with anyhow::Error for custom errors. The Trap type has been replaced with a simple enum Trap { ... } and backtrace information is now stored as a WasmBacktrace type inserted as context into an anyhow::Error. Host-functions are expected to return anyhow::Result<T> instead of the prior Trap error return from before. Additionally the old Trap::i32_exit constructor is now a concrete wasi_commont::I32Exit type which can be tested for with a downcast_ref on the error returned from Wasmtime. #5149

  • Configuration of the pooling allocator is now done through a builder-style PoolingAllocationConfig API instead of the prior enum-variant API. #5205

Fixed

  • The instruction cache is now properly flushed for AArch64 on Windows. #4997

  • Backtrace capturing with many sequences of wasm->host calls on the stack no longer exhibit quadratic capturing behavior. #5049

2.0.2

Released 2022-11-10.

Fixed

  • CVE-2022-39392 - modules may perform out-of-bounds reads/writes when the pooling allocator was configured with memory_pages: 0.

  • CVE-2022-39393 - data can be leaked between instances when using the pooling allocator.

  • CVE-2022-39394 - An incorrect Rust signature for the C API wasmtime_trap_code function could lead to an out-of-bounds write of three zero bytes.

2.0.1

Released 2022-10-27.

Fixed

  • A compilation error when building only the wasmtime crate on Windows with only the default features enabled has been fixed. #5134

Changed

  • The rayon dependency added to cranelift-isle in 2.0.0 has been removed to improve the compile time of the cranelift-codegen crate. #5101

2.0.0

Released 2022-10-20

Added

  • Cranelift has gained support for forward-edge CFI on the AArch64 backend. #3693

  • A --disable-parallel-compilation CLI flag is now implemented for wasmtime. #4911

  • Tier 3 support has been added for for RISC-V 64 with a new backend in Cranelift for this architecture. #4271

  • Basic tier 3 support for Windows ARM64 has been added but features such as traps don't work at this time. #4990

Changed

  • The implementation of the random_get function in wasi-common is now faster by using a userspace CSPRNG rather than the OS for randomness. #4917

  • The AArch64 backend has completed its transition to ISLE. #4851 #4866 #4898 #4884 #4820 #4913 #4942 #4943

  • The size of the sigaltstack allocated per-thread for signal handling has been increased from 16k to 64k. #4964

1.0.2

Released 2022-11-10.

Fixed

  • CVE-2022-39392 - modules may perform out-of-bounds reads/writes when the pooling allocator was configured with memory_pages: 0.

  • CVE-2022-39393 - data can be leaked between instances when using the pooling allocator.

  • CVE-2022-39394 - An incorrect Rust signature for the C API wasmtime_trap_code function could lead to an out-of-bounds write of three zero bytes.

1.0.1

Released 2022-09-26

This is a patch release that incorporates a fix for a miscompilation of an atomic-CAS operator on aarch64. The instruction is not usable from Wasmtime with default settings, but may be used if the Wasm atomics extension is enabled. The bug may also be reachable via other uses of Cranelift. Thanks to @bjorn3 for reporting and debugging this issue!

Fixed

  • Fixed a miscompilation of atomic_cas on aarch64. The output register was swapped with a temporary register in the register-allocator constraints. #4959 #4960

1.0.0

Released 2022-09-20

This release marks the official 1.0 release of Wasmtime and represents the culmination of the work amongst over 300 contributors. Wasmtime has been battle-tested in production through multiple embeddings for quite some time now and we're confident in releasing a 1.0 version to signify the stability and quality of the Wasmtime engine.

More information about Wasmtime's 1.0 release is on the Bytecode Alliance's blog with separate posts on Wasmtime's performance features, Wasmtime's security story, and the 1.0 release announcement.

As a reminder the 2.0 release of Wasmtime is scheduled for one month from now on October 20th. For more information see the RFC on Wasmtime's 1.0 release.

Added

  • An incremental compilation cache for Cranelift has been added which can be enabled with Config::enable_incremental_compilation, and this option is disabled by default for now. The incremental compilation cache has been measured to improve compile times for cold uncached modules as well due to some wasm modules having similar-enough functions internally. #4551

  • Source tarballs are now available as part of Wasmtime's release artifacts. #4294

  • WASI APIs that specify the REALTIME clock are now supported. #4777

  • WASI's socket functions are now fully implemented. #4776

  • The native call stack for async-executed wasm functions are no longer automatically reset to zero after the stack is returned to the pool when using the pooling allocator. A Config::async_stack_zeroing option has been added to restore the old behavior of zero-on-return-to-pool. #4813

  • Inline stack probing has been implemented for the Cranelift x64 backend. #4747

Changed

  • Generating of native unwind information has moved from a Config::wasm_backtrace option to a new Config::native_unwind_info option and is enabled by default. #4643

  • The memory-init-cow feature is now enabled by default in the C API. #4690

  • Back-edge CFI is now enabled by default on AArch64 macOS. #4720

  • WASI calls will no longer return NOTCAPABLE in preparation for the removal of the rights system from WASI. #4666

Internal

This section of the release notes shouldn't affect external users since no public-facing APIs are affected, but serves as a place to document larger changes internally within Wasmtime.

0.40.0

Released 2022-08-20

This was a relatively quiet release in terms of user-facing features where most of the work was around the internals of Wasmtime and Cranelift. Improvements internally have been made along the lines of:

  • Many more instructions are now implemented with ISLE instead of handwritten lowerings.
  • Many improvements to the cranelift-based fuzzing.
  • Many platform improvements for s390x including full SIMD support, running rustc_codegen_cranelift with features like i128, supporting more ABIs, etc.
  • Much more of the component model has been implemented and is now fuzzed.

Finally this release is currently scheduled to be the last 0.* release of Wasmtime. The upcoming release of Wasmtime on September 20 is planned to be Wasmtime's 1.0 release. More information about what 1.0 means for Wasmtime is available in the 1.0 RFC

Added

  • Stack walking has been reimplemented with frame pointers rather than with native unwind information. This means that backtraces are feasible to capture in performance-critical environments and in general stack walking is much faster than before. #4431

  • The WebAssembly simd proposal is now fully implemented for the s390x backend. #4427

  • Support for AArch64 has been added in the experimental native debuginfo support that Wasmtime has. #4468

  • Support building the C API of Wasmtime with CMake has been added. #4369

  • Clarification was added to Wasmtime's documentation about "tiers of support" for various features. #4479

Fixed

  • Support for filestat_get has been improved for stdio streams in WASI. #4531

  • Enabling the vtune feature no longer breaks builds on AArch64. #4533

0.39.1

Released 2022-07-20.

Fixed

  • An s390x-specific codegen bug in addition to a mistake introduced in the fix of CVE-2022-31146 were fixed. #4490

0.39.0

Released 2022-07-20

Added

  • Initial support for shared memories and the threads WebAssembly proposal has been added. Note that this feature is still experimental and not ready for production use yet. #4187

  • A new Linker::define_unknown_imports_as_traps method and --trap-unknown-imports CLI flag have been added to conveniently support running modules with imports that aren't dynamically called at runtime. #4312

  • The VTune profiling strategy can now be selected through the C API. #4316

Changed

  • Some methods on the Config structure now return &mut Self instead of Result<&mut Self> since the validation is deferred until Engine::new: profiler, cranelift_flag_enable, cranelift_flag_set, max_wasm_stack, async_stack_size, and strategy. #4252 #4262

  • Parallel compilation of WebAssembly modules is now enabled in the C API by default. #4270

  • Implicit Cargo features of the wasmtime introduced through optional dependencies may have been removed since namespaced features are now used. It's recommended to only used the set of named [features] for Wasmtime. #4293

  • Register allocation has fixed a few issues related to excessive memory usage at compile time. #4324

Fixed

  • A refactor of Config was made to fix an issue that the order of calls to Config matters now, which may lead to unexpected behavior. #4252 #4262

  • Wasmtime has been fixed to work on SSE2-only x86_64 platforms when the simd feature is disabled in Config. #4231

  • Generation of platform-specific unwinding information is disabled if wasm_backtrace and wasm_reference_types are both disabled. #4351

0.38.3

Released 2022-07-20.

Fixed.

  • An s390x-specific codegen bug in addition to a mistake introduced in the fix of CVE-2022-31146 were fixed. #4491

0.38.2

Released 2022-07-20.

Fixed.

  • A miscompilation when handling constant divisors on AArch64 has been fixed. CVE-2022-31169

  • A use-after-free possible with accidentally missing stack maps has been fixed. CVE-2022-31146

0.38.1

Released 2022-06-27.

Fixed.

  • A register allocator bug was fixed that could affect direct users of Cranelift who use struct-return (sret) arguments. The bug had to do with the handling of physical register constraints in the function prologue. No impact should be possible for users of Cranelift via the Wasm frontend, including Wasmtime. regalloc2#60 #4333

  • Lowering bugs for the i8x16.swizzle and select-with-v128-inputs instructions were fixed for the x86_64 code generator. Note that aarch64 and s390x are unaffected. #4334

  • A bug in the 8-bit lowering of integer division on x86-64 was fixed in Cranelift that could cause a register allocator panic due to an undefined value in a register. (The divide instruction does not take a register rdx as a source when 8 bits but the metadata incorrectly claimed it did.) No impact on Wasm/Wasmtime users, and impact on direct Cranelift embedders limited to compilation panics. #4332

0.38.0

Released 2022-06-21

Added

  • Enabling or disabling NaN canonicalization in generated code is now exposed through the C API. #4154

  • A user-defined callback can now be invoked when an epoch interruption happens via the Store::epoch_deadline_callback API. #4152

  • Basic alias analysis with redundant-load elimintation and store-to-load forwarding optimizations has been added to Cranelift. #4163

Changed

  • Traps originating from epoch-based interruption are now exposed as TrapCode::Interrupt. #4105

  • Binary builds for AArch64 now require glibc 2.17 and for s390x require glibc 2.16. Previously glibc 2.28 was required. #4171

  • The wasmtime::ValRaw now has all of its fields listed as private and instead constructors/accessors are provided for getting at the internal data. #4186

  • The wasm-backtrace Cargo feature has been removed in favor of a Config::wasm_backtrace runtime configuration option. Additionally backtraces are now only captured when an embedder-generated trap actually reaches a WebAssembly call stack. #4183

  • Usage of *_unchecked APIs for Func in the wasmtime crate and C API now take a usize parameter indicating the number of ValRaw values behind the associated pointer. #4192

Fixed

  • An improvement was made to the spill-slot allocation in code generation to fix an issue where some stack slots accidentally weren't reused. This issue was introduced with the landing of regalloc2 in 0.37.0 and may have resulted in larger-than-intended increases in stack frame sizes. #4222

0.37.0

Released 2022-05-20

Added

  • Updated Cranelift to use regalloc2, a new register allocator. This should result in ~20% faster compile times, and for programs that suffered from register-allocation pressure before, up to ~20% faster generated code. #3989

  • Pre-built binaries for macOS M1 machines are now available as release artifacts. #3983

  • Copy-on-write images of memory can now be manually initialized for a Module with an explicit method call, but it is still not required to call this method and will automatically otherwise happen on the first instantiation. #3964

Fixed

  • Using InstancePre::instantiate or Linker::instantiate will now panic as intended when used with an async-configured Store. #3972

Changed

  • The unsafe ValRaw type in the wasmtime crate now always stores its values in little-endian format instead of the prior native-endian format. Users of ValRaw are recommended to audit their existing code for usage to continue working on big-endian platforms. #4035

Removed

  • Support for Config::paged_memory_initialization and the uffd crate feature have been removed from the wasmtime crate. Users should migrate to using Config::memory_init_cow which is more portable and faster at this point. #4040

0.36.0

Released 2022-04-20

Added

  • Support for epoch-based interruption has been added to the C API. #3925

  • Support for disabling libunwind-based backtraces of WebAssembly code at compile time has been added. #3932

  • Async support for call hooks has been added to optionally execute "blocking" work whenever a wasm module is entered or exited relative to the host. #3876

Fixed

  • Loading a Module will now check, at runtime, that the compilation settings enabled in a Config are compatible with the native host. For example this ensures that if avx2 is enabled that the host actually has avx2 support. #3899

Removed

  • Support for Config::interruptable and InterruptHandle has been removed from the wasmtime crate. Users should migrate to using epoch-based interruption instead. #3925

  • The module linking implementation of Wasmtime has been removed to make room for the upcoming support for the component model. #3958

0.35.3

Released 2022-04-11.

Fixed

  • Backported a bugfix for an instruction lowering issue that could cause a regalloc panic due to an undefined register in some cases. No miscompilation was ever possible, but panics would result in a compilation failure. #4012

0.35.2

Released 2022-03-31.

Security Fixes

  • CVE-2022-24791: Fixed a use after free with externrefs and epoch interruption.

0.35.1

Released 2022-03-09.

Fixed

  • Fixed a bug in the x86-64 lowering of the uextend opcode for narrow (i8, i16) integer sources when the value is produced by one of several arithmetic instructions. #3906

0.35.0

Released 2022-03-07.

Added

  • The wasmtime_wasi::add_to_linker function now allows providing a context object of a custom type instead of wasmtime_wasi::WasiCtx, as long as that type implements the required WASI snapshot traits. This allows, for example, wrapping WasiCtx into a struct and providing custom implementations for those traits to override the default behaviour.

Changed

  • WebAssembly tables of funcref values are now lazily initialized which can, in some cases, greatly speed up instantiation of a module. #3733

  • The memfd feature in 0.34.0, now renamed to memory-init-cow, has been enabled by default. This means that, where applicable, WebAssembly linear memories are now initialized with copy-on-write mappings. Support from this has been expanded from Linux-only to include macOS and other Unix systems when modules are loaded from precompiled *.cwasm files on disk. #3777 #3778 #3787 #3819 #3831

  • Clarify that SSE 4.2 (and prior) is required for running WebAssembly code with simd support enabled on x86_64. #3816 #3817 #3833 #3825

  • Support for profiling with VTune is now enabled at compile time by default, but it remains disabled at runtime by default. #3821

  • The ModuleLimits type has been removed from the configuration of the pooling allocator in favor of configuring the total size of an instance allocation rather than each individual field. #3837

  • The native stack size allowed for WebAssembly has been decreased from 1 MiB to 512 KiB on all platforms to better accomodate running wasm on the main thread on Windows. #3861

  • The wasi-common crate now supports doing polls for both read and write interest on a file descriptor at the same time. #3866

Fixed

  • The Store::call_hook callback is now invoked when entering host functions defined with *_unchecked variants. #3881

Removed

  • The incomplete and unmaintained ARM32 backend has been removed from Cranelift. #3799

0.34.2

Released 2022-03-31.

Security Fixes

  • CVE-2022-24791: Fixed a use after free with externrefs and epoch interruption.

0.34.1

Released 2022-02-16.

Security Fixes

  • CVE-2022-23636: Fixed an invalid drop of a partially-initialized instance in the pooling instance allocator.

0.33.1

Released 2022-02-16.

Security Fixes

  • CVE-2022-23636: Fixed an invalid drop of a partially-initialized instance in the pooling instance allocator.

0.34.0

Released 2022-02-07.

Fixed

  • The wasi-common default implementation of some attributes of files has been updated to ensure that wasi-libc's isatty function works as intended. #3696

  • A benign debug assertion related to externref and garbage-collection has been fixed. #3734

Added

  • Function names are now automatically demangled when informing profilers of regions of JIT code to apply Rust-specific demangling rules if applicable. #3683

  • Support for profiling JIT-generated trampolines with VTune has been added. #3687

  • Wasmtime now supports a new method of async preemption dubbed "epoch-based interruption" which is intended to be much more efficient than the current fuel-based method of preemption. #3699

  • On Linux Wasmtime will now by default use copy-on-write mappings to initialize memories of wasm modules where possible, accelerating instantiation by avoiding costly memory copies. When combined with the pooling allocator this can also be used to speed up instance-reuse cases due to fewer syscalls to change memory mappings being necessary. #3697 #3738 #3760

  • Wasmtime now supports the recently-added sock_accept WASI function. #3711

  • Cranelift now has support for specifying blocks as cold. #3698

Changed

  • Many more instructions for the x64 backend have been migrated to ISLE, additionally with refactorings to make incorrect lowerings harder to accidentally write. #3653 #3659 #3681 #3686 #3688 #3690 #3752

  • More instructions in the aarch64 backend are now lowered with ISLE. #3658 #3662

  • The s390x backend's lowering rules are now almost entirely defined with ISLE. #3702 #3703 #3706 #3717 #3723 #3724

  • Instantiation of modules in Wasmtime has been further optimized now that the copy-on-write memory initialization removed the previously most-expensive part of instantiating a module. #3727 #3739 #3741 #3742

0.33.0

Released 2022-01-05.

Added

  • Compiled wasm modules may now optionally omit debugging information about mapping addresses to source locations, resulting in smaller binaries. #3598

  • The WebAssembly SIMD proposal is now enabled by default. #3601

0.32.1

Released 2022-01-04.

Fixed

  • Cranelift: remove recently-added build dependency on sha2 to allow usage in some dependency-sensitive environments, by computing ISLE manifest hashes with a different hash function. #3619

  • Cranelift: fixed 8- and 16-bit behavior of popcount (bit population count) instruction. Does not affect Wasm frontend. #3617

  • Cranelift: fixed miscompilation of 8- and 16-bit bit-rotate instructions. Does not affect Wasm frontend. #3610

0.32.0

Released 2021-12-13.

Added

  • A new configuration option has been added to force using a "static" memory style to automatically limit growth of memories in some configurations. #3503

  • The InstancePre<T> type now implements Clone. #3510

  • Cranelift's instruction selection process has begun to be migrated towards the ISLE compiler and definition language. #3506

  • A pooling-allocator feature has been added, which is on-by-default, to disable the pooling allocator at compile time. #3514

Fixed

  • A possible panic when parsing a WebAssembly name section has been fixed. #3509

  • Generating native DWARF information for some C-produced modules has been fixed, notably those where there may be DWARF about dead code. #3498

  • A number of SIMD code generation bugs have been fixed in the x64 backend by migrating their lowerings to ISLE.

0.31.0

Released 2021-10-29.

Added

  • New Func::new_unchecked and Func::call_unchecked APIs have been added with accompanying functions in the C API to improve the performance of calls into wasm and the host in the C API. #3350

  • Release binaries are now available for the s390x-unknown-linux-gnu architecture. #3372

  • A new ResourceLimiterAsync trait is added which allows asynchronous blocking of WebAssembly on instructions such as memory.grow. #3393

Changed

  • The Func::call method now takes a slice to write the results into rather than returning a boxed slice. #3319

  • Trampolines are now covered when jitdump profiling is enabled. #3344

Fixed

  • Debugging with GDB has been fixed on Windows. #3373

  • Some quadradic behavior in Wasmtime's compilation of modules has been fixed. #3469 #3466

  • Bounds-checks for wasm memory accesses in certain non-default configurations have been fixed to correctly allow loads at the end of the address space. #3462

  • When type-checking memories and tables for satisfying instance imports the runtime size of the table/memory is now consulted instead of the object's original type. #3450

Removed

  • The Lightbeam backend has been removed, as per RFC 14. #3390
  • Cranelift's old x86 backend has been removed, as per RFC 12. #3309

0.30.0

Released 2021-09-17.

Security Fixes

  • CVE-2021-39216: Fixed a use after free passing externrefs to Wasm in Wasmtime.

  • CVE-2021-39218: Fixed an out-of-bounds read/write and invalid free with externrefs and GC safepoints in Wasmtime.

  • CVE-2021-39219: Fixed a bug where using two different Engines with the same Linker-define functions caused unsafety without unsafe blocks.

Added

  • Added experimental support for the in-progress 64-bit memories Wasm proposal.

  • Added support to build Wasmtime without the compiler. This lets you run pre-compiled Wasm modules, without the ability (or potential attack surface) of compiling new Wasm modules. The compilation functionality is gated by the on-by-default cranelift cargo feature.

  • Added support for NaN canonicalization with SIMD vectors.

  • Added support for differential fuzzing against V8's Wasm engine.

  • Added support for fuzzing against the Wasm spec interpreter.

  • Enabled SIMD fuzzing on oss-fuzz.

Changed

  • A variety of performance improvements to loading pre-compiled modules.

  • A variety of performance improvements to function calls, both through Rust and the C API.

  • Leaf functions that do not use the stack no longer bump the frame pointer on aarch64 and s390x.

  • Many updates and expanded instruction support to the in-progress CLIF interpreter.

  • Expanded fuzzing of reference types and GC.

Fixed

  • A number of fixes to both aarch64 and x86_64 support for the Wasm SIMD proposal and the underlying CLIF vector instructions.

  • Fixed a potential infinite loop in the SSA computation for cranelift-frontend. This was not reachable from cranelift-wasm or Wasmtime, but might have affected general Cranelift users.

Removed

  • The wasmtime wasm2obj subcommand has been removed. Generating raw object files for linking natively is no longer supported. Use the wasmtime compile subcommand to pre-compile a Wasm module and wasmtime run to run pre-compiled Wasm modules.

0.29.0

Released 2021-08-02.

Changed

  • Instance exports are now loaded lazily from instances instead of eagerly as they were before. This is an internal-only change and is not a breaking change. #2984

  • All linear memories created by Wasmtime will now, by default, have guard pages in front of them in addition to after them. This is intended to help mitigate future bugs in Cranelift, should they arise. #2977

  • Linear memories now correctly support a maximum size of 4GB. Previously, the limit field was 32 bits, which did not properly support a full 4GB memory. This update is also a necessary change in preparation for future memory64 support. #3013 #3134

  • Injection counts of fuel into a wasmtime::Store now uses a u64 instead of a u32. #3048

Added

  • Support for i128 has improved in the AArch64 backend. #2959 #2975 #2985 #2990 #3002 #3004 #3005 #3008 #3027

  • The s390x backend now supports z14 and atomics. #2988 #2991

  • The wasmtime::Linker type now implements Clone. #2993

  • Support for the SIMD proposal on both x86_64 and AArch64 has improved. On x86_64, all SIMD opcodes are now supported. #2997 #3035 #2982 #3084 #3082 #3107 #3105 #3114 #3070 #3126

  • A Trap can now display its reason without also displaying the backtrace. #3033

  • An initiall fuzzer for CLIF has been added. #3038

  • High-level architecture documentation has been added for Wasmtime. #3019

  • Support for multi-memory can now be configured in Wasmtime's C API. #3071

  • The wasmtime crate now supports a posix-signals-on-macos feature to force the usage of signals instead of mach ports to handle traps on macOS. #3063

  • Wasmtime's C API now has a wasmtime_trap_code function to get the raw trap code, if present, for a trap. #3086

  • Wasmtime's C API now has a wasmtime_linker_define_func function to define a store-independent function within a linker. #3122

  • A wasmtime::Linker::module_async function was added as the asynchronous counterpart to wasmtime::Linker::module. #3121

Fixed

  • Compiling the wasmtime crate into a dylib crate type has been fixed. #3010

  • The enter/exit hooks for WebAssembly are now executed for an instance's start function, if present. #3001

  • Some WASI functions in wasi-common have been fixed for big-endian platforms. #3016

  • Wasmtime no longer erroneously assumes that all custom sections may contain DWARF information, reducing instances of Trap's Display implementation providing misleading information to set an env var to get more information. #3083

  • Some issues with parsing DWARF debug information have been fixed. #3116

0.28.0

Released 2021-06-09.

Changed

  • Breaking: Wasmtime's embedding API has been redesigned, as specified in RFC 11. Rust users can now enjoy easier times with Send and Sync, and all users can now more clearly manage memory, especially in the C API. Language embeddings have been updated to the new API as well. #2897

Added

  • A new InstancePre type, created with Linker::instantiate_pre, has been added to perform type-checking of an instance once and reduce the work done for each instantiation of a module: #2962

  • Deserialization of a module can now optionally skip checking the wasmtime version string: #2945

  • A method has been exposed to frontload per-thread initialization costs if the latency of every last wasm call is important: #2946

  • Hooks have been added for entry/exit into wasm code to allow embeddings to track time and other properties about execution in a wasm environment: #2952

  • A C++ embedding of Wasmtime has been written.

Fixed

  • Multiple returns on macOS AArch64 have been fixed: #2956

0.27.0

Released 2021-05-21.

Security Fixes

  • Fixed a security issue in Cranelift's x64 backend that could result in a heap sandbox escape due to an incorrect sign-extension: #2913.

Added

  • Support for IBM z/Archiecture (s390x) machines in Cranelift and Wasmtime: #2836, #2837, #2838, #2843, #2854, #2870, #2871, #2872, #2874.

  • Improved async support in wasi-common runtime: #2832.

  • Added Store::with_limits, StoreLimits, and ResourceLimiter to the Wasmtime API to help with enforcing resource limits at runtime. The ResourceLimiter trait can be implemented by custom resource limiters to decide if linear memories or tables can be grown.

  • Added allow-unknown-exports option for the run command: #2879.

  • Added API to notify that a Store has moved to a new thread: #2822.

  • Documented guidance around using Wasmtime in multithreaded contexts: #2812. In the future, the Wasmtime API will change to allow some of its core types to be Send/Sync; see the in-progress #2897 for details.

  • Support calls from native code to multiple-return-value functions: #2806.

Changed

  • Breaking: Memory::new has been changed to return Result as creating a host memory object is now a fallible operation when the initial size of the memory exceeds the store limits.

Fixed

  • Many instruction selection improvements on x64 and aarch64: #2819, #2828, #2823, #2862, #2886, #2889, #2905.

  • Improved performance of Wasmtime runtime substantially: #2811, #2818, #2821, #2847, #2900.

  • Fixed WASI issue with file metadata on Windows: #2884.

  • Fixed an issue with debug info and an underflowing (trapping) offset: #2866.

  • Fixed an issue with unwind information in the old x86 backend: #2845.

  • Fixed i32 spilling in x64 backend: #2840.

0.26.0

Released 2021-04-05.

Added

  • Added the wasmtime compile command to support AOT compilation of Wasm modules. This adds the Engine::precompile_module method. Also added the Config::target method to change the compilation target of the configuration. This can be used in conjunction with Engine::precompile_module to target a different host triple than the current one. #2791

  • Support for macOS on aarch64 (Apple M1 Silicon), including Apple-specific calling convention details and unwinding/exception handling using Mach ports. #2742, #2723

  • A number of SIMD instruction implementations in the new x86-64 backend. #2771

  • Added the Config::cranelift_flag_enable method to enable setting Cranelift boolean flags or presets in a config.

  • Added CLI option --cranelift-enable to enable boolean settings and ISA presets.

  • Deduplicate function signatures in Wasm modules. #2772

  • Optimize overheads of calling into Wasm functions. #2757, #2759

  • Improvements related to Module Linking: compile fewer trampolines;

    #2774

  • Re-export sibling crates from wasmtime-wasi to make embedding easier without needing to match crate versions. #2776

Changed

  • Switched the default compiler backend on x86-64 to Cranelift's new backend. This should not have any user-visible effects other than possibly runtime performance improvements. The old backend is still available with the old-x86-backend feature flag to the cranelift-codegen or wasmtime crates, or programmatically with BackendVariant::Legacy. We plan to maintain the old backend for at least one more release and ensure it works on CI. #2718

  • Breaking: Module::deserialize has been removed in favor of Module::new.

  • Breaking: Config::cranelift_clear_cpu_flags was removed. Use Config::target to clear the CPU flags for the host's target.

  • Breaking: Config::cranelift_other_flag was renamed to Config::cranelift_flag_set.

  • CLI changes:

    • Wasmtime CLI options to enable WebAssembly features have been replaced with a singular --wasm-features option. The previous options are still supported, but are not displayed in help text.
    • Breaking: the CLI option --cranelift-flags was changed to --cranelift-set.
    • Breaking: the CLI option --enable-reference-types=false has been changed to --wasm-features=-reference-types.
    • Breaking: the CLI option --enable-multi-value=false has been changed to --wasm-features=-multi-value.
    • Breaking: the CLI option --enable-bulk-memory=false has been changed to --wasm-features=-bulk-memory.

  • Improved error-reporting in wiggle. #2760

  • Make WASI sleeping fallible (some systems do not support sleep). #2756

  • WASI: Support poll_oneoff with a sleep. #2753

  • Allow a StackMapSink to be passed when defining functions with cranelift-module. #2739

  • Some refactoring in new x86-64 backend to prepare for VEX/EVEX (e.g., AVX-512) instruction encodings to be supported. #2799

Fixed

  • Fixed a corner case in srem (signed remainder) in the new x86-64 backend: INT_MIN % -1 should return 0, rather than trapping. This only occurred when avoid_div_traps == false was set by the embedding. #2763

  • Fixed a memory leak of the Store when an instance traps. #2803

  • Some fuzzing-related fixes. #2788, #2770

  • Fixed memory-initialization bug in uffd allocator that could copy into the wrong destination under certain conditions. Does not affect the default wasmtime instance allocator. #2801

  • Fix printing of float values from the Wasmtime CLI. #2797

  • Remove the ability for the Linker to instantiate modules with duplicate import strings of different types. #2789

0.25.0

Released 2021-03-16.

Added

  • An implementation of a pooling instance allocator, optionally backed by userfaultfd on Linux, was added to improve the performance of embeddings that instantiate a large number of instances continuously. #2518

  • Host functions can now be defined on Config to share the function across all Store objects connected to an Engine. This can improve the time it takes to instantiate instances in a short-lived Store. #2625

  • The Store object now supports having typed values attached to it which can be retrieved from host functions. #2625

  • The wiggle code generator now supports async host functions. #2701

Changed

  • The Func::getN{,_async} APIs have all been removed in favor of a new Func::typed API which should be more compact in terms of API surface area as well as more flexible in how it can be used. #2719

  • Engine::new has been changed from returning Engine to returning anyhow::Result<Engine>. Callers of Engine::new will need to be updated to use the ? operator on the return value or otherwise unwrap the result to get the Engine.

Fixed

  • Interpretation of timestamps in poll_oneoff for WASI have been fixed to correctly use nanoseconds instead of microseconds. #2717

0.24.0

Released 2021-03-04.

Added

  • Implement support for async functions in Wasmtime #2434

Fixed

  • Fix preservation of the sigaltstack on macOS #2676
  • Fix incorrect semver dependencies involving fs-set-times. #2705
  • Fix some i128 shift-related bugs in x64 backend. #2682
  • Fix incomplete trap metadata due to multiple traps at one address #2685

0.23.0

Released 2021-02-16.

Added

  • Support for limiting WebAssembly execution with fuel was added, including support in the C API. #2611 #2643
  • Wasmtime now has more knobs for limiting memory and table allocations #2617
  • Added a method to share Config across machines #2608
  • Added a safe memory read/write API #2528
  • Added support for the experimental wasi-crypto APIs #2597
  • Added an instance limit to Config #2593
  • Implemented module-linking's outer module aliases #2590
  • Cranelift now supports 128-bit operations for the new x64 backend. #2539
  • Cranelift now has detailed debug-info (DWARF) support in new backends (initially x64). #2565
  • Cranelift now uses the POPCNT, TZCNT, and LZCNT, as well as SSE 4.1 rounding instructions on x64 when available.
  • Cranelift now uses the CNT, instruction on aarch64 when available.

Changed

  • A new WASI implementation built on the new cap-std crate was added, replacing the previous implementation. This brings improved robustness, portability, and performance.

  • wasmtime_wasi::WasiCtxBuilder moved to wasi_cap_std_sync::WasiCtxBuilder.

  • The WebAssembly C API is updated, with a few minor API changes #2579

Fixed

  • Fixed a panic in WASI fd_readdir on large directories #2620
  • Fixed a memory leak with command modules #2017

0.22.0

Released 2021-01-07.

Added

Changed

Fixed

  • Fixed an issue where the select instruction didn't accept v128 SIMD operands. #2391

  • Fixed an issue where Wasmtime could potentially use the wrong stack map during GCs, leading to a panic. #2396

  • Fixed an issue where if a host-defined function erroneously returned a value from a different store, that value would be leaked. #2424

  • Fixed a bug where in certain cases if a module's instantiation failed, it could leave trampolines in the store that referenced the no-longer-valid instance. These trampolines could be reused in future instantiations, leading to use after free bugs. #2408

  • Fixed a miscompilation on aarch64 where certain instructions would read SP instead of the zero register. This could only affect you if you explicitly enabled the Wasm SIMD proposal. #2548

0.21.0

Released 2020-11-05.

Added

  • Experimental support for the multi-memory proposal was added. #2263

  • The Trap::trap_code API enables learning what kind of trap was raised. #2309

Changed

  • WebAssembly module validation is now parallelized. #2059

  • Documentation is now available at docs.wasmtime.dev. #2317

  • Windows now compiles like other platforms with a huge guard page instead of having its own custom limit which made modules compile and run more slowly. #2326

  • The size of the cache entry for serialized modules has been greatly reduced. #2321 #2322 #2324 #2325

  • The FuncType API constructor and accessors are now iterator-based. #2365

Fixed

  • A panic in compiling reference-types-using modules has been fixed. #2350

0.20.0

Released 2020-09-23.

Added

  • Support for explicitly serializing and deserializing compiled wasm modules has been added. #2020

  • A wasmtime_store_gc C API was added to run GC for externref. #2052

  • Support for atomics in Cranelift has been added. Support is not fully implemented in Wasmtime at this time, however. #2077

  • The Caller::get_export function is now implemented for Func references as well. #2108

Fixed

  • Leaks in the C API have been fixed. #2040

  • The wasm_val_copy C API has been fixed for reference types. #2041

  • Fix a panic with Func::new and reference types when the store doesn't have reference types enabled. #2039

0.19.0

Released 2020-07-14.

Added

Fixed

  • Runtime warnings when using Wasmtime on musl have been fixed. #1914

  • A bug affecting Windows unwind information with functions that have spilled floating point registers has been fixed. #1983

Changed

  • Wasmtime's default branch and development now happens on the main branch instead of master. #1924

Removed

  • The "host info" support in the C API has been removed since it was never fully or correctly implemented. #1922

  • Support for the *_same functions in the C API has been removed in the same vein as the host info APIs. #1926

0.18.0

Release 2020-06-09.

Added

The WasmTy trait is now implemented for u32 and u64.

#1808

0.17.0

Released 2020-06-01.

Added

  • The Commands and Reactors ABI is now supported in the Rust API. Linker::module loads a module and automatically handles Commands and Reactors semantics.

    #1565

The Table::grow function now returns the previous table size, making it consistent with the table.grow instruction.

#1653

New Wasmtime-specific C APIs for working with tables were added which provide more detailed error information and which make growing a table more consistent with the table.grow instruction as well.

#1654

The C API now includes support for enabling logging in Wasmtime.

#1737

Changed

The WASI proc_exit function no longer exits the host process. It now unwinds the callstack back to the wasm entrypoint, and the exit value is available from the Trap::i32_exit_status method.

#1646

The WebAssembly multi-value proposal is now enabled by default.

#1667

The Rust API does not require a store provided during Module::new operation. The Module can be send accross threads and instantiate for a specific store. The Instance::new now requires the store.

#1761

0.16.0

Released 2020-04-29.

Added

  • The Instance struct has new accessors, get_func, get_table, get_memory, and get_global for quickly looking up exported functions, tables, memories, and globals by name. #1524

  • The C API has a number of new wasmtime_* functions which return error objects to get detailed error information when an API fails. #1467

  • Users now have fine-grained control over creation of instances of Memory with a new MemoryCreator trait. #1400

  • Go bindings for Wasmtime are now available. #1481

  • APIs for looking up values in a Linker have been added. #1480

  • Preliminary support for AArch64, also known as ARM64. #1581

Changed

  • Instance::exports now returns Export objects which contain the names of the exports in addition to their Extern definitions, so it's no longer necessary to use Module::exports to obtain the export names. #1524

  • The Func::call API has changed its error type from Trap to anyhow::Error to distinguish between wasm traps and runtime violations (like the wrong number of parameters). #1467

  • A number of wasmtime_linker_* and wasmtime_config_* C APIs have new type signatures which reflect returning errors. #1467

  • Bindings for .NET have moved to https://github.com/bytecodealliance/wasmtime-dotnet. #1477

  • Passing too many imports to Instance::new is now considered an error. #1478

Fixed

  • Spurious segfaults due to out-of-stack conditions when handling signals have been fixed. #1315

0.15.0

Released 2020-03-31.

Fixed

Full release produced for all artifacts to account for hiccups in 0.13.0 and 0.14.0.

0.14.0

This version ended up not getting a full release

Fixed

Fix build errors in wasi-common on Windows.

0.13.0

Released 2020-03-24.

Added

  • Lots of documentation of wasmtime has been updated. Be sure to check out the book and API documentation!

  • All wasmtime example programs are now in a top-level examples directory and are available in both C and Rust. #1286

  • A wasmtime::Linker type was added to conveniently link link wasm modules together and create instances that reference one another. #1384

  • Wasmtime now has "jitdump" support enabled by default which allows profiling wasm code on linux. #1310

  • The wasmtime::Caller type now exists as a first-class way to access the caller's exports, namely memory, when implementing host APIs. This can be the first argument of functions defined with Func::new or Func::wrap which allows easily implementing methods which take a pointer into wasm memory. Note that this only works for accessing the caller's Memory for now and it must be exported. This will eventually be replaced with a more general-purpose mechanism like interface types. #1290

  • The bulk memory proposal has been fully implemented. #1264 #976

  • Virtual file support has been added to wasi-common. #701

  • The C API has been enhanced with a Wasmtime-specific wasmtime_wat2wasm to parse *.wat files via the C API. #1206

Changed

  • The wast and wasm2obj standalone binaries have been removed. They're available via the wasmtime wast and wasmtime wasm2obj subcommands. #1372

  • The wasi-common crate now uses the new wiggle crate to auto-generate a trait which is implemented for the current wasi snapshot. #1202

  • Wasmtime no longer has a dependency on a C++ compiler. #1365

  • The Func::wrapN APIs have been consolidated into one Func::wrap API. #1363

  • The Callable trait has been removed and now Func::new takes a closure directly. #1363

  • The Cranelift repository has been merged into the Wasmtime repository.

  • Support for interface types has been temporarily removed. #1292

  • The exit code of the wasmtime CLI has changed if the program traps. #1274

  • The wasmtime CLI now logs to stderr by default and the -d flag has been renamed to --log-to-file. #1266

  • Values cannot cross Store objects, meaning you can't instantiate a module with values from different stores nor pass values from different stores into methods. #1016

0.12.0

Released 2020-02-26.

Added

  • Support for the WebAssembly text annotations proposal has been added. #998

  • An initial C API for instantiating WASI modules has been added. #977

  • A new suite of Func::getN functions have been added to the wasmtime API to call statically-known function signatures in a highly optimized fashion. #955

  • Initial support for profiling JIT code through perf jitdump has been added. #360

  • More CLI flags corresponding to proposed WebAssembly features have been added. #917

Changed

  • The wasmtime CLI as well as embedding API will optimize WebAssembly code by default now. #973 #988

  • The verifier pass in Cranelift is now no longer run by default when using the embedding API. #882

Fixed

  • Code caching now accurately accounts for optimization levels, ensuring that if you ask for optimized code you're not accidentally handed unoptimized code from the cache. #974

  • Automated releases for tags should be up and running again, along with automatic publication of the wasmtime Python package. #971