20f510671d
* Enable passing host functions to components
This commit implements the ability to pass a host function into a
component. The `wasmtime::component::Linker` type now has a `func_wrap`
method allowing it to take a host function which is exposed internally
to the component and available for lowering.
This is currently mostly a "let's get at least the bare minimum working"
implementation. That involves plumbing around lots of various bits of
the canonical ABI and getting all the previous PRs to line up in this
one to get a test where we call a function where the host takes a
string. This PR also additionally starts reading and using the
`may_{enter,leave}` flags since this is the first time they're actually
relevant.
Overall while this is the bare bones of working this is not a final spot
we should end up at. One of the major downsides is that host functions
are represented as:
F: Fn(StoreContextMut<'_, T>, Arg1, Arg2, ...) -> Result<Return>
while this naively seems reasonable this critically doesn't allow
`Return` to actually close over any of its arguments. This means that if
you want to return a string to wasm then it has to be `String` or
`Rc<str>` or some other owned type. In the case of `String` this means
that to return a string to wasm you first have to copy it from the host
to a temporary `String` allocation, then to wasm. This extra copy for
all strings/lists is expected to be prohibitive. Unfortuantely I don't
think Rust is able to solve this, at least on stable, today.
Nevertheless I wanted to at least post this to get some feedback on it
since it's the final step in implementing host imports to see how others
feel about it.
* Fix a typo in an assertion
* Fix some typos
* Review comments
wasmtime
A standalone runtime for WebAssembly
A Bytecode Alliance project
Guide | Contributing | Website | Chat
Installation
The Wasmtime CLI can be installed on Linux and macOS with a small install script:
curl https://wasmtime.dev/install.sh -sSf | bash
Windows or otherwise interested users can download installers and binaries directly from the GitHub Releases page.
Example
If you've got the Rust compiler installed then you can take some Rust source code:
fn main() {
println!("Hello, world!");
}
and compile/run it with:
$ rustup target add wasm32-wasi
$ rustc hello.rs --target wasm32-wasi
$ wasmtime hello.wasm
Hello, world!
Features
-
Fast. Wasmtime is built on the optimizing Cranelift code generator to quickly generate high-quality machine code either at runtime or ahead-of-time. Wasmtime's runtime is also optimized for cases such as efficient instantiation, low-overhead transitions between the embedder and wasm, and scalability of concurrent instances.
-
Secure. Wasmtime's development is strongly focused on the correctness of its implementation with 24/7 fuzzing donated by Google's OSS Fuzz, leveraging Rust's API and runtime safety guarantees, careful design of features and APIs through an RFC process, a security policy in place for when things go wrong, and a release policy for patching older versions as well. We follow best practices for defense-in-depth and known protections and mitigations for issues like Spectre. Finally, we're working to push the state-of-the-art by collaborating with academic researchers to formally verify critical parts of Wasmtime and Cranelift.
-
Configurable. Wastime supports a rich set of APIs and build time configuration to provide many options such as further means of restricting WebAssembly beyond its basic guarantees such as its CPU and Memory consumption. Wasmtime also runs in tiny environments all the way up to massive servers with many concurrent instances.
-
WASI. Wasmtime supports a rich set of APIs for interacting with the host environment through the WASI standard.
-
Standards Compliant. Wasmtime passes the official WebAssembly test suite, implements the official C API of wasm, and implements future proposals to WebAssembly as well. Wasmtime developers are intimately engaged with the WebAssembly standards process all along the way too.
Language Support
You can use Wasmtime from a variety of different languages through embeddings of the implementation:
- Rust - the
wasmtimecrate - C - the
wasm.h,wasi.h, andwasmtime.hheaders or usewasmtimeConan package - C++ - the
wasmtime-cpprepository or usewasmtime-cppConan package - Python - the
wasmtimePyPI package - .NET - the
WasmtimeNuGet package - Go - the
wasmtime-gorepository
Documentation
📚 Read the Wasmtime guide here! 📚
The wasmtime guide is the best starting point to learn about what Wasmtime can do for you or help answer your questions about Wasmtime. If you're curious in contributing to Wasmtime, it can also help you do that!
It's Wasmtime.