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Currently, the `build.rs` script that generates Rust source from the ISLE DSL will only do this generation if the `rebuild-isle` Cargo feature is specified. By default, it is not. This is based on the principle that we (the build script) do not modify the source tree as managed by git; git-managed files are strictly a human-managed and human-edited resource. By adding the opt-in Cargo feature, a developer is requesting the build script to perform an explicit action. (In my understanding at least, this principle comes from the general philosophy of hermetic builds: the output should be a pure function of the input, and part of this is that the input is read-only. If we modify the source tree, then all bets are off.) Unfortunately, requiring the opt-in feature also creates a footgun that is easy to hit: if a developer modifies the ISLE DSL source, but forgets to specify the Cargo feature, then the compiler will silently be built successfully with stale source, and will silently exclude any changes that were made. The generated source is checked into git for a good reason: we want DSL compiler to not affect build times for the overwhelmingly common case that Cranelift is used as a dependency but the backends are not being actively developed. (This overhead comes mainly from building `islec` itself.) So, what to do? This PR implements a middle ground first described in [this conversation](https://github.com/bytecodealliance/wasmtime/pull/3506#discussion_r743113351), in which we: - Generate a hash (SHA-512) of the ISLE DSL source and produce a "manifest" of ISLE inputs alongside the generated source; and - Always read the ISLE DSL source, and see if the manifest is still valid, on builds that do not have the opt-in "rebuild" feature. This allows us to know whether the ISLE compiler output would have been the same (modulo changes to the DSL compiler itself, which are out-of-scope here), without actually building the ISLE compiler and running it. If the compiler-backend developer modifies an ISLE source file and then tries to build `cranelift-codegen` without adding the `rebuild-isle` Cargo feature, they get the following output: ```text Error: the ISLE source files that resulted in the generated Rust source * src/isa/x64/lower/isle/generated_code.rs have changed but the generated source was not rebuilt! These ISLE source files are: * src/clif.isle * src/prelude.isle * src/isa/x64/inst.isle * src/isa/x64/lower.isle Please add `--features rebuild-isle` to your `cargo build` command if you wish to rebuild the generated source, then include these changes in any git commits you make that include the changes to the ISLE. For example: $ cargo build -p cranelift-codegen --features rebuild-isle (This build script cannot do this for you by default because we cannot modify checked-into-git source without your explicit opt-in.) ``` which will tell them exactly what they need to do to fix the problem! Note that I am leaving the "Rebuild ISLE" CI job alone for now, because otherwise, we are trusting whomever submits a PR to generate the correct generated source. In other words, the manifest is a communication from the checked-in tree to the developer, but we still need to verify that the checked-in generated Rust source and the manifest are correct with respect to the checked-in ISLE source.
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
-
Lightweight. Wasmtime is a standalone runtime for WebAssembly that scales with your needs. It fits on tiny chips as well as makes use of huge servers. Wasmtime can be embedded into almost any application too.
-
Fast. Wasmtime is built on the optimizing Cranelift code generator to quickly generate high-quality machine code at runtime.
-
Configurable. Whether you need to precompile your wasm ahead of time, or interpret it at runtime, Wasmtime has you covered for all your wasm-executing needs.
-
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.