39e57e3e9a
* Migrate back to `std::` stylistically This commit moves away from idioms such as `alloc::` and `core::` as imports of standard data structures and types. Instead it migrates all crates to uniformly use `std::` for importing standard data structures and types. This also removes the `std` and `core` features from all crates to and removes any conditional checking for `feature = "std"` All of this support was previously added in #407 in an effort to make wasmtime/cranelift "`no_std` compatible". Unfortunately though this change comes at a cost: * The usage of `alloc` and `core` isn't idiomatic. Especially trying to dual between types like `HashMap` from `std` as well as from `hashbrown` causes imports to be surprising in some cases. * Unfortunately there was no CI check that crates were `no_std`, so none of them actually were. Many crates still imported from `std` or depended on crates that used `std`. It's important to note, however, that **this does not mean that wasmtime will not run in embedded environments**. The style of the code today and idioms aren't ready in Rust to support this degree of multiplexing and makes it somewhat difficult to keep up with the style of `wasmtime`. Instead it's intended that embedded runtime support will be added as necessary. Currently only `std` is necessary to build `wasmtime`, and platforms that natively need to execute `wasmtime` will need to use a Rust target that supports `std`. Note though that not all of `std` needs to be supported, but instead much of it could be configured off to return errors, and `wasmtime` would be configured to gracefully handle errors. The goal of this PR is to move `wasmtime` back to idiomatic usage of features/`std`/imports/etc and help development in the short-term. Long-term when platform concerns arise (if any) they can be addressed by moving back to `no_std` crates (but fixing the issues mentioned above) or ensuring that the target in Rust has `std` available. * Start filling out platform support doc
73 lines
2.6 KiB
Rust
73 lines
2.6 KiB
Rust
//! Translation of hello example
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use anyhow::{ensure, format_err, Context as _, Result};
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use std::cell::Ref;
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use std::rc::Rc;
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use wasmtime_api::*;
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struct HelloCallback;
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impl Callable for HelloCallback {
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fn call(&self, _params: &[Val], _results: &mut [Val]) -> Result<(), HostRef<Trap>> {
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println!("Calling back...");
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println!("> Hello World!");
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Ok(())
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}
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}
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fn main() -> Result<()> {
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// Configure the initial compilation environment, creating more global
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// structures such as an `Engine` and a `Store`.
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println!("Initializing...");
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let engine = HostRef::new(Engine::default());
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let store = HostRef::new(Store::new(&engine));
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// Next upload the `*.wasm` binary file, which in this case we're going to
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// be parsing an inline text format into a binary.
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println!("Loading binary...");
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let binary = wat::parse_str(
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r#"
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(module
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(func $hello (import "" "hello"))
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(func (export "run") (call $hello))
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)
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"#,
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)?;
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// Compiler the `*.wasm` binary into an in-memory instance of a `Module`.
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println!("Compiling module...");
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let module = HostRef::new(Module::new(&store, &binary).context("> Error compiling module!")?);
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// Here we handle the imports of the module, which in this case is our
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// `HelloCallback` type and its associated implementation of `Callback.
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println!("Creating callback...");
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let hello_type = FuncType::new(Box::new([]), Box::new([]));
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let hello_func = HostRef::new(Func::new(&store, hello_type, Rc::new(HelloCallback)));
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// Once we've got that all set up we can then move to the instantiation
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// phase, pairing together a compiled module as well as a set of imports.
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// Note that this is where the wasm `start` function, if any, would run.
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println!("Instantiating module...");
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let imports = vec![hello_func.into()];
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let instance = HostRef::new(
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Instance::new(&store, &module, imports.as_slice())
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.context("> Error instantiating module!")?,
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);
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// Next we poke around a bit to extract the `run` function from the module.
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println!("Extracting export...");
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let exports = Ref::map(instance.borrow(), |instance| instance.exports());
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ensure!(!exports.is_empty(), "> Error accessing exports!");
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let run_func = exports[0].func().context("> Error accessing exports!")?;
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// And last but not least we can call it!
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println!("Calling export...");
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run_func
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.borrow()
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.call(&[])
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.map_err(|e| format_err!("> Error calling function: {:?}", e))?;
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println!("Done.");
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Ok(())
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}
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