This commit uses the `*.witx` files describing the current wasi API to reduce the boilerplate used to define implementations in the `wasmtime-wasi` crate. Eventually I'd like to remove lots of boilerplate in the `wasi-common` crate too, but this should at least be a good start! The boilerplate removed here is: * No need to list each function to add it to the `wasmtime_runtime::Module` being created * No need to list the signature of the function in a separate `syscalls.rs` file. Instead the `*.witx` file is processed in a single-use macro inside the `wasmtime-wasi` crate. This macro uses the signatures known from `*.witx` to automatically register with the right type in the wasm module as well as define a wrapper that the wasm module will call into. Functionally this is all the same as before, it's just defined in a different way now! The shim generated by this macro which wasmtime calls into only uses `i32`/`i64`/etc wasm types, and it internally uses `as` casts to convert to the right wasi types when delegating into the `wasi-common` crate. One change was necessary to get this implemented, however. The functions in `wasi-common` sometimes took `WasiCtx` and sometimes took a slice of memory. After this PR they uniformly all require both `WasiCtx` and memory so the wrappers can be auto-generated. The arguments are ignored if they weren't previously required.
wasi-common
A Bytecode Alliance project
A library providing a common implementation of WASI hostcalls for re-use in any WASI-enabled runtime.
The wasi-common crate will ultimately serve as a library providing a common implementation of
WASI hostcalls for re-use in any WASI (and potentially non-WASI) runtimes
such as Wasmtime and Lucet.
The library is an adaption of lucet-wasi crate from the Lucet project, and it is currently based on 40ae1df git revision.
Please note that the library requires Rust compiler version at least 1.37.0.
Supported syscalls
*nix
In our *nix implementation, we currently support the entire WASI API with the exception of socket hostcalls:
sock_recvsock_sendsock_shutdown
We expect these to be implemented when network access is standardised.
We also currently do not support the proc_raise hostcall, as it is expected to
be dropped entirely from WASI.
Windows
In our Windows implementation, we currently support the minimal subset of WASI API which allows for running the very basic "Hello world!" style WASM apps. More coming shortly, so stay tuned!
Development hints
When testing the crate, you may want to enable and run full wasm32 integration testsuite. This
requires wasm32-wasi target installed which can be done as follows using rustup
rustup target add wasm32-wasi
Now, you should be able to run the integration testsuite by running cargo test on the
test-programs package with test_programs feature enabled:
cargo test --features test_programs --package test-programs
Third-Party Code
Significant parts of our hostcall implementations are derived from the C implementations in
cloudabi-utils. See LICENSE.cloudabi-utils for license information.