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* a certain subset of io::Errors are expected - these we have a (platform-specific, because windows) method to translate into one of the wasi errno variants in the Error enum. * some io::Errors are unexpected - wasi-common doesnt expect them from the underlying OS. rather than preserve any fidelity in reporting those to the user (only the unix impl attempts this), lets collect those as an `Error::UnexpectedIo(#[source] std::io::Error)`. Rather than trace at the conversion site, we rely on the wiggle error conversion hooks to trace the `Error`'s `Debug` impl, and then we convert all of these unexpected into `Errno::Io` for returning to the guest. This is a different behavior from before, and I don't have any firm guarantees that nobody was depending on the old behavior, but it appears to me that none of those unexpected errnos were reasonable to expect from any of the filesystem syscalls wasi-common is making.
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/test_programs feature enabled:
cargo test --features test-programs/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.