add wasm32-wasip2 support #6893
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Looks ok, but let's wait for the mio PR. |
This adds support for the new `wasm32-wasip2` target platform, which includes more extensive support for sockets than `wasm32-wasip1` (formerly known as `wasm32-wasi`). The bulk of the changes are in tokio-rs/mio#1836. This patch just tweaks a few `cfg` directives to indicate `wasm32-wasip2`'s additional capabilities. In the future, we could consider adding support for `ToSocketAddrs`. WASIp2 natively supports asynchronous DNS lookups and is single threaded, whereas Tokio currently assumes DNS lookups are blocking and require multithreading to emulate async lookups. A WASIp2-specific implementation could do the lookup directly without multithreading. I've tested this end-to-end using https://github.com/dicej/wasi-sockets-tests, which includes smoke tests for `mio`, `tokio`, `tokio-postgres`, etc. I'd also be happy to add tests to this repo if appropriate; it would require adding a dev-dependency on e.g. `wasmtime` to actually run the test cases. Signed-off-by: Joel Dice <[email protected]>
teohhanhui
reviewed
Aug 7, 2025
| #![cfg_attr(docsrs, allow(unused_attributes))] | ||
| #![cfg_attr(loom, allow(dead_code, unreachable_pub))] | ||
| #![cfg_attr(windows, allow(rustdoc::broken_intra_doc_links))] | ||
| #![cfg_attr(all(target_os = "wasi", target_env = "p2"), feature(wasip2))] |
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This doesn't seem like the right thing to do:
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Motivation
This adds support for the new
wasm32-wasip2target platform, which includes more extensive support for sockets thanwasm32-wasip1(formerly known aswasm32-wasi).Solution
The bulk of the changes are in tokio-rs/mio#1836. This patch just tweaks a few
cfgdirectives to indicatewasm32-wasip2's additional capabilities.In the future, we could consider adding support for
tokio::net::lookup_host. WASIp2 natively supports asynchronous DNS lookups and is single threaded, whereas Tokio currently assumes DNS lookups are blocking and require multithreading to emulate async lookups. A WASIp2-specific implementation could do the lookup directly without multithreading.I've tested this end-to-end using https://github.com/dicej/wasi-sockets-tests, which includes smoke tests for
mio,tokio,tokio-postgres, etc. I'd also be happy to add tests to this repo if appropriate; it would require adding a dev-dependency on e.g.wasmtimeto actually run the test cases.Note that this is a draft PR until tokio-rs/mio#1836 is merged, at which point I'll switch the
miodependency back to the upstream project.