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Alex Crichton 2024-08-01 12:16:42 -07:00
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src/doc/rustc/src/platform-support/wasm32-unknown-unknown.md
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@ -6,7 +6,7 @@ The `wasm32-unknown-unknown` target is a WebAssembly compilation target which
does not import any functions from the host for the standard library. This is
the "minimal" WebAssembly in the sense of making the fewest assumptions about
the host environment. This target is often used when compiling to the web or
JavaScript environments as there is not standard for what functions can be
JavaScript environments as there is no standard for what functions can be
imported on the web. This target can also be useful for creating minimal or
bare-bones WebAssembly binaries.
@ -86,13 +86,13 @@ $ file foo.wasm
## Cross-compilation
This target can be cross-compiled from any hosts.
This target can be cross-compiled from any host.
## Testing
This target is not tested in CI for the rust-lang/rust repository. Many tests
must be disabled to run on this target and failures are non-obvious because
println doesn't work in the standard library. It's recommended to test the
`println!` doesn't work in the standard library. It's recommended to test the
`wasm32-wasip1` target instead for WebAssembly compatibility.
## Conditionally compiling code
@ -118,7 +118,7 @@ Changes to WebAssembly go through a [proposals process][proposals] but reaching
the final stage (stage 5) does not automatically mean that the feature will be
enabled in LLVM and Rust by default. At this time the general guidance is that
features must be present in most engines for a "good chunk of time" before
they're enabled in LLVM by default. There is currently not exact number of
they're enabled in LLVM by default. There is currently no exact number of
months or engines that are required to enable features by default.
[proposals]: https://github.com/WebAssembly/proposals
@ -144,7 +144,8 @@ will produce a binary that uses only the original WebAssembly features by
default and no proposals since its inception.
To enable individual features it can be done with `-Ctarget-feature=+foo`.
Available features can be found through:
Available features for Rust code itself are documented in the [reference] and
can also be found through:
```sh
$ rustc -Ctarget-feature=help --target wasm32-unknown-unknown
@ -152,3 +153,5 @@ $ rustc -Ctarget-feature=help --target wasm32-unknown-unknown
You'll need to consult your WebAssembly engine's documentation to learn more
about the supported WebAssembly features the engine has.
[reference]: https://doc.rust-lang.org/reference/attributes/codegen.html#wasm32-or-wasm64