rustc: add wasm32v1-none target

[andresilva]

Rust 1.84 includes a new target wasm32v1-none (https://doc.rust-lang.org/beta/rustc/platform-support/wasm32v1-none.html). This target could be used by some of the packages that are currently targeting wasm32-unknown-unknown, namely polkadot which I maintain (paritytech/polkadot-sdk#7008). I added the target to rustc by adding wasm32v1-none here. Unfortunately this did not work since the rustc build system will by default try to build docs for all targets, including docs for std which will fail for wasm32v1-none since it's a no-std target. To workaround this I tried building rustc with --disable-docs which worked and the wasm32v1-none worked correctly to build polkadot. Not sure how to tune the rustc build to only build docs for std targets.

cc @alyssais

[andresilva]

rustc> Documenting stage2 library {alloc, core, panic_abort, panic_unwind, proc_macro, profiler_builtins, std, sysroot, test, unwind} in HTML format (x86_64-unknown-linux-gnu -> wasm32v1-none)
rustc>    Compiling shlex v1.3.0
rustc>     Checking core v0.0.0 (/build/rustc-1.84.0-src/library/core)
rustc>    Compiling libc v0.2.162
rustc>    Compiling std v0.0.0 (/build/rustc-1.84.0-src/library/std)
rustc>  Documenting core v0.0.0 (/build/rustc-1.84.0-src/library/core)
rustc>    Compiling cc v1.1.22
rustc>    Compiling compiler_builtins v0.1.138
rustc>     Checking rustc-std-workspace-core v1.99.0 (/build/rustc-1.84.0-src/library/rustc-std-workspace-core)
rustc>     Checking alloc v0.0.0 (/build/rustc-1.84.0-src/library/alloc)
rustc>     Checking cfg-if v1.0.0
rustc>     Checking rustc-demangle v0.1.24
rustc>  Documenting alloc v0.0.0 (/build/rustc-1.84.0-src/library/alloc)
rustc>     Checking unwind v0.0.0 (/build/rustc-1.84.0-src/library/unwind)
rustc>     Checking rustc-std-workspace-alloc v1.99.0 (/build/rustc-1.84.0-src/library/rustc-std-workspace-alloc)
rustc>     Checking panic_abort v0.0.0 (/build/rustc-1.84.0-src/library/panic_abort)
rustc>     Checking hashbrown v0.15.0
rustc>     Checking std_detect v0.1.5 (/build/rustc-1.84.0-src/library/stdarch/crates/std_detect)
rustc>  Documenting std v0.0.0 (/build/rustc-1.84.0-src/library/std)
rustc> warning: dropping unsupported crate type `dylib` for target `wasm32v1-none`
rustc> error[E0433]: failed to resolve: use of undeclared crate or module `dlmalloc`
rustc>   --> std/src/sys/alloc/wasm.rs:24:43
rustc>    |
rustc> 24 | static mut DLMALLOC: dlmalloc::Dlmalloc = dlmalloc::Dlmalloc::new();
rustc>    |                                           ^^^^^^^^ use of undeclared crate or module `dlmalloc`
rustc> error[E0425]: cannot find function `fill_bytes` in module `sys`
rustc>   --> std/src/random.rs:67:14
rustc>    |
rustc> 67 |         sys::fill_bytes(bytes)
rustc>    |              ^^^^^^^^^^ not found in `sys`
rustc> error[E0433]: failed to resolve: could not resolve path `dlmalloc::Dlmalloc::new`
rustc>   --> std/src/sys/alloc/wasm.rs:24:43
rustc>    |
rustc> 24 | static mut DLMALLOC: dlmalloc::Dlmalloc = dlmalloc::Dlmalloc::new();
rustc>    |                                           ^^^^^^^^^^^^^^^^^^^^^^^ could not resolve path `dlmalloc::Dlmalloc::new`
rustc>    |
rustc>    = note: this error was originally ignored because you are running `rustdoc`
rustc>    = note: try running again with `rustc` or `cargo check` and you may get a more detailed error
rustc> error[E0433]: failed to resolve: use of undeclared crate or module `dlmalloc`
rustc>   --> std/src/sys/alloc/wasm.rs:24:22
rustc>    |
rustc> 24 | static mut DLMALLOC: dlmalloc::Dlmalloc = dlmalloc::Dlmalloc::new();
rustc>    |                      ^^^^^^^^ use of undeclared crate or module `dlmalloc`
rustc> For more information about this error, try `rustc --explain E0433`.
rustc> error: could not document `std`
rustc> warning: build failed, waiting for other jobs to finish...
rustc> error[E0425]: cannot find function `fill_bytes` in this scope
rustc>   --> std/src/sys/random/mod.rs:94:5
rustc>    |
rustc> 94 |     fill_bytes(&mut buf);
rustc>    |     ^^^^^^^^^^ not found in this scope
rustc> Some errors have detailed explanations: E0425, E0433.
rustc> For more information about an error, try `rustc --explain E0425`.
rustc> warning: `std` (lib) generated 1 warning
rustc> error: could not compile `std` (lib) due to 4 previous errors; 1 warning emitted
rustc> Command has failed. Rerun with -v to see more details.
rustc> Build completed unsuccessfully in 0:01:36
rustc> make: *** [Makefile:20: all] Error 1

[alyssais]

Unfortunately this did not work since the rustc build system will by default try to build docs for all targets, including docs for std which will fail for wasm32v1-none since it's a no-std target. To workaround this I tried building rustc with --disable-docs which worked and the wasm32v1-none worked correctly to build polkadot. Not sure how to tune the rustc build to only build docs for std targets.

This should have been fixed in staging with #382166.

[andresilva]

Great timing, should be easy then :)