Add the wasm32-wasi-preview2 target

Signed-off-by: Ryan Levick <[email protected]>

Author: rylev

Cargo.lock

@@ -2151,9 +2151,8 @@ checksum = "db13adb97ab515a3691f56e4dbab09283d0b86cb45abd991d8634a9d6f501760"
 
 [[package]]
 name = "libc"
-version = "0.2.150"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "89d92a4743f9a61002fae18374ed11e7973f530cb3a3255fb354818118b2203c"
+version = "0.2.151"
+source = "git+https://github.com/rylev/rust-libc?rev=fc437f39b197e7713ca91f1385e4b309b3e9a820#fc437f39b197e7713ca91f1385e4b309b3e9a820"
 dependencies = [
  "rustc-std-workspace-core",
 ]

Cargo.toml

@@ -105,6 +105,8 @@ miniz_oxide.debug = 0
 object.debug = 0
 
 [patch.crates-io]
+libc = { git = "https://github.com/rylev/rust-libc", rev = "fc437f39b197e7713ca91f1385e4b309b3e9a820" }
+
 # See comments in `library/rustc-std-workspace-core/README.md` for what's going on
 # here
 rustc-std-workspace-core = { path = 'library/rustc-std-workspace-core' }

compiler/rustc_target/src/spec/mod.rs

@@ -1574,6 +1574,7 @@ supported_targets! {
     ("wasm32-unknown-emscripten", wasm32_unknown_emscripten),
     ("wasm32-unknown-unknown", wasm32_unknown_unknown),
     ("wasm32-wasi", wasm32_wasi),
+    ("wasm32-wasi-preview2", wasm32_wasi_preview2),
     ("wasm32-wasi-preview1-threads", wasm32_wasi_preview1_threads),
     ("wasm64-unknown-unknown", wasm64_unknown_unknown),
 

compiler/rustc_target/src/spec/targets/wasm32_wasi_preview2.rs

@@ -0,0 +1,63 @@
+//! The `wasm32-wasi-preview2` target is the next evolution of the
+//! wasm32-wasi target. While the wasi specification is still under
+//! active development, the {review 2 iteration is considered an "island
+//! of stability" that should allow users to rely on it indefinitely.
+//!
+//! The `wasi` target is a proposal to define a standardized set of WebAssembly
+//! component imports that allow it to interoperate with the host system in a
+//! standardized way. This set of imports is intended to empower WebAssembly
+//! binaries with host capabilities such as filesystem access, network access, etc.
+//!
+//! Wasi Preview 2 relies on the WebAssembly component model which is an extension of
+//! the core WebAssembly specification which allows interoperability between WebAssembly
+//! modules (known as "components") through high-level, shared-nothing APIs instead of the
+//! low-level, shared-everything linear memory model of the core WebAssembly specification.
+//!
+//! You can see more about wasi at <https://wasi.dev> and the component model at
+//! <https://github.com/WebAssembly/component-model>.
+
+use crate::spec::crt_objects;
+use crate::spec::LinkSelfContainedDefault;
+use crate::spec::{base, Target};
+
+pub fn target() -> Target {
+    let mut options = base::wasm::options();
+
+    options.os = "wasi-preview2".into();
+    options.linker = Some("wasm-component-ld".into());
+
+    options.pre_link_objects_self_contained = crt_objects::pre_wasi_self_contained();
+    options.post_link_objects_self_contained = crt_objects::post_wasi_self_contained();
+
+    // FIXME: Figure out cases in which WASM needs to link with a native toolchain.
+    options.link_self_contained = LinkSelfContainedDefault::True;
+
+    // Right now this is a bit of a workaround but we're currently saying that
+    // the target by default has a static crt which we're taking as a signal
+    // for "use the bundled crt". If that's turned off then the system's crt
+    // will be used, but this means that default usage of this target doesn't
+    // need an external compiler but it's still interoperable with an external
+    // compiler if configured correctly.
+    options.crt_static_default = true;
+    options.crt_static_respected = true;
+
+    // Allow `+crt-static` to create a "cdylib" output which is just a wasm file
+    // without a main function.
+    options.crt_static_allows_dylibs = true;
+
+    // WASI's `sys::args::init` function ignores its arguments; instead,
+    // `args::args()` makes the WASI API calls itself.
+    options.main_needs_argc_argv = false;
+
+    // And, WASI mangles the name of "main" to distinguish between different
+    // signatures.
+    options.entry_name = "__main_void".into();
+
+    Target {
+        llvm_target: "wasm32-unknown-unknown".into(),
+        pointer_width: 32,
+        data_layout: "e-m:e-p:32:32-p10:8:8-p20:8:8-i64:64-n32:64-S128-ni:1:10:20".into(),
+        arch: "wasm32".into(),
+        options,
+    }
+}

library/std/Cargo.toml

@@ -50,7 +50,7 @@ fortanix-sgx-abi = { version = "0.5.0", features = ['rustc-dep-of-std'], public
 [target.'cfg(target_os = "hermit")'.dependencies]
 hermit-abi = { version = "0.3.2", features = ['rustc-dep-of-std'], public = true }
 
-[target.'cfg(target_os = "wasi")'.dependencies]
+[target.'cfg(any(target_os = "wasi", target_os = "wasi-preview2"))'.dependencies]
 wasi = { version = "0.11.0", features = ['rustc-dep-of-std'], default-features = false }
 
 [target.'cfg(target_os = "uefi")'.dependencies]

library/std/src/os/fd/raw.rs

@@ -12,7 +12,7 @@ use crate::os::raw;
 use crate::os::unix::io::AsFd;
 #[cfg(unix)]
 use crate::os::unix::io::OwnedFd;
-#[cfg(target_os = "wasi")]
+#[cfg(any(target_os = "wasi", target_os = "wasi-preview2"))]
 use crate::os::wasi::io::OwnedFd;
 use crate::sys_common::{AsInner, IntoInner};
 #[cfg(target_os = "hermit")]

library/std/src/os/mod.rs

@@ -18,7 +18,7 @@ pub mod raw;
 #[cfg(all(
     doc,
     any(
-        all(target_arch = "wasm32", not(target_os = "wasi")),
+        all(target_arch = "wasm32", not(target_os = "wasi"), not(target_os = "wasi-preview2")),
         all(target_vendor = "fortanix", target_env = "sgx")
     )
 ))]
@@ -27,7 +27,7 @@ pub mod unix {}
 #[cfg(all(
     doc,
     any(
-        all(target_arch = "wasm32", not(target_os = "wasi")),
+        all(target_arch = "wasm32", not(target_os = "wasi"), not(target_os = "wasi-preview2")),
         all(target_vendor = "fortanix", target_env = "sgx")
     )
 ))]
@@ -36,7 +36,7 @@ pub mod linux {}
 #[cfg(all(
     doc,
     any(
-        all(target_arch = "wasm32", not(target_os = "wasi")),
+        all(target_arch = "wasm32", not(target_os = "wasi"), not(target_os = "wasi-preview2")),
         all(target_vendor = "fortanix", target_env = "sgx")
     )
 ))]
@@ -45,7 +45,7 @@ pub mod wasi {}
 #[cfg(all(
     doc,
     any(
-        all(target_arch = "wasm32", not(target_os = "wasi")),
+        all(target_arch = "wasm32", not(target_os = "wasi"), not(target_os = "wasi-preview2")),
         all(target_vendor = "fortanix", target_env = "sgx")
     )
 ))]
@@ -56,7 +56,7 @@ pub mod windows {}
 #[cfg(not(all(
     doc,
     any(
-        all(target_arch = "wasm32", not(target_os = "wasi")),
+        all(target_arch = "wasm32", not(target_os = "wasi"), not(target_os = "wasi-preview2")),
         all(target_vendor = "fortanix", target_env = "sgx")
     )
 )))]
@@ -78,18 +78,18 @@ pub mod linux;
 #[cfg(not(all(
     doc,
     any(
-        all(target_arch = "wasm32", not(target_os = "wasi")),
+        all(target_arch = "wasm32", not(target_os = "wasi"), not(target_os = "wasi-preview2")),
         all(target_vendor = "fortanix", target_env = "sgx")
     )
 )))]
-#[cfg(any(target_os = "wasi", doc))]
+#[cfg(any(target_os = "wasi", target_os = "wasi-preview2", doc))]
 pub mod wasi;
 
 // windows
 #[cfg(not(all(
     doc,
     any(
-        all(target_arch = "wasm32", not(target_os = "wasi")),
+        all(target_arch = "wasm32", not(target_os = "wasi"), not(target_os = "wasi-preview2")),
         all(target_vendor = "fortanix", target_env = "sgx")
     )
 )))]
@@ -155,7 +155,7 @@ pub(crate) mod watchos;
 #[cfg(target_os = "xous")]
 pub mod xous;
 
-#[cfg(any(unix, target_os = "wasi", doc))]
+#[cfg(any(unix, target_os = "wasi", target_os = "wasi-preview2", doc))]
 pub mod fd;
 
 #[cfg(any(target_os = "linux", target_os = "android", doc))]

library/std/src/sys/mod.rs

@@ -38,7 +38,7 @@ cfg_if::cfg_if! {
     } else if #[cfg(target_os = "hermit")] {
         mod hermit;
         pub use self::hermit::*;
-    } else if #[cfg(target_os = "wasi")] {
+    } else if #[cfg(any(target_os = "wasi", target_os = "wasi-preview2"))] {
         mod wasi;
         pub use self::wasi::*;
     } else if #[cfg(target_family = "wasm")] {

src/bootstrap/src/core/build_steps/compile.rs

@@ -346,7 +346,7 @@ fn copy_self_contained_objects(
                 panic!("Target {:?} does not have a \"wasi-root\" key", target.triple)
             })
             .join("lib")
-            .join(target.to_string().replace("-preview1", ""));
+            .join(target.to_string().replace("-preview1", "").replace("-preview2", ""));
         for &obj in &["libc.a", "crt1-command.o", "crt1-reactor.o"] {
             copy_and_stamp(
                 builder,

src/bootstrap/src/lib.rs

@@ -89,7 +89,7 @@ const EXTRA_CHECK_CFGS: &[(Option<Mode>, &str, Option<&[&'static str]>)] = &[
     (Some(Mode::Std), "backtrace_in_libstd", None),
     /* Extra values not defined in the built-in targets yet, but used in std */
     (Some(Mode::Std), "target_env", Some(&["libnx"])),
-    // (Some(Mode::Std), "target_os", Some(&[])),
+    (Some(Mode::Std), "target_os", Some(&["wasi-preview2"])),
     (Some(Mode::Std), "target_arch", Some(&["spirv", "nvptx", "xtensa"])),
     /* Extra names used by dependencies */
     // FIXME: Used by serde_json, but we should not be triggering on external dependencies.

src/doc/rustc/src/platform-support.md

@@ -340,6 +340,7 @@ target | std | host | notes
 `thumbv7a-pc-windows-msvc` | ? |  |
 `thumbv7a-uwp-windows-msvc` | ✓ |  |
 `thumbv7neon-unknown-linux-musleabihf` | ? |  | Thumb2-mode ARMv7-A Linux with NEON, MUSL
+[`wasm32-wasi-preview2`](platform-support/wasm32-wasi-preview2.md) | ✓ |  | WebAssembly
 [`wasm64-unknown-unknown`](platform-support/wasm64-unknown-unknown.md) | ? |  | WebAssembly
 `x86_64-apple-ios-macabi` | ✓ |  | Apple Catalyst on x86_64
 [`x86_64-apple-tvos`](platform-support/apple-tvos.md) | ? |  | x86 64-bit tvOS

src/doc/rustc/src/platform-support/wasm32-wasi-preview2.md

@@ -0,0 +1,30 @@
+# `wasm32-wasi-preview2`
+
+**Tier: 3**
+
+The `wasm32-wasi-preview2` target is a new and still (as of January 2024) an
+experimental target. This target is an extension to `wasm32-wasi-preview1` target,
+originally known as `wasm32-wasi`. It is the next evolution in the development of
+wasi (the [WebAssembly System Interface](https://wasi.dev)) that uses the WebAssembly
+[component model] to allow for a standardized set of syscalls that are intended to empower
+WebAssembly binaries with native host capabilities.
+
+[component model]: https://github.com/WebAssembly/component-model
+
+## Target maintainers
+
+- Alex Crichton, https://github.com/alexcrichton
+- Ryan Levick, https://github.com/rylev
+
+## Requirements
+
+This target is cross-compiled. The target supports `std` fully.
+
+## Platform requirements
+
+The WebAssembly runtime should support the wasi preview 2 API set.
+
+This target is not a stable target. This means that there are only a few engines
+which implement wasi preview 2, for example:
+
+* Wasmtime - `--wasm-features=preview2`