// The wasm32-unknown-unknown target is currently an experimental version of a
// wasm-based target which does *not* use the Emscripten toolchain. Instead
// this toolchain is based purely on LLVM's own toolchain, using LLVM's native
// WebAssembly backend as well as LLD for a native linker.
//
// There's some trickery below on crate types supported and various defaults
// (aka panic=abort by default), but otherwise this is in general a relatively
// standard target.
use super::{LldFlavor, LinkerFlavor, Target, TargetOptions, PanicStrategy};
pub fn target() -> Result<Target, String> {
let opts = TargetOptions {
// we allow dynamic linking, but only cdylibs. Basically we allow a
// final library artifact that exports some symbols (a wasm module) but
// we don't allow intermediate `dylib` crate types
dynamic_linking: true,
only_cdylib: true,
// This means we'll just embed a `start` function in the wasm module
executables: true,
// relatively self-explanatory!
exe_suffix: ".wasm".to_string(),
dll_prefix: String::new(),
dll_suffix: ".wasm".to_string(),
linker_is_gnu: false,
max_atomic_width: Some(64),
// Unwinding doesn't work right now, so the whole target unconditionally
// defaults to panic=abort. Note that this is guaranteed to change in
// the future once unwinding is implemented. Don't rely on this.
panic_strategy: PanicStrategy::Abort,
// Wasm doesn't have atomics yet, so tell LLVM that we're in a single
// threaded model which will legalize atomics to normal operations.
singlethread: true,
// no dynamic linking, no need for default visibility!
default_hidden_visibility: true,
// we use the LLD shipped with the Rust toolchain by default
linker: Some("rust-lld".to_owned()),
lld_flavor: LldFlavor::Wasm,
// No need for indirection here, simd types can always be passed by
// value as the whole module either has simd or not, which is different
// from x86 (for example) where programs can have functions that don't
// enable simd features.
simd_types_indirect: false,
.. Default::default()
};
Ok(Target {
llvm_target: "wasm32-unknown-unknown".to_string(),
target_endian: "little".to_string(),
target_pointer_width: "32".to_string(),
target_c_int_width: "32".to_string(),
// This is basically guaranteed to change in the future, don't rely on
// this. Use `not(target_os = "emscripten")` for now.
target_os: "unknown".to_string(),
target_env: String::new(),
target_vendor: "unknown".to_string(),
data_layout: "e-m:e-p:32:32-i64:64-n32:64-S128".to_string(),
arch: "wasm32".to_string(),
linker_flavor: LinkerFlavor::Lld(LldFlavor::Wasm),
options: opts,
})
}