// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
// 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: "".to_string(),
dll_suffix: ".wasm".to_string(),
linker_is_gnu: false,
// A bit of a lie, but "eh"
max_atomic_width: Some(32),
// 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,
.. Default::default()
};
Ok(Target {
llvm_target: "wasm32-unknown-unknown-wasm".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: "".to_string(),
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,
})
}