compiler/rustc_target/src/spec/targets/wasm32_unknown_unknown.rs

//! A "bare wasm" target representing a WebAssembly output that makes zero
//! assumptions about its environment.
//!
//! The `wasm32-unknown-unknown` target is intended to encapsulate use cases
//! that do not rely on any imported functionality. The binaries generated are
//! entirely self-contained by default when using the standard library. Although
//! the standard library is available, most of it returns an error immediately
//! (e.g. trying to create a TCP stream or something like that).
//!
//! This target is more or less managed by the Rust and WebAssembly Working
//! Group nowadays at <https://github.com/rustwasm>.

use crate::spec::{Cc, LinkerFlavor, Target, TargetMetadata, base};

pub(crate) fn target() -> Target {
    let mut options = base::wasm::options();
    options.os = "unknown".into();

    options.add_pre_link_args(
        LinkerFlavor::WasmLld(Cc::No),
        &[
            // For now this target just never has an entry symbol no matter the output
            // type, so unconditionally pass this.
            "--no-entry",
        ],
    );
    options.add_pre_link_args(
        LinkerFlavor::WasmLld(Cc::Yes),
        &[
            // Make sure clang uses LLD as its linker and is configured appropriately
            // otherwise
            "--target=wasm32-unknown-unknown",
            "-Wl,--no-entry",
        ],
    );

    Target {
        llvm_target: "wasm32-unknown-unknown".into(),
        metadata: TargetMetadata {
            description: Some("WebAssembly".into()),
            tier: Some(2),
            host_tools: Some(false),
            std: Some(true),
        },
        pointer_width: 32,
        data_layout: "e-m:e-p:32:32-p10:8:8-p20:8:8-i64:64-i128:128-n32:64-S128-ni:1:10:20".into(),
        arch: "wasm32".into(),
        options,
    }
}