1 //! A "bare wasm" target representing a WebAssembly output that makes zero
2 //! assumptions about its environment.
4 //! The `wasm32-unknown-unknown` target is intended to encapsulate use cases
5 //! that do not rely on any imported functionality. The binaries generated are
6 //! entirely self-contained by default when using the standard library. Although
7 //! the standard library is available, most of it returns an error immediately
8 //! (e.g. trying to create a TCP stream or something like that).
10 //! This target is more or less managed by the Rust and WebAssembly Working
11 //! Group nowadays at <https://github.com/rustwasm>.
13 use super::{wasm_base, Cc, LinkerFlavor, Target};
14 use crate::spec::abi::Abi;
16 pub fn target() -> Target {
17 let mut options = wasm_base::options();
18 options.os = "unknown".into();
20 // This is a default for backwards-compatibility with the original
21 // definition of this target oh-so-long-ago. Once the "wasm" ABI is
22 // stable and the wasm-bindgen project has switched to using it then there's
23 // no need for this and it can be removed.
25 // Currently this is the reason that this target's ABI is mismatched with
26 // clang's ABI. This means that, in the limit, you can't merge C and Rust
27 // code on this target due to this ABI mismatch.
28 options.default_adjusted_cabi = Some(Abi::Wasm);
30 options.add_pre_link_args(
31 LinkerFlavor::WasmLld(Cc::No),
33 // For now this target just never has an entry symbol no matter the output
34 // type, so unconditionally pass this.
36 // Rust really needs a way for users to specify exports and imports in
37 // the source code. --export-dynamic isn't the right tool for this job,
38 // however it does have the side effect of automatically exporting a lot
39 // of symbols, which approximates what people want when compiling for
40 // wasm32-unknown-unknown expect, so use it for now.
44 options.add_pre_link_args(
45 LinkerFlavor::WasmLld(Cc::Yes),
47 // Make sure clang uses LLD as its linker and is configured appropriately
49 "--target=wasm32-unknown-unknown",
51 "-Wl,--export-dynamic",
56 llvm_target: "wasm32-unknown-unknown".into(),
58 data_layout: "e-m:e-p:32:32-p10:8:8-p20:8:8-i64:64-n32:64-S128-ni:1:10:20".into(),
59 arch: "wasm32".into(),