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>.
14 use super::{LinkerFlavor, LldFlavor, Target};
15 use crate::spec::abi::Abi;
17 pub fn target() -> Target {
18 let mut options = wasm_base::options();
19 options.os = "unknown".to_string();
20 options.linker_flavor = LinkerFlavor::Lld(LldFlavor::Wasm);
22 // This is a default for backwards-compatibility with the original
23 // definition of this target oh-so-long-ago. Once the "wasm" ABI is
24 // stable and the wasm-bindgen project has switched to using it then there's
25 // no need for this and it can be removed.
27 // Currently this is the reason that this target's ABI is mismatched with
28 // clang's ABI. This means that, in the limit, you can't merge C and Rust
29 // code on this target due to this ABI mismatch.
30 options.default_adjusted_cabi = Some(Abi::Wasm);
32 let clang_args = options.pre_link_args.entry(LinkerFlavor::Gcc).or_default();
34 // Make sure clang uses LLD as its linker and is configured appropriately
36 clang_args.push("--target=wasm32-unknown-unknown".to_string());
38 // For now this target just never has an entry symbol no matter the output
39 // type, so unconditionally pass this.
40 clang_args.push("-Wl,--no-entry".to_string());
42 // Rust really needs a way for users to specify exports and imports in
43 // the source code. --export-dynamic isn't the right tool for this job,
44 // however it does have the side effect of automatically exporting a lot
45 // of symbols, which approximates what people want when compiling for
46 // wasm32-unknown-unknown expect, so use it for now.
47 clang_args.push("-Wl,--export-dynamic".to_string());
49 // Add the flags to wasm-ld's args too.
50 let lld_args = options.pre_link_args.entry(LinkerFlavor::Lld(LldFlavor::Wasm)).or_default();
51 lld_args.push("--no-entry".to_string());
52 lld_args.push("--export-dynamic".to_string());
55 llvm_target: "wasm32-unknown-unknown".to_string(),
57 data_layout: "e-m:e-p:32:32-i64:64-n32:64-S128".to_string(),
58 arch: "wasm32".to_string(),