3a07aa9b5e
-export-dynamic was a temporary hack added in the early days of the Rust wasm32 target when Rust didn't have a way to specify wasm exports in the source code. This flag causes all global symbols, and some compiler-internal symbols, to be exported, which is often more than needed. Rust now does have a way to specify exports in the source code: `#[export_name = "..."]`. So as the original comment suggests, -export-dynamic can now be removed, allowing users to have smaller binaries and better encapsulation in their wasm32-unknown-unknown modules. It's possible that this change will require existing wasm32-unknown-unknown users will to add explicit `#[export_name = "..."]` directives to exporrt the symbols that their programs depend on having exported.
55 lines
2.1 KiB
Rust
55 lines
2.1 KiB
Rust
//! A "bare wasm" target representing a WebAssembly output that makes zero
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//! assumptions about its environment.
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//!
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//! The `wasm32-unknown-unknown` target is intended to encapsulate use cases
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//! that do not rely on any imported functionality. The binaries generated are
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//! entirely self-contained by default when using the standard library. Although
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//! the standard library is available, most of it returns an error immediately
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//! (e.g. trying to create a TCP stream or something like that).
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//!
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//! This target is more or less managed by the Rust and WebAssembly Working
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//! Group nowadays at <https://github.com/rustwasm>.
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use super::{wasm_base, Cc, LinkerFlavor, Target};
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use crate::spec::abi::Abi;
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pub fn target() -> Target {
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let mut options = wasm_base::options();
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options.os = "unknown".into();
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// This is a default for backwards-compatibility with the original
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// definition of this target oh-so-long-ago. Once the "wasm" ABI is
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// stable and the wasm-bindgen project has switched to using it then there's
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// no need for this and it can be removed.
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//
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// Currently this is the reason that this target's ABI is mismatched with
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// clang's ABI. This means that, in the limit, you can't merge C and Rust
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// code on this target due to this ABI mismatch.
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options.default_adjusted_cabi = Some(Abi::Wasm);
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options.add_pre_link_args(
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LinkerFlavor::WasmLld(Cc::No),
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&[
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// For now this target just never has an entry symbol no matter the output
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// type, so unconditionally pass this.
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"--no-entry",
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],
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);
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options.add_pre_link_args(
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LinkerFlavor::WasmLld(Cc::Yes),
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&[
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// Make sure clang uses LLD as its linker and is configured appropriately
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// otherwise
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"--target=wasm32-unknown-unknown",
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"-Wl,--no-entry",
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],
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);
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Target {
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llvm_target: "wasm32-unknown-unknown".into(),
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pointer_width: 32,
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data_layout: "e-m:e-p:32:32-p10:8:8-p20:8:8-i64:64-n32:64-S128-ni:1:10:20".into(),
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arch: "wasm32".into(),
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options,
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}
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}
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