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Rollup merge of #146795 - alexcrichton:wasm-limit-rdylib-exports, r=bjorn3

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Enable `limit_rdylib_exports` on wasm targets

This commit updates the target specification of wasm targets to set the `limit_rdylib_exports` value to `true` like it is on other native platforms. This was originally not implemented long ago as `wasm-ld` didn't have options for symbol exports, but since then it's grown a `--export` flag and such to control this. A custom case is needed in the linker implementation to handle wasm targets as `wasm-ld` doesn't support linker scripts used on other targets, but other than that the implementation is straightforward.

The goal of this commit is enable building dynamic libraries on `wasm32-wasip2` which don't export every single symbol in the Rust standard library. Currently, without otherwise control over symbol visibility, all symbols end up being exported which generates excessively large binaries because `--gc-sections` ends up doing nothing as it's all exported anyway.
This commit is contained in:
Guillaume Gomez 2025-09-22 17:17:42 +02:00 • committed by GitHub
commit dc176bd216
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2 changed files with 5 additions and 5 deletions
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5
compiler/rustc_codegen_ssa/src/back/linker.rs
View file

@ -845,6 +845,11 @@ impl<'a> Linker for GccLinker<'a> {
self.sess.dcx().emit_fatal(errors::VersionScriptWriteFailure { error });
}
self.link_arg("--dynamic-list").link_arg(path);
} else if self.sess.target.is_like_wasm {
self.link_arg("--no-export-dynamic");
for (sym, _) in symbols {
self.link_arg("--export").link_arg(sym);
}
} else {
// Write an LD version script
let res: io::Result<()> = try {

5
compiler/rustc_target/src/spec/base/wasm.rs
View file

@ -81,11 +81,6 @@ pub(crate) fn options() -> TargetOptions {
// threaded model which will legalize atomics to normal operations.
singlethread: true,
// Symbol visibility takes care of this for the WebAssembly.
// Additionally the only known linker, LLD, doesn't support the script
// arguments just yet
limit_rdylib_exports: false,
// we use the LLD shipped with the Rust toolchain by default
linker: Some("rust-lld".into()),
linker_flavor: LinkerFlavor::WasmLld(Cc::No),