Pass --no-entry to emcc when linking emscripten cdylib/dylib#157985
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guybedford wants to merge 1 commit into
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Pass --no-entry to emcc when linking emscripten cdylib/dylib#157985guybedford wants to merge 1 commit into
guybedford wants to merge 1 commit into
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A cdylib/dylib has no `main`, but rustc invokes emcc in its default executable mode, which links in emscripten's standalone-wasm entry shim and then fails with `undefined symbol: main`. Mirror the WasmLd linker: emit `--no-entry` for `DynamicDylib`/ `StaticDylib` output kinds in EmLinker::set_output_kind, conditioned on LinkOutputKind so executables keep their entry. Extend the emscripten cdylib run-make test to also link a bin crate with `main`, guarding against regressing the executable entry path.
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r? @camelid rustbot has assigned @camelid. Use Why was this reviewer chosen?The reviewer was selected based on:
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bjorn3
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Jun 17, 2026
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| // An executable has a `main`, so `--no-entry` must NOT be applied: it must | ||
| // still link with its entry preserved. | ||
| bare_rustc().input("main.rs").target("wasm32-unknown-emscripten").crate_type("bin").run(); |
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If --no-entry is passed here, the test would still pass. I think --no-entry not being passed would already be covered by all run-pass tests that run on emscripten anyway.
bjorn3
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Jun 17, 2026
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| fn main() { | ||
| // A cdylib must link without `--no-entry` being supplied by the user. | ||
| bare_rustc().input("foo.rs").target("wasm32-unknown-emscripten").crate_type("cdylib").run(); |
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Why did this work before?
Edit: I think -sSIDE_MODULE=2 already implies --no-entry.
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This doesn't look right to me. As @bjorn3 says, |
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@guybedford do you have an example of a situation in which you get this linker error? |
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A cdylib/dylib has no
main, but rustc invokes emcc in its default executable mode, which links in emscripten's standalone-wasm entry shim and then fails withundefined symbol: main.Mirror the WasmLd linker: emit
--no-entryforDynamicDylib/StaticDyliboutput kinds in EmLinker::set_output_kind, conditioned on LinkOutputKind so executables keep their entry.Extends the emscripten cdylib run-make test to also link a bin crate with
main, guarding against regressing the executable entry path.