GH-49995: [R][Wasm] Fix threading issue under Wasm/Emscripten#49996
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amoeba wants to merge 3 commits into
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GH-49995: [R][Wasm] Fix threading issue under Wasm/Emscripten#49996amoeba wants to merge 3 commits into
amoeba wants to merge 3 commits into
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@github-actions crossbow submit test-r-wasm |
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Revision: dadf0f5 Submitted crossbow builds: ursacomputing/crossbow @ actions-9b0263bfa9
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@github-actions crossbow submit test-r-wasm |
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With dadf0f5, Parquet reading works with my local test. I'm testing the changes separately so I know what's actually fixing things here. |
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Revision: abaacb8 Submitted crossbow builds: ursacomputing/crossbow @ actions-510511a107
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I marked this as ready for review. The PR description hopefully explains all that's needed and I put together a demo at https://amoeba.github.io/arrow-r-wasm/ |
amoeba
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jonkeane
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May 20, 2026
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| bool CanRunWithCapturedR() { | ||
| #ifdef __EMSCRIPTEN__ | ||
| // Threading is not supported under Emscripten/WASM. Always take the | ||
| // synchronous path to avoid attempting pthread_create which will fail | ||
| // with "thread constructor failed: Not supported". | ||
| return false; | ||
| #else | ||
| return MainRThread::GetInstance().Executor() == nullptr; | ||
| #endif |
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Is it possible to add a test (or maybe it's that we actually need to run the tests under wasm(???) to catch this?
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Rationale for this change
#49982 added a basic Wasm build but after doing some testing I ran into an issue with threading.
What changes are included in this PR?
CanRunWithCapturedRso it's always false under Emscripten. This change is the only change that was strictly needed to fix my issue. I'm not a pro with this part of the codebase so scrutiny welcome.options(arrow.use_threads = FALSE)when running under Wasm just in case since it makes sense to not use threads in a Wasm contextAre these changes tested?
Yes. Crossbow jobs show the build works and I have a demo at https://amoeba.github.io/arrow-r-wasm/.
Are there any user-facing changes?
No.