Fix for ArrayIndexOutOfBoundsException in Frame.merge#79
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…ble stack heights")
andreaTP
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Jul 1, 2026
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Hi @RefuX , I checked your wat reproducers carefully against V8 behavior and everything looks correct, I'm reviewing the PR but looks a great starting point.
This also seems worth a patch release, you are clearly targeting a specific .wasm payload, let me know when all issues are addressed and I'll trigger the release.
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@andreaTP Thanks so much for the help! |
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I was hitting this error compiling my own wasm module at runtime.
I wasn't sure whether to file a bug or open a PR — this is outside my area of expertise, and I put the fix together with a lot of help from an AI assistant. So I completely understand if the fix shows a lack of deep understanding, because that would be completely correct.
Symptom: ArrayIndexOutOfBoundsException in ASM Frame.merge ("incompatible stack heights") during runtime compilation.
Cause: when a try_table catch branches out to an enclosing block, the operand-stack values belonging to the blocks it's exiting must be dropped (keeping the caught values), exactly like a normal branch — the catch handler wasn't doing that.
Fix: emit the same DROP_KEEP unwind the compiler already uses for ordinary branches before the catch branches to its target.