Fix array.init_elem to use source offset when reading segment data#8349
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sumleo wants to merge 1 commit intoWebAssembly:mainfrom
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Fix array.init_elem to use source offset when reading segment data#8349sumleo wants to merge 1 commit intoWebAssembly:mainfrom
sumleo wants to merge 1 commit intoWebAssembly:mainfrom
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The interpreter's visitArrayInitElem was ignoring the source offset parameter when reading from the element segment. It used seg->data[i] instead of seg->data[offsetVal + i], meaning it always read from the beginning of the segment regardless of the specified offset. The offset was already correctly computed and used in the bounds check, but not in the actual data access loop. This is now consistent with how visitArrayInitData handles its offset parameter.
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kripken
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Feb 23, 2026
| // in the interpreter. | ||
| data->values[indexVal + i] = self()->visit(seg->data[i]).getSingleValue(); | ||
| data->values[indexVal + i] = | ||
| self()->visit(seg->data[offsetVal + i]).getSingleValue(); |
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Hmm, this looks right, but the spec test array_init_elem.wast does not appear to be disabled, and it appears to have tests with a nonzero offset... how is that possible? @tlively @stevenfontanella any ideas?
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It looks like the segment used in that test only contains the same reference over and over, so there doesn't end up being a difference when we just read the first element repeatedly.
It's also troubling that the TODO a few lines up doesn't cause us to fail any tests!
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@tlively should we file a bug against the spec or spec test suite or something like that?
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Summary
visitArrayInitElemwhere the source offset parameter was ignored when reading from the element segmentseg->data[i]instead ofseg->data[offsetVal + i], always reading from the start of the segment regardless of the specified offsetvisitArrayInitDataTest plan
binaryen-unittests)