fix: convert ccall pointer returns to unsigned in run-pipeline-emscriten#1503
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thewtex merged 1 commit intoInsightSoftwareConsortium:mainfrom Apr 9, 2026
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…pten Emscripten's ccall returns WASM pointers as signed i32. When the heap exceeds 2 GB, pointers above 2^31 wrap negative, causing: RangeError: Start offset -N is outside the bounds of the buffer Apply >>> 0 to all 7 ccall sites that return pointers (4 helper functions + 3 inline output readers) so they are treated as unsigned. Adds a regression test that reuses an Emscripten module across two large-image pipeline calls, reproducing the real-world scenario of a persistent web worker whose heap accumulates past 2 GB.
thewtex
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Apr 9, 2026
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Fix signed pointer overflow in
runPipelineEmscriptenwhen WASM heap exceeds 2 GB. Apply>>> 0to all 7ccallsites returning pointers. Add regression test.Problem
Emscripten's
ccallreturns pointers as signed i32. When a module is reused (web worker pattern) and the heap exceeds 2 GB, pointers above 2^31 wrap negative:Reported via VolView issue loading a 1024x1024x172 Float32 image + NIfTI labelmap on the same worker.
Fix
>>> 0is a no-op for pointers below 2^31, so safe for all heap sizes.Emscripten precedent
The Emscripten settings reference states: "If the maximum heap size is over 2GB, then pointers must be unsigned in JavaScript." The same bug class was fixed in Emscripten's own
library_webgl.js(#20137) and pointer types were changed to unsigned forCAN_ADDRESS_2GBmode (#21278).