Issue 139 - #141
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…#139) computeMaxTempSlots was missing STRUCT_NEW, THROW, ARRAY_NEW_FIXED, and CALL (hasTooManyParameters). When these instructions appeared inside a try_table body, their temp slot usage overflowed into the try-save area, corrupting saved GC ref values. In the Kotlin/Wasm reproducer, struct.new inside a try_table overwrote the try-save slot holding a String literal with an RTTI struct, causing String.plus to receive the wrong reference and eventually array.len to trap on a null array.
…itters Replace the manually-maintained computeMaxTempSlots switch in WasmAnalyzer with a data-driven approach. Each emitter that uses temp slots now declares a TempSlotCalculator at registration time in EmitterMap. This makes it impossible to add a new temp-slot-using opcode without also declaring its slot requirement. - Add TempSlotCalculator interface to Emitters - Extend Builder.intrinsic() with a 3-arg overload - Move all slot calculations from WasmAnalyzer switch to EmitterMap - Replace 140-line switch with 10-line generic loop - Keep assertTempSlotInRange runtime guard as safety net
The Kotlin/Wasm module uses non-canonical LEB128 size encodings from the Kotlin compiler, similar to main.go.wasm.
andreaTP
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Aug 6, 2026
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Almost ready, the testing is solid but the implementation needs a little tweak for human(and machine) readability.
| .intrinsic( | ||
| CompilerOpCode.DROP_KEEP, | ||
| Emitters::DROP_KEEP, | ||
| (ins, module) -> { |
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Counting temp slots in lambdas and inline clutter readability and seems to mix concerns
| .intrinsic( | ||
| CompilerOpCode.BR_ON_CAST_FAIL_CHECK, Emitters::BR_ON_CAST_FAIL_CHECK) | ||
| .build(); | ||
| private static FunctionType resolveTagType(int tagIdx, WasmModule module) { |
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do we have something similar somewhere else in the codebase?
| return ValType.builder().fromId(id).build().resolve(ctx.typeSection()); | ||
| } | ||
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| private static void assertTempSlotInRange(Context ctx, int slotsNeeded) { |
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This is a clear indication for developers, we should make sure this doesn't spill to user land in absence of bugs.
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Fix #139
to be reviewed