Fix sign extension of i32 addresses in interpreter memory access#8348
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kripken merged 1 commit intoWebAssembly:mainfrom Feb 25, 2026
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src/wasm-interpreter.h
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| size_t indexVal = index.getSingleValue().getUnsigned(); | ||
| if (indexVal >= data->values.size()) { | ||
| trap("array oob"); | ||
| } |
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This looks like a correct fix, but the title and description of the PR look unrelated?
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Thanks for catching that! The branch previously contained the wrong change (an array bounds check that was already covered by #8351). I've force-pushed with the actual sign extension fix for |
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src/wasm-interpreter.h
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| Address memorySizeBytes = memorySize * Memory::kPageSize; | ||
| uint64_t addr = ptr.type == Type::i32 ? ptr.geti32() : ptr.geti64(); | ||
| uint64_t addr = ptr.type == Type::i32 ? (uint64_t)(uint32_t)ptr.geti32() | ||
| : (uint64_t)ptr.geti64(); |
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Can this just be getUnsigned()? That returns uint64_t.
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Done — switched to ptr.getUnsigned() in both getFinalAddress and getFinalAddressWithoutOffset. Much cleaner.
Use ptr.getUnsigned() to properly zero-extend i32 addresses to uint64_t in getFinalAddress and getFinalAddressWithoutOffset. Previously, geti32() returned a signed int32_t that sign-extended when assigned to uint64_t, producing incorrect addresses for values >= 0x80000000.
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Summary
getFinalAddressandgetFinalAddressWithoutOffsetin the interpreterptr.geti32()returnsint32_t, which gets sign-extended toint64_tvia C++ ternary promotion rules before being stored asuint64_t0x80000000, this produces incorrect 64-bit values (e.g.,0xFFFFFFFF80000000instead of0x80000000), causing spurious out-of-bounds trapsuint32_tfirst to zero-extend instead of sign-extendTest plan
binaryen-unittests)