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CABI: trap on misaligned waitable-set.{wait,poll} ptr - #741
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unpack_event stored the two i32 event payloads at the guest-supplied `ptr` through store, whose alignment and bounds checks are assertions rather than traps. A misaligned or out-of-bounds `ptr` thus raised an AssertionError in the reference interpreter instead of trapping, and the prose said nothing. Trap unless `ptr` is 4-byte-aligned and `ptr + 8` is within memory, matching the checks lower_flat_values applies to an out-param pointer and what Wasmtime already does. Document this in CanonicalABI.md and the Explainer, whose description of waitable-set.wait wrongly called `payload-addr` 8-byte-aligned: the payload is two contiguous i32s, so 4-byte alignment is all the ABI requires. Assisted-by: claude:claude-fable-5-1 Signed-off-by: Roman Volosatovs <rvolosatovs@riseup.net>
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unpack_event stored the two i32 event payloads at the guest-supplied
ptrthrough store, whose alignment and bounds checks are assertions rather than traps. A misaligned or out-of-boundsptrthus raised an AssertionError in the reference interpreter instead of trapping, and the prose said nothing.Trap unless
ptris 4-byte-aligned andptr + 8is within memory, matching the checks lower_flat_values applies to an out-param pointer and what Wasmtime already does. Document this in CanonicalABI.md and the Explainer, whose description of waitable-set.wait wrongly calledpayload-addr8-byte-aligned: the payload is two contiguous i32s, so 4-byte alignment is all the ABI requires.