Fix throw_ref missing null check on exnref#567
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titzer merged 4 commits intotitzer:masterfrom Mar 5, 2026
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THROW_REF pops an exnref and rethrows it, but does not check for null before casting with Exception.!(exval.val). A null exnref causes a crash instead of properly trapping with NULL_DEREF. Add null check before the cast to trap correctly.
titzer
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Mar 3, 2026
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Thanks, can you add a regression test for this case?
Verifies that throw_ref with a null exnref properly traps with null dereference instead of crashing.
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titzer
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Mar 4, 2026
| } | ||
| THROW_REF => { | ||
| var exval = popr(); | ||
| if (exval.val == null) return void(trap(TrapReason.NULL_DEREF)); |
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The regression test caught a bug in the fast interpreter, which calls into the runtime to do a throw. So we also need a line in X86_64Runtime.runtime_THROW_REF to check for null as well.
The fast interpreter runtime also needs to check for null throwable before calling stack.throw(), matching the V3Interpreter null check.
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Summary
THROW_REFpops an exnref and rethrows it but does not check for null before casting withException.!(exval.val), causing a crash on null exnref instead of trapping withNULL_DEREF.Details
V3Interpreter.v3:330— add a null check before the forced cast.