Fix exception ref-count leak in non-ref catch handlers.#12860
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cfallin wants to merge 1 commit intobytecodealliance:mainfrom
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Fix exception ref-count leak in non-ref catch handlers.#12860cfallin wants to merge 1 commit intobytecodealliance:mainfrom
cfallin wants to merge 1 commit intobytecodealliance:mainfrom
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When a Wasm `throw` instruction executes, the `throw_ref` libcall was cloning the GC ref (incrementing the refcount), but the catch handler never decremented it. This caused every caught exception to leak, leading to unbounded GC heap growth in throw/catch loops. Two fixes: 1. Remove the unnecessary `clone_gc_ref()` in `throw_ref`. The `throw`/`throw_ref` instructions consume the exnref operand, so ownership transfers naturally to `pending_exception` without cloning. 2. In `create_catch_block`, emit a `drop_gc_ref` call for non-ref catches (`Catch::One`, `Catch::All`) after field extraction. These catches consume the exnref without passing it to the branch target, so the refcount must be decremented. Also adds `Store::gc_heap_size()` / `StoreContext::gc_heap_size()` accessors and a `throw_catch_many_times` integration test that throws and catches 100K exceptions in a loop, asserting the GC heap stays within a single 64 KiB page.
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When a Wasm
throwinstruction executes, thethrow_reflibcall was cloning the GC ref (incrementing the refcount), but the catch handler never decremented it. This caused every caught exception to leak, leading to unbounded GC heap growth in throw/catch loops.Two fixes:
Remove the unnecessary
clone_gc_ref()inthrow_ref. Thethrow/throw_refinstructions consume the exnref operand, so ownership transfers naturally topending_exceptionwithout cloning.In
create_catch_block, emit adrop_gc_refcall for non-ref catches (Catch::One,Catch::All) after field extraction. These catches consume the exnref without passing it to the branch target, so the refcount must be decremented.Also adds
Store::gc_heap_size()/StoreContext::gc_heap_size()accessors and athrow_catch_many_timesintegration test that throws and catches 100K exceptions in a loop, asserting the GC heap stays within a single 64 KiB page.