Wasmtime GitHub notifications bot (Apr 01 2026 at 22:35): Wasmtime GitHub notifications bot (Apr 01 2026 at 22:35):fitzgen opened PR #12934 from fitzgen:fix-stack-maps-for-try-call-lowering to bytecodealliance:main:
Branch instructions are skipped in the main lowering loop, which means the stack map forwarding code is never reached for them. The branch lowering path didn't forward stack maps either. This was fine because branch instructions couldn't previously ever be safepoints. However, with the introduction of
try_callandtry_call_indirect, we now have instructions that are both safepoints and branches.This caused GC references live across
try_call[_indirect]instructions to not be traced during garbage collection, leading to use-after-free within the GC heap sandbox when the collector swept those untraced-but-still-live objects.The fix adds stack map forwarding after branch lowering, mirroring the existing logic for non-branch instructions.
Fixes bytecodealliance/wasmtime#11753.
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Wasmtime GitHub notifications bot (Apr 01 2026 at 22:35):fitzgen requested wasmtime-compiler-reviewers for a review on PR #12934.
Wasmtime GitHub notifications bot (Apr 01 2026 at 22:35):fitzgen requested cfallin for a review on PR #12934.
Wasmtime GitHub notifications bot (Apr 01 2026 at 22:35):fitzgen requested wasmtime-core-reviewers for a review on PR #12934.
Wasmtime GitHub notifications bot (Apr 01 2026 at 22:45):fitzgen updated PR #12934.
Wasmtime GitHub notifications bot (Apr 01 2026 at 23:08):cfallin submitted PR review:
LGTM -- good find; thanks!
Wasmtime GitHub notifications bot (Apr 01 2026 at 23:08):cfallin added PR #12934 Preserve try_call[_indirect] stack maps during lowering to the merge queue.
Wasmtime GitHub notifications bot (Apr 01 2026 at 23:54):cfallin merged PR #12934.
Wasmtime GitHub notifications bot (Apr 01 2026 at 23:54):cfallin removed PR #12934 Preserve try_call[_indirect] stack maps during lowering from the merge queue.
Last updated: Apr 12 2026 at 23:10 UTC