relay: defer CrossExecFilter destruction to its target executor - #654
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CrossExecFilter's methods enqueue [this]-capturing lambdas on targetExec_, but nothing keeps the filter alive until they run — owners release it from whatever executor they happen to be on. It can be freed with calls still queued, and the lambda then reads downstream_ off freed memory, seen as a SIGSEGV in beginSubgroup on a v0.3.1 relay. The sibling filters anchor themselves with selfGuard_, but that needs a terminal call and a TrackConsumer has none that is guaranteed. Destruction is guaranteed, so create() installs a deleter that posts the delete to targetExec_ behind every lambda already queued, and PrivateTag makes create() the only way to build one. auto filter = CrossExecFilter::create(targetExec, downstream); Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
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CrossExecFilter's methods enqueue [this]-capturing lambdas on targetExec_, but nothing keeps the filter alive until they run — owners release it from whatever executor they happen to be on. It can be freed with calls still queued, and the lambda then reads downstream_ off freed memory, seen as a SIGSEGV in beginSubgroup on a v0.3.1 relay.
The sibling filters anchor themselves with selfGuard_, but that needs a terminal call and a TrackConsumer has none that is guaranteed. Destruction is guaranteed, so create() installs a deleter that posts the delete to targetExec_ behind every lambda already queued, and PrivateTag makes create() the only way to build one.
This change is