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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Calling `retain` on a closed ArrowBuf revives it, into an undefined state","articleBody":"### Describe the bug, including details regarding any error messages, version, and platform.\n\n```kotlin\n@Test\nfun testArrowBufRetainBug() {\n    RootAllocator().use { al -\u003e\n        val buf = al.buffer(10)\n        buf.close()\n\n        // correctly throws\n        assertThrows\u003cIllegalArgumentException\u003e { buf.referenceManager.retain() }\n\n        assertEquals(0, buf.refCnt()) // nope, it's 1\n\n        // doesn't throw, ref-count is 1 - so the caller assumes they've successfully taken a reference\n        // but the underlying memory has already been reclaimed and re-used\n        assertThrows\u003cIllegalArgumentException\u003e { buf.referenceManager.retain() }\n    }\n}\n```\n\nCaused by the `getAndAdd` in `BufferLedger.retain(int)` - this is what leaves the ref-count positive, so on the next call, this doesn't fail.\n\nSome kind of compareAndSet instead, perhaps?\n\nCheers,\n\nJames","author":{"url":"https://github.com/jarohen","@type":"Person","name":"jarohen"},"datePublished":"2025-11-05T16:52:08.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":8},"url":"https://github.com/906/arrow-java/issues/906"}