pixelherodev commented on code in PR #578:
URL: https://github.com/apache/arrow-go/pull/578#discussion_r2558378255
##########
arrow/ipc/message.go:
##########
@@ -85,7 +84,9 @@ func NewMessage(meta, body *memory.Buffer) *Message {
meta: meta,
body: body,
}
- m.refCount.Add(1)
+ m.ReferenceBuffer(&m.meta, &m.body)
+ m.ReferenceDerived(unsafe.Pointer(&m.msg))
Review Comment:
The msg pointer is _derived_ from the `meta` Buffer, which is itself
allocated by the `Allocator`. `ReferenceDerived` is not for refcounting; it
basically means "when this object goes free, nil out the target to prevent
use-after-free."
Without it, accessing the message after calling Release could potentially
access other memory allocated by the `Allocator` - if integrating with C, this
could _theoretically_ allow access to other heap allocations. Note that the
previous code for Message.Release contains this:
```go
if msg.refCount.Add(-1) == 0 {
msg.meta.Release()
msg.body.Release()
msg.msg = nil
msg.meta = nil
msg.body = nil
}
```
it's releasing the two subresources, but also nilling the one that depends
on one. This is just to replace the `msg = nil` line, basically.
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