Hi Roger, Peter,
On 21/10/15 15:38, Roger Riggs wrote:
Hi Peter,
I've always assumed that the arguments could not be gc'd at least until
the method returns
in part because the caller was holding references. But I suppose in a
completely inlined
case an optimizer might try to make more relaxed conclusions.
Since the new object has not yet been published, the reachability of
objects in a constructor
must have some additional rules to keep objects alive until it is
published.
I've recently been bitten by a test that did the rough
equivalent of this:
Object o = new Object();
ReferenceQueue<Object> queue = new ReferenceQueue<>();
WeakReference<Object> ref = new WeakReference(o, queue);
o = null;
System.gc();
WeakReference<?> wr = queue.remove();
The issue was that the reference 'ref' was sometime
eagerly garbage collected before 'o', and the call to
queue.remove() sometimes never returned.
I should have known (because it had happened to me before)
but these kind of issues are quite easy to miss, and have a
propensity to wait for some weeks after integration before
making themselves known...
I do hope that method parameters are not eagerly gc'ed before
the method returns - that would be yet another thing to
easily miss :-(
best regards,
-- daniel
