bug#71774: 31.0.50; Hash table weakness broken?

[Mattias Engdegård]

> The last form evaluates to #<window 7> here.  In all prior Emacs
> versions I have it evaluates to nil.  IIUC this means that either hash
> table weakness is broken or there is a bug in the collector.  To exclude
> that the behavior is specific to the window handling code, note that the
> recipe you can find here
> 
> https://nullprogram.com/blog/2012/12/17/
> 
> is now broken too.

Thanks for the report, but I wouldn't read too much into that. There could 
always be a stray reference to an object that is otherwise expected to be dead. 
Sometimes because of the conservative roots, sometimes from internal state we 
don't think about.

There is never a guarantee that any particular object is treated as dead by the 
GC. It's more of a general ambition.

As far as I can tell, it works as expected. Sometimes there is a stubborn value 
that just doesn't seem to want to be collected, but it's probably just a stray 
value on the stack, or a hidden reference that got stashed somewhere by the 
REPL.