Subj : The new changes to atom safety in garbage collection
To   : netscape.public.mozilla.jseng
From : "Steven C. Cole" <scole@planetweb.com>
Date : Wed Jul 30 2003 01:48 pm

Brendan & other Spidermonkey code jockeys,

A while ago we learned that calling JS_GC() from within a resolve hook 
was a bad thing to do, because there can be unrooted atoms during a 
resolve call that the GC then removes.

We still wanted to do GCs from within the resolve hook, however (for 
last-ditch help in out-of-memory scenarios), so I wrote a little 
"restricted" GC routine that used the JS_KEEP_ATOMS parameter of js_GC 
to avoid hitting the atoms.

But with the changes that went in last week, this all got changed around 
a bit, and now there's a runtime flag that indicates whether atoms are 
safe for GC or not.  I notice that this flag is set around compilation, 
where the GC used to be disabled.

Here's my question: Is the "keep atoms" flag also set in other places 
where it's not safe to GC them?  In other words, can we go back to 
calling the "official" api JS_GC() call from our out-of-memory hooks 
(which can happen in resolve hooks or any of the other object hooks), 
and remove the "restricted GC" routine that I wrote?

Thanks,
Steve Cole

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