Created attachment 8542335 [details] [diff] [review] doconcatstrings_exception-v0.diff It could return false because we need to GC, or it could return false because we're throwing. I guess we need to handle the throwing case explicitly wherever we use the NoGC/Root/CanGC trick.
I posted a patch in bug 1117085 to pass HandleStrings, so we don't need any rooting and the NoGC/CanGC trick. The very similar code in AddOperation still needs this fix though.
Comment on attachment 8542335 [details] [diff] [review] doconcatstrings_exception-v0.diff Jan has a much better solution in bug 1117085.