0.1.11g, Linux x64. This will crash P8:

x={}
function x:__gc()
end

while true do
 y={}
 setmetatable(y, x)
end

If I change the loop to _update(), it doesn't happen.

However, there's another issue: it seems runtime errors aren't caught inside __gc(). If you put var="abc"+5 in there, it'll keep running until it crashes. If I do that, it will crash even using _update().