finalizer call order in GC cycle during lua_close (Lua 5.2)

[Richard Hundt <richardhundt@...>]

Hi List,

I'm seeing __gc finalizers on userdata objects being called in an 
unexpected order when a Lua state is closed.

I have a buffer udata which holds a reference to a file descriptor udata 
in its associated environment table. During a *normal* GC cycle (run via 
collectgarbage() from Lua), the buffer's __gc metamethod runs before 
that of the fd, as I'd expect since at this point the fd is still 
reachable via the buffer's fenv.

At program termination, though, I'm getting the reverse, which I find 
surprising. It means I can't flush buffer to the file handle during the 
buffer's __gc at normal program termination, since the fd is already 
collected by then, despite the fact that it's still reachable.

Is there a rationale for this, or some way to tame it?

Thanks.

-Rich