joseph stewart wrote:
[...]
I'm familiar with doing this on the 'C' side, I was just trying to
minimize the 'C' code.
Trying to do real work from a finaliser in Lua land is going to
involve a
world of pain, I'm afraid. Consider the following:
- what happens if the garbage collector runs during execution of
your finaliser?
- what happens if your finaliser tries to make the object live
again by
making a reference to it?
- what happens if an error occurs during execution of the finaliser?
- what happens if the garbage collector doesn't run often enough,
and you run
out of whatever resource you're keeping track of in your finaliser?
(Example:
file handles. I've been bitten by this.)
- what happens if your program terminates in such a way that Lua
doesn't
finalise things? (Sounds unlikely, but it can happen.)
Just take a look at the horrible nightmare that is Java
finalisation as an
example --- in particular, look at the state machine diagram here:
http://java.sun.com/docs/books/jls/second_edition/html/
execution.doc.html#44760
Lua avoids this kind of nasty mess by decreeing that finalisers are
not
available from the Lua language. Finalisers only work on userdata
objects, and
you may only set the finalisers from C, which means you are forced
to think
about what you're doing and be aware of the issues.
In general, using finalisers to do anything other than to
deallocate trivial
resources such as memory is generally considered a really bad idea.
That's not
to say that can't also be useful, but, well, You Have Been Warned...
--
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other particles are good
│┈ dg@cowlark.com┈┈┈┈│ approximations to perfectly
elastic spherical
│┈(dg@tao-group.com)┈│ cows." --- David M. Palmer on r.a.sf.c
╰─┈www.cowlark.com┈──╯
