Re: __gc visible to lua code...

[Michael Broughton <mbobowik@...>]

Graham Wakefield wrote:
> ?  You mean, in __gc set the userdata environment to nil, and then in 
> the type-check test if the environment is nil, for example?  Or 
> likewise for a field in the environment?  Probably null-checking the 
> userdata value is easier.

I meant for a field in the environment table... Assuming the table is 
unique for each userdata. I think you are right, though; I have not seen 
a case where this would be better than either of the other two methods.

> Another question: is the userdata's environment garbage collected when 
> __gc is called, or when the userdata itself is garbage collected?

The environment table can be collected like any other table: when there 
are no remaining references to it. Collecting a userdata merely removes 
the reference to its environment table.

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In most of my libraries, I have close metamethods that are exactly 
synonymous for __gc. That is, they call the same C function. This is so 
that I can clean up resources whenever I want, but if I ever forget, the 
garbage collector is there to cover me. I use 'close' because it is 
nicer to write that '__gc'.

Mike