Re: c module, using static variables

[Rob Hoelz <rob@...>]

Here's another thread that I started that discussed this issue:

http://lua-users.org/lists/lua-l/2011-10/msg00830.html

-Rob

On Sun, 15 Apr 2012 21:00:24 +0200
"Thijs Schreijer" <thijs@thijsschreijer.nl> wrote:

> I'm sort of stumbling along in my quest to learn c to create lua
> modules and every time I think I got it all figured out, something
> new pops up.
> 
>  
> 
> So now I'm creating a C module and have defined some static
> variables. Now I read in PiL somewhere (couldn't find it when I went
> looking for it) that static variables are a bad idea, this related to
> multiple lua states.
> 
>  
> 
> So my understanding is now, that if I create a c module 'mymodule'
> with a static variable, then if an application creates 2 lua states
> that each require 'mymodule', the c code of my module will be loaded
> only once, and be executed against the two different lua states.
> 
> This implies that the two states would then share the same static
> variable in my c module. Correct?
> 
>  
> 
> Because I'm using async callbacks (on another OS thread), when one of
> the callbacks arrives, I cannot call into the lua state to collect
> the values from the registry or from an upvalue safely. This prevents
> me from putting all my static variables in a big struct and store
> that as a userdata in the registry or as an upvalue.
> 
>  
> 
> If I would incorporate L (from lua_State *L from a function call)
> into my data structures to identify to which lua state that structure
> belongs, would that be safe? Is L only valid during a single function
> call, or does it remain valid (and unchanged) for as long as that lua
> state exists?
> 
>  
> 
> Whats the best approach? Any help is appreciated.
> 
>  
> 
> Thijs
>

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