Re: Registries

At 17:32 2003-07-16, David Abrahams wrote:
>Daniel Wallin <[email protected]> writes:
>
> > At 15:38 2003-07-15, David Abrahams wrote:
> >>Daniel Wallin <[email protected]> writes:
> >>
> >>I'm not really sure it amounts to much.  The additional complication
> >>should go into the *registration* process instead of the lookup
> >>process, to make sure that lookup stays fast.
> >
> > Right... How would these scopes be specified by the user?
> > What constitutes a scope?
>
>I don't think the user would specify scopes explicitly, except to
>import from them.  They'd follow the nested structure of modules
>precisely, and the user would use module names to refer to them.

Could you explain more how the modules would nest, and how
would the scoping "just work"? How does a module know it's
parent?

> > Ok, there are two use cases:
> >
> >    Build you module as a shared lib and expose some function
> >    that binds all your C++ code to the lua state. There are
> >    some fairly standardized symbol names that are used for this
> >    (luaLM_version, luaLM_import).
>
>So this function goes into lua's global namespace and is called
>explicitly by the user to load the module?  It sounds a bit like the
>module init function used by python.

Well, there are different ways of handling this.. Lua has a built in function
that loads a function from a shared library. Used like this:

   local init = loadlib("mymodule.dll", "init_mymodule")
   init()

there's at least one extension that allows:

   loadmodule("mymodule.dll")

which I guess is almost equivalent to:

   function loadmodule(name)
     local init = loadlib(name, "luaLM_import")
     init()
   end

>Does the shared lib get opened with dlopen, thus ensuring link symbol
>isolation from other modules?

Yes, at least that's what I concluded after investigating the source to some
of the loaders.

> >    Bind your module directly to the interpreter by modifying the lua
> >    state:
> >
> >      lua_pushstring(L, "my_fun");
> >      lua_pushcclosure(L, &my_fun, 0);
>
>How does the code which does the binding get invoked?

Either by doing it in a function that's exposed from a shared lib, or by just
invoking it. :)

   int main()
   {
     lua_State* L = lua_open();
     lua_pushstring(L, "my_fun");
     lua_pushcclosure(L, &my_fun, 0);
     ..
   }

---
Daniel Wallin



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