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On 18-May-06, at 8:52 AM, Roberto Ierusalimschy wrote:



On 17-May-06, at 10:50 AM, Roberto Ierusalimschy wrote:


Suppose I'd like to keep references to a bunch of lua_Objects that
were passed to my C function by Lua. The reference manual (no pun
intended) says that lua_ref() will obtain a reference to the
lua_Object that's on top of the stack, but does this apply for the
"getting arguments" situation? In other words, is this the right way to obtain references to passed arguments (for later use), or am I way 
off? In the likely event that I'm "way off" -- how is this done
correctly?

void my_Lua_callable_function()
{
 int ref_to_param_1 = lua_ref(1);
 lua_pop();
 int ref_to_param_2 = lua_ref(1);
 lua_pop();

 // etc ...
}



This way is fine. If you need to use these parameters in the same
function
after building their references, then you may prefer to copy thm to
the
stack top (with lua_pushobject) and then call lua_ref. But if all
you want
is to build the references, your code is quite Ok. (Except that the
signature of your function should be int foo (lua_State *L), and you
should pass this 'L' when calling lua_ref...)


Well, I forgot to mention that I'm using Lua 3.1 (it's forced by my
target platform, can't upgrade). In this case, I think the prototype
for a Lua callable C function is "void fun(void)", right?


Right. But then you have to change other stuff too...

I am not sure how much I remember about Lua 3.1, but I think the
parameters were not in the stack when the function was called.
So, you should first put them on the stack and then create the reference. 
Something like this:

  lua_pushobject(lua_getparam(1));  /* push first parameter */
  int ref_to_param_1 = lua_ref(1);  /* create reference to it */
Yeah, that was the second way I asked about in my original post. It's not nice, but it's good enough. 

Thanks =)


  ...

-- Roberto