Problems understanding userdata

["Jim Jones" <jjones@...>]

I am currently using the framework Glua-X to bind my C function to the Lua interpreter.  I apologize if you can't answer questions regarding someone else's library, but I can't seem to find a contact address for the author.

 

I am utilizing Lua 4.0.

 

Here is the issue.  Say I have the following function :

  int foo (int x,int *y);

 

'y' will always return a pointer to a newly allocated value.  Say I have that function binded as such :

 

/////////////////////////////////////////////////////////////

GLUA_FUNC(FOO)
{
  int x  = glua_getInteger(1);
  glua_getDone();

 

  int *y;

  int r = foo(x,y);

 

  glua_pushUserdata( y );  // Here is how I want to pass it back
  // glua_pushUserdata( y, glua_newtag("y")); // This is the syntax Glua-X wants
}
GLUA_END

 

GLUA_FUNC(PRINTFOO)
{

  int *x  = glua_getUserdata(1);  // Here is the syntax I expected
  // int *x  = glua_getUserdata(1,tag);  // Here is how Glua-X wants the syntax

 

  glua_getDone();

  printf(*x);

}
GLUA_END

/////////////////////////////////////////////////////////////

 

I don't understand why I have to associate the pointer with a tag.  If I call the FOO function from Lua like this

 

  zzz = FOO(1)  

  PRINTFOO(zzz)

 

isn't zzz my tag? I want the return value to be assigned receiving userdata object.  I am confused.

 

Any help is GREATLY appreciated.

 

Jim