Re: recursively traverse globals table from C API

["Jérôme VUARAND" <jerome.vuarand@...>]

2007/1/19, Raymond Jacobs <raymondj@gmail.com>:
> int idx=LUA_GLOBALSINDEX;
> lua_getfenv(l,idx);
>
> while(lua_next(l,idx)!=0)
> {
>                 const char* key=lua_tostring(l,-2);
>
>                 //get value at -1 index and check type of it
>
>                 //do somthing with key and value based on type of value
>                 //if value is a table call this function again to traverse it, then
> continue here
>
>
>                 lua_pop(l,1);
> }
>
> it seems in theory it should be as simple as doing another lua_next,
> however I've not been able to get it to work, and I end up crashing,
> likely due to corupting the stack; either my logic or how I'm going
> about it is wrong, an example of how to do this in the C API would be
> really helpful.

You forget to push an initial nil on the stack before entering you
while loop (see lua_next documentation example). Here is what your
code could look like :

int dosomestuff(lua_State* L, int index)
{
   // Do something with value at index (which is not a table)
   return 1;
}

int parsetable(lua_State* L, int index)
{
   // Push an initial nil to init lua_next
   lua_pushnil(L);
   // Parse the table at index
   while (lua_next(index)!=0)
   {
       if (lua_istable(L, -1)
       {
           parsetable(L, -1);
       }
       else
       {
           dosomestuff(L, -1);
       }
       // Pop value, keep key
       lua_pop(L, 1);
   }
   return 1;
}

int parseglobals(lua_State* L)
{
   parsetable(L, LUA_GLOBALSINDEX);
   return 0;
}