Re: Problem with table created from C

["Jose Luis Hidalgo" <joseluis.hidalgo@...>]

Hi Steve,

   Just one question, Why lua_settop(m_L, 0) after each function?
Does the SetThreadLuaPointer function create a thread? I'm not sure if
doing a lua_settop to 0 will not destroy data that you expect to be
there after that... When I need to ensure that a function leaves the
stack as it was before it execution I always do that:

// this function is for internal use, as you can see it can not be called from
// lua, is a helper function called by other C functions.
void myFunction(lua_State *L, int param1, int param2, ...) {
     int top = lua_gettop(L); // get the current top
    /*
       here do thins with Lua as you want...
       top var helps to access data too :)
     */
    lua_settop(L,top); //restore the stack
}


May be you can check what kind of data do you have in the stack before
doing a settop to 0. Remember that Threads for example are pushed onto
the stack as other values, so if you remove them without store them in
registry or a table, or whatever... they will be collected.

Hope it helps, :)

Cheers,
    Jose L.


On 9/11/06, Steve Heller <steve@steveheller.com> wrote:
> Hi all,
>
> I'm having a problem when creating a Lua table from
> C++, then asking for its value later. For some reason,
> the table doesn't seem to exist.
>
> Code that shows what I'm doing is at the bottom of
> this message. The
> "GetThreadLuaPointer"/"SetThreadLuaPointer" functions
> use thread local storage to save the Lua environment
> pointer. There are two phases of this program.
>
> 1. Store the rules into the RuleManager table, via
> code like this:
>
> LuaRuleManager RulesObject;
> LuaRuleManager.AddRule(ruleNumber,ruleString);
>
> 2. Retrieve the rules from the RuleManager table, via
> code like this:
>
> LuaRuleManager RulesObject;
> string result = LuaRuleManager.GetRule(ruleNumber);
>
> The storage part works fine; I've confirmed that the
> rules are actually being saved in the RuleManager
> table. Unfortunately, when I try to retrieve the
> rules, the RuleManager object comes up as nil.
>
> Any suggestions as to what the problem may be, or how
> to fix it?
>
> Thanks.
>
> --------------------------------
> LuaRuleManager::LuaRuleManager()
> {
>     m_L = GetThreadLuaPointer();
>
>     if (m_L == 0)
>         {
>         m_L = lua_open();              /* opens Lua */
>         SetThreadLuaPointer(m_L);
>         luaL_openlibs(m_L);            /* open
> standard libraries */
>
>         lua_newtable(m_L);             // create new
> table
>         lua_setglobal(m_L,"RuleManager");    // assign
> it to global variable named RuleManager
>         }
> }
>
> LuaRuleManager::~LuaRuleManager()
> {
> }
>
> void LuaRuleManager::AddRule(int id, const string&
> RuleString)
> {
>     lua_getglobal(m_L,"RuleManager");
>     if (!lua_istable(m_L,-1))
>         __asm int 3; //RuleManager table not found
>
>     lua_pushnumber(m_L,id);
>     lua_pushstring(m_L,RuleString.c_str());
>     lua_settable(m_L,-3);
>     lua_settop (m_L, 0);
> }
>
> string LuaRuleManager::GetRule(int id)
> {
>     lua_getglobal(m_L,"RuleManager");
>     if (!lua_istable(m_L,-1))
>         {
>         PassThrough::DumpStack(m_L);
>         __asm int 3; //RuleManager table not found
>         }
>
>     lua_pushnumber(m_L,id);
>     lua_gettable(m_L,-2);
>     size_t size;
>     const char* rule = lua_tolstring(m_L,-1,&size);
>     lua_settop (m_L, 0);
>
>     return string(rule,size);
> }


--
 Jose L. Hidalgo Valiño (PpluX)
 ---- http://www.pplux.com ----