Re: Problem with Lua in c++ and stl
[
Date Prev][
Date Next][
Thread Prev][
Thread Next]
[
Date Index]
[
Thread Index]
- Subject: Re: Problem with Lua in c++ and stl
- From: Mike Cuddy <mcuddy@...>
- Date: 1999年8月31日 21:09:38 +0100
> BTW, I think LUA is great, I just wish I can get this to work. Thanks.
>
> My app dumps core somewhere within the stl code. Here is the backtrace:
> #0 GameMap::AddTileBitmap (this=0x0, image=0x805f608)
> at /usr/local/include/g++/stl_vector.h:145
> 145 if (finish != end_of_storage) {
> (gdb) bt
> #0 GameMap::AddTileBitmap (this=0x0, image=0x805f608)
> at /usr/local/include/g++/stl_vector.h:145
Here's your clue:
> #1 0x8049b83 in GameMap::AddTile (this=0x0) at game_map.cpp:56
^^^^^^^^^^
You cast the member function GameMap::AddTile to function you registered
with lua. lua has no way to know it's a "thiscall" (i.e.: attached to
an object) so it just calls it like a standard C function (which it isn't).
What I generally do, is make my tables have a "ptr" member, which I
set to point to the C++ object I'm working with. Then in the LUA->C
binding function, I fetch that member from the table passed to the C
function and dereference it to call the object member function.
lua_Object getField(lua_Object t, char *fld)
{
lua_pushobject(t);
lua_pushstring(fld);
return lua_gettable();
}
// push a userdata (void*) object..
void setField(lua_Object t, char *fld, void *data, int tag = 0)
{
lua_pushobject(t);
lua_pushstring(fld);
lua_pushusertag(data,type);
lus_settable();
}
// push a cfunction object..
void setField(lua_Object t, char *fld, void (*data)())
{
lua_pushobject(t);
lua_pushstring(fld);
lua_pushcfunction(data);
lus_settable();
}
// functions to bind to LUA; make sure they are C callable.
// (in general, a C++ function with no args has the same linkage as a
// C function, but that's implementation dependent, so avoid link-time
// errors, by declaring the function as a C function).
extern "C" {
static void lua_myClass_AddTile();
}
// class which is usable from lua. each member function that is to be
// called, should be added as a field ; we might want to create a tag,
// etc. We could also make a "luaObject" baseclass which would do
// all of the common objects-accessable-to-lua initialization.
class myClass {
void AddTile();
lua_Object t;
int ref;
// constructor ..
myClass() {
t = lua_createTable(); // create new lua object
ref = lua_ref(1); // lock it in memory.
// add member function
setField(t,"AddTile", lua_myClass_AddTile);
// add pointer to 'this' for lua linkage
setField(t,"ptr", (void*)this);
}
~myClass() {
if (ref) lua_unref(ref);
// ... etc ..
}
}
// it's a pity that cfunction's in lua don't get to carry userdat, then we
// could pass the object "implicitly" to the C -> C++ binding function.
// instead of digging it out of a table.
static void lua_myClass_AddTile() {
lua_Object table = luaL_tablearg(1); // get table from lua
MyClass *self = (MyClass*) lua_getuserdata( getField(t,"ptr"));
self->addTile();
}
--
Mike Cuddy (mcuddy@FensEnde.com, MC312), Programmer, Daddy, Human.
Fen's Ende Software, Redwood City, CA, USA, Earth, Sol System, Milky Way.
I remember asking why ... Let it rain, and protect us from this Cruel Sun.
Join CAUCE: The Coalition Against Unsolicited Commercial E-mail.
<http://www.cauce.org/>