Re: Lua and C++ (stack)

[Duboucher Thomas <thomas@...>]

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Le 30/05/2010 12:11, Erwin Oegema a écrit :
> 
> Hello,
> 
> I was wondering why my application doesn't get the correct values from the stack with this function under a Release build (it does work under Debug ...):
> 
> int LuaExports::askNumber(lua_State *luaVm) {
>     getNpc(luaVm)->sendGetNumber(lua_tointeger(luaVm, -3), lua_tointeger(luaVm, -2), lua_tointeger(luaVm, -1));
>     return lua_yield(luaVm, 1);
> }
> 
> O.o... Sometimes the values are switched too...
> Using the following code works perfectly:
> 
> int LuaExports::askNumber(lua_State *luaVm) {
> 
>     getNpc(luaVm)->sendGetNumber(lua_tointeger(luaVm, 1), 
> lua_tointeger(luaVm, 2), lua_tointeger(luaVm, 3));
> 
>     return lua_yield(luaVm, 1);
> 
> }
> 
> 
> So I want to know what the correct (best?) way is to get a value from the stack?
> 
> Thanks in advance.
>  

	Are you sure you understand the differences between positive and
negative indexes for the stack? As for me, I prefer using negative
indexes (my teachers told me to always access stack from the top).
	Also, for the differences between debug and release, I suspect that
some aggressive optimization may change the order in which functions are
called. I suppose that getNpc returns some kind of object or structure;
I had problems like this with this kind of code when the compiler has no
clues of how to optimize.

	Thomas.
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