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It was thus said that the Great Ranier Vilela once stated:
> Hi Hackers,
> How should the stack look after the calls below?
>
> lua_pushinteger(L, p1);
> lua_pushinteger(L, p2);
> lua_pushinteger(L, p3);
> lua_pushnumber(L, p4);
> lua_call(L, 4, 1);
> if (lua_isuserdata(L, -1)) {
> value = lua_tonumber(L, -1);
> lua_pop(L, 1);
> }
> lua_pop(L, lua_gettop(L));
>
> What is the correct way to clean the stack?
The lua_call() function is defined as:
void lua_call(lua_State *L,int nargs,int nresults);
The manual states that lua_call() will remove nargs+1 items from the stack,
and push nresults on the stack. So for your example:
lua_pushcfunction(L,myfunc);
lua_pushinteger(L,p1);
lua_pushinteger(L,p2);
lua_pushinteger(L,p3);
lua_pushinteger(L,p4); /* [1] */
lua_call(L,4,1); /* [2] */
At point [1], the stack looks like:
+index -index value
----------------------
n-1 -6 previous entries...
n -5 myfunc
n+1 -4 p1
n+2 -3 p2
n+3 -2 p3
n+4 -1 p4
At point [2], the stack will look like:
+index -index value
----------------------
n-1 -2 previous entries...
n -1 result
In your example, the code should be:
if (lua_is<type>(L,-1))
{
value = lua_to<type>(L,-1);
/* use the value */
}
lua_pop(L,1); /* remove result from stack */
-spc