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- Subject: Re: lua calling exit()
- From: Edgar Toernig <froese@...>
- Date: Tue, 21 Aug 2001 15:44:01 +0200
Bruno Silva wrote:
> I have a newbie question then: how should I call this function in an
> *error-proof* way?
> -- takes 2 strings, returns a boolean
> handled = Function (arg1, arg2)
> // calls Function
> lua_getglobal(s_lua, "Function");
> lua_pushstring (s_lua, arg1);
> lua_pushstring (s_lua, arg2);
> if (lua_call (s_lua, 2, 1) == 0)
> handled = (bool) lua_tonumber (s_lua, -1);
> lua_pop (s_lua, 1);
That is difficult. lua_getglobal, lua_pushstring and lua_tonumber
may raise an error. Even lua_pushcfunction/cclosure may raise one
so it's pretty difficult to call something in a secure way. A
lua_catch function (similar to luaD_runprotected) would help a lot.
> This must work (i.e., leave a clean stack) regardless of what "Function"
> evaluates to and whether the execution of "Function" succeeded or failed
> for whatever reasons. Is it guaranteed to push a value if it succeeds (I
> believe the docs say so)?
If the return value of lua_call is 0 you get exactly the number of results
you say you want (3rd arg). If the function returns less, nils are pushed.
> Is it guaranteed to not leave anything on the stack if it fails (couldn't
> find this in the docs)?
If lua_call returns != 0 it removes the function, its arguments and every-
thing above from the stack so that it is clean afterwards.