Performance hit of accessing the Lua stack

[David Anderson <david.anderson@...>]

Hi,

I'm currently developping a game in which most (read 'all') of the game 
logic will be scripted in Lua. I have just begun integrating and binding 
the interpreter to the C code. Specifically, I need to bind the C 
logging function to lua, so that the game logic can log info through the 
same channels as the C core.

I've been searching the documentation for information on the performance 
impact that lua_getstack and lua_getinfo (both called from C code, 
lua_getinfo with the "Sl" flags) have on a program, in vain: the 
documentation doesn't say anything about the speed of the C debug api, 
it only mentions that the lua debug library slows execution down 
considerably.

So, what sort of speed impact should I expect when calling lua_getstack 
and lua_getinfo?

(long explanation of what the hell I'm trying to do follows - skip if 
you can't be bothered :)

My C logging function takes the current file and line number 
(automagically extracted with a few wrapping macros in the C code) to 
integrate that info in the log. For the Lua binding, I'd like to use 
lua_getstack et al. to extract the lua caller source file and line 
number, so that lua code log lines appear as:

something.lua:42 - Doing this

Instead of:

lua_wrapper.c:193 - Doing this

Therefore, I'd like the C callback of the Lua logging function to 
extract the Lua caller's file/line info and pass it on to my logging 
function, so that the logs actually contain useful debug info.

Thanks in advance,
David Anderson