Using the 'module' function in Lua 5.2? - c++

Question

I have a VC++ project which uses Lua 5.2 for scripting.
I am trying to implement MySQL compatibility into this project.
I do not own this project, so I would prefer to change as little source code as possible, if any at all.
I have downloaded and unzipped the files from this extension into the same base directory as the executable... and in my Main.lua file, I have added the line require('DBI') as stated to do so on this wiki page.
But when I run the application and execute the script, I get:
LUA Fail:
C:\Path\To\bin\DBI.lua:3: attempt to call global 'module' (a nil value)
After some light reading, I found out that the module function was depreciated in Lua 5.2...
But this extension, as well as other MySQL extensions, require the use of the module function.
So what is a workaround for this issue?

Answer 1

You may need to compile your Lua instance with LUA_COMPAT_MODULE; according to the source code: "LUA_COMPAT_MODULE controls compatibility with previous module functions 'module' (Lua) and 'luaL_register' (C)".
This won't be enough though as the module itself is written with Lua 5.1 API in mind. You can either try to find its Lua 5.2 version or use something like Peter Cawley's TwoFace that "allows a Lua 5.2 program to load most 5.1 C libraries without the need for any recompilation".

Answer 2

I used this as a quick and dirty way to get most of my scripting setup working with 5.2.
I didn't use module myself but have the likes of luasocket, copas etc in my stack.
I doubt this helps in your specific case but may be of some use more generally.
Essentially I replicated the C version of module in lua using the debug library to set the function environment. Not pretty but hey.
if not module then
function module(modname,...)
local function findtable(tbl,fname)
for key in string.gmatch(fname,"([%w_]+)") do
if key and key~="" then
local val = rawget(tbl,key)
if not val then
local field = {}
tbl[key]=field
tbl = field
elseif type(val)~="table" then
return nil
else
tbl = val
end
end
end
return tbl
end
assert(type(modname)=="string")
local value,modul = package.loaded[modname]
if type(value)~="table" then
modul = findtable(_G,modname)
assert(modul,"name conflict for module '"..modname.."'" )
package.loaded[modname] = modul
else
modul = value
end
local name = modul._NAME
if not name then
modul._M = modul
modul._NAME = modname
modul._PACKAGE = string.match(modname,"([%w%._]*)%.[%w_]*$")
end
local func = debug.getinfo(2,"f").func
debug.setupvalue(func,1,modul)
for _,f in ipairs{...} do f(modul) end
end
function package.seeall(modul)
setmetatable(modul,{__index=_G})
end
end