Re: How to avoid DLL hell?

[Ralph Hempel <rhempel@...>]

Nick Gammon wrote:
> I have spent a couple of days now trying to get my program (a MUD
> game client) to compile and run with Lua 5.2.
>
> It's taken a while, partly because it took around 2 days to even get
> it to compile, what with the deprecated functions, removal of
> LUA_GLOBALSINDEX, luaL_typerror, lua_equal, lua_unref, lua_getref and
> a few others.

I struggled with that for a while too - then I just set LUA_COMPAT_ALL
in a command line define and the problem went away. There's a lot of
existing libraries that would break otherwise.

> Well, expectation or not, the fact is that there are a lot of Lua
> scripts out there, and major work is likely to be on the horizon for
> them.
>
> But the big issue is the crashes. Why are there crashes? Because of
> the DLLs (I am talking Windows here, and yes I know it would be good
> to avoid Windows if possible).
>
> I have modules that use luasocket, for example. Now the DLLs that
> ship with that are linked against lua5.1.dll - and since it can find
> a lua5.1.dll in the path, it loads it. So I now have the main program
> pulling in lua52.dll and some modules loading in lua5.1.dll - and
> sooner or later the whole thing crashes, because of the malloc/free
> problems with clashing DLLs.

Time to rebuild and relink against 5.2 then.

> So how do we avoid all this? Short of completely upgrading from Lua
> 5.1 to Lua 5.2 and removing all traces of Lua 5.1 from my system
> (hardly a practical choice), we need a way of making the Lua 5.2
> modules pull in Lua 5.2-compiled DLLs (like luacom, luasocket, and so
> on). But I'm not sure how this is achieved easily. Right now, for
> example, luasocket itself pulls in two DLLs, rather confusingly named
> core.dll and core.dll (in different directories).
>
> Is the solution to rigorously keep DLLs into their own directory
> paths - even those with the same names (eg. core.dll and core.dll)?
> Or is it to impose a naming convention on then (eg.
> luasocket5.2.dll)?

I have a build system for the Lua core under Linux that builds
for Windows using mingw32 and friends.

With a bit of fiddling in the luaconf.h file customisation
section, I can force Lua to look in certain places for DLLs.

The output of my build system looks like this:

usr/local/bin/lua52.exe and lua52.dll

usr/local/lib/lua/5.2/*.*

I can put the "usr" root anywhere in the Windows file system
and as long as I run programs from that spot, it always finds
the DLLs

Or, I can put it under C:/ and customize luaconf.h and run
Lua from anywhere on the Windows system.

Maybe I'm just lucky, but 5.2 offers a lot of really nice additional
features for embedded guys like me, especially the new emergency GC.

Ralph