Re: Path change to LUA_CPATH in Lua Binaries

[Ross Berteig <Ross@...>]

On 8/27/2008, RJP Computing wrote:
> Yes I think this is a bit of a heavy approach, plus we still 
> need to be able
> to run 'lua' on the command line so the PATH will still need to 
> be updated.

One approach would be to patch package.loadlib() for Windows so 
that the PATH is updated in the current process environment just 
before each DLL is loaded. The updated PATH should include both 
lua.exe's folder and the folder from package.cpath where the DLL 
was found. That would permit Lua modules that need additional 
DLLs to get them from the "standard" DLL search path without 
requiring that the system PATH be modified any more than 
necessary to support command-line use of lua.exe. In fact, an 
application based on wlua.exe and IUP need not modify the system 
path at all in this case.

Another (better?) approach might be to patch package.loadlib() 
for Windows to use LoadLibraryEx() with the flag 
LOAD_WITH_ALTERED_SEARCH_PATH instead of LoadLibrary(). That 
flag is supposed to modify the search path used for implicitly 
linked DLLs to include the folder where the explicitly loaded 
DLL is located. According to MSDN, this feature has existed 
since Win95, although this is the first time I've noticed it in 
the documentation myself.

On a new enough version of Windows (XP SP2 I think), 
SetDLLDirectory() could probably be used instead of changing PATH.

Incidentally, I suspect that LuaRocks will have issues unless 
something like this is done because it scatters its installed 
rocks in a tree and implicit DLLs required by (and delivered 
with) a rock will have trouble loading when the rock is loaded 
by its customized require().

In any case, this is clearly something that should be done in 
the low level  module loader, and not imposed as an external 
requirement on PATH to get complex DLL modules to work right.


Ross Berteig                               Ross@CheshireEng.com
Cheshire Engineering Corp.           http://www.CheshireEng.com/