Re: LoadLibrary and 5.2

[David Burgess <dabsoft@...>]

Answering you query ther are a lot more posts from Lua 5.0, onwards 
methinks.

At the risk of the discussion starting all over again...

The current strategy (I believe) is that Lua loads DLLs from a known set 
of locations which is in effect controlled by package.cpath which can be 
controlled by the environment variable LUA_CPATH. The default value is 
"!\\" which expands to the executable directory path.

The strength of this approach is that Lua DLL loads are by default loads 
from an explicit path, this is multiple orders of magnitude faster than 
allowing windows to search for a DLL (by just using a file name). This 
is also compatible with Microsofts recommendation of where to put your 
application DLLs (WRT the executable) , <QUOTE>It is good practice to 
install application DLLs in the same directory that contains the 
application</QUOTE>ref: 
http://msdn.microsoft.com/en-us/library/ms682600%28VS.85%29.aspx.

Again to quote MS from 
http://msdn.microsoft.com/en-us/library/ms682586%28VS.85%29.aspx, "Note 
that the standard search strategy and the alternate search strategy 
specified by LoadLibraryEx with LOAD_WITH_ALTERED_SEARCH_PATH differ in 
just one way: The standard search begins in the calling application's 
directory, and the alternate search begins in the directory of the 
executable module that LoadLibraryEx is loading."

This means that with the way loadlib.c currently works the only time 
when LOAD_WITH_ALTERED_SEARCH_PATH would have an effect is when your 
executable and DLLs are in different directories and one has modified 
LUA_CDIR and/or LUA_CPATH to *not* use absolute path loads.

MS have change the search strategy with different OSs and indeed with 
service packs, as it stands Lua has been immune to this hackery.

Of the requests for change that I have read it would seem that the 
solution is not to use LOAD_WITH_ALTERED_SEARCH_PATH but to change or 
add a path to the default package.cpath.

In choosing the best solution I note that DLL redirection and 
manifests/assemblies complicate the Windows scene.

So maybe the solution to keep more people happy is to set the 
package.cpath default to something like:

".\\?.dll;"  LUA_CDIR"?.dll;" LUA_CDIR"\dll\?.dll;" LUA_CDIR"loadall.dll"

or my preference is to use absolute paths

LUA_CDIR"?.dll;" LUA_CDIR"\dll\?.dll;" LUA_CDIR"loadall.dll"


Finally a question, does anyone have a Windows SxS assembly for a Lua 5 
DLL using VS2008?

DB

Theodor-Iulian Ciobanu wrote:
> On Tue, 12 Jan 2010 08:36:30 +1100
> David Burgess <dabsoft@gmail.com> wrote:
>
> > Sometime ago some powerful arguments for no change were placed on the 
> > list. I believe the arguments are still valid.
>
> These were the arguments I found so far:
> http://lua-users.org/lists/lua-l/2008-05/msg00397.html
> http://lua-users.org/lists/lua-l/2008-08/msg00618.html
>
> But maybe I haven't searched the archive deep enough because I'd like
> to see this change being made as well - I've been using it for some
> time for myself.